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THE POTENTIAL OF TEPHROSIA CANDIDA FOR AGROFORESTRY IN MIDLAND VINH PHU PROVINCE
by
Nguyen Thu Phuong Center for Natural Resources Management and Environmental Studies (CRES)
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THE POTENTIAL OF TEPHROSIA CANDIDA FOR AGROFORESTRY
IN MIDLAND VINH PHU PROVINCE
1. INTRODUCTION
Vinh Phu province is the Midland region of North Vietnam. It is an intermediate zone between the flat lowlands and mountainous highlands.
The differentiation of climatic factor, terrain, alitude, and geophysial conditions, the rock weathering happended strongly to form red grafit soil which is defficient of alkaline metals, specially ion Mg and ion Ca, whereas it accumulate ion
Fe and Al high ; pH : 3.4-4.6.
Nowadays, there are many reasons to affect on this Midland that have been appearing many bare hills, declining humus content such as humus content: 1^5 - 1.91 % ; total of nitrogen: 0.087 -
0.089 % ; K20: 0.027 - 0.071 % ; P205: 0.048 - 0.068 %, increas• ing erosion ( lost than 150 -200 tons/ha/year, Nguyen Quang My 1985)/ descrearsing food crop yields.
However, Midland Vinh Phu province has a great potential that is suitable for many plants, such as industrial crops
(eucalyptus, manglietia, pinus, stirax) ; perenial plants (tea) ;
food crops (cassava). In order to enhance food crop yields,
restoring ecological conditions, specially in improvement of
soil, agroforestry has been carrying out in Midland Vinh Phu province. Tephrosia Candida, in recent years, has increasingly become regarded as a superrious tree for agroforestry because of
it's characteristics are suited for climatic factors, altitude,
and the type of soil.
In order to recognize the potential of Tephrosia Candida for
agroforestry in Midland Vinh Phu province. In this working paper,
I base on the basis theoretics to analyse. It is drawn from "
HUMAN ECOLOGY Human social systems and ecolosystems have an
interactive relationship, so that the structure of society is modifed by it's relations to the environment, just as the struc•
ture of ecosystem is influences by human activities (Rambo 1984)
(Fig.l). BIOMASS PRODUCTION LIGHT
HOUSEHOLD
EROSION
7
GREEN MANURE
LEAtHING FERTILIZER, IF APPLIED
THE EFFECTIVE RHIZOBIUM STRAINS
FIG. \ THE INTERACTIVE RELATIONSHIP BETWEEN AGROFORESTRY AND HOUSEHOLD i i 2. CHARACTERISTICS OF TEPHROSIA CANDIDA
The leguminosae family is an entremely diver sified family that has existed since the Cretaceous period in hot and tempera• ture regions of the world. There are about 750 genera and 20,000 species, including numerous cultivated plants that provide part of human diet, livestock feed, wood, essential oils, gums, alka• loids, ect. as well as numerous shrubs and herbaceous plants that play a major role in various ecosystems. In Midland Vinh Phu province, Tephrosia Candida, is a low shrub from the north• western Himalaya to tenasserim, has characteristics to be suited for food crops, industrial crops, perennial plants. This is the potential for developing Midland vinh Phu province.
a. Native tree easy to plant as well as adaptable to acid soil and the adverse condition in Vietnam. b. Nitrogen fixing capacity. Tephrosia Candida is a nitrogen fixing legume, this is potentially useful. Due to nitrogen is one of the most essential elements to plants. It is found in abundance in the atmosphere and in the soil but not in the form that the plants can stimulate. Nitrogen fixation which reduces nitrogen to ammononium, that is form usable by plant.
This process requires much energy. Fortunately, certain microorganisms can fix atmospheric nitrogen by using enzyme nitrogenese. It can be estimated at 175 million metric tons per year i.e. about 70% of all nitrogen fixed on the earth each year
(J.J.Drevon 1983).
Nitrogent fixation Millions of metric tons per /year
Industrial fixation (Haber-Bosch). 40
Atmospheric fixation
(lighting, ect.,) 10
Combustion (indutry, automobiles) 20
Ozonization 15
Biological fixation of nitrogen 175.
The biological nitrogen fixation take place by the free- living organisms in the soil, organisms associal with the plant in a rhizosphere, and. particularly on cultivated land have been symbiotic fixation by legume-rhizobium association. Soil bacteria enter the roots of legume tree. This infection stimulates plant to form a structure on it's root called a nodule. With this nodule, rhizobium multiply while taking nitrogen from the air and converting it into form that are used by plant to make protein, aminoacid. Therefore, rhizobium use energy, hydratcarbon of plant which are formed through photosynthesis.
Rhizobium strains not only differ in their ability to from nodules with a given legume, but also in their capacity to fix nitrogen in association with the particular host. The property of nitrogen fixation is a function of both host and bacterium.
And a strain of rhizobium may be highly efficcient. Effective nodules can be distinguished by their pink coloration, which is due to a red internal pigment, leghemoglobin (oxygen tranport protein).
The nodule formation is very important for symbiotic nitrogen fixers existing in nodules:
- Nodule have an internal for supplying photosynthesis.
- The nodular structure protect rhizobium from competition with other microorganisms.
- Leghemoglobin forms a barrier to the free diffusion of oxygen and there by protects the nitrogenese against oxygen.
- They have a efficient system for transferring fixation products to the various aerial parts of the host plant. Nodules are usually located on the root, they may be formed on the root surface (Pisum, Glicine), or the stele and are strongly attached to the root (Arachis, Aerchynomene). Some species have nodules on the stem (Sesbania rostrata).
Nodule size varies considerably, for example, Tephrosia
Candida, soybean and vigna nodules are 3-10 mm in diameter while colver nodules are less than 1 mm, it is difficult to distingguish the charateristic red tint in a croos section, so
Cajanus nodules can reach 2-3 cm in length.
The legume-rhizobium symbiotic is undoubtedly the most important biological mechanism for adding nitrogen to the soil- plant system. The nitrogen fixing capacity of legume trees are different. Henell (1968), Gibson, and Jordan (1983) provide evidence that rates of nitrogen fixation by symbiotic of legume- rhizobium association have been achieved about 300 kg ofnitrogen per ha per year in tropics and 600 kg of nitrogen per ha per year in temperate regions. For Tephrosia Candida, it is estimated about 44 kg of nitrogen per ha per year. These capacity depends on many factors, but the seasons in Vinh Phu provine effect on strongly (Fig.2 ). The nitrogen fixing activity of nodules in• creased, reaching a yearly maximum in April. It is spring-rainy season. From October to January it is dry season, these activity discreased because of leaves failed, and photosynthesis dis- creased.
In consequence of symbiotic nitrogen fixation of legume rhizobium association, nitrogen sources increase considerable.
8 June Aug. Oct. Jan. Apr. July
1988 1989
Fig£ Variation of specific nodule activity in Tephrosia Candida as a function of time Special in the root system of Tephrosia Candida develope strongly, it also breaks up impervious subsoil layers, and the nodules appear together. Hence, Tephrosia Candida has a important role in Midland-Vinh Phu province, it enrich soil and aid neigh• boring plant, improve moisture penetration and decreasing surface run-off.
c. Prolific seed producer. Tephrosia Candida has the ability to bear seeds early and they are quite prolific. The seed-sowing is start on February or March and the harvest is from on October or November. The prolificacy of Tephrosia
Candida is usefully significant for farmers, they assure a continuing and sufficient supply of seeds for natural regeneration or establishment of new forest in other agroforestry or plantation areas.
d. Survival ability. Like many legume trees, Tephrosia
Candida can survive and thrive in unfavorable on extreme condition. Such as, acidic soil (pH:3.5 - 4.2), we know that
Leucaena. glauca is a famous tree in Southeast Asia, but it could not grow in this soil. Even Tephrosia Candida can develope well in the soil that very poor in organic matter and fertilizing: K,
P, Ca, Mg, Mn and Mo deficences. For example, amount of organic matter: 0.7; nitrogen: 0.04%; P205:0.06%. Therefore, they are useful in the rehabilitation of degraded lands, where other species could not grow. After a period of an acumulation of nitrogen-rich organic matter on the soil surface, the farmer can plant food crops. e* The size of leaves is favourable to models of agroforestry. like most legume tress, the leaves of leaflets of
Tephrosia Candida suited to intercopping with annual food crops, they allow enough sunlight to reach the food crops and fall- leaves decompose more rapidly, nutrient return to the soil cjuik- iy.
g. Rapid growth and regrowth rate. Tephrosia Candida grow quikly and regenerate strongly. The rapid growth is useful for farmers, about 90 days after sowing they can harvest biomass production, leaves and branches make geen manure to supply food crops. On the other hand, the rapid regrowth of Tephrosia Candida after cutting is an aid in attempts to intensify cycling of nutrients to associated crop. Thus, the farmers can save labor- day and money for replanting.
h. Improving soil and increasing of food corp yields. When planting Tephrosia Candida in the bare hills where other species could not grow or with food crops, nutrient contents in the soil change considerably, yields of food crops increase. For example, yield of cassava increase about 25% and the nutrient contents in the soil increase 30-35% when planting with Tephrosia Candida.
Treatment yield of cassava
Without Tephrosia Candida 13 - 15 tons/ha
With Tephrosia Candida 19 - 20,4 tons/ha Without T.Candida With t.Candida Treatment Fertility N P205 Fertility N P205
Cassava (1 year) 1.43 0.06 0.04 2.12 0.15 0.03
Cassava (2years) 1.4 0.05 0.03 2.21 0.17 0.03
Because of the soil in Midland Vinh Phu province is too poor, the farmer must plant Tephrosia Candida for improvement soil before planting other crops. Recent results show that:
Nutrient contents in the soil (%) Treatment Fertility N K205
-Bare hill 1.5 0.07 0.03
-Planted-Tephrosia
Candida (1 year) 2.25 0.13 0.03
-PIant ed-Tephro s i a
Candida (2years) 4.0 0.21 0.01
For the tea plant, the nutrient content chance, specially content of organic matters
Nutrient contents in the soil (%)
Treatment Organic matter N P205
Tea-Extensive cultivation 1.52 0.07 0.05
Tea-Intensive cultivation 1.92 0.10 0.06
Tea-Tephrosia Candida 2.12 0.11 0.09
11 Particularly, for the eucalyptus is major material for providing to the paper Mill and construction in Vinh Phu province, so some species of eucalytus have been blamed for dessicating the soil, such as moisture depletion, eucalypton (C
H 0) in leaves may inhibit the developing of microorganisms and fauna. However, for satisfation of material sources and soil conservation, Eucalytus camaldunesis - Tephrosia Candida have been planting in bare hills in Midland Vinh Phu province.
Results show that the ability of Eucalyptus camaldunensis growth and soil fertility change considerable.
Rate of growth
Cultivated structure H (m) D 1,3 (cm)
Eu.camaldunenis-Extensive cultivation 4.38 4.36
Eu.camaldunensis-Intensive cultivation 6.05 4.20
Eu. camaldunensis-T.Candida 7.55 5.30
With agroforestry systems, output of Eucalyptus camaldunen• sis is about 100 - 120 metrics per ha in 10 years.
i. Supplying the biomass production for green manure. Te• phrosia Candida came into use as a green manure about 1900
(I.H.Burkill, M.A., F.L.S.; 1966), and is one of the best plants for the purpose. Tephrosia Candida can provide biomass produc• tion about 12-18 tons/ha/year when mixing cassava, and 20 - 40 tons/ha/year in monoculture, somtimes more. However, the biomass production depend on the cut-off times, for example, the farmer
12 can harvest biomass two or three times per year because of the farmers are in difficulties about fertilizer, they must to har• vest biomass production sometimes in the year, production of biomass are different, about 15 - 45 tons/ha/year (Fig 3) . The biomass of Tephrosia Candida makes excellent green manure because of nutrient contents in the stems, branches or leaves are high
(Table 1). In Midland Vinh Phu province, Tephrosia Candida planted along dikes are often used to fertilize nearby crops. It is considered and excellent support and nurse crop for other forest tree species and annual crops. It's the foliage is rich in nitrogen and falling leaves enrich the soil beneath the trees or the farmer cut off branches, leaves to make green manure or folage can also be cut and used to fertilize nearby crop.
Nutrient content (%) Biomass N P205 K20 CaO
Leaves 2.430 0.269 1.409 0.499
Root 1.185 0.146 0.660 0.230
Table 1 . The nutrient content in the leaves, roots of
Tephrosia Candida (Nguyen van Truong, 1985).
Recent results, in Phong Chau State farm, show that 18.3 tons of biomass of Tephrosia Candida are equal to 572 kg of nitrogen and 102 kg of K205. Similarly, studies in Van Hung
State farm show that 18 tons biomass of Tephrosia Candida are equal to 4 tons of animal manure. And if use green manure from
13 30n
25J
CO 20H o h- 15j CO CO < 10H O CD With 3 cuttings \ 195
0 40 80 120 160 200 DAYS (after sowing)
Flg.S Biomass production of Tephrosia Candida as affected by different numbers of cuttings biomass of Tephrosia Candida manured directly cassava, harvest increase 45 - 50%.
Treatment Yield of cassava
Without green manure 8-10 tons/ha
With green manure 17 -24 tons/ha
k. Root systems of tephrosia Candida develope strongly. The wide roots have many nodules that increase nitrogen sources in the soil through symbiotic nitrogen fixation. The deep roots, deepend about 50 - 150 cm, allow nutrient uptake from deeper in the soil profile, cycling inaccessible nutrients to surface soil horizons and intercepting nutrients leached beyond the reach of associated crops. On other hand, the root systems inhibit ero• sion and keep soil moisture.
3. NITROGEN CYCLE IN AGROFORESTRY .SYSTEMS
Fig.l shows the main features of nitrogen cycle in agrofor estry systems. Nitrogen is that which is most often the limiting factor on crop yield in the tropics. It is supplied from:
i. the organic matter (havest waste, green manure, animal cadavers and waste products),
ii. nitrogen fertilizer (nitrates, ammonia, urea, ect.),
iii. nonbiological nitrogen fixation, for exaple, the elec• trical fixation of nitrate in thunderstorms, it bring 10 - 15 kg of nitrogen per ha to the soil each year, iv. Particularly, biological fixation, free-living fixer, associative bacteria in the rhizosphere. Specially, symbiotic nitrogen fixation of Tephrosia candida-Rhizobium sp. association.
Organic matter in the soil develope by mineralization, humification, ammonification, nitrification. These are available for plant root uptake, but the same time subject to losses by leaching and erosion of volatilization. Hence, in the agroecosys• tem, in order to restric the loss of nitrogen content in the soil, we can modify this cycle:
i. To increase the capability of symbiotic nitrogen fixation through use legume trees,
ii. To increase internal cycle, where one or more parts of the tree component such as leaves, fruits, branchs, and roots,
iii. To reduce the losses from erosion and volatilization,
iv. To maintain soil humus
4. THE ROLE OF AGROFORESTRY IN MIDLAND VINH PHU PROVINCE.
For Midland Vinh Phu province, agroforestry have a great significant. It is any suitainable landuse system that maintain or increases total yield by combining food crops with tree crops.
(Vergara 1982). This is a effective way of minimizing the adverse ecological impacts on, and enhancing the stability of household.
Essentially, agroforestry systems carry more significantly bene-
15 fit such as ecology, economic , and society.
Ecological benefits. Tree planted with food crops can be able to reduce the terrestrial ecosystems, include:
- Reduction of micro-climate in the soil, such as soil atmosphere, soil moisture.
Increase of soil nutrients, specially nitrogen sources.
And soil structure can be to improve positively.
- Reduction of the speed and erosive force of surface run• off.
Beside the ecological benefits, there are environmental benefits, such as the protection of environmental deterioration in bare hills as well as protection of midland ecological sys• tems .
Economical benefits. Agroforestry systems can bring significant economic benefits to the farmers, include:
- Economize farmer's labor-day,
- Increase in and maitenance of farmer's income.
Increase in, outputs of human diet, fuelwood, fodder, fertilizer,ect.
Soicial benefits. Agroforestry systems reduce positively ecology, environment, and economic. Therefore, it effect on social problems i.e it accurue to the rural people to improve their quality of life (Rambo 1983), such as improvement of rural
16 living standards as well as nutriels and health. On other hand, agroforestry sytems stabilize and improve the communities.
5. INOCULATION
Now an urgent requirement is how to use land to increase output of food crops, restore the ecological conditions, and improve soil. In order to satisfy to a certain degree, in agroforestry in Midland Vinh Phu province , the increase of symbiotic nitrogen fixing capability through use Tephrosia
Candida is of great significance and the collection of effective
Rhizobium sp. is necessary.
Relation between legume - rhizobium have demonstrated , for increasing of soil fertility and output of food crops. Inocula• tion is very important, means providing a legume with the effec• tive rhizobium strains. Particurlarly this operation is necessary when the soil does not contain the makes it possible for the legume to form nodule that fix atmospheric nitrogen.
For Tephrosia Candida, we isolated nodules from roots
(Vincent 1970). Then, we mesure acetylene reducing activity of the 50 nodule samples (Hardy R.W.F. , Holesten R.D. , Jackson
E.K. ; and Burns R.C. 1968). For the effective nodules, we continued to isolate rhizobium. Results obtained 14 rhizobium strains.
In order to determine the nitrogen fixing capacity of Te
17 o RH3 120H o
100-4 o RH 41 cn 80H °RH 5 ORH 31 X
60A CM RH native
40 10 30 50 70 Ethylene Produced, uM/g nodule
Fig4 N2 fixed by T. Candida as related to activity of nodules inoculated by different strains of Rhizobium phrosia Candida , 14 rhizobium strains are inoculated into the roots. The results show that there are 4 effective rhizobium strains. Particularly, with RH3 Tephrosia Candida fixed 122 kg of nitrogen/ha/year is necessary (Fig.4).
The collections of effective rhizobium strains and the inoculation contribute noticeably nitrogen source that continue to attend at nitrogen cycle in agroforestry.
18 6. RESEARCH NEEDS
Agroforestry has considerable potential, not as the only way to improve agricultural production, but as one important way to enhance and maintain overall productivity of farmer. However, beside the benefits of agroforestry systems we continue to study:
i. The impact between farmer and agroforestry:
- Tradition and experiences of famer for using Tephrosia
Candida
- The application of scientific knowledge to develope agroforestry systems in Midland.
i.i. The negative environmental factors:
The food crop yields may discrease because of competition of space, sunlight, moisture and nutrient between Tephrosia
Candida and food crops.
- Rapid regeneration of Tephrosia Candida that displace food crops and take over entire fields as well as to be difficult to harvest food crops.
- Tephrosia Candida as hosts of insect pests that are harm• ful to the seed harvest and food crop yields. For example, insect pests named Maruca testulalis geyer destroyed flowers of
Tephrosia Candida, so the harvest of seeds suffer damage about
75 - 80 % (Tran An Phong, 1973)
- The effects of edaphic fators on symbiotic nitrogen fixation Tephrosia candida-rhizobium sp.
19 REFERENCES
1. Nutman P.S. , 1965. The relation between nodule bacteria and the legume host in the rhizosphere and in the process of infec• tion. Ecology of Soil-borne plant pathogens, eds: K.F.Baker and
W.C.Snyder (University of California Press Berkely, LosAngeles), pp.231-247.
2. Fred E.B. , I.L.Baldwin, and E.Mccoy, 1932. Root nodule bacte•
ria and Leguminous. Plants.
3. Hardy R.W.F, R.D.Holsten, E.K.Jackson, and R.C.Burns., 1968
The acetylene-Ethylene assay for nitrogen fixation: Laboratory and field Evaluation. Plant Physiol 43, pp. 1185-1207.
4. Klaus Muntz, 1987. Symbiotic nitrogen fixation of Legumes:
Discovered 100 years ago, what do we know at present ?;
Biol. zent. bl. 106; pp.547-567.
5. Le Trong Cue, 1988. Agroforestry Practices in Vietnam.
6. Mulder E.G, T.A.Lie, K.Dilz, and A.Houwers, 1966. Effects of pH on symbiotic nitrogen fixation of some leguminous plants.
Proc. 9th. Int. Congr. Microbiol. pp.151-153.
7. Nguyen Quang My, 1985. The results of The soil erosion.in
Midland Vinh Phu province.
20 8. Nguyen Van Truong, 1985. The management of agroforstry in
Vietnam
9. Nutman P.S, 1965. The relation between nodule bacteria and the legume host in the rhizosphere and in the process of infection.
Ecology of soil-borne plant pathogens, eds: K.F.Baker and
W.C.Snyder , pp. 231-247.
10. Raintree T.B, 1984. Human factor in agroforestry.
11. Rambo A.Terry, 1983. Conceptual Approaches to human ecology.
Research report No. 14.
12. Rambo A.Terry and Percy E.Sajise, 1984. An introduction to human ecology research on agricultural systems in Southeast Asia.
13. Richards B.N., 1987. The microbiology of terrestrial ecosys• tems.
14. Stewart W.D.P., 1966. Nitrogen fixation in plants, pp.39-57.
15. Tran An Phong, 1973. The green manure-trees
16. Vincent J.M., 1965. Environmental factors in the fixation of nitrogen by the legume. Soil nitrogen, eds. : W.V.Bartholomew and
F.E.Clark (Am. Soc.Agronomy, Agronomy No.10). pp.385-435.
17. Vincent J.M., 1970. Manual for the practical study of the root-nodule bacteria. I.B.P. hand book No.15.
21 18. Vergara T.Napoleon, 1982. New directions in agroforestry .
The potential of tropical legume trees. Improving agroforestry in the Asia-Pacific tropics.
19. Wilson P.W., 1940. The biochemistry of symbiotic nitrogen fixation, pp. 114-141.
22 ACKNOWLEDGMENT S
I would like to thank the East - West Center Environment and Policy for sponsoring my visit and for providing the exellent research resources and staff support.
I especially thank Dr. A.Terry Rambo who gave us valuable lectures and useful surggestion in this worshops.
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RESEARCH PROPOSAL: THE FUELWOOD CRISIS AND POSSIBLE SOLUTIONS IN YUNNAN, CHINA
by
Liu Dachang Lecturer Southwest Forestry College
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RESEARCH PROPOSAL
THE FUELWOOD CRISIS AND POSSIBLE SOLUTIONS IN YUNNAN, CHINA
BY
DACHANG LIU
SOUTHWEST FORESfRY COLLEGE, KUNMING, CHINA
Paper for Presentation at " the Workshop on Rural Systems Sustainability ",
Jan. 9 — Apr. 7,1990, East-West Center, Honolulu,Hawaii 96848
RESEARCH PROPOSAL:
THE FUELWOOD CRISIS AND POSSIBLE SOLUTIONS IN YUNNAN, CHINA
BY
DACHANG LIU
SOUTHWEST FORESTRY COLLEGE, KUNMING, CHINA
INTRODUCTION
An astonishing amount of energy is consumed by man. It is estimated that 58.7 x lO1^ kcal of fossil energy and
12.5 x lO1^ kcal of biomass energy are consumed per year in the world (USBC, 1982; Linden, 1980). In rural areas of developing countries, because of both economic and social reasons, biomass remains the major source of energy. People rely on biomass in the form of fuelwood, crop residues and dung for energy. In the tropics about 1,200 million m^ of wood is used for fuel annually
(King, 1980). This accounts for 90% of all wood harvested per year (Vergara,1981).
Further development in rural areas depends on adequate supplies of food and fuelwood. However, over half of the rural people face inadequate fuelwood supply. On the one hand, the shortage of fuelwood is leading to increased deforestation; on the other hand, more residues and dung are being burned. Of the biomass used for fuel annually, about half is fuelwood, 33% is
crop residues, and 17% is dung. In China, crop residues account for 55% of its biomass fuel (ONLGM, 1981). This burning of crop residues and dung causes loss of soil nutrients which in turn causes reduction in the yield of food and other goods. This reduction causes extreme economic and social conditions.
The selection of fuelwood species as well as afforestation and reforestation of fuelwood plantations are strategies which protect forest cover and prevent soil erosion. The integration of trees with agricultural crops is the essence of agroforestry.
Rural development in Yunnan faces many problems. The shortage of fuelwood, facing forestry, is one of these problems.
Unfortunately, there are a few studies or publications on fuelwood species and fuelwood plantations.
Yunnan province is situated in southwestern China and has an area of 390,000 km2, 84% of which is mountainous area, and is borded by Vietnam, Laos and Burma to the south and southwest.
About 32 million people live in this area and 90% of these in rural areas.
There is a vast range of plant genetic resources in Yunnan.
There are more than 15,000 species of seed plants, 5,000 species of which are woody plants, accounting for half of species of seed plants in China. At present, Yunnan's forest cover is 24%, compared to the percentage of forest cover in other province, this number is high. However, there is an unequal distribution of these resources in
Yunnan. Forest cover is distributed mainly in the south; while in
other rural areas, forest cover is sparse and fuelwood is
lacking.
It is estimated that nearly 50% of all rural people have
inadequate fuelwood supply to varying degree. Fuelwood needs come not only from cooking, but also from other needs such as heating
in the winter, brick and lime manufacture, brewing, and tobacco and rubber curing. This fuelwood shortage has resulted in
increasing deforestation. Annual cutting in Yunnan, 80% of which is used for fuel, is at least two times the annual growth.
In the mountains where no trees exist, the people mow grass to meet their fuel needs. In areas where there is small stand trees are overpruned, and the fallen needles of pine trees (Pinus) are collected for fuel. As a result, the forest land has little mulch left. These practices result in soil erosion and lower soil
fertility in mountainous areas.
A solution to problem of fuelwood shortage is necessary to
improve rural living conditions and promote rural development as well as beneficial to protect forest cover and control soil erosion in Yunnan. OBJECTIVES
I intend to study fuelwood species and fuelwood plantation as well as agroforestry. The study will include following objectives:
1. The selection of the trees and shrubs suitable for fuelwood
At least 40 species of ligneous plants will be chosen for their suitability to be used as fuelwood due to diversity of physical conditions in Yunnan.
2. The afforestation and reforestation of fuelwood plantations
It is true that the Dai nationality of Yunnan has traditional fuelwood cultivation practices which succeed in meeting their fuel requirements and protecting the vegetation of " the Holl
Hill". It seems that other 22 nationalities in Yunnan have no such practices. So it is important at this point to study approaches to afforestation and reforestation of fuelwood plantations.
3. The study and application of agroforestry
"Agroforestry includes a wide range of cultivation systems, ranging from traditional shifting cultivation to man-made plantations intercropped with annuals" (Vergara, 1981) . Vergara grouped it into three classes: the Cyclical system (traditional swidden cultivation or shifting cultivation), the Tungya system, and the Integral system. 3.1. The Tungya system
The Tungya system is the system which annuals and perennials are simultaneously on site initially, but limited only to the latter eventually.
3.2. The Integral system
The Integral system is the system which both annuals and perennials are simultaneously and continuously on site. This system is also called the Simultaneous cropping system
(Weinstock, 1985) .
An mutual exclusiveness of forestry and agriculture exists in
Yunnan. The study of the Tungya system and the Integral system will help end such exclusiveness, provide a reliable supply of food and fuelwood, and improve rural living conditions.
RESEARCH PLAN
1. To decide selective criteria and method of fuelwood species
1.1 . The selective criteria
The selective criteria includes:
a. Trees must be fast growing species.
b. Trees must be adaptive to the region where they will be planted. Yunnan is a mountainous province of which topography varies considerably with an elevation of 86 m to more than
4,000 m. There are different kinds of climates and soils at different heights above sea level. There are tropic and subtropic climates as well as temperate climate. Hence, the adaptability of trees is an important factor. What readily works in one region will not necessarily work in another.
c. Trees must be multi-purpose species. Those trees that can
provide fodder, fruit,food,income, or assist in the production and sustenance of these items by maintaining and improving soil fertility will be chosen. For instance, Canianus cajan, a tree of
Papilionaceae, is an excellent host tree of the lac insect; this tree's grower can make money from the lac. The tree's seeds can be used as fodder, and the trunk and branch can be fuel. It is also a nitrogen-fixing tree. Alnus nepalensis is another example.
This tree is believed to be a nitrogen-fixing one. Its leaves, with high content of nitrogen, are superior green manure.
Peasants say, "two plants equal one sheep".which means " the leaves of these two trees equal one sheep's dung." Its timber, without peculiar smell, is quality material of tea-packing box.
It is also a fast-growing fuelwood species.
d. Trees must be burn well and give a high heat yield.
Trees should not only be chosen from native species, but also from exotic species. Eucalyptus spp., natives of Australia, were introduced into southern China where they grow well.
1.2. The selective method
The method to be used to choose fuelwood species will include a combination of plant classification and field survey. The classification of most taxa of Yunnan flora has been studied and corresponding publications have been printed. Before planning field surveys, researchers need to consult these publications, analyze and compare all ligneous plants on the basis of selective criteria mentioned above, and understand their attributes and uses. Some methods of Rapid Rural Appraisal, such as observation, assessment of indicators, question-and-answer, etc., will be adopted in field surveys.
2. To study and apply agroforestry
2.1, The Tungya system in Yunnan
Menzies (1988) reports the Tungya system also found its way into Yunnan. In fact, there are a number of combinations of trees and crops which are reasonable. The combination of Dalberqia obtusifolia, a host tree of the lac insect, with corn is one of them. Cassia siamea—rice system, Alnus nepalensis—rice system are other examples.
There are some uncultivated lands and denuded forest lands in many places. Fuelwood trees and agricultural crops will be intercropped in such lands,and various combinations of trees and crops will be tried.
2.2. The Integral system in Yunnan
Some practices of the integral system are found in Yunnan. For example, a few kinds of fruit tree and annunal crop systems which perennials are planted randomly amid the annuals have been practiced for a long time near Kunming. The fruit trees are mainly Pvrus (pear), Prunus (peach) and Malus (apple), while annunal crops are corn, wheat and so on. They are grown mainly towards market demand.
Where there are no uncultivated lands and denuded forest lands, possible solution to fuelwood shortage is to integrate tree into agricultural crop. A little farm land is used to grow trees for fuel and other purposes. According to Salem (1981), 2 to 5 % of farm land can grow trees for fuel and other purposes without any loss in agricultural production. Goodman (1987) points out that this can be done without affecting crop yields.
3. To encourage farmers to grow their fuel on do-it-yourself basis
A project in rural development often fails, if it is not received by farmers. So it is important for farmers to grow their trees and to meet their fuel needs on a voluntary basis.
4• To experiment and extend
According to differences in the site conditions ( e.g. climate, soil fertility and topography, etc. ), 2-3 sites for certain combination of conditions will be selected for experimentation on the afforestation and reforestation of fuelwood plantations. The experiments should be carried out in areas where fuelwood plantations are planted, and should be made by researchers in collaboration with farmers who are willing to grow their fuelwood plantations.
8 On an experimental basis, the successful results will be extended to areas which are similar to the selected sites, helping solve the problem of the fuelwood shortage in Yunnan. ACKNOWLEGEMENTS
I'd like to give my thanks to EAPI, the East-west Center for inviting me to take part in the Workshop on Rural Systems Sus• tainability, and to Dr. A. Terry Rambo and his assistants for their friendly help.
REFERENCES
Goodman, G.T. 1987. Biomass Energy in Developing Countries: Prolems and Challenges. Ambio. XVI (2-3):111-119
King, K.F.S. 1980. Forestry's Contribution to Social and Economic Development. Commonwealth Forestry Review vol. 59.no.4. Oxford, U.K.
Linden,H.R. 1980. 1980 Assessment of the U.S. and World Energy Situation and Outlook. Gas Research Institute, Chicago,IL.
Menzies, N. 1988. Three Hundred Years of Tungya: A Susutainable System of Forestry in South China. Human Ecology, vol. 16, no. 4.
ONLGM, 1981. (Office of National Leading Group of Methane). Developing Methane is an Important Way for Solving Rural Energy Source in China. Nongyuan no. 6. (in Chinese)
Salem, B.B. and Tran Van Nao. 1981. Fuelwood Production in Traditional Farming Systems. Unasylva. 33 (131):13-18.
USBC, 1982. Statistical Abstract of the United States 1982. 103rd. ed. — U.S. Bureau of the Census. U.S. Government Printing Office, Washington, D.C.
Vergara, N.T. 1981. Sustained Yields from Stabilized Ecosystems. Working Paper, EAPI,East-West Center, Honolulu.
Weinstock, J.A. 1985. Alternate Cycle. Agroforestry. EAPI, East-West Center, Honolulu. /WWWWW\AAAAAAAAAAAAAAAAAA/WWW\AAAAAAA/WWW\AA/WVW\A
SOME INITIAL RESEARCH RESULTS FROM A STUDY OF HOMEGARDENS IN THUA THEN HUE
by
Le Quang Minn Lecturer in Agricultural College No. 2 Hue City, Viet Nam
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SOME INITIAL RESEARCH RESULTS FROM A STUDY OF HOMEGARDENS IN THUA THIEN HUE
by
Le Quang Minh Lecturer in Agricultural College No. 2, Hue City, Viet Nam
INTRODUCTION
Thua Thien-Hue is a province in the South of the Binh Tri
Thien area. The North adjoins Quang Tri province. The West is blocked by the Truong Son mountains, the South is blocked by the
Hai Van pass, and to the East is the Eastern Sea (Map 1).
Although it is a small province, its topography is complex (see
Table 1).
Total temperature is 7200-9200° C; total rainfall is 2700-
3600 mm/yr, which while abundant, is distributed unevenly throughout the year. This creates the two seasons: the dry season and the rainy season. The dry season lasts from February to August. Sunlight is abundant and is favorable for the photosynthetic process of plants. During thiss season there is often a dry hot wind from the west which can raise the as high as 40° C and adversely affects crop plants. The rainfall of the year is concentrated in this season, sometimes causing floods in the lowlands (the plains and coastal areas). Thua Thien-Hue is one of the peovinces which commonly suffers from strong winds and typhoons that damage farm crops and properties.
In these severe natural conditions, the homegarden has become an inseparable part of the life of the local people. In the urban area of Hue City, over 50% of households have homegardens and in the suburbs over 85% of households have homegardens. Hue city has four ecologically different zones: the mountains, midlands, ^lowlands, and coast. Hue itself is an old imperial city of the Nguyen dynasty (1825-1945). Many valuable fruit trees, beautiful flowers, and ornamental plants are planted in the city. Over a long period of time, Hue has become a garden city.
Much research has been done on homegardens in other parts of the world but in Vietnam there is still very little written on this subject.
OBJECTIVES OF THE STUDY
- To study plant species, vertical structure, and
agroforestry in homegardens;
- To identify the type and quantity of livestock in the pen
system;
- To study the distribution of labor and the economic
effect of the homegardens;
- To study the influence of natural, social, and.economic
conditions on homegarden structure; and To study the material and energy flows within a
homegarden system and between the homegarden and other
systems (paddy system, social system).
METHOD
- Time period of study: November, 1989
- Places of study:
1. Urban area' (places: Kim Long, Thuan Hoa
precinct; 5 households)
2. On the out-skirts of the urban area
(place: Phu Mau commune, 5 households).
3. In an area of low hills (place: Huong
Bang commune, 5 households)
4. In coastal area (place: Thuan An commune,
5 households)
5. Huong toan commune, Huong Dien district
(5 households)
I interviewed the heads of households, surveyed homegardens, drew maps, and took photographs of the homegardens.
After analyzing the collected data, I made generalizations based on human ecology analysis.
RESULTS
Home gardens
Plant species In the homegardens of 25 households, I collected 106 plant species (see Table 2). If classsified by their main use, the plants may be divided into these groups: fruit trees, industrial crops, food plants, forest trees, medicinal plants, flowers and ornamental plants and other plants (Table 3). Fruit trees are dominant both in components and in number compared with other plants.
There are differences in the quantity and structure of plant species between the different study sites (Table 3).
Compared to other places, the urban area is more suitable for homegardens because the soil is more fertile. Plant species are more abundant there (77 species). In contrast, the coastal sandy soil area is less suitable for homegardens because the soil is very poor, so plant species are fewer (10 species). In the rural area of Huong Dien district, the plant species (20 species) are also fewer than in the urban area. The urban homegarden is not only economically significant but it is also a place to rest, so flowers and ornamental plants are abundant (35 species). In contrast, the homegardens in the coastal sandy soil area and rural areas have no flowers or ornamental plants.
Vertical structure
Because there are many plant species in the garden, the structure of the canopy is multi-layered. It may be divided into four canopies. The first canopy is of high wood trees such as jac fruit, and coconut trees. The second canopy is medium wood trees such as sapodilla and milk tree. The third canopy is low bushy trees such as orange and lemon. The fourth canopy is herbs such as sweet potato (see Table 4, Map 2). The multi- layered structure of the canopies takes full advantage of light energy and nutrients at different soil levels.
Types of agroforestry
In the homegardens surveyed, agroforestry also exists
(Table 5). There are two combinations of agroforestry. In the first, forest trees such as bamboo, sea pines, and Eucalyptus
(see Maps 3 and 4) are planted as a fence to protect cultivated plants inside the homegarden. In the second, forest trees such as Wrighitia anamensis (see Map 5) planted as support for vines
(pepper). These trees are intermixed with other plants inside the garden.1
Livestock
Livestock pens are common in homesteads (Table 6).
Livestock includes pigs, chickens, and ducks. There is more livestock in the- rural areas than in other places surveyed.
Aside from pigs raised for meat, many families in the rural areas also raised sows to produce piglets. A special point here is that farmers in this area do not raise buffalos and cows like in other places. Instead of buffalos, they use simple farming tools to till the soil.
The number of livestock is not enough to supply fertilizer
Maps of numerous other homegardens can be seen in the Appendix, Maps 6-14. for the homegardens. The farmer overcomes this situation by taking silt from the bank of the rivers in the area to supply fertilizer for plants in the garden.
Economic significance of the home garden
I will have to investigate the economy of the homegarden more in the future. I need to account in detail the inputs and ouputs that affect the homegarden and I need to compare the homegarden economy with other economic behavior. I will continue to research those problems in the future. However,
from the data collected, I may infer some preliminary conclusions:
- Apart from the homegarden supply of fruits, vegetables, and food used by households, some homegarden products
(especially fruit, vegetables, and flowers) are sent to the market to be exchanged for goods.
- A number of households in the urban and suburban area make their living based on the homegarden, while in other areas the homegarden is only a minor aid to the household economy.
If I do not take into account the cost of inputs, the households whose living is based on the homegarden have an
average income of 1350 dong/nrvyear, or 2740 dong/day, the equivalent of 5.4 kg rice/day. In the rural area, average
income from rice paddies is 420 dong/m2/year or 600 dong/day, the equivalent of 1.2 kg rice/day. The average income of the
coastal area from fishing is 10,000 dong/day, equivalent to 20
kg rice/day. However, people in the coastal area are able to fish for only six months out of a year.
General analysis
The existence of homegarden in Thua Thien Hue reflects the influence of natural, economic, and social conditions (see Fig.
1). Among the natural conditions that influence the homegarden is climate. The abundant sunlight and rainfall of this region is favorable to the growth and development of many plant species in the homegarden. Thua Thien Hue has dry and rainy seasons like those of the South and therefore has some fruit trees characteristic of the South (milk tree, avocado tree, mangosteen, etc.). These trees grow well in Thua thien Hue, but they do not grow north of this area (past the Ngang Pass). On the other hand, Thua thien Hue is rather cold in the winter, so some fruit trees common in the North (apple, persimmon, etc.) grow well in Thua thien Hue, but they do not grow south of this area (past the Hai van Pass).
Another natural factor is the fact that Thua thien Hue adjoins the sea. There is an abundance of fish and other marine products in the dry season, making fish ponds unnecessary. The main homegarden type in Thua thien Hue is the Garden/Livestock
Pen (G-P).
Social factors also evidently influence the structure of the homegarden. Hue is an old capital of the Nguyen dynasty, so many valuable fruit trees were planted to be presented to the
King and the Court. With natural and artificial selection over a long period of time, Thua thien Hue has a few special famous fruit trees such as Nguyet bieu grapefruit, the Huong can tangerine (Citrus reticulata Blanco), Truoi Baccaurea (Baccarea sapida Marell Arg), and so on. Their distribution is very limited.
Buddhism is popular in Hue City. There are a lot of small and large pagodas in this city. The devotees of Buddhism take ceremonial offerings to the pagodas on special occasions such as celebratins and on the first and fifteenth of every month.
Marigold (Tagetes patula L.) and flamboyants, uncommon in other places, are planted a great deal in the homegardens of Hue City for supply as ceremonial offerings.
Habit has also influenced the composition of homegardens.
For example, although the apple tree is common in the Northern
Provinces and can grow well in Thua thien Hue, it is not commonly grown in the homegardens there because it does not suit the taste of the local people.
Marketing is also a factor influencing the structure and composition of the homegarden. For example, the long time egg- fruit tree (Lucuma mamosa Gaetn) was a common tree in the garden in Thua thien Hue, but not it is less frequently planted because the market price of egg-fruit is getting cheaper.
Material and energy flows
There is a close interaction between components within the homegarden system (garden-fish pond-livestock pen) through the exchange of material and energy. The homegarden is a component of the agroecosystem. The protection of the balance between
8 components of the agroecosystem maintains the stability and sustainability of the system. The agroecosystem is also closely connected with other systems through the flow of materials, energy, and information (see Figure 2).
CONCLUSION AND KEY QUESTIONS
Conclusion
From the data collected on homegardens in Thua.thien Hue, the following points may be inferred:
1. The plant species in the homegardens are relatively
numerous and multi-layered. There are 106 plant
species in the homegardens of 25 households. These
include fruit trees, industrial crops, food trees,
medicinal plants, forest trees, flowers and ornamental
plants, and others. Among these, fruit trees are
dominant in number of species and in quantity.
2. Thus thien Hue has special natural characteristics
(topography, climate, soil, etc.) which allow
ecologically varied types of trees from the South and
from the North to grow well there.
3. Through a long tradition of artificial selection, the
homegardens of Thua thien Hue has some special fruit
trees (such as Nguyet bieu grapefruit, Truoi Baccaurea,
Huong can tangerine, etc.). These are valuable genetic
resoures and should be protected.
4. The multi-layered structure ofd the varied plants take
full advantage of light energy from the atmosphere, and water and nutrients from the soil layers.
5. Agroforestry has two combinations: forest trees planted
as fences to protect cultivated plants inside the
garden, or forest trees planted as support for vines
and inter-cropped with other plants inside the garden.
6. Livestock predominantly consists of pigs, chickens, and
ducks. The homegardens of the households surveyed are
of the Garden/Livestock Pen model.
7. Products of homegardens that are main supplies for the
household do not have a high economic return. However,
with households that are good at tending their
homegardens, the garden products slowly become market
goods.
8. There are differences between homegardens surveyed in
different zones. These differences are influenced by
natural and economic conditions and habit or cultural
tradition.
9. The homegardens in Thua thien Hue is not only of
economic significance but also of landscape and
environmental significance.
10. The homegarden is part of the agroecosystem. It is
closely connected with components inside the system and
between systems through material, energy, and
information flows.
Key questions
1. What is the relationship between the homegarden and the natural, economic, and social conditions?
What are the differences and motivations for maintaining and developing the homegarden in each place?
What are the effects of science, technology, and policy on the human ecology and the increase in economic efficiency of the homegarden?
Map i. 771IM IMfN-hUE PROVINCE ( 1 i 5OOOOG) Table 1 SOME NATURAL CHARACTERISTICS OF ECOLOGYCAL REGIONS IN THUA THIEN HUE
Temperature C Total season Area Topography Soil temper- annual aver max min tature rainf al 1 dry rainy ( Ha ) per year season season
- yellow-red feral- mountainous 200,000 elevation : it "exhausted gray pod-jg Feb.-May June-Jan region 19 33 7300- 3600 300 ( amsl ) zolic on ancient 7400 alluvial
elevation : light j el low and je- midland How red feral it on 160,000 50 m ( amsl ) 24- 2S 40 9200 2700- Feb.-May Jun-Jan sedimentary stone region 3000
lOw land 100,000 rather flat alluvial soil 25 40 10 9200 2800- Feb.-August Sept area 3200 Jan.
flat sandy areas coastal 37,000 separated by 98% sandy soil * region sand dunes
Hue city 47:000 25 38 10 3000 Feb.-August Sept Jan.
Plant species Latin name FRUIT TREES I jackfruit Artocarpus heterophyllus y/ y/ y 2 custard-apple Anona squamosa Linn • y / 3 sapodilla Achras sapota Linn y/ . y y 4 coconut-tree Cocos nucifera L . y/ y 5 grape-fruit tree Citrus grandis (Linn) Osbeck y y S y 6 lemon Citrus limon Burm • 7 carambola Averrhoa carambola Linn y 8 litchi Litchi sinensis Sonn y y 9 guava Psidiuro guajava Linn s/ y y 10 Spondias dulcis Soland ex P. >/ y 11 pine-apple Ananas comosus Merr y y 12 banana Musa sapientum L . y 13 milk tree Chrysophyllum cainite L . y y/ y y 14 persimon Diospiros kaki Linn V V y 15 jaboticata Eugenia javanica Kamk y y 16 mangosteen Garcinia mangostana Linn y v' y 17 papaya Carica papaya Linn y y/ 18 orange Citrus sinensis Osbeck y y y 19 longan Euphoria longana Lamk y y 12 Plant species Latin name 1 2 3 4 5 y/ 20 avocado tree Persea americana Mill yf 21 apple Ziziphus mauritiana Lamk V 22 Baccaurea sapida Marell Arg x/ 23 tangerine Citrus reticulata Blanco 24 Flacourtia jangonmas Miq V V 25 egg-fruit tree Lucuma mamosa Gaetn . y/ V 26 Elecagnus Eulacagnus latifolia L . y/ 27 plum Eugenia malaccensis Linn 28 medlar Nephlelium lappaceum Linn INDUSTRIAL TREES : 29 coffee tree Coffea arabica V \y 30 tea Thea sinensis v' \f 31 pepper Piper nigrum 32 sugar-cane Saccharum officinarum FOOD AND FOOD STUFF PLANTS : 33 Allium fistulosum \s 34 ma1aba A/ 35 red peper Capsicum 36 chayote Sechium edule w 37 sweet potato Ipomea batatas vC * y/ y 38 cassava Maniot esculenta V y/ y/ v/ 39 cabbage V' 13 Plant species Latin name 1 2 3 4 5 40 jam Dioscorea esculenta 41 French bean Phaseolus vulgaris V 42 taro Colocasia esculenta 43 salad 44 coriander Coriandrum sativum L 45 even-stem cabba• Brassica oleracea ge 46 maranta Maranta 47 mustand green Brassica sinensis L • \y 48 tomato Lycopersicum esculentum 49 arrow-root Marantia arundinacea 50 corn Zea mays FOREST TREES : 51 bamboo Bambusa arundina V 52 Eucalyptus Eucalyptus \S 53 sea pine Casuarinaceae equisifolia • 54 peltophora Bassia pasquiere V 55 Wrighitiaanamensis V 56 sinamon tree Sinamomum cassia MEDICINAL PLANTS : 57 saffron Curcuma longa V 14 Plant species Latin name 58 calus Calceolaria V V 59 plantain sf 60 ginger Zingiber officinalis 61 peppermint Mantha piperita *S J 62 yerba-de-tajo Eclipta alba s/ 63 wormwood 64 talahil Saccharum spontaneum 65 Peperonica Polyscia fruticosa 66 FLOWER AND ORNAMENTAL PLANTS : 67 rose Rosa sinensis 68 bougainvillia 69 fragrant cynanthe Pergularia minor Andr V 70 Apricot blossom y/ 71 frangipani s/ 72 Phyllo cactus grandis >s 73 framboyant \l 74 cat us J 75 orchid Orchis 76 laurel Laurus nobilis 77 gerbera 78 peony Paeconia montan V 15 Plant species Latin name 1 2 3 4 5 79 symbolic flower Celosia cristata Lin v 80 canation Dianthus caryophyllus V 81 Sophora javanica v* v 82 marigold Tagetes patula L „ ^ v 8 3 snapdragon Ant irrhinum ^ 84 mangnolia Mangnolia v 85 Tropaeolum v/ 86 rose-bush Camellia >/ 87 lotus Nelumbium nucifera V 88 nenupha V 89 cheery-apple fl- Thea amplexicaulis y ower 90 jasmine Jasminum sambac ^ 91 hyacinth Hyacinthus \f 92 Narcissus V 93 hibiscus Hibiscus rosa sinensis *J ^ 94 plan tree ^ 95 dahlia Dahlia variabilis ^ 96 tuberose Polianthes tuberosa */ y> 97 fir-tree ss 98 thuya v 99 cycad j 16 Plant species Latin name 100 draceana 101 cycas OTHER PLANTS : 102 Acalypha siamensis Olia 103 soapberry Gleditchia australis 104 areca-tree Areca catechu 105 Piper betle 106 fig Ficus Note -1 : Urban area -2 : On the out skirts of urban area -3 : on the low hill -4 : Rural area -5 : on the sandy soil 17 Table 3 PLANTS CLASSIFIED BY MAIN USE IN HOMEGARDEN OF THUA THIEN HUE Total fruit food and food flower and plant tree industrial stuff medicinal forestry Qther plants ornamental SPeCieS Cr°PS «1ant s trPPQ plants plants trees plants Urban area 77 23 35 on the outskirts 46 24 . 3 of urban area on flhe low hills 38 19 on the sandy 10 soil Rural area 20 12 Table 4 CANOPY LAYER IN HOMEGARDEN IN THUA THIEN HUE type of main canopies multi canopy gardens mono canopy garden firt layeT : coconut tree; jakfruit tree ( Artocarpus heterophyllus ) only layer : Grebera second layer : milk tree( Chrysophyllum cainito L); sapodilla (Achras Urban area sapota L )... third layer: orange ; lemon ... fourth layer : pine apple (Ananas comosus Merr); sweet potato*.. -first layer coconut tree; jakfruit tree .„» on the out skirts -second layer milk tree ;persimmon ( Diospyros kaki L ) . -third layer lemon ; apple ... of urban area -fourth layer pine apple •,. first layer : jakfruit tree ; Areca-nut tree ( Areca catechu ) , .„ ii , , -second layer mangosteen ( Garcinia mangostana Linn )0.B 3 on the low hill , , ' G\ -third layer orange ; lemon ... •fourth layer : pine apple ... -first layer Eucalyptus ; sea pine ( Casuarinaceae equisitifolia ) on the sandy soil_second iaver guava ( Psidium guajava Linn )... -third layer sweet potato... -first layer : Eucalyptus ; bamboo ( Bambusa arundina ) Rural area -second layer : milk tree ... - third layer : orange ; tea ( Thea sinensis ) ... -fourth layer : pine apple ; sweet potato ... Map 2: Layout of a homegarden at Thuan an commun; Hue city 4. Legend: 1: Acalypha siamensis ) ; 2: Artocarpus heterophyllus ; 3: mangosteen ( Garcinia mangostana ); 4:sapod ilia ( Achras sapota ) ; 5: milk tree ( Chrysophylfliym cainite ) ; 6: madlar ( Nephelium lappaceum ); 7: orang e (Citrus sinensis ); 8: lemon ( Citrus limon ); 9: guava ( Psidium guajava ); lo: custard apple (Anona squam osa ); 11: coconut tree (Cocos nucifera ); 12: cinamon tree ( Cinamonum ); 13: papaya (Carica papaya ); 14 : cassava (Hjanihot esculenta ); 15: pineapple ( Ananas comosus ); 16: banana ( Musa sapientum ); 17: Gerbera; 18: flower and ornamental plants Table 5 TYPES OF AGROFORESTRY IN HOMEGARDENS IN THUA THIEN HUE Regions Types of agroforestry Notes on arrangement of different plants Urban area bamboo are planted in rows acting like fences protecting on the out-skirt agricultural plants inside the garden and used as constr• bamboo + fruit tree uction material of urban area -peltophore ( Bassia pasquiere ) + petophore are planted around the garden to take full ad• fruit tree vantage of land space and used as contruction material on the low hill -Wrighitia anamensis + piper -Wrighitia anamensis are planted as support for vines ( peper ) - Eucalyptus ; sea pine (Casuarinac Eucalyptus ; sea pine are planted around the garden eae equisitifolia ) + fruit tree ; as wind break ; protecting agricutural plants inside on the sandy soil vegetable the garden ; use for contruction ; fuel bamboo are planted in rows acting like fences protec• - bamboo + fruit tree , foodstuff ting agricutural plants inside the garden and use as plants Rural area contruction material Map 3: Layout of a homegarden at Phu mau commun; Hue city Legend : Acalypha siamensis; 2: bamboo (Bambusa arundina ); 3: Artocarpus heterophyllus Linn; 4: Baccaurea sapida flare11 Arg; 5: mangosteen(Garcinia panpostana Linn) ;6: rose appla e (EugeniA a a javanica Lamk);7rcarambola( Averrhoa liiailgUb LCCil (,udi uxllxa r'allpus tana 1.11111 ) , »-» . A wov- "FF ^ V ""S"" J dvdlllLa L.cunr\ ) , / . v-ai UHUU X O V. "VV» * carambola Linn ); 8: milk treef Chrysophyllum cainite L ); ?: orange (Citrus sinensis Osbeck);Jo: guava (Psidiu m guaiava Linn) ; ll:Spondias dulcis Soland ex Park; 12: Apricot blossom ; 13: tea (Thea sinensis >;I4: Piper bet le ; 15: com (ZZe< a mays ); 16: pine apple ( Ananas comosus Merr ) ; 16: mustand green (Brassica ) Legend : 1: sea pine ; 2: coconus tree ( Cocos nucifera L ) ; 3: guava ( > 4: arrow root ; 5: sweet potato ; 6 : tomato Map 5; Layout of a homegarden at Kimlong precinct; Hue city Legend: Acalypha siamensis; 2: longan ( Euphoria longana Lamk ); 3: Grape- fruit tree ( Citrus gra ndis Osbeck ); 4: Artocai»pus heterophyllus ); 5: mangosteen; 6: persimon ( Diospyros kaki Linn ) ;7:litchi ( Litchi sinensis Sonn ); 8: guava ( Psidium guajava Linn ); 11: papaya Carica papaya ) 12: banana ( Musa sapientum L ); 13 pepper (Piper nigrum ); 14: Apricot blossom ; 15: flower and ornamental plants ; 16: Ficus 9 Table 6 AVERAGE HEADS OF LIVESTOCK IN EACH HOUSEHOLD Urban area 1.4 6.0 0.0 on the out- skirt of urban area 1.0 7.0 5.2 on the low hill 1.4 12.0 0.0 on the sandy soil 1.0 12c0, 3u 8' Rural area 2.6 13.4 5.0 Figure 1 INFLUENCE OF NATURAL, ECONOMIC AND SOCIAL CONDITIONS ON STRUCTURE OF HOMEGARDENS IN THUA THIEN HUE topography water climate plants and livertock STRUCTURE OF HOMEGARDEN economy of market household religion cultural Figure 2 INTERACTION BETWEEN HOMEGARDEN AND OTHER SYSTEMS APPENDIX Nap 6: Layout of a homegarden at Phu mau precinct; Hue city Legend : l:Acalypha siamensis; 2: carambola ( Averrhoa carambola Linn ); 3: banana ( Musa sapientum L ) ; 4: Lucuma mamosa Gaetn; 5:.mustand green ( Brassica sinensis L ); coriandrum (Coriandrum sativum L ); 6: salad MAp 7 Layout of a homegarden at Phu mau commune; Hue city Legend : Acalypha siamensis; 2: bamboo (Bambusa arundina ) 3: coconut tree ( Cocos nucifera ); 4:Baccaurea sapida Marell Arg ; 5: Artocararpup s heterophyllus Linn; 6: persimmon (Diospyros kaki Linn ): 7; miil k tree ( Ch % 1 een^ (Ga c1 n i n mangoostan a Linn ): 9: sapodilla (Achras sapota Linn ); 10: grape truit t ree (CiiLitru- s gramdii" Osbeck 7 11: coffee~( CoffeCoffeaa arabicarabicaa ));; 1212:: guavguavaa (Psidiu(Psidiumm guajavguajavaa LinLinnn ));; 1313:: carambolcarambolaa (Averrhora carambola Linn );14: rose apple ( Eugenia javanica Lamk ); 15: banana (Musa sapientum L);16: cassava (Manihot esculenta ); 17: Spondias dulcis Soland ex Park; 18: fish pond Map 8: Layout of a homegarden at Phu mau commune; Hue city Legend : 1: bambu (Bambusa arundina ); 2: Artocarpus heterophyllus Linn ; Baccaurea sapida Marell Arg ;4: Areca catechu ); 5: coconus tree ( Cocos nucifera L ); 6: rose apple( Eugenia javanica Lamk ); 7: mangos teen (Garcinia mangostana Linn ); 8: milk tree (Chrysophyllum cainite L ) ; 9: banana (Musa sapientum ) ; lo: pineapple (Ananas comosus Merr ) ; 11: tea ( Thea sinensis ) Map 9: Layout of a homegarden at Thuy bang commune; Hue city Legend : Artocarpus heterophyllus ; 2: Areca tree ( Areca catechu ); 3: tea(Thea 4: tuberose Map 10: Layout of a homegarden at Thuy bang commune; Hue city Legend : gate ; 2: Acalyppha siamensis; 3: areca tree (Areca catechu );4: mangosteen ( GaTcinia mangostana Lin ) ; 5: Ficus ; 6! papaya ( Carica papaya Linn ) ; 7: pineapple ( Ananas comosus Merr ) ; 8: banana Musa sapientum L ) MaP 11: Layout of a homegarden at Thuan an commune; Hue city Legend : sea pine ; 2: conns tree ( Cocos nucifera L ) ; 3: p.uava (Psidium guajava Linn Map 12: Layout of a homegarden at Thuan an commune; Hue city Legend ; X: gate ; 2: sea pine; 3: Huong lau grass; 4: guava (Psidium guajava Linn) 5: sweet potato ( Ipomea batatas ) ; 6: mustand green ( brassica sinensis ) Map 13: Layout of a homegarden at Huong toan commune; Huong dien district Legend : Acalypha siamensis ; 2: bamboo ( Bambusa arundina ) ; 3: Artocarpus heterophyllus L ;4: Litchi sinensis Sonn; 5 : orange ( Citrus sinensis Osbeck ); 8: pine apple (Ananas como sus Merr ) ; 9:cabbage ; 10 : Hibicus (Hibiscus rosa sinensis ); 11: water trench Map 14: Layout of a homegarden at Huong toan commune; Huong dien district Legend : bamboo ( Bambusa arundina ); 2: orange ( Citrus sinensis Osbeck ); 3: guava ( Psidium guajava Linn ); 4: sapodilla ( Achras sapota Linn ) ; 5: milk tree (Chrysophyllum cainite L ); 6 :.banana ( Musa sapientum ); 7: sugar cane ; 8: sweet potato ; 9: must and green ( Brassica sin nensis L ) ; lo : bean ; 11: Eucalyptus REFERENCES : Abdoe11ah , Oeken Soekotjo and Geral Marten 0 1984 „ PRODUCTION OF HUMAN NUTRIENS FROM HOMEGARDEN , UPLAND-FIEL ( KEBUN ) ,AND RICE-FIEL AGRICULTURAL SYSTEM IN THE JATIGEDE AREA C WEST JAVA ) . working paper .East-West Environment and policy Institute , Honolulu ,Hawwii Achmad , Hisyam , Anwar Martadihardja , Suharto . 1979 . SOCIAL AND CULTURAL ASPECTS OF HOMEGARDENS . Paper presented at the 5tn International symposium of tropical Ecology . Ku• ala lumpur ,Malaysia . April 16-21 , 1979 6 Anderson , James N. 1979 TRADITIONAL HOME GARDEN IN SOUTHEAST ASIA : A PROLEGOMENON FOR SECON GENE• RATION RESEARCH . Paper presented at 5*^ International Symposium of Tropical Ecology . 16-21 April 1979 , kuala Lumpur , Malaysia » Cristanty » Linda , 1981 . AN ECOSYSTEM ANALYSIS OF WEST-JAVANESE HOME GARDEN e Institute of Ecology , Padjadjaran Univ. Indonesia „ Christanty , Linda 1985 . HOMEGARDEN IN TROPICAL ASIA : A SPECIAL REFRENCE TO INDONESIA . Paper presented at the first Internationalworshop on Tropical homegarden ,2-9 December 1985 . Bandung , Indonesia • Christanty , Linda , Priyona . 1979 . MEASUREMEN OF PHOTOSYNTHESIS IN HOME GARDEN PLANTS . 37 Paper'presented at the 5^ International simposiuin of Tropical Ecology . Kuala Lumpur , Malaysia . April 16T21 » 197? . Cue , Le Trong . 1988 . AGRO-FORESTRY PRACTICES IN VIETNAM „ East-West Center , EAPI; . Karyono . 1981 0 STRUCTURE OF HOMEGARDEN IN THE RURAL AREA OF CITARUM WATERSHED , WEST JAVA . Universitas Padjadjaran . Indonesia . Marten , Gerald G . A NUTRITIONAL CULCULUS FOR HOMEGARDEN DESIGN : CASE STUDY FROM WEST JAVA Paper presented at 1st International conference on'Tropica,! homegarden . Institute of Ecology , Padjadjaran Univesity , Bandung , Indonesia . Mudiyanselage , Konara and Abhaya Kendaragama . CROP COMPOSITION AND INCOME DISTRIBUTION OF HOME GARDENS IN GAMPAHA DISTRICT , SRI LANCA . Promona college Program in food , Land and Power in Sri Lanka . Rambo, A. Terry and Percy E. Sajise „ 1984 . AN INTRODUCTION TO HUMAN ECOLOGY RESEARCH ON AGRICULTURAL SYSTEM IN SOUTHEAST ASIA East-West Center and Univ. of the Philipines at Los Banos- . Rambo, A Terry „ 1983 . CONCEPTUAL APPROACHES TO HUMAN ECOLOGY . East-West Environment and Policy Institute . 38 AA/WWWWW\A/WVW\A^ THE IMPACT OF CLIMATE ON PROPERTIES OF AGROECOSYSTEMS IN THE MIDLANDS (VINH PHU PROVINCE) FROM THE HUMAN ECOLOGY VIEWPOINT by Nguyen Khanh Van Geographic Researcher Institute of Geography and Natural Resources, National Center for Scientific Research AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA^ 0 1 THE IMPACT OF CLIMATE ON PROPERTIES OF AGROECOSYSTEMS IN THE MIDLANDS (VINH PHU PROVINCE) FROM THE HUMAN ECOLOGY VIEWPOINT by Nguyen Khanh Van Geographic Researcher Institute of Geography and Natural resources National Center for Scientific Research of Viet nam (Research Intern, EAPI,EWC,USA. March 1990) 2 CONTENTS INTRODUCTION 3 I. RESEARCH OBJECTIVES AND METHODOLOGY 6 1/Research objectives 6 2/ Methodology 11 * Human ecology 11 ** Indigenous knowledge 13 *** Agroclimat.e analysis 17 **** Agroecosystem analysis 18 ***** Rapid Rural Appraisal 19 II. CLIMATE AND PROPERTIES OF AGROECOSYSTEMS IN THE MIDLANDS OF VINH PHU PROVINCE 21 1/ Climate condition and internal interactions between components of the agroecosystems in the Midlands 21 * Climate condition 21 + Solar radiation 22 + Temterature 24 + Rainfall 26 ** Soil 32 *** Vegetation 33 2/The impact of climate on the human-managed agroecosystems 38 * Farming technology 38 ** Climate and the human-managed agroecosystems 39 CONCLUSION 47 REFERENCES 4 9 INTRODUCTION. " Midlands are hilly to mountainous areas, where ecologically destructive human activities are being practiced resulting in loss of vegetation cover, excessive runoff, soil erosion and declining agricultural productivity" [ DENR ](*). Vinh phu is one of the Provinces in the Midlands of nortern Viet nam. Like other regions of the country, Vinh phu has high mean population densities of about 250 to 450 persons per km2. Although in the last few years there have been some national population control and family planning programmes, only in urban areas have they achieved any success. Families in the rural areas of Viet nam in general and Vinh phu in particular are still large. The rate of population growth in Vinh phu is high, about 2,9 to 3.3% (1989); these are high rates even for an agricultural province. The high population growth brings with it the continuously increasing need for food and fuel. Alternative: Thus, people destroy forests as they find it necessary to cut trees for fuel and to expand cultivation. The landscape of the Midlands of Vinh phu has almost completely changed in the last 20 years. Therefo• re, in the study of the agroecosystem of Vinh phu, both human ecology and geography share a common conceptual approach: each ecological or geographical system consists of several main * DENR - Department of Environment and Natural Resources of Philippines. 1989. Overview of Upland Development Issues and Problems in the Philippines. IESAM, University of the Philippines at Los Banos. components. Here scientists must take a systems viewpoint and look at the components as a system where interactions between components or any change to one component will lead to the change the other components. As an example, some changes of the soil or vegetation cover components, will certainly lead to changes in climatic conditions (especially microclimate). Moreover, there is dialectic relationship between climate or microclimate on the one hand, and the agroecosystem as a whole, on the other. Actually, the main properties of the agroecosystems, such as productivity,- stability, and sustainability, are closely affected by climate conditions. In this paper, by "climate condition" I mean all factors or characteristics, whose variation directly or indirectly affect major properties of an agroecosystem. In this working paper, I will discuss some agroecosystems in the Midlands of Vinh phu Province. This will be an introductory discussion, but some types of landscapes will be discussed in detail. Interactions between the social system and the ecosystem will be discussed too, and the major part of the working paper is devoted to studying the effects of climate and microclimate on the properties of rural agroecosystems in the Midlands of Vinh phu Province. Acknowledgements In doing this report a grateful acknowledgment is rendered to all the workers of EAPI for their daily help during my stay in Hawaii. Especially, many thanks to Dr. Terry Rambo for giving me the opportunity to attend the workshop on Rural Systems Sustainability. I also would like thank to Dr. Michel Dove and Dr. Le Trong Cue for their comments, and Kathleen Gillogly and Vy Ton for their editing of this paper. 6 RESEARCH OBJECTIVE AND METHODOLOGY 1/. Research objective The Midlands reasion of Vinh phu Province consists mostly of small hills- Generally, the hills tilt gently from the north- northwestern corner towards the south-southeastern one. Although the Midland's geography consists of small upside-down hills, they seem to be like small valleys - miniwatersheds. The average height of the hills is about 100m above sea level. From the summit down to the foot of the hills there are several different types of vegetation (Figure 1). * Miniwatershed forests on the top of hills: "poor" natural forests (poor in sense of economic value), secondary forests, reforestated areas. ** Industrial forests and plantations include Eucalyptus forests, Mangletia glauca forests, tea plantations, and lacquer plantations on high slopes. *** Crops on middle slope, which include sweet potato, corn, cassava, beans, soya-bean. **** Homegardens on the lower slopes, which include perennial, annual, and traditional medical plants, houses,livestock pens, and fish ponds. ***** Rice paddy in the low land. Figure 1: A TYPICAL LANDSCAPE IN MIDLANDS OF VINH PHU PROVINCE 8 All of the aforementioned types of soil-vegetation combinati• ons establish an agroecosystem typical of the Midlands. Changes in these agroecosystems under the influence of climate and microclimate conditions are the main subjects of this study. For the purpose of conceptual approaches to Midland agroecosy• stems in Vinh phu Province we should start our study with miniwatersheds. These systems are small, but thay are very complicated and so worth analyzing in detail. Social systems in the Midlands of Vinh phu and their interact• ions with ecosystems are like any rural system in Viet nam but at the same time, due to special reasons (geographical conditions, historical reasons, traditional types of farming, and belief systems) social systems in the Midlands are distinguishable from other rural systems. Generally, a rural social system is similar to one represented in Figure 2. In this hierarchy from Commune (village) to Coopera• tive (s) level with all its parts (chairman, shop, nursery schools, medical, survey, planning, accounting), the upper horizontal part of the hierarchy is similar to the structure found in the Lowlands of Viet nam. The lower part of the hierarc• hy, from the production brigade-level down to the many different small working groups, describing the complicated diversity of natural and social systems of Midlands Viet nam. In the last decades the population of Viet nam in general, and in Midlands of Vinh phu in particular, has continuously increas• ed. Although the rate there is not as large as it is in the 9 Government 1 t Province District Commune (village) Cooperative(s) Shop Nursery Medical Chairman/ Survey Planning Accounting schools Pol. Secretary) Production Brigades Rice Brigades(Work Teams) 7^ Leaders Animal Cash Forest Brick Lime Agro- Hus- Propj Plan• Making] Pro- Fore• bandary tation cessinc stry Figure 2 Hierarchy of social system in Midlands [6]. Lowland area (the Red river delta region), .it is still higher than 2.5%. There are two reasons for the increasing population: * Natural increase of local population, ** Resettlement from other crowded regions. Year after year, under the pressure of an increasing populati• on, the need for food and for housing are increasing. The total area of crop land has been expanded, and people using backward technology have chaotically opened up high slope land, even during the rainy season. Moreover, to meet fuel needs, many hectares of miniwatershed forests have been destroyed. Natural pastures under the "poor" palm forests are overgrazed. For many years the government policy on land-use in Midland areas has been inflexible and therefore has given the landusers no sense of responsibility for soil conservation. Briefly, the ecosystem, of which climatic factors are one part, does not exist separately from or outside of interactions with the social system. Thus through human ecology, with its systems viewpoint and natural and social scientific approaches, we can analyze the impact of climate on rural agroecosystems. Interaction between climate, or microclimate and some agroecosys• tem components must be studied in consideration with human activity. 11 21. MPfhodoloqv To achieve the main goals of this research on agroecosystems in the Midlands of Vinh phu, I will use a variety of concepts and methods: human ecology, indigenuos knowledge analysis, agroclim- ate analysis, agroecosystem analysis, and rapid rural appraisal. * Human ecology Human ecology is the scientific study of the relationship between people and the natural world in which they live. It is based upon the assumption that there are systemic relations between the human society (the social system) and the natural environment (the ecosystem)[8]. A social system consists of human population, technology, knowledge, belief, values, social structure, and institutions. An ecosystem is composed of physical components (soil, climate, water) and biotic components (plants, animals, and microorganisms). The goal of human ecology research is to identify and understand the characteristics of the interactions occuring between these systems and the way that these interactions shape the specific forms taken by both social and ecological systems [6]. Population size, composition, social structure, and even institutions are extremely important factors which determine the 12 impact of the social system on the ecosystem. Some physical factors seem to be relatively unchangeable and stable, such as microclimates. However, under natural changes and social effects they are also correspondingly changed. This is particularly evident when the social effects are durable like man-made degradation of vegetation cover of an entire miniwatershed. Interactions that take place between ecosystems or between the social system and ecosystem, occur in the form of flows of energy (solar radiation), materials (nutrient supply, rainfall) and information (traditional farming knowledge concerned with the weather or the climate condition)(Figure 3). Within the ecosystem, climatic factors, although rather independent components, are slightly affected by other natural components. However, climatic factors actively influence other properties of the ecosystem. Endless examples coud be cited of how the productivity, stability and sustainability of the ecosystem vary under climatic changes. However, interactions associated with increasing human activity can be explained as the folowing: To meet the need of food and fuel for an increasing population, the social system requires steady flows of energy and materials from the ecosystem. These flows have to be satisfied by cutting forests, expanding the acreage of cultivated land, and continuously rotating crops. Poor fertility of soil, a lot of barren land, backward farming technology, and lack of understading about national use of natural resources lead to the • © # 9 9 e e F/gure 3 : Interactions belwe.cn social system and^gnDecosjs/e/n £6) degradation of environment. At the very least, a degraded environment causes microclimatic or even climatic changes. In brief, the relationship between the social system and ecosystem is a dialectical one, and any change in one system not only affects the structure and function of the system itself, but also affects the other system as well. Technology is another important factor in human interactions with the environment. Vietnamese peasants, through practical experience, employ many indigenous technologies to maintain soil fertility and recycle nutrients [6]. Peasants of the Midlands try to construct terraces using their knowledge about climate conditions to reduce the effect of soil erosion caused by uneven distribution of rainfall. However, at the present time, this level of technology requires so much labor that it is impossible to realize without intensive capital input. Social structure and institutions (e.g., political and administrative organizations and the roles that govern land tenure and labor allocation) play an extremely important role in regulating interactions between people and their environment [6). The same population under the same climate conditions will have different impacts depending on the specific social institutions that regulate activities of the systems. ** Indigenous knowledge When cultivation began in Viet nam a thousand years ago, the weather, the climate and especially the microclimate have becam attractive subjectives to cultivators. Therefore the peasants' common sense, their understanding of the climate, and the ways they apply their knowledge for successful agriculture are rich and numerous. Unlike local peasants who have lived in intimate contact with their environment for many years and who must successfully manage their ecosystem in order to survive, scientists are only able spend relatively short periods of time observing any one particular local system. Also, the salaries of the scientists are guaranteed, regadless of whether or not their ideas work in practice. Therefore, the better way for studying of any ecosystem is through indigenous experiences. Local knowledge is not the same as scientific knowledge. However, it is based upon the trial and error learning rather than the systematic experimental testing of comprehensive theories. It is most useful for indentifying problems and constraints affecting management of the agroecosystem. It is also very valuable as a sourse of information about long-term trends and unusual events which may not occur during the short time periods that scientists spend in an area [6]. Unfavourable weather can immediatly and directly affect the production of some cultigens or domestic animals, and 16 the effects are visible. However, climate and microclimate effects on properties of the agroecosystem are unrecognizable through only systematic experiments conducted in a short period of time. Information on the degradation of several environmental components such as soil quality, water reserves and water quality, and the quality of agricultural products could be obtained simply by asking and interviewing experienced peasants. Terry Rambo, in the study of agroecosystems in Vinh phu Province of Viet nam [6], stated: " By learning to take advantage of indigenous knowledge, it is possible to vastly increase the research capabilities of Vietnamese scientists. There are only a few hundred environmental scientists but there are millions of farmers. If we can make them our research partners we can greatly increase our ability to collect data on rural ecology". Derived from the perspective offered by human ecology, we can use peasants' indigenous knowledge as our principal source of information when studying agroecosystems. In order to improve the sustainable of the agroecosystem, we should employ more detailed research approaches such as agroclimate analysis and agroecosystem analysis. *** Agroclimate analysis Agroclimatology is one of the linkages between two natural sciences: climatology and ecology. It is the study of climate and microclimate conditions, or the weather and its changes, which affect the physiology and ecology of vegetation and cultivated crops. Agroclimatology does not study all the factors (elements) of the climate. Rather, it focuses on several concrete factors that play decisive roles during growth periods of vegetation and which influence the productivity of the agroecosystem a great deal. These important factors are: + Photosynthesis radiation of vegetation ++ Thermo-moisture regime of atmosphere and soil: relative humidity, rainfall. For rain-fed agriculture both amount and pattern of rainfall are very important factors. +++ Frequency and probability (capacity) of unfavourable weather for tropical agrocultures (e.g. typhoons, heavy showers, hails, drought spells, especially for the Midlands: frosts or floods, etc). Agroclimate analysis aims at finding out the crucial points, problems or constraints represented for each agroecosystem. Depending very much on the chosen method of agroclimate "analysis, productivity can be stable and the sustainability of the agroecosystem can be guaranteed. 18 As a result of scientific systems analysis these key-points are completelly different from one agroecosystem to another. ***» Agroecosystem analysis For research, we will focus on certain critical properties. In this case, these properties are strongly influenced by human action and desired by the human managers of the agroecosystem. For the purpose of a more detailed research, our greatest concerns are: productivity and sustainability. Productivity is the system's output of goods and services (e.g., kilograms of rice per hectare). Sustainability is the ability of the system to maintain productivity over an extended period of time [6J. There are three steps in agroecosystem analysis: 1. Delineation of the agroecosystem and its key components and the description of important interactions and flows among these components as they affect the above-mentioned properties of the system; 2. Indentification of constraints and oppotunities for management of the system; 3. Indentification of the key questions regarding the functioning of the system, paying a particular attention to possible ways to overcome constraints in order to enhance productivity and sustainability. These key questions are intended to suggest promising directions for future in-depth research on the human ecology of the Midlands [6]. ***** Rapid rural appraisal As mentioned earlier, it is sometimes impossible to make one scientific conclusion on the impact of a few factors merely through data base analysis. This is particulary true when dealing in the long-run with ecosystem components such as climate or microclimate. That is why getting information from farmers is important. SUAN has paid much attention on finding ways to collect information on agroecosystems and rural resource management through quick and economical ways. These methods are termed Rapid Rural Appraisal (RRA). RRA approaches were developed to address the problem by compromising between costly and time- consuming "academic" methods. These inventiveness, and versatility were emphasized [6]. RRA is most efficiently conducted by small teams made up of specialists from several different disciplines, representing both the natural and social sciences [6]. There is variety of data collection techniques. The most commonly used are observation and semi-structured interviewing. By visiting a site and looking at the landscape and the nature of the activities being managed by the peasants, a research team can learn a great deal. Such observation is very helpful for coming up with questions during the semi-structured interviews which follow. Informal interviewing, which allows farmers to talk about the full range of their knowledge and practic, is a preferred 20 interview technique in RRA [9], Informal interviewing appears to be simple, but skill or training is required to elicit farmer's perspectives. Informal language to achieve rapport, technically opening to new types of knowledge, analysis of replies, polite and appropriate follow-up questions, method to re-check inconsistencies are a few factors which must be carrefully prepared. In short, interviews are made with the topics in mind, but half followed and half guid the conversations. CLIMATE AND THE PROPERTIES OF AGROECOSYSTEMS IN THE MIDLANDS 1/. Climate condition and internal interactions between components of agroecosystems in the Midlands of Vinh phu province *. Climate condition: The climate of Vinh phu Province is classified by the majority of Vietnamese climatologists as monsoonal tropical climate, having a cold winter and a heavy rainfall in summer [10]. This is considered a transitional climate between the Lowlands and Highlands of Viet nam. There, are two recognisable seasons: the cool season (the cold and low-rain winter months) and the rainy season (mainly the summer months). These seasons are influenced by the northeast and southwest monsoons that occur not only in Viet nam but throughout Southeast Asia as well. The characteristics of the tropical climate are: -A high total annual temperature of about 8400°-8600° C, which guarantees the capacity to cultivate a great number of species of tropical plants. -The uneven distribution of rainfall, with the high concentration of rainfall within one half of the year. This presents some difficulties for agriculture and soil conservation in Midlands (see Table 3) . 22 The monsoon climate with cool winter is characterised by reduction of the temperature platform, resulting from activities of cold spells existing in northeast monsoon. This factor, on one hand, permits the Midlands of vinh phu to cultivate several species of plants of the temperate zone, but on the other hand is harmful to tropical vegetation in winter. As a result of interactions between atmosphere circulation and topography, the latter consisting mainly of small hills and low mountains, the climate of Vinh phu is characterized by the following traits: + Solar radiation Agriculture is an explotation of solar energy. In the basic photosynthetic process the chlorophyll utilizes the visible light to produce carbonhydrates out of water and carbon dioxide. When temperature is hot limiting and the carbon dioxide concentration in the air remains constant, the photosynthetic rate of a single leaf usually increases with solar radiation to a point, known as the saturation light intensity, beyond which there is a little or no further increase in photosynthesis [1]. The intensity of solar radiation and the daylehgth are two important factors that determine the structure of intercropping and agricultural timing-schedule of cultivated plants. It seems to be that in the Midlands of Vinh phu Province the year-round solar radiation is usually sufficient and available for vegetation and crops (see Table 1). e e & & e e e e e TABLE 1: SOME CHARACTERISTICS OF SOLAR RADIATION IN THE MIDLANDS OF VINH PHU PROVINCE* CHARACTERISTICS J * F * M A M Total Solar Radiation: Kcal / cm 2 : 5,6 : 4.9 : 6.0 : 8.3 : 11.5 : 9,8 : 10,9 : 11.1 : 10.8 : 9.5 : 8.2 : 5.4 BaKcr/°cmR2diation: 2-2 ; 2-° ; 3a ; s-1 ; 7-7 ; 6-5 ; 8>2 ; 7-5 ; 7>°; 5-6 ; 3»6 ; 2-x The day length : : : : : : : : : : : : Hours : 10,8 : 11.3 : 11.8 : 12.5 : 13.0 : 13,3 : 13,2 : 12,8 : 12u2 : 11.6 : 11.0 : 10.7 : : : : : : : : : : The total of sunlight : g6 : 43 43 87 177 140 192 185 188 172 131 94 Hours : : : :. : : : : : : : : TABLE 2 : THE MONTHLY MEAN AIR TEMPERATURE ( °C )IN THE MIDLANDS OF VINH PHU PROVINCE * D Average Total 15.9 ' 16.9 * 19.8 * 23,5 ' 27.1 ' 28.2 ' 28.5 ' 27.8 * 26.7 ' 24.3 " 20.5 * 17,3 * 23.0 ' 8410 * Date from meteorological station Phu Ho Vinh phu Province. 24 In the begining of winter (October and November) the total of sunlight is reduced from 170 to 130 hours/month. During this time the intensity of solar radiation is not very high but is still favourable enough for the process of photosynthesis of vegetation and crops. Toward the end of winter there are a lot of cloudy days: 24.5 days in February and 26.8 days in March (on cloudy days 8/10 of the sky is covered by clouds ). Such cloudy and humid weather, typical for this period of Northern Viet nam, is called Mua phun (drizzle). The amount of sunlight during the drizzle is the lowest in the year, about 40 - 50 hours/month. This combination of low solar radiation and high humidity affect the process of photosynthesis and evopotranspiration of vegetation. If the drizzle lasts over a long period of time, it makes the growth of vegetation and crops difficult and directly influences the productivity of the agroecosystem. Study of the potential agricultural productivity in respect to sunlight (7] shown that in the condition, where sunlight is utilized to the fullest by an efficient crop canopy with a normal C02 content (in the air surrounding the crop leaves) and with optimum temperature, moisture, soil conditions and nutrient supply, more than 90% of the dry matter of the crop plant is derivered from the photosynthetic fixation of C02 . That is why sunlight is one of the important factor affecting the productivity of the agroecosystems. ++ Temperature Our knowledge of the effect of temperature on crop growth and 25 development is rether poor. The control exercised by temperature over plant process is mainly related to the activity of enzyme systems and our understanding of these and mechanisms affecting their activities is still far from satisfactory. By empirical study we know that rice begin to grow when the threshold temperatures from 12° to 15° C are reached, and the optimum temperatures range from 22° or 25° to 35° C, so these date are quite useful for a provisional estimation of potential productivity [7]. It is not enough for the assessment of the productivity of the concrete cropping systems. The net assimilation rate of a plant is the excess of its photosynthetic rate over the respiration loss. In most mature forest the photosynthetic rate is nearly the same as respipation loss. The high temperatures, particularly minimum temperatures at night in tropics,promote the respiration loss, and the latest is about 35% of the photosynthesis produc in the tropics [2], Unlike other tropic zones which have a warm climate around the year and usually provide plants with a fairly broad optimal temperature range for growth, monsoon tropics like North Viet nam have low temperatures during the winter, in one side limits growth of several species of tropical plants and in another side allows many plant species to flower and develop properly. Apparently some substance in the plants that has been destroyed by high temperature can be restored only when a cold period triggers the reproductive cycle. As mentioned above and as practice has shown, a cold period of winter in the Midlands of Vinh phu is a favorable and a necessary factor for the good quality of a number of plants. Actually, the quality of tea at the end of Autumn or beginning of Winter is considered the best in comparison with other seasons. In Vinh phu, winter or cool season extends from November to February of the following year. The weather during this period is generally dry and cold in the first half and damp, cool in the later half, depending on the way in which the northeast monsoon comes to Viet nam. At first glance the annual total temperature of about 8400° C seems to be enough for tropical plants (see Table 2). With more detailed study, however, we noted that the cold period, with low absolute minimum temperature in winter resulting from activities of cool waves in northeast monsoon, often considerably reduces the temperature, sometimes to 3.1°-3.7° C. It is the absolute minimum temperature that plays an important limiting factor in the reproduction and growth of vegetation and plants. Except in winter, high soil temperature leads to very rapid breakdown of litter, with subsequent leaching of soil nutrients before they can be taken up by plants [3]. +++ Rainfall The most important fluctuating characteristic of seasons in the tropics is rainfall. Anomalies in rainfall are common throughout the tropics. The variation of rainfall from year to year and within the year is considerable and unpredictable. Rainfall in the tropics is usually too much or too little [3]. In Vinh phu the average annual total rainfall is about 1500-1900 mm, but in one year there may be 1.5 or 2 times as much rain as the next year, or it may not rain evenly throughout a given season of the year, but fall in torrents within brief periods. Drought tends to come during the hottest and windiest part of the year, so that loss of water by evaporation and transpiration is high. As soon as we discuss the distribution of rainfall (table 3) we noted that average annual rainfall is not distributed evenly. The rainy season extends 7 months from April to October. The pattern of rainfall has one peak in August which is conected with the activity of typhoons on the Midlands of Vinh phu. It accounts for about 87 to 90% of the annual total. The remaining 5 months consist of winter and transitional months and account for just 10 to 13% of the annual total. Another important characteristic of rainfall in the tropics is its very high intensity, reaching over 50 mm (2 inches) an hour. Even very short periods of high density fails can have serious effects on soils, crops, and water supplies. Figure 4 is a graph showing the relationship between rainfall and temperature in the Midlands of Vinh phu province. It is well- known by the name: "Bioclimate Diagram of Gaussen". The equation of the relationship is: R = 2 T Where: R - Monthly mean rainfall [mm], T - Monthly mean temperature [°C] Here, we consider 2T as the capacity of evapotranspiration of TABLE 3 : THE MONTHLY MEAN RAINFALL [ mm J OF MIDLANDS VINH PHU PROVINCE • • • • I Rainy season: Dry season Ication ; J S o ; N ; D ;YEAR J ; F ; M ; A ; M ; J ; ; A ; | 1 1 T % T % Phu ho 27 41 52 100 187 248 298 316 214 137 44 27 1689 1489 * 89 ' 191 ' 11 Viet tri ; 20 ; 29 ; 39 ; 89 ; 193 ; 250 ; 302 ; 322 ; 223 , 132 ; 53 ; 22 ; 1678 ; 1511 ; 90 ; 163 ; 10 Doan hung ; 15 ; 25 ; 48 ; 88 ; 185 ; 231 ; 220 ; 289 ; 197 , 110 ; 44 ; 25 ; 1477 ; 1320 ; 89 ; 157 ; 11 Ha hoa ; 20 ; 32 ; 56 ; 114 ; 201 ; 302 ; 313 ; 360 ; 269 I 136 ; 88 ; 34 ; 1925 ; 1695 ; 88 ; 230 ; 12 Thanh ba ; 31 ; 44 ; 65 ; 103 ; 223 ; 241 ; 277 ; 322 ; 273 , 159 ; 60 ; 37 ; 1835 ; 1598 ; 87 ; 237 ; 13 Date from meteorological stations. 29 Figure 4: BTOCLIMATE DIAGRAM Agroneteorological station Phu ho Water deficit Water deficit 1 t Water sufficiency Water surplus Water sufficiency PHU HO I 36 m J [ 23,0°C 1689 nun ) C 26 - 27 3 RCmm) o T C 300 200 100 30 50 20 10 30 vegetation. If at any time the rainfall is higher than evapotranspiration, the vegetation have enough or more than enough water for growth and production (50 mm< R< 100 mm - water sufficiency; R> 100 mm - water surplus). On Midlands of Vinh phu the period of water deficit lasts for 2 months, from December to January of the following year. Joining the Bioclimate Diagram to the Agricultural Timing-schedule of several cultivated crops (Figure 5), we note that: - For annual crops such as rice, cassava, and peanut, there little difficulty with water supply, except for the winter rice in December and January. Fortunately, rice paddies are located in the valley or at a little higher, so thay^ can get water during this time from streams of miniwatershed. - For perennial crops such as tea, the water deficit has a strong influence on growth and reproduction. The tea plantation at that time does not produce and tea can even die in some years because of water deficit. Tea has been one of the main cultivated perennial plants in the Midlands of Vinh phu Province for the past several decades. Depending on climate conditions, tea plants produce young shoots in two periods: spring and summer-autumn. Spring tea is harvested at the end of February to March, for all of April the tea stops giving shoots, and summer-autumn tea is harvested over a long period from May to the end of November. Then from December to the end of January of the following year tea stops giving shoots again, because of the water deficit and cold weather. 31 Figure 5: AGRICULTURAL TIMING - SCHEDULE F M A M J J A S 0 Summer rice Z Winter rice 7 z Cassava 7 Spring peanut Z 7 Summer peanut z 7 Tea zzz.w.z 7 Water deficit Water deficit Water sufficiency Water surplus Water sufficiency There are two possible hypotheses to explain the April resting spell: first, the spell is in one of the coldest months of Viet nam - Ret thang Ba, meaning the cold in March in the Lunar calendar, which is equivalent to April in the Solar calendar. The second is that the tea plants after suffering a long period of water deficit and cold weather in March, are still weak and unable to produce continuously and therefore need a "resting period." ** Soil. Ecologically, it is widely accepted that tropical soil is less fertile than that at the temperate zone. In the latter, a large portion of organic matter and available nutrients is at all times in the soil, but in the tropics a much larger percentage is in biomass and is recycled within the organic structure of the ecosystem, not in the soil. Therefore, when a temperate forest is cleared, the soil retains nutrients; on the contrary cutting forest in the tropics, destroys the vegetation cover, leading to accelerated soil erosion. Geographical sciences assume that:"Like climate - Like soil"!. The flow of energy such as solar energy and the flow of materials such as rainfall actively participate in the process of soil formation. Under high intensity solar radiation in the tropics and the defined rhythm of climate seasons (large annual and day- night amplitudes of temperature, deep contrast in seasonal 33 rainfalls), most upland soils in Midlands are highly weathered. They are red to reddish yellow in color, high in oxides of iron and aluminum, presumably low in base saturation, and are reportedly highly acidic (pH 4.5 to 5.7). These soils are classified as oxisols (soil taxonomy) or ferealsols (FAO) [6]. Soil texture is silty to sandy loam, well-aggregated with very strong structure. The parent material is from both sedimentary and metamorphic rocks. A strong tendency of laterization in pedological layer is observed especially on hillsides, where the vegetation cover is poor or has been destroyed and water supply is sufficient or available for the process of evaporation of soils. Soil moisture is a very important factor also. It acts as a buffer system for the plants between times of water supply and demand. Thus, in farming system on hillslopes, the properties of the soil become increasingly important with increasing irregularity of rainfall and with increasing dryness. *** Vegetation The numerious plants, animals, and microorganisms in monsoonal tropical forests in the Midlands of Vinh phu interact in a complex fashion that serves to maintain the integrity of the forests. The first process of biological activity is production: "Production ( also called primary production ): The growth of green plants that results from photosynthesis. The carbon from carbon dioxide is joined into carbon chains that form the plants' living tissues (i.e., biomass )" [8]. The equation of the process is: 6 CO + 6 H 0 + hv 2 2 v ^ ' * •* ' Non-living part Energy of sunsight Living part-Biomass Depending on the degree of energy provided by sunlight, vegetation with its secret genetics, passes the minerals from the non-living part of the ecosystem into the biological part of the cycle in the course of production. Biological energy flow refers to the transfer of energy into living organisms by photosynthesis (production) -the first process, and from one organism to another through the food chain (consumption) -the second process. In terms of energy flows, in the ecosystem is not a closed cycle. Soil and plants absorb sunlight and emit infrared radiation; warm air carries heat energy as it passes to areas of cooler air, heat passes between the soil and air above, and between the vegetation and the atmosphere in one direction during the day, and the opposite direction at night [8]. Energy is incorporated into living tissues by photosynthesis. When sunlight energy is bound into the carbon chains containing potential energy, the plants can use this energy to drive the metabolic reaction by which they grow and maintain themselves. The internal consumption of energy for metabolic purposes is respiration, and some of this energy is lost as heat. The net 35 energy that goes into the growth of the plant after energy loss through respiration (e.g., its net accumulation of potential energy in carbon chains) is the net primary production [8] . People often consider vegetation as primarily a product of climate, geography assumes that: "Like climate -Like vegetation!" and as a result of interaction between climate and pedology. Many years ago the vegetation cover of the Midlands of Vinh phu was very abundant. Most of the forest types fall into the closed seasonal tropical evergreen category. The forest was dominated mostly by species of the Dipterocarpaceae, Moraceae, Meliaceae. Lauraceae, Fagaceae, Brucetaceae, and Sapindaceae. The remnant forest on Nghia hung mountain is evidence of this forest type. Under pressure of clearing and burning, the forests have been destroyed and replaced by secondary forests, with the present result that forest remains in only about 20% of the total area. The remaining forest is commonly characterized by bamboo thickets, normally nua (Neohouzeana) or giang (Dendrocalamus). Some areas, where the soil moisture is maintained and where there is good protection from fire and grazing, the vegetation succession can rapidly regenerate into secondary forests, with fast-growing species, such as Macaranqa denticulata, Trema orientalis, T. angustifolia, Mallotus apelata, M. cochinchinensis, Rhus chinensis, and Mangletia glauca. At first these forests have a low species diversity and a simple structure, but succession may in time, if uninterrupted, restore them to their original state [6]. 36 Figure 6 shows the ecological succession of natural vegetation cover in the Midlands of Vinh phu Province under various forms of human activities [5]. As noted, ecological succession of the vegetation cover in the case of expanding human action is quite different from the ecological succession which takes place in small scale shifting cultivation. If the agricultural fields are overused by the intensification of the rotation cycle, or degraded by erosion, the vegetation succession will go to bare land. In this case, changes in the microclimate conditions are unavoidable, and the process is irreversible. Consequently, we can not study the impact of any natural factor without connection with social problems. 9 9 © © © e e e e e SECONDARY If the microclimate condition didn't change FOREST left fallow many jye^ars. (rarely!) I \ ORIGINAL NATURAL cutting" SHIFTING CULTIVATION TALL GRASS AND FOREST and burning smal 1 areas left SHRUBS cutting fire, over grazing AGRICULTURAL FIELD over explotation Figure 6: ECOLOGICAL SUCCESSION OF VEGETATION COVER IN MIDLANDS OF VINH PHU PROVINCE. 38 2/. The impact of climate and Human-managed agroecosystems. * Farming technology. Before 1954, the Midlands were sparsely populated by non- Vietnamese tribal groups. After 1954 the Vietnamese Government began a program to resettle people from the crowded Red River Delta into the Midlands. The ethnic Vietnamese now constitute the majority population of the Midlands. To the lowland Kinh, skilled paddy farmers by tradition, the midlands environment presented new problems. Dryland cultivation on sloping terrain is unfamiliar to them and they are not very skilled in this. Adoption of the traditional shifting cultivation employed on hill land by the minorities is out of the question. Aside from natural and legal constraints, this technique requires much traditional knowledge to be successful, and this knowledge is inter-linked with certain social and ritual institutions that are entirely foreign to Kinh society. The Kinh people have isimply brought their lowland production technology to the Midlands which has accelerated soil loss and destruction of the natural habitat, and reduced sustainability of agroecosystems [6]. Many original forests were cut for agricultural development. These activities led to environmental changes. 39 ** Climate and the human-managed agroecosystems: Gordon R. Conway [4] says that with the exception of a clear goal in the form of increased social value (e.g. productivity), now is a time when humans seek more for the future - a degree of security over the longer term. "In practice, an assessment of an agroecosystem's performance has to be made not in terms of the theoretical goal but in relation to those key system properties that contribute most directly to realizing the goal". There are four primary agroecosystem properties: productivity, stability, sustainability and equitability. The first three correspond to the properties of the natural ecosystem; the last one has no direct counterpart in the natural ecosystem. Therefore, for the purpose of assessing the impacts of natural factors like the climate or microclimate, I vill study only the first three properties. + Productivity: Productivity is defined here as the output of valued product per unit of resource input. Common measures of productivity are yield or income per hectare. Yield may be in terms of kilograms of grain, tubers, leaves, meat or fish, ect [4] . ++ Stability: Stability may be defined as the consistency of productivity in the face of minor disturbances arising from the normal fluctuations and cycles in the surrounding environment. The fluctuations may be in the climate or in the market demand for agricultural products. Stability, measured by the coefficient of variation in productivity, is determined from a time series of 40 productivity measurements. Since productivity may be level, rising or falling, stability will refer to the variability of a trend [4]. +++ Sustainability: Sustainability is defined as the ability of an agroecosystem to maintain productivity when subject to a major disturbing force. This potential disturbance may be caused by an intensive stress (frequent or continuous) [4]. Erosion, continuous shortage of underground water source, and degradation of environment (such as the reduction of rainfall in many years) have negative effects on cultivated crops, and will eventually cause productivity of agroecosystems to collapse. The factors which directly influence the productivity of an agroecosystem in the Midlands may be physical or social ones (see Table 4). Sometimes it is difficult to determine exactly which percentage of productivity has been influenced by physical factors and which by social factors. Figure 7 shows the fluctuation of the productivities of two major crops in Midlands. We noted that both tea productivity and rice productivity are variable in a large scale from year to year and from place to place; a high harvest may be gained in one district while a failure will occur in the next. Productivity is a function of many variables, which may be either agroclimatic or social tactors such as agricultural policies, as shown in the following detailed analysis. The rising of average paddy rice production of three Thanh hoa, Doan hung, Lap thach districts in the period 1981 - 1983 can be related to two factors: gure 7; Changes of Productivities of major crops in Midlands of Vinh phu 42 TABLE 4. FACTORS AFFECTING PROPERTIES OF AGROECOSYSTEMS IN MIDLANDS 1. SOCIAL FACTORS * * FARMING TECHNOLOGY: - Shifting cultivation, - Use of different kinds of manure, green manure, and fertilizer, - Inadequate transfer of farming technology, - Use of pesticides in "suitable concentration" to increase productivity of tea. ** POLICY IN AGRICULTURE: - Land tenure: + Before liberation in 1945 land was owned by absentee landlords, ++ Land reform 1955 -1957, land was appropriated by the state and local farmers, +++ In 1960 land was put together into cooperatives and state enterprises for large-scale production, ++++ In 1980 most of land was divided between households. 2. NATURAL FACTORS: - Soil conditions, - Use of new varieties, - Climate conditions, + Radiation, ++ Temperature, +++ Rainfall, ++++ Unfavorable weather conditions. * Le Trong Cue. 1990. Agroforestry in Viet nam EAPI. 43 First, the new land tenure, by which most of the land has been divided among households. Therefore, the farmers have better opportunities to carry on soil conservation and to put in more laber days or to make more inputs by using different kinds of manure in order to receive higher yield. Second, the use of the new rice paddy varieties which have higher yields. Commonly, under experimental field conditions, when we are able to fix other factors we can calculate the fluctuation of productivity of tea in respect to climatic variables. Figures 8a,b,c represent the relationship between tea productivity and rainfall. We found that the relationship between total annual tea productivity and annual rainfall is not clear. But there is a strong relationship between rainfall and the productivity of summer-autumn tea. This is because during this period temperature is favorable and rainfall is the limiting factor. For spring tea, besides rainfall, temperature also influences tea production. Therefore, the relationship between production and rainfall is not very good. Based on the summer-autumn data we tried to calculate a simple regression (Figure 9). Here the correlated coefficient is about 0.6 because in climate affect except the affect of annual rainfall there are other factors for example unfavorable weather, that happens in a short period of time but makes big influence on productivity of tea. FIGURE 9 : Summer-Autumn Tea Productivity in Relation to Rainfall 30, 1200 1400 1600 180 0 2000 2200 2400 2600 2800 ' 3000 Rainfall (mm) 47 CONCLUSION Studying the impact of climate and microclimate on properties of agroecosystems in the Midlands I have following remarks: 1. The agroecosystems in the Midlands of vinh phu Province are now human-managed ecosystems. At the present time, it is impossible study the effect of any natural factors as climate or microclimate in our case on ecosystem properties without considering interactions with the social system. 2. Human ecology is a superior conceptual framework for studying and analyzing the interrelationship between climate and agriculture because of its systems viewpoint. It is also more efficient than tranditional methods. 3. The productivity of agroecosystems in general or of any cultivated plants in particular are closely related to both physical and social factors. These correlations are not simple, but multicorrelations. 4. It is difficult to evaluate the effect of climatic changes for the following reasions: the weather with its characterictics fluctuates greatly from day to day, while the climate and microclimate are rather stable components of agroecosystems from year to year. So, for the future we should try to apply different mathematic methods to discover these constraints. 48 From these studies of the impact of climate and microclimate on the properties of agroecosystems in the Midlands of Vinh phu Province, there are some points for further research: 1. For the purpose of intercropping we should study the radiation conditions in different types of agroforestry, especially the regime of radiation in cloudy and drizzling weather. 2. Study the effect of cold temperature in the end of the summer- autumn period on tea productivity. We should also study the effect of winter temperatures on tea quality. 3. In respect to climate conditions we should try to understand the significance of the tea "resting period" in April. 4. Study the regime of soil moisture in respect to the different models of agroforestry. 5. Try to calculate the percentages of productivity made up by social or natural factors. 49 REFFERENCES 1. Chang, Jen-hu. 1968. The agricultural Potential of Humid Tropics. The Geografical Review. (3). 2. Chang, Jen-hu. 1977. Tropical Agriculture: Crop Diversity and Crop Yields. Economic Geography. (3). 3. Chitman, Vanida. 1978. The Choice of Appropriate for the Rural Sectors in Tropical Countries. Regional Conference on Technology for Rural Development. Kuala Lumpur, Malaysia. April 1978. 4. Conway, Gordon R. 1985. Agricultural Ecology and Farming System Sesearch. Peper presented at the Farming Systems Research (FSR) Workshop. Hawkesbury Agricultural College under the Auspices of the Australian Council for International Agricultural Research. 5. Cue, Le Trong. 1988. Agroforestry Practices in Viet nam. East- West Center/EAPI. 6. Cue, Le Trong, Rambo, A. T. and Kathleen Gillogly (eds). 1989. Agroecosystems in the Midlands of vinh phu province. East- West Center/EAPI. 7. Huang, Ping-wei. 1981. Environmental Factors and the Potential Agricultural Productivity of China: An Analysis of Sunlight, Temperature and Soil Moisture.The Environment: Chinese and American Views. New York: Menthuen and Co. Ltd. 50 8. Rambo, A. T., Sajise, P. E. 1984. An Introduction to Human Ecology Research on Agricultural Systems in Southeast Asia. East-West Center/ EAPI. 9. Sam, Fuj isaka. 1985. Interactive Informal Interviewing: RRA Training and Experiences from the Farming Systems Development Project -eastern Visayas. 10. Uy ban Khoa hoc Ky thuat Vinh phu. 1983. Dac diem khi hau Vinh phu. Vietnamese.