Silva Balcanica, 15(2)/2014

BIOMASS OF YOUNG TREE SAPLINGS OF MAIN FOREST SPECIES IN AND ITS ROLE AS A CARBON DEPOT

Violeta Dimitrova1, Mariyana Lyubenovа2, Dimitar N. Dimitrov3 1University of Forestry - Sofia 2University of Sofia, Faculty of Biology 3Forest Research Institute – Sofia Bulgarian Academy of Sciences

Abstract

The data about the biomass and state of young tree saplings in forest ecosys- tems may support for outlining some successional trends and let us know the future composition and vitality of tree layer. The aim of the present research is to establish the plant mass of young tree saplings as well as their carbon content. Representative sample plots in the ecosystems of main forest species in Bul- garia were used for the research. Classical methods for biomass studying along with a computer programme were applied for the study. The observed state and vitality of the investigated forest ecosystems is a result mainly from the management and the climate changes. The adaptive management of forests is needed of comparative analysis and discussion about future state of impor- tant for the country forest types. Key words: biomass, carbon accumulation, young tree saplings

Introduction

The biomass is one of the main indicators for assessment of functional state of communities. Establishing and analysis of plant mass in forest communities which are the main producers of organic mater is of great importance for the whole knowl- edge of the biosphere. The quantity of biomass and the state of young tree saplings in forest ecosys- tems are of great importance for the regeneration capacity and future composition of studied forests, e.g. for outlining the future successional trends. The investigations in this area are oriented to establishing the biomass of main tree species for the country: Lyubenova, Bondev (1987, 1998) - for oak forests, Vulchev (1999), Tonchev et al. (2012) – for beech forests, Vulchev, Nikolov (1999), Michov (1985) - for Scotch pine forests, etc. Mainly the aboveground plant mass was discussed in these works. The biomass store in ecosystems is also an important issue for international investigators. The investigations of Hristovski et al. (2009),

35 Brumme, Khanna (2009), Le Goff, Ottorini (2001) for beech communities are some examples. Results of the root biomass as a significant carbon depot could be found in Helmisaari (2002) and Kurz et al. (1996) and an summarizing view in Brunner, Godbold (2007), etc. In spite of this, concrete data for root systems as biomass accumulator and their role in a biological turnover of forest ecosystems are insufficient on national as well as international level. The root biomass is one of the main accumulators of organic carbon in the biosphere (Van Noordwijk et al., 1996). The roots are excep- tionally important component in the carbon cycle. According to assessments they represent around 30% of the total tree biomass (Larcher, 1978). The investigations for the functional role of plant mass of young tree saplings in the forest ecosystems are almost absent although the possibilities to use this com- ponent for the goals of biomonitoring. The goal of the present research is to establish the plant mass of young tree saplings of main forest species in Bulgaria and also the carbon content in their aboveground and belowground sphere.

Materials and methods

Studied sites The biomass and carbon stocks of young tree saplings were investigated in four representative ecosystems of Quercus frainetto Ten., Fagus sylvatica L., Pinus sylvestris L. and Picea abies (L.) Karst. These ecosystems represent the main forest tree species in Bulgaria. Their characteristics are shown in Table 1. Sample plot 1 (SP 1) is situated in beech community on the territory of Petrohan Experimental and Educational Forest Enterprise (EEFE ‘Petrohan’), vil- lage Barzia situated at the northeast slopes of West ( mountain). The altitude is around 950 m. The region is related to continental climate. The annual average precipitation is between 800 mm – 1100 mm. The soils are Eu- tric Cambisols. SP 2 is situated in oak community in State Forestry ‘Govezhda’, Northwest Bul- garia, Montana district near village Georgy Damyanovo. The altitude is between 300 and 600 m. The region is related to continental climate. The average annual tempera- ture is 9.8°C and annual average precipitation is 800 mm. The soils are Orthic luvisols. The oak forests are the main part of the vegetation between 150 and 600 m a.s.l. Sample plots 3 and 4 for spruce and Scots pine communities are situated on the territory of EEFE ‘G. Avramov’, situated in pass between mountains and West Rhodopes, Yundola (Fig.1 ). The altitude is between 110 and 1600 m. The re- gion is related to mountain climate. The annual average precipitation is around 1200 mm. The soils are Humic Cambisols.

The detailed characteristics of sample plots and the list of plant species are given in Dimitrova et al. (2014).

36 Fig. 1. Location of sample plots

Aboveground biomass. The aboveground biomass was investigated through classical methods (Rodin et al., 1968; Lyubenova, 2009). 20 young tree saplings of investigated species from each sample plots were gathered. Their heigh and diameter were measured. The age was determined through counting up the age rings. The density was determined through counting the individuals in five experimental plots per 1 2m located in each SP. The average characteristics obtained are given in Table 2. Aboveground plant mass was divided into stem and leaves and was dried at 85°С for 48 h until constant weight was reached and then the dry mass was measured.

Table 1 Characteristics of the sample plots in the investigated ecosystems - (cm) N 1,3 Soil Slope H (m) species Canopy cies (N) Exposure Area (hа) D Site index Age, years Altitude (m) Density (N /hа) composition/tree Layers (N)/total spe

Cambisols, SP 1 0,25 950 N 7° beech 60 0,8 I-II 768 17 20 2/45 CM Orthic mixed/ 0,6- SP 2 0,25 310 SE 1° 65 III 628 20 13 2/46 Luvisols oak 0,7 N 8° Humic SP 3 0,25 1600 spruce 70 0,9 I 432 34 27 2/42 Cambisols mixed/ Humic SP 4 0,25 1100 S 16° Scots 120 0,8 III 460 33 30 2/30 Cambisols pine

37 Тable 2 Characteristics of young tree saplings

SP 1 SP 2 SP 3 SP 4 (F. sylvatica) (Q. frainetto) (P. abies) (P. sylvestris) d (mm) 3.8 2.6 5.8 9.3 H (cm) 30.6 14.9 29.9 46.5 Density (n/m2) 1 22 1 1 Age (years) 4 6 6 7

Belowground plant mass. Belowground plant mass was analyzed according the methods of Rodin et al. (1968) and through computer program Winrhizo (2009). The whole root systems of 20 young tree saplings from each sample stand were excavated (Fig. 2). After that the root samples were washed from the soil and were scanned. The images were analyzed with above cited program and data for length, average diameter and the volume of the root systems were obtained. After that the roots were dried at 85°С for 48 h until constant weight was reached and then the dry mass was measured. The investigations were carried out at the end of the vegetation season (October 2012) when the accumulation of the biomass was reached its maxi- mum for the current year. Carbon content was calculated according to Larcher’s ratio (Larcher 1978; Lyubenova, 2009).

Fig. 2. Spruce young tree sapling

38 Statistical analysis The data were analyzed with Statistica 7 (McGarigal et al., 2000). The stan- dard errors and the representative of the average values was calculated at the level of significance 0.05.

Results and Discussion

The young tree saplings at the oak ecosystem are the smallest according to their diameter and height but with the biggest density (Table 2). The young tree sapling of Scots pine forest are with the biggest values of these indexes. There are young tree saplings of spruce in this sample plot while in all others - they are only of the dominant tree species. The results about the biomass of young tree saplings at four forest communi-

Table 3 Biomass stores (g.m-2 abs.dry.m) of young tree saplings with average values, standard deviation (SD) and standard errors (SE) of the mean

Plant mass Aboveground Belowground Total ) 2 Above- ) S ana- ) 3 Be- 3 ground lyzed

low- l/V and Total

Stems area Leaves V (cm V d (mm) ground (cm/m below (cm2) Root S (cm ground

SP 1 1.142 0.444 1.586 0.976 162.439 36.788 0.536 229.808 0.476 2.562 SD 0.777 0.279 1.018 0.702 58.677 22.297 0.079 154.467 0.266 1.72 SE 0.039 0.014 0.051 0.035 2.934 1.115 0.004 7.723 0.013 0.086 SP 2 12.902 7.549 20.451 30.509 117.239 33.167 0.828 129.856 0.660 50.938

SD 0.319 0.184 0.454 16.595 39.167 11.396 0.144 53.044 0.207 17.049

SE 0.016 0.009 0.023 0.829 1.958 0.569 0.007 2.652 0.010 0.852

SP 3 7.019 4.751 11.771 2.652 268.423 122.67 0.734 569.636 2.149 14.423

SD 4.736 3.524 8.187 1.589 72.625 71.260 0.120 402.803 1.007 9.776

SE 0.279 0.207 0.482 0.093 4.539 4.454 0.008 25.175 0.063 0.575

SP 4 10.227 6.352 16.579 3.965 260.498 90.063 0.705 424.867 1.56 20.544

SD 3.836 2.136 5.784 1.827 93.689 30.871 0.127 181.855 0.480 7.611

SE 0.192 0.107 0.289 0.091 4.684 1.544 0.006 9.093 0.024 0.38

39 ties are given in Table 3. It was established the bigger quantity of total plant mass (above and belowground) for oak (50.938 g.m-2) and for Scots pine (20.544 g.m-2). The ratio between the aboveground and belowground plant mass for the coniferous species was 80 to 20% accordingly. The participation of the belowground plant mass in the total stores of the plant mass was increasing for the broad-leaved young tree saplings. For the beech it was 62 to 38%. The aboveground plant mass was lower in comparison with belowground – 40 to 60% only for the oak young tree saplings. The stem was around 60-72% and the leaves were 28 to 40% from the total aboveground plant mass for all species although the different age. The roots of the coniferous spe- cies were with approximately same diameter (0.7 mm). For the deciduous species beech roots investigated were thinner that the oak ones (0.536 mm). For oak they are 0.828 mm. The spruce roots were longest (56.6 cm) and had the largest volume (2.1 cm3) and the oak ones were the shortest (129.9 cm3). The reason for this could be very high content of stones in the soil in the oak community. Calculated average values for plant mass stores in aboveground and belowground biomass of young tree saplings are representative. The obtained data for the aboveground plant mass of oak tree sapling correlate with published data for Quercus sp. – 21.1 g.m-2 in urban area, Zapaden park, Sofia (Dimitrova, Zhiyanski, 2011). Our results are similar to these for FYRMacedonian beech forests also. For example the total biomass of beech saplings was 0.353 kg.ha-1 from which – above-

Table 4 Carbon stores (g.m-2) of young tree samplings with average values, standard deviation (SD) and standard errors (SE) of the mean

Aboveground plant mass Belowground Total Stems Leaves Total plant mass

SP 1 0.624 0.242 0.866 0.533 1.399 SD 0.424 0.152 0.556 0.383 0.939 SE 0.021 0.008 0.028 0.019 0.047 SP 2 7.044 4.122 11.166 16.646 27.812 SD 3.897 2.247 5.547 9.061 14.608 SE 0.195 0.112 0.277 0.453 0.73 SP 3 3.832 2.594 6.427 1.448 7.875 SD 2.586 1.924 4.470 0.868 5.338 SE 0.152 0.113 0.263 0.051 0.314 SP 4 5.584 3.468 9.052 2.165 11.217 SD 2.094 1.198 3.158 0.972 4.130 SE 0.105 0.060 0.158 0.049 0.207

40 ground plant mass was 0,293 kg.ha-1 and belowground - 0.061 kg.ha-1 (Hristovski et al., 2009). It is most probably due to the similar ecological conditions and the state of the forests. The carbon content varied from 1.399 g.m-2 for beech tree saplings to 27.812 g.m-2 - for oak tree saplings (Table 4). Calculated average values of carbon stores in aboveground and belowground plant mass of young tree saplings are representative. The allocation of this quantity in aboveground and belowground plant mass follows its stratification in these two spheres. The carbon content is about 54% of the abso- lutely dry mater. It is about 45% of the absolutely dry mater in other our investiga- tions of tree saplings in urban oak parks in Sofia (Dimitrova, Zhiyanski, 2011).

Conclusion

The results from the presented investigation are that the quantity of the total (aboveground and belowground) plant mass strongly varied. The possible reasons for this are the forest age and their management. They confirm the views that tree saplings represent the significant carbon depot in the forest ecosystems. The calculated different ratio of the plant mass and carbon stores in aboveg- round and belowground spheres of the investigated tree saplings gives an idea of the ecological mean of the types of forest as a carbon depot and for their geochemical role. About 80% of plant mass and carbon are accumulated in aboveground sphere for the coniferous tree saplings. The importance of the belowground stores is in- creased almost twice for the beech young tree saplings, and three times for the oak saplings in comparison with the coniferous. The significance of the belowground plant mass of the oak saplings is 1.5 times bigger compared to the aboveground plant mass. The calculated stratification of the plant mass once again confirms the big soil and hydrology role of the oak forests in their regions of distribution.

Acknowledgements: The study was realized with the financial support of NSF at the Ministry of Education, Youth and Science of Bulgaria, through a project entitled: ‘The role of the belowground plant mass in annual fixation of CO2 from main forest ecosystems in Bulgaria’, www.belowgrownd_ phytomas.com.

References

Brunner, I., Godbold, D. 2007. Tree roots in a changing world. Journal of Forest Research, 12, 78-82. Brumme, R., Khanna P. 2009. Functioning and Management of European Beech Ecosystems. Ecological Studies, 208, ISSN 0070-339-4, 479. Dimitrova V., Lyubenovа M., Zhiyanski M. 2014. The role of the belowground plant mass in the an-

nual fixation of СО2 from main forest ecosystems in Bulgaria. Publishing house of University of Forestry, 112. Dimitrova V., Zhiyanski M. 2011. Plant mass of Herbaceous Floor in Urban Forest Parks of Sofia, Bulgaria. Journal of Balkan Ecology, 14, 2, 187-195 (In Bulgarian). Helmisaari, H.-S., Makkonen, K., Kellomaki, S., Valtonen, E., Malkonen, E. 2002. Below and

41 aboveground biomass, production and nitrogen use in Scots pine stands in eastern Finland. For. Ecol. Manag., 165, 317-326. Hristovski, S., Melovski, L., Shushlevska, М., Grupche, L. 2009. Belowground plant mass and pro- duction in beech ecosystem Calamintho grandiflorae-Fagetum in National park ‘Mavrovo’. IV. Belowground plant mass in the grass layer. Ekol. Zašt. Život. Sred. 12 (1/2), 3-8. Kurz, W., S. Beukema, M. Apps. 1996. Estimation of root biomass and dynamics for the carbon budget model of the Canadian forest sector. Can. J. For. Res., 26(11), 1973–1979. Larcher, V. 1978. Plant ecology. М., Mir, 381. (In Russian). Le Goff, N., Ottorini, J.-M. 2001. Root bio­mass and biomass increment in a beech (Fagus­ sylvatica L.) stand in North-East France. Ann. For. Sci., 58, 1-13. Lyubenova M., Bondev I. 1987. Belowground plant mass of tree layer of ass. Quercus frainetto+Quercus cerris - Festuca heterophylla+Poa nemoralis in the area of Gabra, Sofia region. Proc. of IV National botany conference, 72-76 (In Bulgarian). Lyubenova М., Bondev I. 1998. Overground annual production and biomass of oak forests in the Bal- kan mountains. Ecologie, 29 (1-2), 389-392. Lyubenova M. 2009. Functional biocoenology. An- Di, Sofia, 368 pp. (in Bulgarian). McGarigal K., S. Cushman, S. Stafford. 2000. Multivariate Statistics for Wildlife and Ecology Research, Springer-Verlag New York, Berlin, Heidelberg, 283p. Mihov, I. 1985. Content of mineral substances for Scots pine (Pinus sylvestris L.) on three types of soils. 35 -43. Rodin, L., N. Remezov, N. Bazilevich. 1968. Methodological Instructions for Study Dynamics and Biological Cycle in Phytoceanosis. Science Publisher, Leningrad, 9-24. Tonchev, T., Dimitrova, V., Dimitrov, M., Mihov, I. 2012. Investigation of the aboveground plant mass and annual growth of the beech forests. Forestry Ideas, 18, 2. Van Noorwijk, M., et al., 1996. Root distribution of trees and corps; competition and/or complementarity: In. Ong., C.K., Huxley P., Tree-corp Interactions: A Physiological Approach, CAB International. Wallingford, Oxon GB 386 S, pp. 319-364 Vulchev, V, Nikolov, V. 1999. Primary production and reserves of the above-ground plant mass of two Pinus sylvestris L. communities in the Malyovitsa Divide of the Rila Mountains. Phytologia Bal- canica, 5(1), 75-84. Vulchev V., 1999. Above – ground plant mass reserves of a Fagus orientalis Lipsky community in Strandza Mountain. Phytologia Balcanica, 5(1), 69-73. Winrhizo 2009 Regent instruments Canada Inc. Computer program.

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