ecological engineering 29 (2007) 117–124

available at www.sciencedirect.com

journal homepage: www.elsevier.com/locate/ecoleng

Ecological effects of desertification control and desertified land reclamation in an oasis–desert ecotone in an arid region: A case study in Hexi Corridor, northwest China

Yong Zhong Su a,b,∗, Wen Zhi Zhao a, Pei Xi Su a, Zhi Hui Zhang a, Tao Wang b, Raghuvanshi Ram c a Linze Inland River Basin Comprehensive Research Station, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou 730000, China b Key Laboratory of Desert and Desertification, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou 730000, China c Regional Research Laboratory (CSIR), Bhopal, MP 462026, India article info abstract

Article history: Desertification around oases is the major obstacle for sustainable development of oases Received 21 January 2005 in arid regions of northwest China. An effective way of maintaining the stability of oases Received in revised form is to recover the relatively stable ecological zone between an oasis and desert from the 26 September 2005 destroyed ecological rift zone. This paper presents a typical case of successful efforts in eco- Accepted 24 October 2005 logical restoration and desertified land reclamation of oasis–desert ecotone. On the basis of stabilization of mobile dunes and agricultural use of reclaimed land, some successful tech- niques including established straw checkerboards and planting drought-tolerant indigenous Keywords: shrubs, leveling sand dunes and drawing water for irrigation, closing dunes for grass reser- Oasis vation were carried out in 1975. In the restoration area, a stable artificial protective forest Desertification system had been developed. Pedological analyses indicate that the fine particle fraction (silt Soil development and clay content) in 0–10 cm soil surface layer has been increased from 2.6% on the untreated Sand transportation rate mobile sandy land to 9.3–37.3% in the restoration areas, and correspondingly, soil organic C − Transitional zone between oasis and has been increased from 0.63 to 1.88–9.70 g kg 1 during the 28 years of restoration period. In desert these 28 years, a 10 cm depth of minero-organic topsoil in the irrigated Picea sylvestris forest- Arid area land has been developed. It is also observed that sand transportation rate during sandstorm events has been significantly reduced. The increase of vegetation cover indicates a remark- able environmental improvement. Overall, the ecological restoration approach in this study is of practical significance for the rebuilding of rift zone ecosystem and maintenance of the stability of oasis in the arid regions of northwest China. © 2005 Elsevier B.V. All rights reserved.

1. Introduction in the arid region of northwest China (Cheng et al., 1999). These oases formed naturally in river deltas or were established in Such a wide desert, or Gobi, interspersed with many oases of alluvial–diluvial plains and edges of diluvial–alluvial fans by different sizes and shapes is the main geomorphologic feature drawing the water for irrigation from the rivers in different

∗ Corresponding author. Tel.: +86 931 4967070; fax: +86 931 8275241. E-mail addresses: [email protected], [email protected] (Y.Z. Su). 0925-8574/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.ecoleng.2005.10.015 118 ecological engineering 29 (2007) 117–124

historical periods (Zhang et al., 2003). In this region, oases is 117 mm. Mean annual pan-evaporation is around 2390 mm, represent only a very small portion (4%) of the land surface; 20 times greater than the annual precipitation. The frost-free they are important for agricultural and human activity, with season lasts 165 days on average. Accumulated temperature of ◦ ◦ − more than 95% of the population and more than 90% of social ≥10 C is about 3088 C. Mean annual wind velocity is 3.2 m s 1, wealth (Han, 1999). To maintain the stability of oasis ecosys- and prevailing wind direction is northwest. Gales with wind − tem, therefore, has become an important issue for sustainable velocity >17 m s 1 occur 15 or more days per year (Su et al., development in the arid region. 2004). The depth of groundwater level ranges from 4 to 10 m. Oasis evolution in arid and semi-arid regions has two oppo- The main soil types are Aripsamment and Calciorthids with site processes, oasification and desertification (Zhang et al., loose structure and very low organic matter, and are very sus- 2003). Under the overexploitation and irrational use of water ceptible to wind erosion (Chen et al., 1998). The natural vegeta- and soil resources by humans, the stability of oasis system tion at the edge of oasis is composed of Calligonum mongolicum is mainly affected by both desertification in the oasis–desert Turcz., Calligonum gobicum (Bge.) A. Los., Nitraria sphaerocarpa ecotone and soil salinization in the interior of the oasis (Han, Maxim., Reaumuria soongorica (Pall.) Maxim., Haloxylon ammod- 1999; Pan, 2001). In the arid regions of northwest China, the endron (C.A. Mey.) Bge., Caragana korshinskii Kom., Hedysarum transitional zones between oasis and desert or oasis–desert scoparium Fisch. et Mey., and Tamarix chinensis Lour. The staple ecotones have become the ecological rift zones to jeopar- crops are spring wheat (Triticum aestivum L.), maize (Zea mays dize oases due to intensive anthropogenic disturbance such L.) and cotton (Gossypium hirsutum L.) in the oasis. as overgrazing and fuel collection in conjunction with highly erodible soils and a harsh climate. Therefore, an effective way 2.2. Features of desertified land priori to restoration in of maintaining the stability of oasis is to recover the relatively the study area stable ecological zone from the destroyed ecological rift zone (Pan and Chao, 2003). Desertification and oasification are two extreme opposite Over the past several decades, the ecological restora- geographical processes in arid regions (Zhang et al., 2003). tion and desertification control of the oasis–desert ecotone Irrational reclamation of land and over utilization of natural has become a principle strategy to maintain the ecologi- resources in oases by humans can led to deterioration in oasis cal security of the oasis ecosystem in the northwest China environments, resulting in development of desertification. (Research Group of “Study on Combating Desertification/Land Desertification around Pingchuan oasis margin was developed Degradation in China”, 1998). Some successful experiences rapidly during the second half of the 20th century and reached and significant achievements pertaining to establishment of climax in the mid-1970s. At its peak, the original fixed shrubby sand-protecting system and desertified land reclamation have sand dunes at the fringe of the oasis were mobilized as a result been obtained in some areas of the desert–oasis ecotone. This of vegetation devastation due to over-gathering of fuelwood paper presents a typical case of successful efforts in ecological and overgrazing, leading to encroachment of shifting sand on restoration and desertified land reclamation in the middle of the oasis. The farmlands endangered by shifting sand from the Hexi Corridor, northwest China, which is a representative residual dunes of Gobi led to soil erosion, and the resulting of oasis–desert ecotone in arid regions. We attempt to evaluate abandonment of cultivated land further induced a southward the long-term effects of ecological restoration by investigating retreat of the oasis by 200–300 m. Severe desertified land made soil development and environmental improvement follow- up 54.6% of the total land area (Research Group of “Study on ing ecological restoration of 28 years. The aim is to provide Combating Desertification/Land Degradation in China”, 1998). an effective and feasible model for ecological restoration in oasis–desert ecotone of arid region. 2.3. Techniques of ecological restoration

In 1975, Lanzhou Institute of Desert Research, Chinese 2. Method and materials Academy of Sciences established the Linze Station of Deser- tification Research at Pingchuan to monitor desertification 2.1. Description of study area processes and develop effective techniques to restore veg- etation and rehabilitate desertified land. According to the The study area, covering Wulidong village, Pingchan town, topographical features and desertification extent in the study Linze county in the middle of Hexi Corridor region of area, plan for ecological rehabilitation was made and some Gansu province, is located between 39◦19–39◦19N and stabilization and reclamation techniques including shelter- 100◦02–100◦21E at the southern edge of Badain Jaran Desert, belts, land enclosure, straw checkerboards planted with with an altitude ranging from 1368 to 1380 m. Pingchan town is indigenous shrubs, shelter belt establishment, dune level and a narrow stretch of oasis and Wulidong village is located at the irrigation were applied. The specific way of technical applica- fringe of the oasis, which is connected with dense moving and tion in the study area was as follows. denudation residual dunes as well as Gobi. This region has a First of all, sand breaks 10–50 m wide were built along typical temperate desert climate: dry and hot in summer, cold trunk canals at the peripheries of the oasis by planting poplar in winter, plenty of sunshine, very little precipitation, strong (Populus gansuensis) and narrow-leafed oleaster (Elaeagnus winds, and frequent drifting sands. According to the statistics angustifolia). Since Populus gansuensis functions more effec- of the Linze Weather Station, the annual mean air temperature tively in providing shelter from the wind, it is mostly planted is about is 7.6 ◦C, with an absolute maximum of 39.1 ◦C and an in places overlaid with soil horizons, while E. angustifolia is absolute minimum of 27 ◦C. The normal annual precipitation luxuriant and works better as barrier protecting against sand, Download English Version: https://daneshyari.com/en/article/4391279

Download Persian Version:

https://daneshyari.com/article/4391279

Daneshyari.com