若尔盖沙化草地恢复过程中土壤特性及水源涵养功能

1995年以来,政府大力开展对若尔盖沙化草地生态系统的恢复重建工作,其生态恢复效益受到广泛关注。而水源涵养功能作为衡量草地生态系统恢复程度的重要生态指标,其变化对水分循环及全球气候变化有一定的影响和响应。以若尔盖县不同治理年限的沙化草地治理区为研究对象(包括1995年、2007年、2009年、2010年、2011年的治理区,2012年的正常放牧区和2012年的无治理区),采用野外采样和室内分析相结合的方法,将土壤含水量作为研究指标,结合土壤的理化性质,分析沙化草地在恢复重建过程中水源涵养功能的变化及其影响因素,结果表明:若尔盖草地在恢复重建过程中,(1)土壤质地发生变化,由紧砂土逐渐恢复成砂壤土,保水能力及保肥性都得到显著提高;土壤容重随着治理时间的增加而降低,由无治理区的1.7 g/cm~3下降到正常放牧区的1.3 g/cm~3;(2)土壤p H值随着治理时间的增加而逐渐降低,由7.6逐渐下降到6.7,土壤总体上为中性土,适宜植被生长;土壤有机质的变化相对不明显,但治理区的有机质远低于正常放牧区的土壤有机质,总体呈缓慢上升趋势;(3)土壤含水量呈"V"型变化趋势,在治理初期,土壤含水量先减小,2009年治理区的含水量最低,仅为6.8%,但到了治理后期,土壤的含水量开始增加,1995年的沙化治理区含水量达到了12.1%,说明水源涵养能力得到相应的提升;(4)经过相关分析,土壤含水量和有机质、土壤质地、土壤p H值、生物量以及土壤碳含量呈显著相关关系,其中,含水量与有机质、土壤质地以及土壤碳含量呈极显著正相关,而与p H值呈显著负相关;(5)随着治理时间的增加,土壤退化指数逐渐减小,土壤状况得到不断的改善。

Changes in water conservation and soil physicochemical properties during the recovery of desertified grassland in Zoigê, China

The restoration and reconstruction of desertified grassland has been continually initiated by the central government of China since 1995, and the ecological benefits of grassland restoration gained attention both home and abroad. In particular, the water conservation function of grassland is regarded as the primary indicator of the ecosystem''s restoration and is one of the most important grassland ecosystem services. Changes in water conservation are related to the water cycle and global climate change. The present study investigates the moisture and physicochemical properties of desertified grassland soil over several years (managed sample plot in 1995, 2007, 2009, 2010, and 2011; non-managed sample plot in 2012; and normal grazing area in 2012) in Zoigê County, using both field investigation and experiments to analyze the dynamics of water conservation and its determinants. During the recovery process, 1) Soil texture had changed that tight sandy soil was gradually converted to sandy loam, water conservation and fertilizer preservation capacity were increased, and bulk soil density decreased from 1.7 g/cm³ in the non-managed area to 1.3 g/cm³ in the normal grazing area. 2) Soil pH value decreased from 7.6 to 6.7 with the duration of management, and according to the classification of soil pH, the soil was neutral soil which was suitable for vegetation growth. Meanwhile, soil organic matter of the treatment areas was far lower than that of the normal grazing area, although the organic matter exhibited an upward trend. 3) Soil moisture exhibited a V-shaped trend that the content decreased in the early stage of management and the content of managed area in 2009 was lowest for only 6.8%. But in the late stage of management, the content increased from 6.8% to 12.1% in the managed area in 1995, in which the grassland had been restored and water conservation got improvement. 4) Correlation analysis indicated that soil moisture was significantly correlated with organic matter content, soil texture, pH, biomass, and soil carbon content, although the relationship between soil moisture and pH was negative. 5) As the duration of treatment increased, the soil degradation index decreased, and the soil conditions improved greatly.