若尔盖湿地退化过程中土壤水源涵养功能μ

Dynamics of soil water conservation during the degradation process of the Zoigê Alpine Wetland

若尔盖湿地是青藏高原上面积最大的沼泽湿地,也是长江、黄河两大河流的水源区,对区域水循环起重要调节作用。近年来在全球变化及放牧的影响下,若尔盖湿地出现了不同程度的退化。为了查明若尔盖湿地退化过程中水源涵养功能的变化趋势,2009年8月对该区域的沼泽草甸、草原草甸和沙化草甸3个阶段的土壤水源涵养功能进行了调查。结果为:若尔盖湿地由沼泽草甸向草原草甸和沙化草甸的退化过程中,土壤容重显著增加(P<0.01),毛管孔隙度和总孔隙度显著下降(P<0.01),且容重和孔隙度在土壤剖面自然分布规律也发生变化;沼泽草甸的土壤自然含水量、毛管持水量、最小持水量和最大持水量均显著高于草原草甸和沙化草甸(P<0.01);0—100 cm深度范围内的沼泽草甸土壤的最大持水量(8486.27 t/hm2)显著高于草原草甸(4944.98 t/hm2)和沙化草甸(4637.96 t/hm2)(P<0.01)。土壤持水量与有机质含量、毛管孔隙度和总孔隙度有显著正相关(P<0.01),与土壤容重呈显著负相关(P<0.01),并受植被盖度和泥炭层厚度的影响。研究结果表明,若尔盖湿地退化过程中植被盖度、土壤有机质含量及泥炭层厚度的下降和土壤质地沙化是导致若尔盖湿地水源涵养功能下降的主要原因。

Zoigê wetland,located on the eastern Qinghai-Tibetan Plateau,is the largest area alpine wetland and headwaters of Yangtse Rive and Yellow River,and plays an important role in the water cycling.But in recent decades,Zoigê wetland degraded seriously under the influence of global change and human disturbance.The investigations were conducted at three degradation stages of swampy meadow,grassland meadow and sandy meadow to study the dynamics of soil water conservation functions during the alpine wetland degradation progress.The result showed that：（1） the soil bulk density increased significantly（P〈0.01）,and the capillary porosity and total porosity decreased significantly（P〈0.01） during the alpine wetland degenerating from swampy meadow to grassland meadow and sandy meadow,with change of vertical distribution along soil profile,（2） significant decreases（P〈0.01） were recorded in the natural water holding-capacity,capillary water-holding capacity,minimum water-holding capacity and maximum water-holding capacity during the degradation process;（3） the maximum water-holding capacity within 0—100 cm soil depth significantly reduced（P〈0.01） from 8486.27 t/hm2 of swampy meadow to 4944.98 t/hm2 of grassland meadow and 4637.96 t/hm2 of sandy meadow and（4） the soil water-holding capacities are positively correlated（P〈0.01） with the soil organic material content,capillary porosity and total porosity,but negatively with soil bulk density（P〈0.01）,as well as influenced by plant coverage and depth of peat soil indirectly.These results indicated that the degradation of Zoigê alpine wetland can led to the decline of soil water conservation function and the decreases of plant coverage,soil organic material and peat soil depth are the basically reasons for the reduce of water conservation function.