生物土壤结皮的斥水性特征及其潜在的生态效应研究

Soil water repellence (SWR) has significantly effects on the runoff and infilitration in surface soil, which had attracted many attentions in last decades. Our preliminary studies indicated that the colonization and development of the biological soil crusts in desert ecosystems can result in a significant increase in SWC degree of the soil surface. Thus,the hypothesis can be forwarded that increase of SWR of the crusts may possibly lead to an important modification on the eco-hydrological processes and play a significant role in maitaining a desert ecosystem with sparse shrubs. To deeply understand the the ecological functions of SWR in a desert ecosystem，the SWR properties of the biological soil crusts that developed in the revegetation enclosures with different ages will be systematically studied based on the experiment both in field and Laboratory in this study. The redistribution mechanisms of the mositure resulted by the SWR in the surface soil, as well as its effects on the stabilities of the sparse shrub communities will also be hopeflly clarified sensible with the achievements if the propoal was suppoted by the National Natural Science foundation of China. The achievement will also contributed to the breakthrough and fill the gap in the field of eco-hydrological function of the biological soil crust in a desert ecosystem.

土壤斥水性(SWR)能够显著地影响地表径流、降水入渗等生态水文过程，受到了广泛的关注。在荒漠生态系统中，生物土壤结皮的拓殖与发育，能够导致地表土壤斥水性程度的显著增加，并可能通过调控地表生态水文过程，维持稀疏灌木与结皮的"镶嵌"分布格局。基于过去三年的初步研究，本项目将依托中科院沙坡头沙漠研究试验站，以腾格里沙漠东南缘人工植被区及临近天然植被区典型土壤结皮的斥水性特征为研究对象，采用野外观测与室内控制试验相结合的方法，研究不同类型生物土壤结皮的斥水性特征，评估结皮发育对地表斥水性的影响程度，揭示结皮发育过程中土壤性质及土壤环境因子对地表斥水性的影响机理，阐明斥水性程度对雨后土壤水分时空分布的调控作用，系统分析结皮斥水性对地表生态水文过程的影响，揭示生物土壤结皮的斥水性特征对荒漠生态系统稳定性的影响机理。研究结果有望基于一个相对新颖的视角，丰富荒漠地区生物土壤结皮的研究内容。

以腾格里沙漠南缘人工植被区及典型的白刺灌丛沙堆不同发育程度的生物土壤结皮为研究对象，对植被-土壤系统演替过程中土壤斥水性特征进行了探讨，发现了随着生物土壤结皮发育程度的提高，土壤斥水性特征出现明显变化。土壤斥水性随沙丘固定时间增加而呈增强.不同粒径段土壤斥水性差异显著，随着粒径的不断增大，土壤斥水性呈减小趋势。植被区土壤斥水性的增加可能与大气降尘在固定沙丘表面不断沉积、生物土壤结皮形成，尤其是藻类和地衣的形成有关，斥水性的增强将影响到植物种在沙丘上的有效水分利用。不同演替阶段的白刺灌丛沙堆表层土壤斥水性不同，表现为，极端退化阶段＞开始退化阶段＞稳定阶段＞发育良好阶段>新发育阶段＞流沙。影响土壤斥水性的因子有很多，有机质含量、全氮含量能显著增加土壤斥水性，而全磷的含量并不会影响土壤斥水性的大小。土壤质地是土壤斥水性的关键影响因子，粘粉粒含量增加能显著增加土壤斥水性，而砂砾含量的增加却显著的降低了土壤斥水性。较低的Ph值更有利于土壤斥水性的发生。K+、Ca2+、Mg2+、Na+四种阳离子以及cl-、SO42-两种阴离子能显著增加土壤斥水性。然而，CO32- 离子的存在能减弱土壤斥水性。此外HCO3-离子的存在并不会影响土壤斥水性。