生物土壤结皮对黄河源区人工草地植被与土壤理化性质的影响

为探讨高寒地区生物土壤结皮（Biological Soil Crusts，BSCs）在人工草地演替中的生态作用，揭示其对人工草地植被与土壤养分恢复的影响规律。本研究选择在青海省玛沁县5个建植年限（18，14，11，4，和1年）的人工草地，调查各年限草地中BSCs的分布情况，以及BSCs的特征与植被分布特征和土壤理化性质的关系。结果表明：不同建植年限人工草地中BSCs的类型、盖度、厚度各不相同，较长建植年限人工草地中BSCs的多样性大、种类多，主要包括苔藓、地衣以及藻类，而建植年限短的人工草地中仅分布少量的苔藓，但厚度较大。BSCs盖度与禾本科（Gramineae）植物盖度、密度以及地上生物量显著正相关（P<0.05），但与植被平均高度以及0~10 cm地下生物量显著负相关（P<0.05）。BSCs能调节pH，对累积土壤养分有明显作用，能显著增加建植年限长（14和18年）的人工草地中表层（0~5 cm）土壤速效养分以及建植年限短（1和4年）的人工草地中的全效养分含量（P<0.05）；在建植年限短的草地中，BSCs可减小（P<0.05）土壤粒径，增加（P<0.05）土壤细颗粒（细砂粒、黏粉粒）含量。本研究揭示，建立人工草地有利于增加BSCs盖度、厚度以及多样性，同时BSCs对人工草地地上生物量的增加和土壤结构和养分的恢复具有重要意义。

Effects of Biological Soil Crusts on the Physical and Chemical Properties of Soil and Vegetation of Artificial Grassland in the Yellow River Source Zone

In order to explore the ecological functions of biological soil crusts (BSCs) and reveal BSCs-triggered soil nutrient changes in artificially restored grasslands,BSCs properties in artificial grasslands of five restoration periods (18,14,11,4 years and 1 year) were studied in relation to plant distribution,soil physical and chemical properties in Maqin County,Qinghai Province. The main results were as follows:The species,coverage and thickness of BSCs were different in grasslands of different restoration years. There was a high diversity of BSCs such as mosses,lichens and algaes in the grasslands of a long restoration period,but the proportion of mosses was lower in the grasslands of a short recovery period. BSCs coverage was positively correlated with grass coverage,density and aboveground biomass (P<0.05),but negatively correlated with average height of vegetation and 0~10 cm underground biomass (P<0.05). BSCs exerted a significant effect on cumulative soil nutrient and regulating soil pH. They could increase the content of soil available nutrients significantly in the surface layer (0~5 cm) in the artificial grasslands of a long recovery period,and the total nutrients in the artificial grassland of a short restoration period (<4 years) (P<0.05);They could reduce the soil particle size and significantly increase the content of soil fine particles (fine sand,clay powder),especially in artificial grasslands of short restoration lengths (eg.1 and 4 years). Therefore,the establishment of artificial grassland is conducive to the recovery of BSCs coverage,thickness and diversity,and BSCs can also promote the productivity and improve soil quality of restored artificial grasslands.