Investigation of the Spatial Distribution and Multiple Ecological Functions of the Biological Soil Crusts in Mu Us Sandland
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【Author in Chinese】 李新凯；
【Supervisor】 卜崇峰（Li Sitian）；
【Author's Information】 中国科学院大学(中国科学院教育部水土保持与生态环境研究中心)， 环境工程（专业学位）， 2018， 硕士
【Abstract in Chinese】 生物结皮在维管植物生长受限的干旱、半干旱生态系统中广泛分布,在防止水土流失、调节土壤水文、促进土壤养分循环等生态系统功能方面发挥着重要作用。掌握生物结皮的空间分布及其生态功能,对合理评估生物结皮的贡献,对生物结皮资源的科学管理与保护具有重要意义。为从区域尺度上了解生物结皮的空间分布状况及其多种生态功能,本研究基于40个样地的样方调查和1个典型样地的定位监测,结合室内分析测定,获取了各样地的立地环境指标、生物结皮生长指标,以及监测小区的土壤水分和风蚀数据,系统探讨了毛乌素沙地生物结皮的空间分布状况及其对土壤养分、土壤水分和土壤风蚀的影响,并借助结构方程模型分析了环境因子对生物结皮的影响。主要结论如下:1)藻结皮和藓结皮在毛乌素沙地分布广泛,平均盖度分别为14.1%和11.3%,平均厚度分别为4.5 mm和7.5 mm;苔藓植物的平均株高度2.0 mm,平均生物量为2.2 g/cm~2。藓结皮盖度自西北向东南呈递增趋势,藻结皮在北部地区盖度较高并呈现出自北向南减小的趋势。苔藓植物生物量自西向东呈逐渐增加的趋势。2)地块尺度上:生物结皮多呈斑块状分布于水分条件较好的灌木林地、沙丘间低洼地,并呈现出不同的发育阶段;移动沙丘、沙化草场、农田以及城市内部等区域几乎不存在生物结皮。区域尺度上:藓结皮在东南部和东北部的沙地边缘地区为主导的生物结皮类型,而藻结皮在中部和西北部地区占主导;西南部地区生物结皮比较稀少。中西部地区藻结皮多为发育中期,北部、东部和南部沙地边缘的藻结皮均能达到发育末期;除西部少数地区,整个区域的藓结皮大多发育至中期和末期。3)毛乌素沙地的藻结皮和藓结皮均能提高结皮层及其下伏5 cm土壤层的有机碳、全氮和全磷含量。相较于植被下的裸地,藻结皮存在能够提高沙蒿下0-30cm土层以及柠条和沙柳下30-80 cm土层的水分含量;藓结皮存在能够提高3种灌木下方0-80 cm土层的水分含量。藻结皮和藓结皮覆盖后能够减少沙蒿、沙柳和柠条这3种灌木下方土壤的风蚀量。4)结构方程模型的分析显示,由坡度、坡向、海拔表征的地形因子以及放牧干扰因子与藻结皮生长状况、土壤因子、植被因子之间的相关性微弱;干燥度与植被盖度呈显著负相关,表明干旱对植物生长有抑制作用;干燥度与藻结皮生长状况之间呈不显著的负相关,干旱抑制植被生长可能对藻结皮生长产生间接影响。干燥度与藓结皮的生长状况之间呈显著的正相关,干旱抑制植物生长可能对藓结皮生长产生促进作用;植被盖度对藓结皮下伏5 cm土壤有一定的积极影响,藓结皮下伏5 cm的土壤状况与藓结皮生长状况之间呈不显著的正相关。
【Abstract】 The biological soil crusts are widely distributed in arid and semi-arid ecosystems where the growth of vascular plants are limited,which play important roles in many ecosystem functions including preventing water and soil loss,regulating soil hydrology and promoting nutrient cycling.Understanding the spatial distribution and ecological functions of biological soil crusts is of significance for the scientific management and protection of biological soil crusts and,for the valid assessment of the contribution of biological soil crusts.For getting hold of the growth conditions,spatial distribution and ecological functions of biological soil crusts,this research based on quadrat surveys in 40 sites and long-term monitoring experiment in the typical site in Mu Us Sandland,combined with analysis and measurement in the laboratory,which acquired the local environmental factors,growth factors of biological soil crusts and the data of soil moisture and wind erosion in the monitoring plots.The growth conditions and the spatial distribution of biological soil crusts,the influence of biological soil crusts on soil nutrition,soil moisture and wind erosion were investigated systematically,and the effects of environmental factors on biological soil crusts were analyzed by the structural equation model.The main conclusions are as follows,1)The algae and moss crusts widely contributing in the Mu Us Sandland,the average coverages of algae and moss crusts are 14.1%and 11.3%respectively,the average thicknesses of algae and moss crusts are 4.5 mm and 7.5 mm respectively;the average height of moss crust is 2.0 mm and the average biomass of moss crusts is 2.2 g/cm~2.The coverage of moss crusts appears to an increasing trend from the northwest to southeast,the coverage of algae crusts is higher in the north and decreases from north to south;the biomass of moss crusts increases form the west to the east.2)In the plot scale,the algae crusts and moss crusts within different development phases mostly distribute in the shrubland and the bottom land among the sand dunes where the water conditions are better than surrounding areas;there are almost no biological soil crusts in travelling dune,grassland of desertification,farmland,and other areas like inner city.In the regional scale,the moss crusts are dominant in the southeast and northeast of the frontier area,the algae crusts are dominant in the central and northwest;there are sparse moss or algae crusts in the southwest.The developmental phrase of algae crusts in the central and western region mainly are medium,the algae crusts in the northern,eastern and southern region are able to come up to late phrase;the moss crusts mainly come up to medium and late phrase in the whole area except part of regions in the western.3)The algae and moss crusts are able to increase the contents of organic carbon,total nitrogen and total phosphorus in the crusts and the soil of 5 cm below the crusts,which is benefit for increasing the soil nutrition in this area.The algae crusts can improve the soil moisture of 0-30 cm under Artemisia desertorum Spreng.,and 30-80cm under Caragana korshinskii Kom.and Salix mongolica C.;the moss crusts can increase the soil moisture of 0-80 cm under these 3 shrubs.The algae and moss crusts are able to reduce the soil loss by wind under Artemisia desertorum Spreng.,Caragana korshinskii Kom.and Salix mongolica C.4)The analysis results by the structural equation model reveal that,there is slight correlation among the landform factors represented by slope,slope and elevation,as well as the grazing disturbance,with algae crusts growth,soil factors and plant factors;there is a significant negative correlation between the aridity and plant growth,which means the drought has an inhibiting effect on plant growth;there is no significant negative correlation between the aridity and the growth of algal crust,the drought may has an indirect influence on the growth of algae crusts by restraining plant growth.There is a significant positive correlation between aridity and the growth of moss crusts,the drought may promote the growth of moss crusts by restraining plant growth;the coverage of plants has an negative impact on moss crusts growth;the coverage of plants has insignificant positive influence on the soil of 5 cm under moss crusts,while there is an indistinctive positive correlation between soil condition of 5cm under the moss crusts and moss crusts growth.