| The Loess Plateau is one of the most serious areas of vegetation degeneration and soil erosion,the development of biological soil crusts play an important roles in preventing water loss and soil erosion,improving soil physical and chemical properties and protecting the ecological vegetation,however,some parts of the biological soil crusts have been seriously damaged and even disappeared large area by human activities.In order to realise the development of biological soil crusts on the function process of soil fertility and provide technical guidance purport for the planting and reconstruction of biological soil crusts in the process of degraded ecosystem restoration of the Loess Plateau.This study selected the biological soil crusts of typical grassland on the Loess Plateau as the research object,studied the development of biological soil crusts and the characteristics of microenvironments soil nutrients and the releationships between the distribution of biological soil crust and microhabitats soil nutrients,at the same time,contrast analyzed the development of biological soil crusts and the soil nutrients characteristics of the microenvironments between fenced and grazed.The main conclusions are as follows:(1)The existence of different biological soil crust resulted in the varies of microenvironment cortex soil nutrients enrichment characteristics,the contents of moss layer soil SOC,TN,TP,Na,Ca,Mg,Cu and Zn existed significant enrichment phenomenon,while AN and AP contents of algae cortex had obvious enrichment phenomenon.In addition,the biological soil crusts layer soil SOC,TN,the AN contents with TP and AP all showed the significant positive correlations relationships each other,but SOC and TN with K and Ca were significantly negative correlations,respectively;the subcutaneous layer of SOC,TN,AN,TP and AP with K showed the significant positive correlations(except AP-AN and AP-K).(2)The differences of different biological soil crusts organisms on the absorption and enrichment of elements in the environment,The contents of TP,Na,K,Cu,Fe,Mg,Mn and Zn in mosses organisms were significantly higher than that of lichens,and Ca contents was lower than that of lichens organisms significantly;meanwhile,the bioaccumulation effects of mosses organisms on TN,TP,Cu and Zn were higher,while the bioaccumulation effects of lichens organisms TN,TP and Ca were higher.In addition,moss crusts corresponding TN contents in the soil was significantly higher than that of lichen crusts,and TP,Na,K,Ca,Cu,Fe,Mg,Mn and Zn contents of lichen crusts corresponding soil had no obvious differences.However,between the development coverage of biological soil crusts and its corresponding soil nutrients contents had no significant linear relationships.(3)The development of different soil crusts on fenced and grazed disturbance response was consistent,all showed the biological soil crusts coverage of fenced were significantly higher than grazed,and the biological soil crusts thickness and biomass had no significant difference.However,the biological soil crusts cortex and its subcutaneous layer of soil nutrients contents of fenced and grazed was not the same,the contents of algae cortex soil SOC,TN,Ca,Cu and Zn and the subcutaneous layer of SOC,TN,K,Fe,and Zn contents in the fenced were significantly higher than that of grazed,and the contents of TP and Na of fenced were lower than grazed significantly.Moss layer soil Fe,Mg and Zn contents in the fenced were significantly higher than that of grazed,and the contents of TP and Ca were significantly lower than grazed,and subcutaneous layer soil SOC,TN and Fe content was significantly higher than that of grazed,but the contents of TP,Na,K,Ca,Cu,Mn and Zn were significantly lower than the grazed.In addition,fenced or grazed,there was a positive correlation relationships of the algae cortex SOC with TN,TP,Na,K,Mn,respectively;but negatively correlated relations with Ca;Moss cortex Mg,Mn and Zn were positively correlated with SOC,respectively;yet,negatively related with TN. |
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