Influence Of Biological Soil Crusts On Soil Moisture In Artemisia Ordosica Community In The Mu Us Desert

Biological soil crusts(BSCs)are widely distributed in Artemisia ordosica community in the Mu Us Desert.They have been proved to play vital hydrological and ecological roles in desert ecosystems.Whereas,how the BSCs influence hydrological processes remains uncertain and controversial.This study conducted a field experiment with two treatments(undisturbed and removed)for two kinds of BSCs(lichen crusts and moss crusts)in A.ordosica community in the Mu Us Desert.Soil infiltration,evaporation and soil water volume in crust-covered and crusts-removed soil were compared.The results are as follows:(1)Both Lichen crusts and moss crusts had an effect on restraining water from infiltration,and the inhibitory effect of lichen crusts was greater.These two kinds of BSCs both decreased the initial infiltration rate,the stable infiltration rate and the cumulative infiltration(P<0.05).They also extended the response time of the soil to water infiltration and shallowed the response depth.Under the experimental conditions,the model "Horton" applied greatly to the infiltration processes.The simulate effect of "Philip" model took the second place.The simulate effect of "Kostiakov" model was the worst.(2)The influence of BSCs to soil evaporation was related to the kind of biological crusts and evaporation stages and it was limited by rain conditions.The impact of lichen crusts on soil evaporation was lower than expected.Under different rainfall conditions,the impact of lichen crusts on the rate of soil evaporation and cumulative evaporation was not obvious(P>0.05).Moss crusts promoted soil evaporation under small-size rainfall conditions(2 mm?5mm)(P<0.05).They did not affect evaporation when rainfall condition was 10 mm.While under the conditions of middle-size rainfall(20 mm)and heavy rainfall(30 mm),moss crusts inhibited evaporation with high water content and promoted evaporation with low water content.They had an ability of delaying soil evaporation.In addition,moss crusts reduced the amount of evaporation slightly and had an ability of holding water.(3)BSCs could affect the distribution pattern of soil moisture and the effect was related to the kind of BSCs.Generally,the soil moisture above 40 cm depths under crust-covered soil was higher than that in crusts-removed soil,but opposite in moss soil.The soil moisture at each layer above 40 cm depths in crust-covered soil was higher than that in crust-removed soil.Compared with the crusts-removed soil,soil moisture in crusts soil was higher at 5 cm and 10 cm,but lower at 20 cm and 40 cm.In addition,the influence of BSCs on the soil moisture was limited by rainfall variation of years.The influence on Lichen crusts was more obvious,while that on moss crusts is less.The results indicate that lichen crusts should be reserved with no disturbance.The moss crusts should bereserved or disturbed need further discussion.The results highlight the different hydrological roles of lichen and moss crusts and provide important implications for the management of soil water resource in semiarid areas of Northwest China.