Study On Plant-Hydrological Effects Of Biological Soil Crusts

Biological soil crust plays an important and crucial role in the dynamics and distribution pattern of desert steppe vegetation.Clarifying the plant and hydrological effects dominated by biological soil crusts has extremely important theoretical and applied research value for understanding the stability mechanism of desertified grassland in desert steppe.Artemisia scoparia is a dominant species in the study area,and it is also a typical 1-year-old shallow root plant.It analyzes the dynamic changes of root growth and soil moisture under the cover of biological soil crust,which helps to clarify the study of Artemisia scoparia.The adaptive mechanism of dominant species in the area can also be used as an indicator plant to better understand the plant and hydrological effects of soil crusts in desert steppe.Based on this,we compared the soil hydrological and physical characteristics of the surface layer with or without crust,the growth dynamics and size of the roots of Artemisia scoparia,and the change of water source.The main findings and conclusions are as follows:(1)Effects of Biological Soil Crust on Hydrological and Physical Characteristics of Surface Soil:Compared with the non-crust covering,the moisture content of the crust layer in the surface soil with crust cover showed a diametrically opposite pattern in the dry season and the rainy season.The water holding effect was mainly in the small precipitation,and the summer evaporation was strong.Typically,the relative water holding effect of the crust that enters the rainy season is weakened or even lost.Due to the seasonal conversion of biological crust activity,surface soil bulk density,saturated water content and total porosity have changed to varying degrees on seasonal scales.Whether in the dry season or the rainy season,the presence of biological crust reduces the soil water infiltration performance,and the soil water infiltration rate in the rainy season is lower than that in the dry season with or without crust cover.(2)Effects of Biological Soil Crust on Morphology and Growth of Shallow Roots of Artemisia scoparia:The changes of the morphological indexes of the roots of the genus Artemisia argyi in the whole growing season with different skin layers were observed.It can be seen that the root weight of the roots of the genus Artemisia serrata in the fixed volume increased with the increase of drought degree in the dry season in May and June.The root length,surface area,volume,number of root tips and number of branches showed an increasing trend,and all indicators reached the maximum value of the whole growing season,entering the rainy season from the dry season(June)(July)The root morphological index values of Artemisia scoparia were sharply reduced.In July,August and September,only the root weight showed an increasing trend with the increase of the month.The other indicators showed no obvious trend.The presence or absence of crust covering had a certain effect on the growth of roots and the morphological indexes of Artemisia scoparia On the whole,the dry weight,root length,root surface area,volume,number of root tips and branches of the roots of Artemisia scoparia in different soil layers without crust cover were larger than those with crust cover,especially in June.Most significant(P<0.05).At the beginning of the rainy season,the indicators of roots under different skin layers in July,August and September were not significantly different Bio-soil crust significantly changed the surface soil environment and the response of the root system of Artemisia scoparia.In the dry season,compared with the crust-covered area,the C.sinensis under the crust-free cover extended the root length,increased the root surface area and increased the root.The number of peaks and the number of branches are adapted to this more arid environment and exhibit better morphological plasticity.(3)The effect of biological soil crust on the water source dynamics of Artemisia scoparia:Overall,whether in the dry season or the rainy season,the water source of Artemisia scoparia was concentrated in shallow soil(2-30 cm soil layer)with or without crust cover.Among them,under the condition of crust cover,the water use efficiency of the dry season was 55.1%,the coefficient of variation was the lowest(111.6%),followed by the biological soil crust(22.5%).After entering the rainy season,The surface soil moisture condition was significantly improved.Although the water source of Artemisia scoparia was still concentrated in shallow soil(53%),the contribution rate of soil soil crust water decreased significantly from 22.5%to 9%.For deep soil and The water use efficiency of the parent layer increased from 13.8%and 8.6%in the dry season to 20%and 18%,respectively.On the whole,under the condition of crust cover,from the dry season to the rainy season,the concentration of water sources of Artemisia scoparia extends from the biological soil crust layer and the shallow soil layer to the shallow soil layer and the deep soil layer.Relatively speaking,under the condition of no crust cover,the water source structure of the dry season of Artemisia scoparia showed a more concentrated pattern.The water use efficiency of the shallow soil reached 83%,and the coefficient of variation was the lowest(18.65%).The water use efficiency of the soil crust layer is only 5%;after entering the rainy season,the water source structure of Artemisia scoparia has changed significantly,and the water use efficiency of the biological soil crust layer has risen to 22.4%,while the water use efficiency of the shallow soil has decreased.At 39.4%,the water use efficiency of the deep soil and the parent layer was also significantly improved;the overall showed a change in the water use pattern from the concentrated season in the dry season to the rainy season.