Formation Of Litter Crusts And Its Ecological Effects In The Sandy Land Of Thewind-water Erosion Crisscross Region

Land desertification is one of the major problems of global environmental change,and is a matter of great concern to scientists and policy makers.The Mu Us Desert is a representative area affected by wind and water erosion.The degradation of soil and vegetation has substantially damaged the stability of ecosystem functions.Litter crust plays an important role in vegetation restoration and management in sandy ecosystems.In this study,the litter crusts in the water-wind erosion crisscross region of the northern Loess Plateau were studied.The characteristics of soil surface micro-habitat,soil properties,seedling establishment and microbial community diversity in litter crusts were studied,to reveal the ecological effects of litter crust.The study aim to provide a new idea for desertification control and ecological restoration in sandy land.This study has the following main conclusions:(1)The formation of litter crusts in sandy land significantly improved the sand surface microhabitat and promoted the establishment of seedlings.Compared with the bare sand,the sand surface soil moisture in the 0-5 cm soil layer was increased by an average of 17.0%,and the soil temperature was decreased by an average of 16.6%,indicating that the litter crusts had better water retention and temperature regulation functions.Litter crusts significantly changed the sand surface soil physical and chemical properties.Compared to the bare sand,the soil water storage increased by an average of 53.3%,the soil total porosity increased by an average of 16.3%,and the soil organic matter content increased by an average of 77.5% and 80.8% in the 0-5 cm and 5-10 cm soil layer.Litter crusts provided favorable micro-habitat conditions for seedling colonization,so the richness,coverage and plant height of the seedlings on the litter crusts are about 3.5 times,3 times and 2.5 times than bare sand,and are increased by 41.7%,46.5% and 28.2% than biocrusts,respectively.(2)Litter crusts significantly improved the sand surface soil structure and soil fertility,and became the driving force for promoting the development of sandy soil to loamy soil.The results showed that with the increase of litter crusts age,the content of silt and clay in the surface soil significantly increased,but the content of sand decreased.At the same time,litter crusts increased the content of large-size aggregates and the total porosity of the surface soil,and changed the surface soil structure to achieve water retention.Due to the decomposition of litter crusts,the soil organic matter content increased significantly,and a large amount of nutrients such as N,P and K nutrients are input into the surface soil.In the 0-5 cm soil layer,the soil available phosphorus concentration under 5 years and 3 years litter crusts were about 94% and 71% higher than that of bare sand,respectively.The soil available potassium concentration was richest in the 5 years litter crust,followed by 3 years litter crust,1 year litter crust,biological crust and bare sand.With the development of litter crusts,their positive effects on surface soil properties become more significant.(3)Litter crust significantly enriched the diversity of sand surface soil microbial communities.Compared with bare sand,the diversity and richness of microbial community under litter crusts were significantly improved.With the increase of litter crusts age,the Shannon diversity index of the microbial communities increased gradually,and reached the highest in the 5 years litter crusts.The microbial community diversity index and abundance index showed significant positive correlations with sand surface soil available potassium,available potassium,total nitrogen and soil porosity(P < 0.05),and showed significant negative correlations with soil bulk density(P < 0.05),indicating there were significant correlations between sand surface soil micro-habitat factors and the diversity of microbial communities.Litter crusts in the sandy land is a typical crust type of the water-wind erosion crisscross zone.Compared with bare sand and biological crusts,the formation of litter crusts significantly changed sand surface soil structure and fertility,improved the water retention and temperature regulation,enriched the diversity of soil microbial communities.Litter crusts has become an important driving force for the evolution of sandy soils to loamy soils.The existence and development of litter crusts are of great significance for the management and restoration of sandy ecosystems in the water-erosion wind erosion crisscross region.