Biological soil crusts are widely distributed in arid and semi-arid regions,whose formation and development have an important impact on the restoration process of the desert ecosystem.In order to explore the relations...Biological soil crusts are widely distributed in arid and semi-arid regions,whose formation and development have an important impact on the restoration process of the desert ecosystem.In order to explore the relationship between surface airflow and development characteristics of biological soil crusts,we studied surface airflow pattern and development characteristics of biological soil crusts on the fixed dune profile through field observation.Results indicate that the speed of near-surface airflow is the lowest at the foot of windward slope and the highest at the crest,showing an increasing trend from the foot to the crest.At the leeward side,although near-surface airflow increases slightly at the lower part of the slope after an initial sudden decrease at upper part of the slope,its overall trend decreases from the crest.Wind velocity variation coefficient varied at different heights over each observation site.The thickness,shear strength of biological soil crusts and percentage of fine particles at crusts layer decreased from the slope foot to the upper part,showing that biological soil crusts are less developed in high wind speed areas and well developed in low wind speed areas.It can be seen that there is a close relationship between the distribution of biological soil crusts in different parts of the dunes and changes in airflow due to geomorphologic variation.展开更多
Soil moisture is a critical state affecting a variety of land surface and subsurface processes. We report investigation results of the factors controlling vertical variation of soil moisture and sand transport rate of...Soil moisture is a critical state affecting a variety of land surface and subsurface processes. We report investigation results of the factors controlling vertical variation of soil moisture and sand transport rate of three types of dunes on the southeastern margin of the Mu Us Sandy Land. Samples were taken from holes drilled to a depth of 4 m at different topographic sites on the dunes, and were analyzed for soil moisture, grain-size distribution and surface sediment discharge. The results show that:(1) The average soil moisture varies in different types of dunes, with the following sequences ordered from highest to lowest: in the shrubs-covered dunes and the trees-covered dunes the sequence is from inter-dunes lowland to windward slope to leeward slope. The average moisture in the bare-migratory sand dunes is sequenced from inter-dunes lowland to leeward slope to windward slope.(2) Vegetation form and surface coverage affect the range of soil moisture of different types of dunes in the same topographic position. The coefficient of variation of soil moisture for shrubs-covered dunes is higher than that of other types of dune.(3) The effect of shrubs on dune soil moisture is explained in terms of the greater ability of shrubs to trap fine-grained atmospheric dust and hold moisture.(4) The estimated sand transport rates over sand dunes with sparse shrubs are less than those over bare-migratory dunes or sand dunes with sparse trees, indicating that shrubs are more effective in inhibiting wind erosion in the sandy land area.展开更多
基金supported by National Natural Science Foundation of China(Grant No.41201050)Scientific Re-search Funds of Institute of Water Resources and Hydro-power Research of China and National"Twelfth Five-Year"Plan for Science&Technology(2012BAD16B0202)
文摘Biological soil crusts are widely distributed in arid and semi-arid regions,whose formation and development have an important impact on the restoration process of the desert ecosystem.In order to explore the relationship between surface airflow and development characteristics of biological soil crusts,we studied surface airflow pattern and development characteristics of biological soil crusts on the fixed dune profile through field observation.Results indicate that the speed of near-surface airflow is the lowest at the foot of windward slope and the highest at the crest,showing an increasing trend from the foot to the crest.At the leeward side,although near-surface airflow increases slightly at the lower part of the slope after an initial sudden decrease at upper part of the slope,its overall trend decreases from the crest.Wind velocity variation coefficient varied at different heights over each observation site.The thickness,shear strength of biological soil crusts and percentage of fine particles at crusts layer decreased from the slope foot to the upper part,showing that biological soil crusts are less developed in high wind speed areas and well developed in low wind speed areas.It can be seen that there is a close relationship between the distribution of biological soil crusts in different parts of the dunes and changes in airflow due to geomorphologic variation.
基金funded by the National Natural Science Foundation of China (41140028, 41340043)the Central University Research Foundation, Chang'an University (310827152014)the State Key Laboratory of Loess and Quaternary Geology (SKLLQG)
文摘Soil moisture is a critical state affecting a variety of land surface and subsurface processes. We report investigation results of the factors controlling vertical variation of soil moisture and sand transport rate of three types of dunes on the southeastern margin of the Mu Us Sandy Land. Samples were taken from holes drilled to a depth of 4 m at different topographic sites on the dunes, and were analyzed for soil moisture, grain-size distribution and surface sediment discharge. The results show that:(1) The average soil moisture varies in different types of dunes, with the following sequences ordered from highest to lowest: in the shrubs-covered dunes and the trees-covered dunes the sequence is from inter-dunes lowland to windward slope to leeward slope. The average moisture in the bare-migratory sand dunes is sequenced from inter-dunes lowland to leeward slope to windward slope.(2) Vegetation form and surface coverage affect the range of soil moisture of different types of dunes in the same topographic position. The coefficient of variation of soil moisture for shrubs-covered dunes is higher than that of other types of dune.(3) The effect of shrubs on dune soil moisture is explained in terms of the greater ability of shrubs to trap fine-grained atmospheric dust and hold moisture.(4) The estimated sand transport rates over sand dunes with sparse shrubs are less than those over bare-migratory dunes or sand dunes with sparse trees, indicating that shrubs are more effective in inhibiting wind erosion in the sandy land area.
