Discussion on wind factor influencing the distribution of biological soil crusts on surface of sand dunes

摘要

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.