中文摘要：

基于课题组已有研究成果,选取陕北水蚀风蚀交错区内气候条件相同但土壤质地迥异的试验区,探讨黄土地和沙地生物结皮发育特征及其生态效应的异同。结果表明：（1）苔藓结皮是2种土地生物结皮的重要类型,其中,黄土地的优势藓种为尖叶对齿藓[Didymodon constrictus（Mitt.）Saito.]、真藓（Bryum argenteum Hedw.）、狭网真藓（B.algovicum Sendt.）;沙地的优势藓种为黄色真藓（B.pallescens Scheich.）、弯叶真藓（B.recurvulum Mitt.）、银叶真藓（B.argenteum Hedw.）。沙地乔灌植物下生物结皮盖度（77.5%）、厚度（11.8 mm）及容重（1.9 g·cm^-3）均高于黄土地生物结皮,而黄土地多年生草本植物下生物结皮抗剪强度（26.5 k Pa）高于沙地生物结皮,总体上,沙地生物结皮发育的更好。（2）黄土地的入渗增幅和0-200 cm剖面的平均土壤含水率增幅均显著高于沙地（P〈0.05）,且在旱季和雨季其0-200 cm剖面的平均土壤含水率增幅分别比沙地高1.4%和1.9%。（3）两地生物结皮均表现出了较好的减蚀作用,其减蚀效率分别为81.0%和90.6%。

英文摘要：

Biological soil crusts play an important role in arid and semiarid ecosystems. Based on the available research achievements of our team,the experimental areas with the similar climatic conditions and different soil textures in the wind-water erosion region on the Loess Plateau were selected to study the similarities and differences of development and ecological functions of biological soil crusts between loessland and Mu Us sandy land. The results are as follows：（1） The main biological soil crust species in both loessland land and sandy land were moss crusts.The species composition of moss crusts were Bryum argenteum Hedw.,B. caepititicium Hedw. and B. algovicum Sendt. in loessland,but the B. pallescens,B. recurvulum and B. argenteum in sandy land. The highest coverage of biological soil crusts under arbor-shrub vegetation was 77. 5% in sandy land,and the lowest one under perennial herbs was 50. 5% in loessland. In sandy land the thickest biological soil crust under annual herbs was 11. 8 mm,and the thinnest one under perennial herbs was 9. 5 mm; the highest shear strength of biological soil crusts under perennial herbs in loessland was 26. 5 k Pa,and the lowest one under perennial herbs in sandy land was 3. 5 k Pa; the highest density of biological soil crusts under annual herbs in sandy land was 1. 9 g·cm^-3,and the lowest one under perennial herbs in loessland was 1. 1 g·cm-3;（2） When the values of precipitation in loessland and sandy land were8. 0 mm and 40. 5 mm respectively,the soil infiltration rate in loessland was significantly higher than that in sandy land,but for the total infiltration（ sum of increased soil moisture）,there was no significant difference between loessland and sandy land;（3） The average increase of soil moisture content at 0-200 cm soil profile in loessland was1. 4% and 1. 9% higher than that in sandy land;（4） Whether there were herbs or not,biological soil crusts had positive effects on soil loss reduction in both loessland and sandy land,and the highest contrib