中文摘要：

【目的】分析黄土丘陵区不同类型生物结皮的发育特征及土壤微生物的分布特征,以明确生物结皮形成过程对土壤微生物的影响。【方法】采用野外调查和室内分析相结合的方法,调查黄土丘陵区浅色藻结皮、深色藻结皮、藻＋少量藓结皮、藓＋少量藻结皮及藓结皮5类生物结皮的发育特征,并测定生物结皮层及结皮下0~2cm土层的土壤微生物数量和化学性质,最后分析了不同生物结皮发育特征和土壤化学性质与土壤微生物数量之间的相关性。【结果】研究区浅色藻结皮、深色藻结皮、藻＋少量藓结皮、藓＋少量藻结皮及藓结皮的结皮厚度分别为1.13,3.26,6.31,8.91,12.61mm,藻盖度分别为100%,98.67%,71.61%,27.33%,7.80%,藓盖度分别为0%,0.80%,24.90%,65.87%,81.30%。不同类型生物结皮土壤细菌数量占微生物总数的比例为53.12%~72.09%,放线菌所占比例为27.49%~46.80%,真菌所占比例为0.08%~0.92%。在生物结皮层,土壤微生物总数和细菌数量从浅色藻结皮到藓结皮总体呈增加趋势,藓结皮土壤细菌、放线菌和真菌数量显著高于其他生物结皮;在结皮下0~2cm土层,土壤微生物总数和放线菌数量表现为藓结皮〉浅色藻结皮〉深色藻结皮〉藓＋少量藻结皮〉藻＋少量藓结皮,藓结皮土壤细菌、放线菌和真菌数量显著高于其他生物结皮。在生物结皮层,藓结皮土壤细菌比例较藻结皮有所增加,放线菌比例相应减少,藓结皮真菌比例最高;藓结皮下0~2cm土层真菌比例显著大于其他生物结皮。垂直分布上,生物结皮层土壤细菌数量和比例、真菌数量和比例均大于结皮下0~2cm土层,但放线菌数量和比例小于结皮下0~2cm土层。在生物结皮层和结皮下0~2cm土层,不同类型生物结皮土壤化学性质存在明显差异。生物结皮层微生物总数、细菌数量和比例、真菌数量与藓盖度和结皮厚度呈显著或极显著正相关关系,放线菌比

英文摘要：

[Objective] This study explored the developmental characteristics of different biocrusts in moss crust were higher than the other biocrustal types. In 0--2 cm soil layer, the quantity of total microor- ganisms and actinomycetes were showed like moss crust 〉light cyanobacteria crust〉dark cyanobacteria crust〉moss with tiny cyanobacteria patches crust〉cyanobacteria with sparse moss crust,the quantity of bacteria,actinomycetes and fungi in moss crust were higher than the other biocrustal types. Bacterial ratio of moss crust in biocrust layer was higher than cyanobacteria crust, while actinomycetes ratio was differ- ent. The fungi ratio in moss crust was higher than in other types. In soil layer of 0--2 cm, there was no sig- nificant difference in ratio of bacteria and actinomycetes between biocrustal types,except that in moss crust was higher than in other types. The quantity and ratio of bacteria and fungi in biocrust layer were higher than that in 0--2 cm soil layer, but those of actinomycetes were opposite. In biocrust and 0--2 cm soil lay- er, significant differences were found in soil chemical properties between different biocrusts. Total microbial quantity, bacterial quantity, fungal quantity, and bacterial ratio were significantly positively correlated with moss coverage and biocrustal thickness. Actinomycic ratio was significantly negatively correlated with moss coverage and biocrustal thickness. The quantity of total microorganisms, bacteria and fungi, and ratios of bacteria and fungi were positively correlated with soil organic carbon, total nitrogen, ratio of carbon to ni- trogen, and electrical conductivity, while the quantity of bacteria and fungi, and the percentage of bacteria and fungi were negatively correlated with soil pH. [Conclusion] Biocrusts had significantly effects on quan- tity of microorganisms in the semi-arid region. Compared with other biocrust types, moss crust significantly increased soil microbial quantity.