Study on soil nutrients and moisture as well as soil microorganism at grassland-forestland interface in gully region of Loess Plateau

chinois. 对黄土高原沟壑区林草景观界面（包括林地、草地和林-草界面3种生态系统）土壤的养分（有机质、氮、磷、钾和pH）含量、水分含量和微生物（细菌、真菌和放线菌）数量进行测定，分析比较了其养分、水分和微生物分布特征。结果表明，林草景观界面3种生态系统土壤养分分布不平衡，有机质、全氮、水解氮和速效钾在0~40 cm土层的平均含量为林地＞草地＞林-草界面；全磷平均含量为林地＞林-草界面＞草地；速效磷平均含量为草地＞林地＞林-草界面；全钾平均含量和pH为林-草界面＞草地＞林地；各种养分含量在各生态系统土壤剖面中有明显的层次性，表层0~20 cm土层的养分含量基本上高于20~40 cm土层；不同土层的土壤水分在水平方向上,随着水平距离梯度的变化表现出上升或下降的趋势，草地和林地内水分变化不显著，而在林-草界面内不同距离梯度上的含水量变化极显著；随着土层深度的增加，土壤平均含水量在草地区逐渐升高，在刺槐林地中呈逐渐降低趋势，而在林-草界面区域则表现为先降低后升高的趋势；林草景观界面下土壤中各种微生物数量存在明显差异，在总体数量上均以细菌为主，占微生物总量的98%以上，微生物总数量为林-草界面＞草地＞刺槐林地；微生物数量的垂直动态明显，林-草界面和草地0~20 cm土层数量较20~40 cm土层显著增多，而林地0~20 cm土层微生物数量少于20~40 cm土层。

anglais. The content of soil nutrients and moisture as well as microorganisms quantity at the landscape interface of forestland-grassland in gully region of Loess Plateau were studied. The results showed that soil nutrients were unevenly distributed and there was obvious hierarchy characteristics in forestland, grassland and forestland-grassland; with changing horizontal distances, soil moisture showed increasing or reducing tendency between different soil layers in horizontal direction, and the soil moisture variation in forestland and grassland was insignificant but significant at the forestland-grassland boundary; the mean soil moisture content increased with the increasing of soil depths in grassland but reduced in forestland while and showed a tendency of increasing first then reducing in grassland-forestland interface; the populations of soil-inhabiting microorganisms under the interface presented different for different kinds; the total amounts of microorganisms in forestland-grassland were higher than those in forestland and grassland. In addition, the amount of microorganism in 0-20 cm soil layer was significantly much more than that in 20-40 cm, and the microorganisms amounts changed a lot in vertical distribution.