Gully erosion is an important environmental hazard in the black soil region of northeastern China. It is a primary sediment source in the region which needs appropriate soil conservation practices. Gully incision in rolling hills typical of this region was monitored using real-time kinematic GPS to assess the rates of gully development and the resultant sediment production. From 2002 to 2005, gully heads in the study area retreated between 15.4 and 33.5 m, giving an average retreat rate of 8.4 m yr− 1. Field measurements showed that total sediment production due to gully erosion during the three years ranged between 257 and 1854 m3 yr− 1, which is equivalent to 326 to 2355 t yr− 1, with gully-head retreat accounting for 0 to 21.7% (4.4% in average). The sediment delivery ratio was especially high during the summer rainy season (56% in average). Sediment production by ephemeral gullies and permanent gullies was 1.5 times greater than that from surface erosion. Gully heads retreated faster in the spring freeze–thaw period than in the summer. The stage of gully development could be identified based on short-term changes in the gully erosion rate. 相似文献
为了探究施氮对土壤有机质(SOM)的激发效应,本研究在施氮梯度样地(0、4和16 g N m–2 yr–1)上进行了13C标记葡萄糖的原位添加实验,并对土壤CO_2排放量和磷脂脂肪酸(PLFA)含量进行了测定。研究发现施氮降低了土壤CO_2排放、土壤PLFA含量以及土壤真菌细菌比。在0 g N m–2 yr–1样地上葡萄糖添加导致的正向激发效应最强,同时4 g N m–2 yr–1样地释放的葡萄糖来源的碳最多。因此,施氮减少了土壤中SOM转化产生的CO_2,微生物碳的来源由SOM转变为添加的易分解碳。本研究采样早期土壤微生物生物量和群落结构稳定,表明该草原存在"表观激发效应",因此未来研究应着重对微生物功能的多样性进行探讨。 相似文献