桂西北喀斯特地区不同土地利用方式土壤的有机碳含量及养分特征

分析喀斯特峰丛洼地次生林(CL)、灌草丛(GC)、牧草地(MC)、玉米地(YM)共4种典型土地利用方式下土壤的有机质含量及养分特征，探讨不同土地利用方式对土壤养分含量的影响。结果表明：0~30 cm土层土壤有机碳、全氮含量随土地利用强度的增加而降低，与YM土壤相比，CL土壤的有机质含量高38.5%~100%，全氮含量高63%~130%(P<0.05)；4种土壤的全磷含量间差异和全钾含量间差异均达极显著水平(P<0.01)；速效磷含量受土地利用方式影响明显，CL土壤的速效磷含量最低，GC土壤的次之，YM土壤的最高；速效钾含量受植被覆盖和水土流失状况的影响较明显，CL土壤和GC土壤的速效钾含量均高于MC土壤和YM土壤的；土地利用方式是影响土壤有机碳、全氮、全磷、速效钾等养分含量变化的重要因素，不同土地利用方式下，土壤氮、磷、钾养分含量间的差异达显著水平(P<0.05)；耕作、施肥等人类活动使土壤养分含量发生变化，从而导致土壤退化，而植被恢复等措施可以培肥土壤。

Soil organic carbon and nutrients content at different land use types in the in the karst region of Northwest Guangxi

Four land use types (secondary forest land (CL), shrub land (GC), pasture land (MC) and corn field (YM)) were selected to research their effects on soil organic carbon and nutrients in karst region at Northwest of Guangxi province. The results showed that the content of soil organic matter (SOM) and total N (TN) in shrub land and secondary forest land were higher 38.5%100% and 63%130% than those of in pasture land and corn field, respectively. The contents of soil total P (TP) and total K (TK) in different land use types were significant difference. Soil available P (AP) content was mainly affected by fertilization, while soil available K (AK) content was controlled by vegetation cover and water & soil loss. Land use types were the dominant factors affecting the content of SOM, TN, TP and TK. Extensive cultivation could decrease soil nutrients content and resulted in soil degradation of cropland, on the contrast, ecological restoration could improve soil fertility. Therefore, in karst region, the measures as changing extensive cultivation into intensive farming, applying organic fertilizers, balance fertilization, and vegetation restoration will keep the sustainable utilization of land resources.