晋西黄土区三种林地土壤养分随林分生长的变化

目的]研究不同林分类型以及林龄对晋西黄土区土壤养分的改良效应,以期为森林可持续经营提供参考、丰富该区域的生态服务评估资料。方法]采用林分调查、土壤取样和室内分析方法,于2011年和2016年7—8月对3种不同林龄(山杨中龄林、油松幼龄林、侧柏中龄林)林地内的不同土层有机碳、全氮、全磷含量进行分析,并研究林内各土层间的C、N、P化学计量关系。结果]表明:各林地土壤养分都有极强的表聚性,0~30 cm土层内有机质、全氮、全磷含量占0~100 cm土层的70%以上;经过5年时间,山杨、油松和侧柏林地0~50 cm土层内平均全氮含量分别增长了9.4%、7.4%、7.5%,全磷含量分别增长了11.6%、12.2%、21.4%;0~100 cm土层内碳储量分别增加了21.17、23.74、2.21 t·hm-2。不同林地之间土壤C:N值随土层深度逐渐减小,而N:P、C:P值随土层变化并没有规律;随着林龄的增加,土壤表层(0~10 cm)的N:P和C:P值明显减小,而C:N值变化不明显。结论]根据全国土壤养分分级标准,试验林地内碳和氮含量较为丰富,而全磷平均含量为0.36~0.46 g·kg-1、为4~5级标准。在试验林地内,对土壤碳储量、全氮、全磷改良效果相对较好的分别为油松林、山杨林和侧柏林。

Changes of Soil Nutrients with Stands Growth of Three Kinds of Forestlands in Loess Area of Western Shanxi

Objective] To explore the effects of different forest types and ages on soil nutrients in the loess area of western Shanxi province, so as to provide reference for sustainable forest management and enrich the ecological service assessment data. Method] Forest investigation, soil sampling and laboratory analysis were used to analyze the contents of organic carbon, total nitrogen and total phosphorus in different soil layers at three plantations with different ages (mid-aged Populus davidiana, Young Pinus tabulaeformis and mid-aged Platycladus orientalis), and studied the C, N, and P stoichiometry in different soil layers in July and August of 2011 and 2016. Result] The soil nutrients of different forest lands were accumulated in surface:the content of organic carbon, total nitrogen and total phosphorus in 030 cm soil layer accounted for more than 70% of the total in 0100 cm soil layer, the soil nutrients decreased with soil depth. After 5 years, the average soil total nitrogen content of 050 cm in Populus davidiana, Pinus tabulaeformis and Platycladus orientalis forests increased by 0.26, 0.20, 0.17 g·kg^-1, the total phosphorus content increased by 0.05, 0.06, 0.09 g·kg^-1; the carbon storage of 0100 cm layer increased by 21.17, 23.74, 2.21 t·hm^-2 respectively. The C:N of soil in different forest lands decreased gradually with the depth of soil layer, while the N:P and C:P in different soil layers changed irregularly; the N:P and C:P of soil surface layer (010 cm) decreased significantly with forest age, while the change of C:N was not obvious. Conclusion] According to the national soil nutrients classification standards, the carbon and nitrogen in the experimental forests are relatively rich. The total phosphorus content was 0.360.46 g·kg^-1, which is at level 4 or 5. Pinus tabulaeformis, Platycladus orientalis and Populus davidiana perform better in improving soil organic carbon storage, total nitrogen and total phosphorus in the experimental forests.