黄土高原不同年限刺槐土壤化学计量特征分析

通过对陕北黄土高原4种不同年限(10,15,25,40年)刺槐林地0—200cm土壤的采集与分析,研究不同刺槐种植时间对土壤营养元素及化学计量比的影响。在每个林龄的林地内设3个小区,每个小区采用随机采样法选取3个采样点分层采集土壤样品,进行土壤碳、氮、磷、钾测定,计算化学计量比。结果表明:(1)有机碳和全氮、全钾含量随刺槐年限增加呈基本增大的趋势,全磷随刺槐年限的增长变化不大;有机碳、全氮和全磷呈极显著的正相关关系;(2)在0—200cm土层,有机碳、全氮空间分布基本一致,随土层深度增加均呈先减少后趋于稳定的变化趋势;全磷在整个空间中的分布较为均匀,其空间变异性低于有机碳和全氮;全钾含量高于碳氮磷含量,且随土壤深度变化不大;(3)土壤C∶N比,C∶P比,N∶P比和C∶N∶P比均随刺槐年限的增长呈先降低后升高的趋势,都在15年处有最低值;(4)土壤C∶N比随土层深度在一定范围波动,C∶P和N∶P比均随土层深度的增加呈先减少后趋于稳定的变化趋势。

Ecological Stoichiometric Characteristics of Soil in Robinia Pseudoacacia Forests of Different Ages on the Loess Plateau

In order to clarify the effects of different ages of Robinia pseudoacacia forest on soil nutrient and ecological stoichiometric characteristics,we selected four kinds of artificial Robinia pseudoacacia forests of different ages (10 years,15 years,25 years,and 40 years) located in Yan'an,Shanxi Province to investigate the distribution patterns of soil organic carbon (SOC),total nitrogen (TN),total phosphorus (TP) and total potassium (TK) in the 0-200 cm soil layer,and analyzed the ecological stoichiometric characteristics.Three sample sites were set up in each selected Robinia pseudoacacia forest and three sampling points were set randomly.Soil samples were collected to analyze soil C,N,P,K and stoichiometry.The results showed that:(1) SOC,soil TN and TK increased with the growth of Robinia pseudoacacia forest on the whole,but the change of soil TP with the growth of Robinia pseudoacacia was not obvious.There were significant positive correlations among SOC,soil TN and TP.(2) The spatial distribution of SOC and soil TN were quite consistent,showing the same trend of declining first then tending to be relatively stable with soil depth,and they were higher in the surface layers than in the subsurface layers.TP was lower than SOC and TN in spatial variability.The content of TK was higher than that of SOC,TN and TP,and it did not change much with soil depth.The 15 years occured the minimum Value.(3) Soil C ∶ N ratio,C ∶ P ratio,N ∶ P ratio,C ∶ N ∶ P ratio all decreased first and then deceased with the growth of Robinia pseudoacacia forest.(4) Soil C ∶ N didn't change much,as soil C ∶ P,N ∶ P showed the same trend with SOC and TN with soil depth.