坡向与植物群落对水蚀风蚀交错带土壤有机碳氮的影响

Effects of Slope Aspects and Plant Community Types on Soil Organic Carbon and Nitrogen in the Crisscross Area of Wind-Water Erosion

以黄土高原北部水蚀风蚀交错带六道沟流域内的1个支沟为对象,通过植被调查和采样分析,研究了坡向和植物群落类型对土壤有机碳(SOC)、全氮(TN)含量、碳氮比(C/N)和有机碳氮密度(SOCD、TND)的影响。结果表明:(1)坡向对0—20cm土壤SOC和TN含量及0—60cm C/N均有显著影响。SOC、TN含量及C/N分别表现为:半阴坡>半阳坡>沟头半阴坡>半阳坡=沟头及半阳坡>半阴坡≥沟头的趋势;(2)植物群落对0—10cm SOC和TN含量及0—20cm C/N均有显著影响。半阴坡分布的3种豆科群落达乌里胡枝子、紫花苜蓿及白花草木樨间土壤碳氮差异不显著,但均显著高于禾本科的长芒草群落;半阳坡分布的达乌里胡枝子和紫花苜蓿群落SOC和TN含量相当,均显著高于茵陈蒿群落(菊科)和长芒草群落;沟头的达乌里胡枝子群落SOC、TN显著高于长芒草。豆科草本植物更有利于促进土壤碳氮的积累;(3)坡向主要影响表层0—20cm SOCD和TND,其对60cm剖面SOCD和TND贡献率分别为45%～55%和47%～53%。不同植物群落下土壤表层及整个剖面SOCD和TND均有显著差异。研究支沟内SOCD平均为2.13kg/m2,远低于黄土高原其他地区。上述结果对于水蚀风蚀交错带土壤碳氮储量的精确评估及植被合理建造有一定指导价值。

A branch gully of Liudaogou watershed in the wind-water erosion crisscross region of the northern Loess Plateau was selected as the object,and the effects of slope aspects and plant community types on soil organic carbon(SOC),total nitrogen(TN)content,ratio of carbon-nitrogen(C/N)and soil organic carbon and nitrogen density(SOCD,TND)were studied through vegetation survey and sampling analysis.The results showed that:(1)Slope aspects had significant effects on the SOC and TN contents in0-20cm,and C/N in0-60cm.The SOC,TN contents and C/N followed the order of semi-shady slope>semi-sunny slope>gully-head,semi-shady slope>semi-sunny slope=gully-head,and semi-sunny slope>semi-shady slope≥gully-head,respectively.(2)Plant communities had significant effects on the SOC and TN contents in0-10cm and C/N in0-20cm.There was no significant difference in SOC and TN contents between three kinds of leguminous communities growing in the semi-shady slope,namely,Lespedeza davurica,alfalfa and sweet clover,but they were significantly higher than that of the Stipa bungeana community.The SOC and TN contents in Lespedeza davurica and alfalfa communities were similar in the semi-sunny slope,which were significantly higher than those of the Artemisia capillaris and Stipa bungeana communities.The SOC and TN contents in Lespedeza davurica community were significantly higher than that of the Stipa bungeana community in the gully-head,indicating that legume herb was more conducive to the accumulation of soil carbon and nitrogen in the study area.(3)Slope aspects mainly affected the SOCD and TND in surface layer of0-20cm,and their contribution to SOCD and TND of60cm soil profile were45%~55%and47%~53%,respectively.There were significant differences in SOCD and TND between the surface layer and the whole soil profile under different plant community types.The average SOCD in the studied branch gully was estimated to be2.13kg/m2,which was far lower than other parts of the Loess Plateau.These results had important role in evaluating soil carbon and nitrogen storage accurately and rational construction of vegetation in the crisscross area of wind-water erosion on the Loess Plateau.