坡向对云雾山典型草原枯落物分解特性的影响

Effects of Different Slope on Litter Decomposition Characteristics in the National Natural Reserve of Yunwu Mountain

为探讨不同坡向对草地枯落物分解特性的影响,应用尼龙网袋法研究云雾山典型草原主要优势种本氏针茅(Stipa bungeona)和铁杆蒿(Artemisia sacrorum)(茎、叶)枯落物在阴阳坡1年内的分解失重情况及营养元素动态。结果表明:枯落物分解残留率呈逐渐下降趋势,1年后失重率在18.8%～39.94%之间,分解速率呈快-慢-快变化。指数回归方程拟合得到分解速率常数k值大小顺序为铁杆蒿叶(0.446)>本氏针茅(0.321)>铁杆蒿茎(0.220),阳坡(0.355)>阴坡(0.301),且不同物种和不同坡向对分解速率影响差异显著(P<0.001)。枯落物50%分解和95%分解所需的时间在1.39～3.45年和6.22～15.12年之间。Pearson相关分析显示分解速率常数k与枯落物初始氮含量成显著正相关(r=0.895),与C/N比成极显著负相关(r=-0.940)。枯落物1年分解过程中氮浓度波动上升,磷浓度波动下降,钾浓度持续下降。总体上N,P,K元素绝对量均下降,养分累积指数NAI<100%。不同元素由于在枯落物中初始含量、存在方式及降解中微生物作用的不同,释放和积累模式也不同。

In order to explore the effects of different slope on litter decomposition characteristics,the litter decomposition and nutrient element dynamic of Stipa bungeana and Artemisia sacrorum（stem and leaf） in the national natural reserve of Yunwu Mountain were studied using the method of nylon mesh bag during a year.Results showed that the rates of litter decomposition were declining gradually.Weight-loss ratio was between 18.8% and 39.94%.The process of decomposition rate followed fast-slow-fast tendency.The values of decomposition rate constant k were obtained using index regression equation and were order as the leaf of A.sacrorum（0.446）S.bungeana（0.446）Stem of A.sacrorum（0.220）,sunny slope（0.355）shady slope（0.301）.Variance analysis showed that the effects of different species and different slopes on the decomposition rate were significantly different（P〈0.001）.Pearson correlation analysis showed that the relationship between the decomposition rate constant k and the initial nitrogen content of the litter was a significant positive correlation（r=0.895） and the relationship between the decomposition rate constant k and the C/N ratio was a significant negative correlation（r=-0.940）.The time needed for 50% decomposition of the litters was between 1.39 and 3.45 year,and the time needed for 100% decomposition of the litters was between 6.22 and 15.12 year.The nitrogen concentration was fluctuating rise;the phosphorus concentration was fluctuating decline and the potassium concentration was continuous decline in the process of litter decomposition during one year.Overall,the element accumulation index（NAI） values of N,P,K in both species were less than 100% indicating a release of the element absolute quantity.The release and accumulation of litter elements were different,which may be associated with the initial element content,the existing state of litter and the role of microbiological degradation.