不同石漠化草地凋落物对土壤养分的贡献

Contribution of litter to soil nutrient in different rocky desertification grasslands

凋落物是草地生态系统的重要组成部分和养分循环的重要途径,为探明草地凋落物对土壤养分的贡献,于2017年3月至2018年1月,采用土钻法、收集器法和分解袋法研究3种石漠化(潜在、中度和强度)草地凋落物的产量、组成、分解、养分释放及对石漠化的响应。结果表明:3种石漠化草地的凋落物组成以叶为主,占比84.39%—89.73%;凋落物产量随时间均呈现先增大再降低的趋势,在9月达到峰值;凋落物年产量相对较低,为157.16—222.40 g·m^(-2);凋落物分解速率呈现先快后慢的趋势,年分解率分别为59.20%、50.38%、41.24%;凋落物养分释放共有4种模式,其中有机碳释放模式为“淋溶—释放”,氮、钾释放模式为“淋溶—富集—释放”,磷释放模式为“淋溶—富集—释放”和“富集—释放—富集—释放”两种;有机碳、全氮、全磷、全钾等4种主要营养成分的年归还量分别为15.04—34.51 g·m^(-2)、0.25—0.57 g·m^(-2)、0.025—0.06 g·m^(-2)、0.085—0.15 g·m^(-2);相关分析显示凋落物年产量、分解速率和养分归还量随石漠化程度加剧呈逐渐降低的趋势。

Litter is an essential composition of the grassland ecosystem and an important pathway of the nutrient cycle.The objective of this paper was to explore the contribution of litter to soil nutrients.From March 2017 to January 2018,the litter productivity,composition,decomposition,nutrient release and the response to rocky desertification were studied using the methods of soil drilling,litter collector and decomposition bags in three grasslands including potential,medium and severe rocky desertification grasslands.Leaf dominated the litter composition of the three rocky desertification grasslands in the three rocky desertification grasslands,and had a percentage of 84.39%-89.73%.Litter productivity increased initially and thereafter decreased with time,and reached a peak in September.The three rocky desertification grasslands had a relatively small annual litter productivity,which was 157.16-222.40 g·m^(-2).The litter decomposition rate showed a trend from fast to slow,with annual decomposition rates of 59.20%,50.38%and 41.24%in the three rocky desertification grasslands,respectively. There were four patterns of litter nutrient release, among which the pattern of organic carbon release was "leaching - release", the pattern of nitrogen and potassium release was "leaching-concentrating-release", and phosphorus release had two patterns of "leaching-concentrating-release" and "concentrating-release-concentrating-release". The annual returns of organic carbon, total nitrogen, total phosphorus and total potassium to soil were 15.04-34.51 g·m^(-2), 0.25-0.57 g·m^(-2), 0.025-0.06 g·m^(-2) and 0.085-0.15 g·m^(-2) in the three rocky desertification grasslands, respectively. The annual productivity, decomposition rate and nutrient return of litter gradually decreased with the intensifying of rocky desertification.