热带季节雨林与人工橡胶林土壤碳氮比较

Comparison of soil C and N in rubber plantation and seasonal rain forest

选取我国西南部西双版纳地区的热带季节雨林和人工橡胶林为对象,比较了2006—2007年两种土地利用方式下凋落物输入、土壤总碳氮含量及活性碳、氮的季节性变化.结果表明：与热带季节雨林相比,橡胶林的地上年凋落物量较低,而地面凋落物残留量较高,反映了橡胶林凋落物分解速率（凋落物消失率常数值,K）较低;橡胶林凋落物和土壤的C/N比值较高,暗示了其林内有机物的可降解性较热带季节雨林弱;橡胶林表层土壤总有机碳、生物活性有机碳和微生物生物量碳含量只有热带季节雨林土壤的60%~70%,硝态氮含量较少,pH值则比热带季节雨林土壤低1.1.说明热带季节雨林转变为橡胶林后,林内地上凋落物向土壤输入的碳、氮量减少,土壤碳、氮含量和有效性降低,并且土壤呈现酸化倾向.应制定合理的橡胶林土壤管理措施,阻止土壤质量的下降趋势,以维持橡胶林的生产可持续性.

With the rubber plantation and seasonal rain forest in Xishuangbanna of Southwestern China as test objectives, a comparative study was conducted on their litter input, soil total C and N contents, and seasonal changes of soil active C and N from 2006 to 2007. Comparing With seasonal rain forest, rubber plantation had lower amount of aboveground litterfall and higher amount of floor mass, reflecting the lower decomposition rate （turnover coefficient, K） of litters, and had higher C/N ratio of litters and soil, indicating that the organic matters in rubber plantation were more resistant to degradation. The surface soil total organic C, labile organic C, and microbial biomass C concentrations in rubber plantation accounted for 60%-70% of those in seasonal rain forest, and the soil NO3 - -N concentration and pH value in rubber plantation were lower than those in seasonal rain forest, indicating that the conversion from seasonal rain forest to rubber plantation decreased the C and N inputs from aboveground litterfall and the availability of soil C and N, and caused soil acidification. Moderate land management strategies for rubber plantations were needed to prevent the degradation of soil quality and to maintain the productive sustainability.