北热带喀斯特季节性雨林土壤和6个常见树种凋落物的C、N、P化学计量学特征 / C, N and P stoichiometric characteristics of soil and litter fall for six common tree species in a northern tropical karst seasonal rainforest in Nonggang, Guangxi, southern China
凋落物是森林生态系统的有机质和养分储藏库, 是土壤和植物间物质交换的枢纽, 是森林土壤肥力的主要来源之一。本文选取弄岗喀斯特季节性雨林15 ha森林动态监测样地中布设的90个凋落物收集器自2014年3月至2015年2月收集的6个常见种的凋落叶, 结合2014年7月沿海拔梯度(185-368 m)采集的50个土壤样品, 研究了土壤和凋落物的C、N、P化学计量学特征及其沿海拔梯度的变化趋势。结果表明, 除P含量在高坡位及峰顶较低外, 土壤中的C、N、P含量均达到了全国第二次土壤普查分类标准中的一级水平; 土壤的C、N含量及C : P和N : P与海拔呈正比, P含量和C : N与海拔呈反比。因本文采样的海拔差异较小, 推测上述土壤养分含量与海拔的关系主要是由于微地形引起的土壤差异而不是海拔差引起的气象因子差异所致。与其他森林生态系统相比, 这6个常见种凋落叶的C、N、P含量的平均值呈现出高C和N、低P的格局; 而不同海拔凋落叶的C、N、P并未表现出类似土壤中的变化规律; 6个常见种凋落叶均表现出春季较高的C含量和夏季较高的N、P含量。虽然桂西南喀斯特季节性雨林中土壤的C、N、P含量总体水平较高, 但其单位面积内的胸高断面积之和却远低于其他森林生态系统, 表现为生物承载量较低; 受个体生长环境差异的影响, 同种凋落叶的C、N、P化学计量学特征可能会存在个体间差异。研究结果将为我国西南地区典型喀斯特生态脆弱区的生态功能恢复与植被重建提供科学依据。
Litter fall provides organic matter and nutrients to forest ecosystems and is central to the exchange of substances between soil and plants. It plays a vital role in the maintenance of soil organic matter and nutrient cycling in forest ecosystems and it is one of the main sources of soil fertility. We used litter fall data for six common tree species collected between March 2014 and February 2015 from 90 litter fall traps, and fifty soil samples collected in July 2014 along an altitudinal gradient from 185 to 368 m in a tropical karst forest in Guangxi, China. We studied the C, N and P stoichiometric characteristics of soil and litter fall, and their trends along an altitudinal gradient. Soil C and N contents were all positively associated with altitude, while P content was negatively associated with altitude. Soil C : N was negatively associated with altitude, while C : P and N : P were positively associated with altitude. Due to the narrow altitudinal range of the soil samples, we speculate that the association of soil nutrients with altitude is due to the effect of micro-topography and not a climatic effect. Apart from the higher slope and summit, the soil C, N, P contents reached the first classification level of the national criterion of soil nutrients. Compared with other forest ecosystems, we found greater C and N contents and lower P content than the average value of C, N, P contents for litter fall of six common species. There were no trends for C, N and P stoichiometric characteristics of the mixed sample of leaf litter for the six common tree species along an altitudinal gradient. The six common tree species have higher C content in spring and higher contents of N and P in summer. The per unit total basal area of trees in this forest was much lower than other forest ecosystems, indicating its low biomass stock. This study provides useful information for ecological restoration of a typical vulnerable karst ecosystem in China.
Abstract in Chinese and English; article in Chinese only.