选择南亚热带森林演替过程3个阶段(初期、中期和后期)的典型森林生态系统为研究对象,在测定植物与土壤中全N、全P含量的基础上,阐明了森林演替过程中植物与土壤的N、P化学计量特征。结果显示:1)土壤中全N含量随演替进行而增加,马尾松(Pinus massoniana)林(初期)、混交林(中期)和季风林(后期)0-10cm土层中全N含量分别为0.440、0.843和1.023g·kg^-1;混交林肛10cm±层中全P的含量最为丰富,为0.337g·kg^-1,马尾松林和季风林土壤全P含量分别为0.190和0.283g·kg^-1。2)植物叶片中全N、全P的含量随演替呈减少的趋势,但根系中全N、全P的含量都以马尾松林为最多,混交林和季风林含量彼此相当。3)各土层中N:P随演替的进行呈现明显增加趋势,马尾松林、混交林和季风林0-10cm土层中N:P分别为2.3、2.5和3.6:植物各器官中N:P随演替的进行也呈增加趋势,且叶片和根系中的N:P相近,马尾松林、混交林和季风林叶片中N:P分别为22.7、25.3和29.6。基于上述结果,探讨了南亚热带森林生态系统植物与土壤中N:P特征、森林演替过程中植物与土壤中N:P变化规律以及P对南亚热带森林生态系统的限制作用。结果表明,P已经成为南亚热带森林生态系统生物生长和重要生态过程的限制因子。
Aims Nitrogen (N) and phosphorus (P) are two key elements of life and are major limiting nutrients in many ecosystems across the world. The balance of N and P has become the focal point of global change ecology and biogeochemistry, especially as aggravated by atmospheric nitrogen deposition. Although N:P stoichiometry has proved useful in studies of nutrient limitation, biogeochemical cycles, forest succession and degraded land, little is known about it in lower subtropical forest succession. Therefore, our objective is to better understand nutrient controlling factors of plant-soil interaction and reveal interactions of N and P to provide insight and theoretical fundamentals for forest management. Methods We measured total N and P of organs of dominant species and different soil layers in three forests in Dinghushan Biosphere Reserve, Southern China: pine forest (PF, early successional stage), pine and broad-leaved mixed forest (MF, middle stage) and monsoon evergreen broad-leaved forest (MEBF, advanced stage). Important findings Soil N content in the 0-10 cm soil layer increased with succession; values in PF, MF and MEBF were 0.440, 0.843 and 1.023 g·kg^-1, respectively. The largest value of P content in the same layer was in MF (0.337 g·kg^-1); the values in PF and MEBF were 0.190 and 0.283 g·kg^-1, respectively. Plant foliage N and P content decreased with succession; the largest values for roots were in MF, and the values in PF equaled those in MEBF. Soil N:P ratio in the 0-10 cm layer significantly increased with succession; 2.3, 2.5 and 3.6, respectively. The N:P ratio of various plant organs also increased with succession, and the value in foliage was close to that in roots; the foliage N:P ratios were 22.7, 25.3 and 29.6, respectively. We discussed the characteristics of N:P ratios in soil and plants of the lower subtropical forest ecosystem, the law of N:P ratios in soil and plants in successional series, and the limiting effect of P on the lower subtropical fore