以喀斯特峰丛洼地3 种常见次生林及其建群树种为研究对象,测定3 种林分建群种的不同器官及凋落物、土壤的氮含量及氮同位素丰度值(δ15 N),探讨植物-凋落物-土壤氮含量及稳定氮同位素组成变化及内在联系.结果显示:3 种次生林建群种植物中叶片氮含量最高,茎的氮含量最低,3 种次生林建群树种叶片氮含量均显著高于掉落物和土壤氮含量,0~30 cm土壤氮含量显著高于30~90 cm土壤氮含量,土壤养分主要集中于表层土壤;白栎、栓皮栎和光皮桦器官中δ15 N变化范围分别为-2.82‰~14.94‰、-1.37‰~9.35‰和-4.39‰~26.06‰,3 种建群种器官间氮同位素组成均表现出显著差异(P<0.05);3 种建群种群落表层土壤δ15 N差异显著,3 种林分中0~30 cm土壤δ15 N均显著低于30~60 cm和60~90 cm的土壤,δ15 N可能是这些群落土壤氮循环过程中的敏感指标,光皮桦叶片氮含量略大于白栎和栓皮栎,光皮桦林土壤表层δ15 N大于白栎林和栓皮栎林,光皮桦可能比白栎和栓皮栎更为适应喀斯特生境.
In this study,three common secondary forests and their constructive tree species in Karst peak-cluster depression were used to determine the nitrogen content and nitrogen isotope abundance of different organs,litter and soil.The changes and internal relations of plant-litter-soil nitrogen content and stable nitrogen isotope composition were discussed.The results showed:Among the three seconda-ry forest constructive species,the leaf nitrogen content was the highest,the stem nitrogen content was the lowest,and the leaf nitrogen content was higher than the litter and soil nitrogen content of the three secondary forest constructive species.The soil nitrogen content of 0~30 cm was significantly higher than that of 30~90 cm,and the soil nutrients were mainly concentrated in the surface soil.The varia-tion ranges of δ15 N in the organs of Quercus fabrei,Quercus variabilis and Betula luminifera were-2.82‰~14.94‰,-1.37‰~9.35‰and-4.39‰~26.06‰,respectively.There were signif-icant differences in nitrogen isotope composition among the three constructive species(P<0.05).There were significant differences in δ15 N of different tree species stands.0~30 cm soil δ15 N values in three stands were significantly lower than those in 30~60 cm and 60~90 cm soils.δ15 N may be a sensitive index in the process of soil nitrogen cycle under these communities.The leaf nitrogen content of Betula luminifera was slightly higher than that of Quercus fabrei and Quercus variabilis,and the sur-face soil nitrogen content of Betula luminifera forest was also higher than that of Quercus fabrei forest and Quercus variabilis forest.Betula luminifera may be more adapted to Karst habitat than Quercus fab-rei and Quercus variabilis.