中亚热带森林转换对凋落物养分归还及养分利用效率的影响

为了解中亚热带森林转换对森林生态系统碳及养分循环的影响,以中亚热带米槠天然林、森林转换后的米槠次生林和杉木人工林为对象,对3种林分的凋落物量、养分归还量和养分利用效率进行4年研究。结果表明: 米槠天然林转换为米槠次生林和杉木人工林后,年凋落物量分别下降29.0%和45.7%,凋落物氮归还量分别下降34.0%和72.7%,磷归还量分别减少38.1%和56.4%。米槠天然林的凋落物碳归还量比米槠次生林和杉木人工林分别高25.6%和44.3%。对于杉木人工林、米槠次生林和米槠天然林的养分利用效率,凋落物氮的利用效率分别为175.4、94.8和92.0 kg·kg^-1,凋落物磷的利用效率分别为3031.0、2791.6和2537.2 kg·kg^-1,杉木人工林比米槠天然林和次生林受氮限制影响程度更大,3种林分受磷限制的影响程度相近。

Effects of forest conversion on litterfall nutrient return and nutrient use efficiency in Mid-subtropical China.

To understand the impacts of mid-subtropical forest conversion on carbon and nutrient cycling, we conducted a 4-year investigation to examine litterfall, nutrient return and nutrient use efficiency of Castanopsis carlesii natural forest, C. carlesii secondary forest and Cunninghamia lanceolata plantation which were transformed from C. carlesii natural forest. The results showed that after C. carlesii natural forest was transformed into C. carlesii secon-dary forest and C. lanceolata plantation, the annual litter production decreased by 29.0% and 45.7%, nitrogen return of litter decreased by 34.0% and 72.7%, and phosphorus return decreased by 38.1% and 56.4%, respectively. The amount of carbon returned from litterfall in C. carlesii natural forest was 25.6% and 44.3% higher than that in C. carlesii secondary forest and C. lanceolata plantation, respectively. For C. lanceolata plantation, C. carlesii secondary forest and C. carlesii natural forest, nitrogen use efficiency of litterfall was 175.4, 94.8 and 92.0 kg·kg^-1, respectively, and phosphorus use efficiency of litterfall was 3031.0, 2791.6 and 2537.2 kg·kg^-1, respectively. It was concluded that C. lanceolata plantation was more limited by nitrogen compared with C. carlesii natural forest and secondary forest, and the effects of phosphorus limitation had similar effects on the three forests.