[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.