[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 natural forest, secondary forest and plantation which were transformed from natural forest. The results showed that after natural forest was transformed into secon-dary forest and 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 natural forest was 25.6% and 44.3% higher than that in secondary forest and plantation, respectively. For plantation, secondary forest and natural forest, nitrogen use efficiency of litterfall was 175.4, 94.8 and 92.0 kg·kg, respectively, and phosphorus use efficiency of litterfall was 3031.0, 2791.6 and 2537.2 kg·kg, respectively. It was concluded that plantation was more limited by nitrogen compared with natural forest and secondary forest, and the effects of phosphorus limitation had similar effects on the three forests.