The Response Of Litter Decomposition To Carbon, Nitrogen And Phosphorus Additions For Four Typical Tree Species In Mid-Subtropical Zone

Leaf Litter, as the source of decomposers matter and energy plays an important role in the process of nutrient cycling in ecosystems. In this paper, the representative tree species in slash pine(Pinus elliottii) forest,pine (Pinus massoniana) forest, mixed forest and evergreen forest were selected to study their foliar litter decomposition. On the purpose of understanding the basic nutrient return regulation and the response to global changes of litter, the method of Nylon mesh bags was used to study the response of litter decomposition to carbon, nitrogen and phosphorus additions in mid-subtropical zone, China. All these are helpful to provide some scientific basics for forest management. Major conclusions as follows:(1) The results of effects of nitrogen and phosphorus additions to the decomposition of slash pine needles showed that:N addition ([N]) increased the N concentration in the process of litter decomposition, N accumulated in the early time of decomposition time, and released in the late time of decomposition time. P addition ([P]) increased the P concentration in the process of litter decomposition, P accumulated in the whole time of litter decomposition. N and P addition ([N+P]) increased the N and P concentration, N and P accumulated in the early time of decomposition, and released in the late period of decomposition. But C at all treatments released during the whole experiment period. N and P additions play a coupling effect for litter decomposition rate and nutrient release.(2) The results of effects of carbon, nitrogen and phosphorus additions to the litter decomposition of Masson pine and Castanopsis sclerophylla showed that:The effect of C addition to litter C concentration of Masson pine is not significant, but litter C concentration increased for Castanopsis sclerophylla. [N] increased the litter N concentration of Masson pine, but the N concentration of Castanopsis sclerophylla was not significant different between [N] and without N addition. [P] increased litter P concentration of both species, and [P] also increased litter N concentration of Masson pine. The effect of [C], [N] and [P] to mass loss rate of both species were not significant.(3) The results of effects of carbon, nitrogen and phosphorus additions to mixed litter Masson pine and Liquidambar formosana (1:1) showed that:The litter C concentrations for [C] and [C+N+P] were lower than for other treatments; The N concentrations for [N] and [C+N+P] were higher than for other treatments; The P concentrations for [P] and [C+N+P] were higher than for other treatments; and the effect of [C+N+P] on litter decomposition rate was significant higher than these of [C], [N] and [P], separately. The effects of different treatments on litter mass loss were differences and decomposition models showed the fast-slow-fast tendency.(4) The effect of carbon, nitrogen and phosphorus additions on litter decomposition could be reflected by the diversity of microbial groups and soil key enzyme activities under the litters. [C] improved the surcase activity when litters were decomposed after 180 days and 540 days, and improved the acid phosphatase activity after the decomposition of 180 days; [N] improved the acid phosphatase activity at the period of 180 days, while [P] improved the acid phosphatase activity at the period of 540 days.In conclusion, the responses of litter decomposition to carbon, nitrogen and phosphorus additions were complicated, and varied with tree species. The nutrient return through litter decomposition with C, N and P alteration need be further studied in forest ecosystems of mid-subtropical region, China.