长期氮磷添加对热带季风次生林地上凋落物产量与分解速率的影响

Impacts of Long-term Nitrogen and/or Phosphorus Additions on Litterfall Production and Decomposition Rates in a Tropical Monsoon Secondary Forest

摘要:

季风次生林是华南热带地区重要的生态系统，其凋落物产量与分解速率对长期氮(N)磷(P)添加的响应少见报道。该文报道了华南热带季风次生林长期NP添加实验样地12 a地上凋落物产量与4 a分解速率。试验设置了2因素(N添加与P添加) 2水平(添加与不添加)，包含对照、单独添加N、单独添加P和同时添加NP共4个处理。结果表明，12 a间4个处理的地上凋落物总产量依次为(11544±1115)、(12649±1087)、(13694±1456)和(11761±712) g/m²。P添加显著提高了凋落物产量，N添加具有增加凋落物产量的趋势，N与P添加有显著交互作用，NP添加效应不随年份与季节变化。4 a间4个处理的分解速率常数依次为(1.44±0.07)、(1.76±0.09)、(2.10±0.10)和(1.81±0.08)。P添加显著影响凋落物分解速率，N添加无显著作用，N与P添加不存在显著交互作用。长期P添加显著提高该生态系统的地上凋落物产量，长期N添加影响较弱，N与P添加有显著交互作用，NP添加效应不随处理时间与干湿季变化。地上凋落物分解主要受P限制，对N添加无响应。该研究揭示了长期NP添加对热带季风次生林地上凋落物产量与分解的影响，有助于理解该生态系统对养分有效性增加的长期响应机制。

Abstract:

Monsoon secondary forests are important ecosystems in tropical South China, but reports on their long- term response to nitrogen (N) and phosphorus (P) addition in terms of litter production and decomposition rates are scarce. This paper prbesents the results of a 12-year study on aboveground litter production and a 4-year study on decomposition rates in a long-term NP addition experiment in a tropical monsoon secondary forest in South China. The experiment employed a two-factor (N addition and P addition) and two-level (addition and no addition) design, including control, N-only addition, P-only addition, and combined NP addition treatments. The results showed that over 12 years, the total aboveground litter production for the four treatments was (11544±1115), (12649±1087), (13694±1456), and (11761±712) g/m², respectively. P addition significantly increased litter production, while N addition showed a trend of increasing litter production. There was a significant interaction between N and P addition, and the effects of NP addition did not vary with year or season. During the 4-year decomposition rate study, the decomposition rate constants for the four treatments were (1.44±0.07), (1.76±0.09), (2.10±0.10), and (1.81±0.08), respectively. P addition significantly affected litter decomposition rates, while N addition had no significant effect, and there was no significant interaction between N and P addition. Long-term P addition significantly increased aboveground litter production in this ecosystem, while long-term N addition had a weak effect. There was a significant interaction between N and P addition, and the effects of NP addition did not change with treatment duration or dry/wet seasons. Aboveground litter decomposition was mainly limited by P, with no response to increased N availability. Therefore, it was suggested that the effects of long-term NP addition on aboveground litter production and decomposition in tropical monsoon secondary forests, contributing to the understanding of long-term response mechanisms of this ecosystem to increased nutrient availability.