中亚热带次生林和人工林凋落枝水溶性碳氮磷动态特征

Abstract

凋落枝是森林地上部分凋落物的重要组分，揭示其水溶性碳氮磷的动态规律对于认识森林物质循环过程具有重要意义，但目前研究集中于凋落叶，而对凋落枝缺乏必要关注。因此，以中亚热带典型马尾松（Pinus massoniana）人工林、杉木（Cunninghamia lanceolata）人工林和米槠（Castanopsis carlesii）次生林为研究对象，在一个自然年内调查了凋落枝水溶性碳、氮、磷含量及其芳香化指数以及化学计量比的动态变化过程。结果显示：（1）米槠次生林凋落枝水溶性碳、氮、磷含量及芳香化指数明显大于马尾松和杉木人工林；（2）水溶性碳和磷、水溶性碳比磷、水溶性氮比磷和芳香化指数有明显的季节变化；（3）水溶性碳、水溶性磷、水溶性氮比磷和芳香化指数在不同林分和季节间有交互作用。（4）马尾松和杉木人工林、米槠次生林凋落枝水溶性物质含量的季节变化多数与气温和降水呈显著负相关。这些结果表明亚热带次生林可能相对于人工林具有更为高效的以凋落枝为载体的物质循环过程，在未来气候变暖背景下亚热带森林由凋落枝归还给土壤的养分浓度可能降低。;Twig litter is an important component of forest litter. It is of great significance to reveal the dynamics of water soluble carbon, nitrogen and phosphorus for understanding the forest material cycle. However, the previous researches paid more attention to leaf litter than twig litter. In this regard, we investigated water soluble carbon, nitrogen, phosphorus, and aromatization index as well as stoichiometric ratio dynamics of twig litter in a year round in Pinus massoniana plantation, Cunninghamia lanceolata plantation and Castanopsis carlesii secondary forest. Our results showed that:(1) water soluble carbon, nitrogen and phosphorus as well as aromatization index of twig litter in Castanopsis carlesii secondary forest were significantly higher than those of Pinus massoniana and Cunninghamia lanceolata plantations; (2) water soluble carbon and phosphorus, water soluble carbon- phosphorus ratio and nitrogen-phosphorus ratio, as well as aromatization index of twig litter varied significantly in different seasons; (3) there were significant interactions between forest types and sampling seasons in affecting water soluble carbon and nitrogen, water soluble nitrogen-phosphorus ratio, and aromatization index. (4) the seasonal variation of water soluble substance of twig litter in Pinus massoniana, Cunninghamia lanceolata plantation and Castanopsis carlesii secondary forest were negatively correlated with air temperature and precipitation. These results suggest that subtropical secondary forests may have a more efficient nutrients cycling process based on twig litter than plantations, and the concentrations of nutrients cycling back to soil via twig litter will decrease in subtropical forests under future warming scenarios.