南亚热带人工林林下芒萁层的凋落物拦截

在中国南亚热带人工林生态系统中，大面积的林下层被密集的蕨类植物芒萁所占据。作为森林土壤最重要的养分来源，很多冠层树种的凋落物在到达地表之前，会被芒萁拦截。通过调查南亚热带4种人工林林下芒萁层对冠层树种叶片的拦截量与拦截比例，发现林下芒萁层对凋落物的拦截量排序为湿地松＞厚荚相思＞尾叶桉＞红椎，而林下芒萁层对尾叶桉叶片的拦截比例最高，达99.8%，其次分别为厚荚相思（73.5%）、湿地松（56.3%）和红椎（27.0%）；所有人工林林下芒萁的下半层（0~50 cm）拦截了更大比例的凋落叶，最大为尾叶桉（64.7%），最小为红椎（23.1%）。林下芒萁层的凋落物拦截效应可能会改变森林生态系统的地上过程和地下过程，进而影响整个森林的碳循环等生态系统功能。通过凋落物拦截实验，开展林下层植物对人工林生态系统碳循环的影响的相关机理研究，有助更好地理解在生态系统水平上林下植被对整个森林生态系统功能的影响。

Litterfall Interception of Understory Fern Dicranopteris Dichotoma in Plantations of South China

China is considered as the largest country with artificial plantations. The plantations are considered as important carbon pool and would influence climate change at regional scale. As a major species for forest restoration, carbon fixation, and economic improvement for farmers, Pinus elliottii, Acacia crassicarpa, Eucalyptus urophylla and Castanopsis hystrix, have been widely planted in South China due to their fast growth and woody characteristics. The understory of these plantations is often occupied by densefern (Dicranopteris dichotoma). Understory vegetation as transitional layer links ecosystem processes between aboveground and underground. The ecosystem functions of understory vegetation were mostly ignored due to the lower biomass. However, not only they can accumulate biomass per se, but also facilitate carbon fixation in soils. The densefern intercepts canopy tree leaf litters before they reach the ground in these plantations of South China. Litter is the most important nutrient origin of forest soil. In order to explore the effect of litterfall interception on ecosystem processes and functions about leaf litters, we should first know the basic questions: 1) how many leaf litters are intercepted by the fern? and 2) which factors affect the litter interception? We investigated the physical traits of leaf litter and the biomass of Dicranopteris Dichotoma, and conducted an experiment to quantify the mass and proportion of intercepted litters in four kinds of plantation ecosystems in South China. The results showed that the order of litterfall interception mass in different plantations was Pinus elliottii＞Acacia crassicarpa＞Eucalyptus urophylla＞Castanopsis hystrix, which is related to the total litter mass, canopy cover and ferncover, while the order of litterfall interception proportion was Eucalyptus urophylla (99.8%)＞Acacia crassicarpa (73.5%)＞Pinus elliottii (56.3%)＞Castanopsis hystrix (27%), and more leaf litters were intercepted by the bottom layer (0-50 cm) than that by top layer (50-100 cm) of understory fern Dicranopteris Dichotoma in all four plantations, that resulted from aboveground biomass of understory fern and physical characteristics of the litters. These results indicated that litter mass was not underestimated in calculating net primary production in South China, but spatial distribution of litterfall changed, which may change ecosystem processes, such as litter decomposition and soil respiration. These topics should be explored in the future.