摘要:粗木质残体（coarse woody debris，CWD）是森林生态系统中重要的结构性和功能性组成要素，是维护系统完整性和稳定性的关键。对CWD空间格局的研究将有助于深入探索种群格局的形成和森林生态系统的维持机制。采用g（r）函数对茂兰喀斯特常绿落叶阔叶混交林1.28 hm²固定样地内不同径级、不同腐烂等级、不同存在形式的CWD的空间分布格局及空间关联性进行了研究。结果表明：1）在40 m的空间尺度内，CWD总体在0-12 m尺度上表现为集群分布，随着尺度的增加格局强度降低，趋于随机分布，剔除生境异质性后，格局尺度降低至7 m。2）CWD径级格局表现为：小径级 > 中径级 > 大径级。拔根倒和干中折断在整个研究尺度上为随机分布，其他不同径级、不同腐烂等级、不同存在形式的CWD均在小规模尺度（2-8 m）表现为集群分布，随着尺度的增加聚集强度急剧变小，趋于随机分布或均匀分布。3）除了干中折断与树段之间、大径级与小径级之间的CWD在空间上相互独立，其他不同径级、不同腐烂等级或不同存在形式的CWD之间均在小规模尺度（2-8 m）上表现为显著的正相关，随着尺度的增加空间关联性降低。喀斯特常绿落叶阔叶混交林CWD的分布格局可能是在小尺度内由密度制约、在大尺度内由生境过滤和个体自然衰老等生态学过程所形成，大径级对临近的小径级、先死亡对后死亡、站杆对倒下的个体具有一定的正向影响作用，在一定程度上揭示了该林型天然更新的作用和机制。



Abstract:Coarse woody debris (CWD) is one of the most important components in the structure and function of forest ecosystems and it is also key for maintaining system integrity and stability. Therefore, studying spatial patterns of CWD can help us understand the formation of population patterns and the maintenance mechanisms of forest ecosystems. Karst evergreen broadleaved mixed forest is one of the best preserved primordial subtropical forests. To date, there have been few studies of spatial patterns and correlations in this forest, especially research on CWD and its spatial distribution. The pair correlation function g(r) was used to study the spatial distribution patterns and correlations of CWD of different forms, decomposition levels, and diameter classes in a 1.28 hm² fixed plot in Maolan karst mixed evergreen and deciduous broadleaf forest. The results showed that 1) at a spatial scale of 40 m, overall CWD showed a clustered distribution at spatial scales ≤12 m. With an increase in scale, CWD tended to be randomly distributed. After removing habitat heterogeneity, the pattern scale was reduced to 7 m. 2) The distribution pattern of CWD diameter classes was: small tree > medium tree > large tree. CWD, in the form of root inversion and breakage at trunk, was randomly distributed throughout the study area and other types of CWD of different diameters, decay levels, and forms were clustered at a small scale (2-8 m). With an increase in scale, the intensity of aggregation decreased sharply and CWD tended to be randomly or regularly distributed. 3) Aside from the spatial independence of CWD between breakage at trunk and segment, and large and small diameter classes, there were significant positive correlations between different diameter classes, decay levels, and forms at a small scale of 2-8 m. With an increase in scale, the spatial correlation decreased. The distribution patterns of CWD in this Karst forest may be formed by ecological processes such as small-scale density restrictions, large-scale endogenous habitat filtration, and individual natural senescence. The large diameter, earlier mortality, and standing individuals had a positive effect on nearby small diameter, later mortality, and fallen individuals, respectively, which revealed the mechanism of natural regeneration of this forest type.





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