弄岗喀斯特季节性雨林蚬木种群时空格局动态研究

Dynamic Study on the Spatio-Temporal Pattern of Excentrodendron tonkinense Population in Nonggang Karst Seasonal Rainforest, South China

摘要:

蚬木(Excentrodendron tonkinense)是国家II级重点保护野生植物，也是喀斯特季节性雨林建群种之一，但种群仍面临环境干扰的威胁。为探究其种群空间分布动态特征，该研究基于广西弄岗喀斯特季节性雨林15 hm²样地2011—2021年的种群和环境调查数据，采用空间点格局方法和零膨胀模型研究了种群分布动态与环境因子之间的关系。结果表明，10 a间种群个体数量从1 851株减少到1 786株，不同年份小径级(1~5 cm)数量占比均超过50%，径级结构均呈倒“J”型。3个年份种群在0~50 m尺度为显著的聚集分布，且种群整体聚集强度变化主要受到小树空间分布格局聚集程度的驱动。种群分布范围主要受到生境中土壤含水率、全磷和全钾的显著影响，其多度变化受到生物和非生物因子的共同影响。种群空间分布有较强的生境特异性，成年树偏好凹凸度小且多样性较低的生境，而小树则偏好植物多样性高的生境。在保护较好的条件下，仍需对蚬木种群数量进行动态监测。在具体保护实践中，需要重点保护坡地生境，减少人为干扰。

Abstract:

Excentrodendron tonkinense, a national second-class key protected wild plant and one of the dominant species in the karst seasonal rainforest, still faces the threat of environmental disturbances. To explore the spatial distribution dynamics of its population, this study analyzed the relationship between population distribution dynamics and environmental factors based on the population and environmental survey data of a 15 hm² plot in the karst seasonal rainforest of Nonggang, Guangxi from 2011 to 2021, using spatial point pattern methods and zero-inflated models. The results showed that the number of individuals in the population decreased from 1851 to 1786 over 10 years. The proportion of small diameter classes (1–5 cm) was over 50% in all years, and the diameter class structure was inverted “J” shaped. The population was significantly aggregated at the 0–50 m scale in three years, and the overall aggregation intensity of the population was mainly driven by the aggregation degree of the spatial distribution pattern of small trees. The distribution range of the population was significantly affected by soil moisture content, total phosphorus and total potassium in the habitat, and its abundance changes were influenced by both biotic and abiotic factors. The spatial distribution of the population had strong habitat specificity. Adult trees preferred habitats with low concavity and low diversity, while small trees preferred habitats with high plant diversity. Under well-protected conditions, the population size of E. tonkinense still needs to be dynamically monitored. In specific conservation practices, it is necessary to focus on protecting slope habitats and reducing human disturbances.