桂西南喀斯特季节性雨林幼树更新的空间分布格局及机制

Spatial distribution pattern and mechanism of sapling regeneration in karst seasonal rainforest in southwestern Guangxi

幼树是维持森林生态系统物种多样性的重要组分,关系着森林的群落结构和生长动态。因此,开展幼树更新的空间分布格局及其潜在机制研究对森林群落动态至关重要。本文以广西弄岗桂西南喀斯特季节性雨林15 ha森林动态监测样地为研究对象,选取2011-2016年的调查数据,采用空间点格局和冗余分析方法对5年间样地内新增幼树(DBH≥1 cm)的个体数量、空间格局特征和影响因子等进行分析。结果表明:5年间样地内新增幼树共101种,占2011年调查物种的45.3%,幼树密度为196.5株/ha。新增幼树在0-7 m和10-16 m尺度上呈聚集分布,在16 m尺度以上主要呈随机分布。海拔是影响幼树更新的主要因素,其次是地形湿润度,而生物因子对幼树更新的影响较弱。幼树数量与海拔呈负相关,与地形湿润度呈正相关。成树个体与幼树更新中度正相关。在喀斯特季节性雨林中,幼树更新及其空间分布格局受多种影响因子协同作用,可能与种子扩散限制和生境异质性有关。

Aims:Saplings are an important component of maintaining the species diversity of forest ecosystems.Their diversity is related to forest community structure and growth dynamics.Therefore,it is very important to study the spatial distribution pattern and potential mechanism of sapling regeneration for forest community dynamics.To strengthen the understanding of the dynamic changes of the northern tropical karst seasonal rainforest,we will study the spatial distribution pattern and mechanism of sapling regeneration in 15 ha northern tropical karst seasonal rainforest dynamics plot in Nonggang,southwestern Guangxi.Methods:Based on the survey data from 2011 to 2016,the individual number,spatial pattern characteristics,and influencing factors of new saplings(DBH≥1 cm)in five years were analyzed by spatial point pattern and redundancy analysis.Results:A total of 101 species of new saplings were observed,accounting for 45.3%of the surveyed species in 2011,and the sapling density was 196.5 ind./ha.The newly increased saplings showed aggregated distribution at 0-7 m and10-16 m scale,and random distribution above 16 m scale.Altitude is the main factor affecting the regeneration of saplings,followed by topographic wetness.Biological factors had a weak impact on sapling regeneration.The number of saplings was negatively correlated with increasing altitude,and positively correlated with topographic wetness.Moderate positive correlation between adult tree individuals and young tree regeneration was observed.Conclusion:In this karst seasonal rainforest,sapling regeneration and spatial distribution pattern are synergistically affected by various influencing factors,which may be related to limited seed dispersal and habitat heterogeneity.