尺度变化对关帝山庞泉沟云杉次生林空间分布格局的影响

林分空间格局研究对认识和理解森林群落结构的生态学过程具有重要作用。适宜的样地尺度不仅可以有效降低工作和时间成本,也可以提高林分属性的精确估计。同时,抽样尺度的适宜程度对科学评价林分空间结构调整也具有重要的现实意义。以关帝山庞泉沟4 hm²云杉次生林固定监测样地为研究对象,运用样地划分法和空间点格局的K2函数,评估了林分主要树种空间格局随样地面积变化的规律。结果表明:通过重要值排序,选取云杉(青杄+白杄)、华北落叶松、桦树(白桦+红桦)+其它阔叶树(花楸+辽东栎+山杨+山楂)作为主要树种(组)。随着样地尺度的减小(从4 hm²到0.25 hm²),空间分布格局主要表现为较小尺度(≤ 4 m)的聚集分布过度为随机分布与均匀分布,以及聚集和随机分布交替出现。所有树种的次级样地与参考样地的一致性指数差异显著,云杉和华北落叶松组合1 hm²样地一致性指数最高,而桦树和其它阔叶树完整1 hm²样地一致性指数最高;此外,云杉、华北落叶松和桦树0.25 hm²样地与组合1 hm²样地空间格局一致性指数组间差异显著。研究认为1 hm²样地尺度可以作为该地区云杉次生林空间分布格局的最小尺度。研究为探索云杉次生林空间格局的变化规律及样地抽样尺度的选取方面,提供了一定的理论基础和技术依据。

Effect of scale change on spatial distribution pattern of Spruce secondary forest in Pangquangou, Guandi Mountain, Shanxi Province

Investigation of spatial patterns in forest stands plays a crucial role in comprehending the ecological processes governing the structure of forest communities. Suitable plot scales not only reduce costs and time requirements but also enhance the precise estimation of stand attributes. Additionally, the appropriate degree of sampling scale is important for scientifically evaluating the adjustment of the spatial structure of stands. In this study, we employed a fixed monitoring plot measuring 4 hm² in Pangquangou, Guandi Mountain to evaluate variations in plot size and spatial pattern among major tree species using the plot division method and K2 function. According to the ranking of importance values, we chosed spruce (Picea wilsonii+Picea meyeri), Larix Principis, birch (Betula platyphylla + Betula albosinensis), and the other broad-leaved trees (Sorbus pohuashanensis+Quercus wutaishanica+Populus davidiana+Crataegus kansuensis) as the dominant tree species (group). The findings revealed that a transition in the spatial pattern of the dominant tree species from pronounced intraspecific aggregation to random and uniform distribution, as the plot size decreased (from 4 hm² to 0.25 hm²), with alternated occurrences of aggregation and randomness. Moreover, the agreement indexes of all tree species'' subplots exhibited significant deviations from those observed in the reference plot. The highest agreement index values were observed for the species groups of Picea and Larix principis in the combined 1 hm² plots, while the species group of Betula and other broadleaved tree species showed the highest agreement index values in the entire 1 hm² plots. Furthermore, the significant intergroup differences in the agreement index were found between 0.25 hm² plots and combined 1 hm² plots for both Picea/Larix Principis and Betula species groups. Our investigation suggests that 1 hm² plot can serve as the minimum size for assessing the spatial distribution pattern of spruce secondary forests in the study area. The study provides a solid theoretical and technical foundation for investigating the dynamic patterns of spatial distribution in spruce secondary forests and determining appropriate sampling sizes.