江西官山亚热带常绿阔叶林景观粒度效应研究

Grain size effect of landscape in Jiangxi Guanshan subtropical evergreen broad-leaved forest

关键词:  最佳粒度, 景观格局, 景观类型, 景观指数, 敏感度

Key words:  optimal grain size, landscape pattern, landscape type, landscape index, sensitivity

摘要:

确定合理的粒度是景观格局分析和生态研究过程的关键。为深入了解空间的多样性和景观格局的动态特征,该研究基于2015年、2020年江西官山国家级自然保护区12 hm²森林大样地调查数据,分析8种不同景观类型的各个景观指数在5～50 m粒度范围内的粒度效应; 通过变异系数揭示不同景观格局指数随粒度增大的变化特征,并结合各项景观指数变化拐点选取最佳粒度。结果表明:(1)根据重要值分析得出,大样地内乔木层划分出8种不同的景观类型,分别为林窗、竹林、杉木林、马尾松林、阔叶林、杉松混交林、竹松混交林、竹杉混交林。(2)整体景观的斑块分布较为均衡,分布形式变化不大; 更大的空间粒度下,各景观类型的聚集度增加,发生景观融合的概率增加,而小粒度下,景观类型有明显的破碎化趋势,能更全面地展示各景观类型的数量、密度、形状等特征; 斑块密度(PD)、斑块数量(NP)、边缘密度(ED)、景观形状指数(LSI)、平均分维指数(FRAC_MN)、蔓延度(CONTAG)随粒度的增加而增加,而平均斑块面积(AREA_MN)、香农多样性指数(SHDI)、香农均匀度指数(SHEI)随粒度的增加而减少。(3)景观指数中PD、NP、ED、LSI、AREA_MN的变异系数最大; 综合景观结构稳定性和多样性,不同景观指数的变化主要集中在5 m处的拐点。综上认为,江西官山亚热带常绿阔叶林景观格局研究的最佳粒度为5 m。该研究结果为森林资源、林分结构的恢复提供了有利证据。

Abstract:

Determining an appropriate grain size is crucial in landscape pattern analysis and ecological research. In order to gain deeper insights into the spatial diversity and dynamic characteristics of landscape pattern, based on the survey data of the 12 hm² large plot inJiangxi Guanshan National Nature Reserve in 2015 and 2020, the grain size effect of landscape indices in eight different landscape types within the range of 5-50 meters were analyzed; the variation coefficients were used to reveal the changing characteristics of different landscape pattern indices as the grain size increased, and the optimal grain size was selected based on the inflection points of changes in various landscape indices. The results were as follows:(1)Based on the importance value analysis, eight different landscape types were identified in the arbor layer of the plot, including forest gap, bamboo forest, Cunninghamia lanceolata forest, Pinus massoniana forest, broad-leaved forest, bamboo and Cunninghamia lanceolata mixed forest, bamboo and Pinus massoniana mixed forest, Cunninghamia lanceolata and Pinus massoniana mixed forest.(2)The overall distribution of patches in the landscape was relatively balanced, and the distribution pattern remained relatively stable. At larger spatial grain size, the aggregation of each landscape type increased, leading to a higher probability of landscape merging. In contrast, at smaller granularity, there was a noticeable trend of fragmentation in landscape types, providing a more comprehensive display of the quantity, density, and shape of each landscape type. Patch density(PD), number of patches(NP), edge density(ED), landscape shape index(LSI), mean fractal dimension index(FRAC_MN), contagion index(CONTAG)exhibited significant negative correlations with increasing grain size, while mean patch area(AREA_MN), Shannon's diversity index(SHDI), Shannon's evenness index(SHEI)exhibited significant positive correlations with increasing grain size.(3)The coefficients of variation for landscape indices PD, NP, ED, LSI, and AREA_MN were the highest, combining landscape structural stability and diversity, the changes in different landscape indices were primarily concentrated around the inflection point at 5 meters. These results illustrate the diversity of landscape types, with the coefficient of variation reflecting the most sensitive characteristics of landscape pattern changes. This study suggests that a grain size of 5 meters is optimal for studying the landscape pattern of subtropical evergreen broad-leaved forests in Guanshan, Jiangxi. This study provides favorable evidence for the restoration of forest resources and stand stucture.