滇中高原半湿润常绿阔叶林的岛屿化与物种多样性

Islandization and species diversity of semi-humid evergreen broad-leaved forests in the Central Yunnan Plateau

森林破碎化(或岛屿化)是导致当前生物多样性丧失的重要成因之一。滇中地区地带性的半湿润常绿阔叶林(semi-humid evergreen broad-leaved forests,SEBFs)具有显著的岛屿化特征。当前村寨周边面积大小、形状不一的“岛状”森林为研究破碎化的半湿润常绿阔叶林及其物种多样性特征提供了理想对象。本文通过植被遥感制图和群落样方调查,运用空间统计、物种多样性分析、群落排序及环境解释,探讨了滇中高原半湿润常绿阔叶林的岛屿化特征及其对群落物种多样性的影响。结果表明:(1)滇中高原现存半湿润常绿阔叶林仅占其潜在分布范围的1.5%,面积≥100 ha的林斑有92块,而面积<10 ha的林斑占斑块总数的54.6%和总面积的7.8%;该植被类型面积萎缩和破碎化严重;(2)99%的林斑到村寨的距离<3 km,距离村寨越远,林斑平均面积越大,但样方物种α多样性除均匀度外变化不显著;不同面积等级斑块中样方物种α多样性也仅物种丰富度有显著变化,面积超过100ha的大斑块有更高的物种丰富度;离村寨越近,样方群落物种组成简单化和同质化现象加强;(3)样方群落β多样性主要由物种替换引起。森林岛屿化是导致半湿润常绿阔叶林群落物种组成变化的主要因子,而人类干扰强度对群落物种组成的影响高于局部生境异质性(水分条件)和区域气候梯度(低温限制)的影响。滇中高原半湿润常绿阔叶林以破碎小斑块大量存在于村寨周边,在人为干扰下群落退化明显,亟待引起足够重视,并采取必要措施加强保护。

Aims:This study focuses on the semi-humid evergreen broad-leaved forests(SEBFs)in Central Yunnan Plateau,a zonal vegetation characterized by varying patches sizes and shapes distributed around rural villages.Through remote sensing based vegetation mapping and field vegetation investigation,we aimed to explore the spatial patterns of fragmented SEBF patches,the changes in plant species diversity of SEBFs in relation with its patch size and distance class from villages,and assess the effects of environmental and anthropogenic factors on the species composition of SEBFs communities.Methods:This study investigated the fragmentation features of SEBFs and their impact on species diversity.We conducted spatial analysis and species diversity assessments using the patch and community data from SEBFs.SEBFs’patches were derived from Landsat 8 OLI imageries in combination of supervised classification and visual interpretation.αdiversity andβdiversity were compared among the plot community types.And the species composition was compared using non-metric multidimensional scaling to indicate the importance of environmental drives.Results:(1)In Central Yunnan Plateau,the existing SEBFs only accounted for 1.5%of their potential,climate-determined distribution range.This area comprised 92 forest patches covering a space greater than 100 ha,whereas forest patches covering an area of<10 ha accounted for 54.6%of the total patch number but only 7.8%of the total area.This highlighted the significant shrinking and fragmenting of this vegetation type’s area.(2)Remarkably,99%of forest patches were within 3 km from rural villages.A trend emerged where patches farther away from villages had larger area,but the speciesαdiversity did not show significant changes except for species evenness.For sample plots in patches with different area classes,αdiversity only showed significant changes in species richness;larger patches exceeding 100 ha exhibited higher species richness.In contrast,the closer a patch was to a village,the more simplified and more homogeneous its species composition tended to be.(3)βdiversity among plot communities was primarily driven by species replacement.Forest islanding was a key factor influencing changes in species composition of SEBFs communities.Moreover,the impact of human interference on species composition was significantly greater than that of local habitat heterogeneity(water conditions)and regional climate gradients(low temperature limitations).Conclusion:The SEBFs in the Central Yunnan Plateau are abundant near villages with fragmented small patches,and these areas are experiencing notable degradation due to human interference.This situation is urgent and demands attention and the implementation of necessary protective measures.