边缘效应对卧龙自然保护区森林-草地群落交错带地表甲虫多样性的影响

Influence of edge effect on diversity of ground-dwelling beetles across a forest-grassland ecotone in Wolong Natural Reserve, Southwest China

本文研究了卧龙国家自然保护区地表甲虫群落在天然落叶阔叶林森林边缘与森林内部和周围草地间多样性差异,在科级水平上探讨边缘效应对地表甲虫群落的影响。调查共设5个重复样带(间距大于500m);每个样带以距离梯度(25m)的方式设置样点,分别由边缘深入到森林内部和草地中央100m,共设45个样点,通过巴氏罐诱法调查地表甲虫群落组成和季节变化。本研究采集甲虫标本4736号,隶属于28个科,步甲科、隐翅虫科和叩甲科分别占总数的49.5%、23.5%和13.0%,共同构成本研究地区地表甲虫的优势类群。甲虫的个体数量从森林内部、边缘到周围草地依次降低,而科多样性和均匀度则依次增高,都达到了显著差异。主坐标分析(PCoA)排序表明,森林内部和周围草地间的地表甲虫群落组成差异较大;而森林边缘的群落组成与两者都有较高程度的相似性,反映了森林边缘的地表甲虫群落已经与森林内部的群落组成发生明显分化,除了森林物种成分外,还包含了若干从周围草地环境扩散来的物种成分。从季节动态看,森林边缘和森林内部在丰富度和个体数量的季节变化曲线方面相似性更高;捕食类和腐食类地表甲虫的季节变化在森林内部和边缘相似性更高,而植食类则在森林边缘和草地的相似性更高。多元回归分析表明,枯落物覆盖率是影响地表甲虫科多样性和均匀度的决定因素,枯落物厚度和林冠层覆盖率是决定甲虫个体数量分布的重要因素。以上结果表明,在科级水平上,地表甲虫群落在天然落叶阔叶林边缘已经与森林内部生境发生分化,而且正在加剧的森林片断化进程将会产生更多的森林边缘,因此,保留大面积的天然落叶阔叶林免受破坏和干扰是保护地表甲虫多样性的必要措施。

This paper studies the influences of edge effect on ground-dwelling beetles （Coleoptera） across a forest-grassland ecotone, where the forest interior, the forest-grassland edge and the grassland are compared using beetle diversity （abundance and composition in family level） as the main indicator. The study was conducted in Wolong Natural Reserve （102°52′ - 103°24′E, 30°45′ -31°25′N）, Sichuan, Southwest China. Beetles were collected with pitfall traps in 45 plots along five replicated transects extending 100 m from the edge into the forest interior and 100 m into the grassland, with a 25 m interval between different plots. During the field research, a total of 4 736 beetles were collected. Of these beetles belonging to 28 families, Carabidae comprised 49.5 %, Staphylinidae 23.5 %, and Elateridae 13.0 % of the total, being considered as dominant groups. From forest interior to forest edge and then to grassland, family abundance decreased in sequence, but family diversity and evenness increased in sequence. Based on the family composition and abundance, grounddwelling beetles from the forest interior and those from the grassland were separated from each other by PCoA ordinations; but the beetle assemblages in the forest edge were similar to those found in both the forest interior and grassland, suggesting that the beetle assemblages on the forest edge were dispersed from both of the two adjacent habitats. Seasonal dynamics of family richness and abundance in the forest edge were more similar to the forest interior than to grassland. Predators and scavengers of ground-dwelling beetles showed the similar seasonal changes between the forest interior and edge, while the seasonal variation of the phytophagous in the forest edge was more similar to that in grassland. Multiple linear regression analyses showed that litter cover was the most important factor determining the family diversity and evenness of ground-dwelling beetles, and litter depth and canopy cover affected the family abundance. The results indicated the forest edge had obviously different composition of ground-dwelling beetles from that in forest interior at the family level. Since increasing forest fragmentation would result in more edge, it is so necessary to preserve a large enough area of undisturbed deciduous broad-leaved forest for protecting the diversity of ground-dwelling beetles.