黔中北亚热带喀斯特次生林动态监测样地：物种组成与群落结构

Abstract

多年来强烈的人为干扰导致我国西南喀斯特原生森林丧失殆尽并呈现植被灌丛化, 甚至石漠化现象。贵州普定县残存的片段化喀斯特次生林是黔中地区北亚热带森林植被的典型代表, 可作为监测该区域植被结构和动态的样本。在普定县天龙山建立2 hm²(200 m×100 m)森林固定样地, 对样地内胸径≥ 1 cm的所有木本植物进行了每木调查, 分析了木本植物的物种组成、区系特征、径级结构和空间分布格局。结果表明, 样地内有木本植物独立个体14, 025株, 隶属于34科55属66种。重要值最大的前3个科依次是壳斗科、胡桃科和樟科。在区系成分上, 温带区系成分占总属数的52.7%, 而热带区系成分占40.0%, 温带成分多于热带成分。稀有种有21种, 占总种数的31.82%。重要值≥ 1的物种共有13种, 贡献了88.81%的重要值, 重要值排名前三的物种分别是窄叶石栎(Lithocarpus confinis)、化香树(Platycarya strobilacea)和云南鼠刺(Itea yunnanensis)。样地内所有个体的平均胸径仅为5.12 cm, 整体径级分布呈倒“J”, 表明群落更新良好。部分优势种的空间分布表现出较明显的聚集性, 这可能与喀斯特生境的高度异质性有关。对北亚热带喀斯特次生林开展长期监测研究, 将有助于掌握亚热带喀斯特植被恢复过程中生物多样性维持和群落构建的机制。;China has the largest and widest karst regions in the world, which is mainly distributed in the subtropical mountainous regions of southwest China where a unique type of karst vegetation grows. However, the karst forests in these regions have been degraded seriously due to strongly anthropogenic disturbance over many years. Therefore, vegetation thicketization and even rocky desertification have occurred in most karst regions in southwest China. The fragmented karst secondary forest in Puding County is a typical representative of the north subtropical forest vegetation in central Guizhou Province, and can be used as a sample for monitoring the vegetation structure and dynamics in this region. In this study, a 2 hm² (200m×100m) permanent forest plot was established in Tianlongshan in Puding County. Within this plot, all woody plants with a diameter at breast height (DBH)≥1 cm were mapped and identified at species level. Based on these data, the community composition and spatial structure of the vegetation community were analyzed. Results indicated that there were 14, 025 woody plant individuals belonging to 66 species, 55 genera and 34 families. The families with high importance values (Ⅳ) are Fagaceae, Juglandaceae, Lauraceae, Saxifragaceae, Rosaceae, Betulaceae, Rhamnaceae, etc. There were more temperate elements (52.7%) than tropical elements (40.0%) found both at genus level, which showed that the flora was mainly the type of transition from tropical to temperate in the study area. Twenty-one rare species (those with individual number fewer than two in the plot) accounted for 31.82% of the species total. The distribution of rare species in Tianlongshan plot might be determined by multi-dimensional factors such as climate, topography, biogeographic processes, as well as anthropogenic disturbance. In the plot, the 13 species with Ⅳ≥1 contributed 88.81% to the Ⅳ of the community. The species with high Ⅳ are Lithocarpus confinis, Platycarya strobilacea Itea yunnanensis, Machilus cavaleriei, Carpinus pubescens, Pittosporum brevicalyx, Lindera communis, etc. The average DBH of all individuals in the plot was only 5.12 cm, and DBH size-class distribution followed a reverse J shape, indicating abundant regeneration. The spatial distribution of some dominant woody species showed obvious aggregation pattern in plot scales possibly related to high habitat heterogeneity in karst landscape. Monitoring and research on secondary forests in the north subtropical karst region will contribute to further understanding the mechanisms of biodiversity maintenance and community assembly in the process of vegetation restoration. Further studies should concentrate on the maintenance mechanisms of diversity and stability of forest community, the coupling relationships between above-ground and underground ecological processes, and the response and adaptation of vegetation to short-term disturbance events and long-term climate change in the north subtropical karst regions in southwest China.