桂西北喀斯特人为干扰区植被自然恢复22年后群落特征

采用全面调查和样方调查的方法，以坡面为尺度，以顶极群落为对照，运用干扰理论和多样性分析方法，研究了桂西北喀斯特4类典型干扰区自然恢复22a之后植被特征及空间分布的变化。结果表明，干扰区的物种多样性丧失严重，共出现维管束植物91科206属241种，仅有自然保护区的26．6％，6种植被类型的顺向演替系列为石漠化稀疏草丛→草丛→灌丛→藤刺灌丛→落叶阔叶林→常绿落叶阔叶混交林片段。随着坡位的上升，群落的高度、盖度、生物量和物种多样性急剧下降。密度则呈少、多、次少的单峰分布状态，各项指标均远低于自然保护区。不同干扰方式对植被自然恢复的影响不同，其中整坡火烧＋垦殖的破坏性最大，呈现了石漠化景观，整坡火烧＋放牧次之，采樵属选择性干扰，采樵＋放牧＋坡脚火烧的恢复相对较快，没有放牧干扰的采樵＋坡脚火烧恢复更好。此外还针对性地提出了桂西北喀斯特干扰区在不同立地类型上人工与自然相结合的4条植被恢复途径。对因各种人为干扰导致的桂西北喀斯特生态系统处于极度退化状态下的植被恢复建设和生态重建具有重要的理论价值和实际意义。

Changes in vegetation after 22 years' natural restoration in the Karst disturbed area in northwestern Guangxi, China

Disturbance of ecosystem is ubiquitous in the world,which would primarily affect plant communities.The variations of plant vegetation and spatial distribution were investigated in the areas of four typical disturbances,which had been under natural restoration for 22 years in the karst area in the northwest of Guangxi while the climax plant community was utilized as control.The slope scale and disturbance theory was used to study plant diversity in whole area and selected plots.It is clear that the disturbances had resulted in severe loss of plant species,only 241 species of vascular plant that belong to 91 families and 206 genera survived in the disturbed areas,it was only 26.6% of that in natural conservation area.The consequent succession of plant vegetation types were sparse grass of rocky desertification,grass,shrub,liana-shrub,deciduous broad-leaved forest,and mixed segment of evergreen and deciduous broad-leaved forest.The height,coverage,biomass and species diversity of plants decreased sharply with slope elevating and the plant density appeared with normal distribution.Compared with the natural conservation area all criteria of plant vegetation in disturbed areas were much worse.Furthermore,different types of disturbances showed various affections on natural vegetative restoration,among them,tillage after whole slope burned caused the worst impact where rocky desertification was the consequence,followed by depasturing after whole slope burned.While cutting was selective disturbance,the vegetative restoration in the area with combination of cutting,depasturing and slope foot burning was relatively fast,however,it was even better in the area with combination of cutting and slope foot burning.Based on our studies,four strategies for vegetative recovery considering both natural and artificial approaches were established,which were suitable for the karst area in the northwest of Guangxi.