[Objective] To explore the changes in vegetation community characteristics of the Acacia mangium plantation under natural restoration, which could provide theoretical basis for promoting the transformation of A. mangium plantation into the natural forest in Hainan Island Ecological Public Welfare Forest and Hainan Tropical Rainforest National Park.
[Method] Using the method of space instead of time, A. mangium plantations with different natural restoration times (10, 15 and 20 years) were selected as the research objects in the Fengmu Experimental Forest Farm of Hainan, and the natural secondary forest with good natural restoration was used as the control. The vegetation of the tree layer, shrub layer and herb layer was investigated, and the stand structure, growth status, species composition and species diversity characteristics of A. mangium plantations with different natural restoration times and their differences with natural secondary forests were analyzed.
[Result] In A. mangium plantation, with the increase of natural restoration time, the density of A. mangium decreased gradually, and the canopy density decreased gradually. There was no significant difference in tree regeneration layer density, shrub layer density, average height of shrub layer, and average height of herb layer between A. mangium plantation and natural secondary forest after 20 years of natural restoration ( P>0.05, the same below), while the average height of tree regeneration layer and coverage of herb layer were significantly lower than those of natural secondary forest ( P<0.05, the same below). The diameter distribution of the tree regeneration layer of A.mangium plantation with different natural restoration times conformed to the Weibull distribution, and its shape parameter c was less than 1, which was an inverted J-type distribution. The scale parameter b gradually approached the natural secondary forest tree layer with increased natural restoration time. With the increase in natural restoration time, the number of species in A. mangium plantation community increased, and the composition of dominant species in each forest layer changed greatly. Principal coordinate analysis (PCoA) results showed that the species composition of the tree layer and shrub layer gradually evolved into a natural secondary forest. With the increased natural restoration time, the Patrick index and Shannon index of the tree layer of the A. mangium plantation increased gradually, while the Simpson index and Pielou index changed slightly. However, the species diversity index of A. mangium plantation tree layer after 20 years of natural restoration was still significantly lower than that of natural secondary forest. With the increase in natural restoration time, the diversity index within the shrub layer of A.mangium plantation first increased and then decreased, while that within the herb layer first decreased and then increased. There was no significant difference in the Shannon index, Simpson index and Pielou index in shrub layer and herb layer between the A. mangium plantation with natural restoration for 10 years and 20 years and natural secondary forest, but patrick index was significantly lower than natural secondary forest.
[Conclusion] The stand structure, species composition, and species diversity of A. mangium plantation under natural restoration are gradually approaching to those of natural secondary forest, but there is still a certain gap. With the increase in natural restoration time, the stand structure of A. mangium plantation becomes more diverse and complex, and the community has the potential for natural regeneration and positive succession.
摘要:【目的】 探究自然恢复下马占相思人工林植被群落特征变化, 为推动海南岛生态公益林和海南热带雨林国 家公园内马占相思人工林向天然林转型提供理论依据。 【方法】采用空间代替时间的方法, 在海南省枫木实验林场选 取不同自然恢复时间 (10、15和20年) 的马占相思人工林作为研究对象, 并以自然恢复良好的天然次生林为对照, 对乔 木层、灌木层和草本层进行植被调查, 分析不同自然恢复时间马占相思人工林的林分结构、生长状况、物种组成和物 种多样性特征及其与天然次生林的差异。 【结果】马占相思人工林中, 随着自然恢复时间的增加, 马占相思密度逐渐下 降, 林分郁闭度也逐渐降低。自然恢复20年的马占相思人工林乔木更新层密度、灌木层密度、灌木层平均高度和草本 层平均高度与天然次生林均无显著差异 ( P>0.05, 下同), 而乔木更新层平均高度和草本层盖度均显著低于天然次生 林 ( P<0.05, 下同) 。不同自然恢复时间的马占相思人工林乔木更新层的直径分布符合Weibull分布, 其形状参数 c均 小于1, 为倒J型分布, 尺度参数 b随着自然恢复时间的增加逐渐接近天然次生林乔木层。随着自然恢复时间的增加, 马占相思人工林群落物种数量增加, 各林层优势种组成变化较大, 主坐标分析 (PCoA) 结果表明乔木层和灌木层的物 种组成逐渐向天然次生林演替。随着自然恢复时间的增加, 马占相思人工林乔木层的Patrick指数和Shannon指数均 逐渐增加, 而Simpson指数和Pielou指数均变化较小, 但自然恢复20年的马占相思人工林乔木层各物种多样性指数仍 显著低于天然次生林; 随着自然恢复时间的增加, 马占相思人工林灌木层的各物种多样性指数呈先升高后降低的变 化趋势, 草本层的各物种多样性指数呈先降低后升高的变化趋势, 自然恢复10年和自然恢复20年马占相思人工林的 灌木层及草本层Shannon指数、Simpson指数、Pielou指数与天然次生林均无显著差异, 但Patrick指数显著低于天然次 生林。 【结论】自然恢复下马占相思人工林的林分结构、物种组成和物种多样性逐渐接近天然次生林, 但仍有一定差 距。随着自然恢复时间的增加, 马占相思人工林的林分结构趋于复杂化, 群落具有天然更新和正向演替的潜力。
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