海南岛木麻黄林林下植物天然更新影响因素的研究

木麻黄海防林是海南岛重要的海岸生态屏障,天然更新对其持续发挥防护功能具有重要意义。调查发现海南岛大多数木麻黄林林下天然更新困难,然而却存在局部更新良好的现象。为了探究天然更新存在巨大差异的原因,并为促进海南海防林由人工林向近自然林转化提供一定的理论基础,通过分析不同林地更新质量的差异,研究影响木麻黄海防林林下天然更新的主要影响因素。该研究在海南岛木麻黄海防林中共设置73块临时样地,采用方差分析和相关分析等统计方法,分别研究林地所属气候区、林分条件、土壤因子和凋落物累积量对天然更新质量和密度的影响。结果表明:(1)湿润气候区的木麻黄林下更新要显著优于半干旱区;(2)木麻黄林分密度与更新密度和草本盖度存在显著负相关,但林分条件其他因子对更新影响不大;(3)不同更新质量样地的土壤pH和养分均无显著性差异,但铵态氮对幼苗、有机质对幼树的更新存在一定的促进作用;(4)凋落物的累计整体不利于天然更新的进行。结果说明气候因子、木麻黄林分密度、木麻黄凋落物积累量是木麻黄海防林林下植物天然更新的主要影响因素。

Impact factors of undergrowth natural regeneration for Casuarina equisetifolia forests in Hainan Island

Casuarina equisetifolia coastal protection forest(C. CPF)is an important barrier of coastal ecology in Hainan Island, and natural regeneration is of great significance for it to play a role of protection function continuously. It is found that undergrowth natural regeneration is difficult in the most area of C. equisetifolia forests in Hainan Island, however, there is a phenomenon of good regeneration in the local area. In order to explore the cause of the great disparity in the natural regeneration, and to provide certain theoretical basis for promoting the transformation of C. CPF from plantation to near-natural forest, the main factors affecting the natural regeneration of C. CPF were studied through the analysis of the differences of regeneration quality for different forest lands. Seventy-three temporary plots were established in the C. CPF in Hainan Island, and statistical methods, such as variance analysis and correlation analysis, were used to study the effects of climate zones, stand conditions, soil factors and litter accumulation on natural regeneration quality and density. The results were as follows:(1)The regeneration of C. CPF in wet zone was significantly better than that in dry zone;(2)There was significantly negative correlation between C. equisetifolia stand density and regeneration density or herb coverage, but other factors of stand conditions had little effect on regeneration;(3)There was no significant diffe-rences in soil pH value and nutrients in the sample plots with different regeneration qualities, but ammonium nitrogen promoted the regeneration of seedlings and organic matter did the regeneration of saplings to some extent;(4)The accumulation of litter was not conductive to natural regeneration as a whole. The results indicate that the climate factor, density of C. equisetifolia stands and accumulation quantity of C. equisetifolia litters were the main impact factors for the natural regeneration of undergrowth in C. CPF.