气候变化背景下树木径向生长对于生物和非生物因子的响应是当今生态学的研究热点之一。亚热带季风区拥有较多的植被类型和更高的生产力水平，而该地区的树木年轮学研究由于地区生态系统的复杂性和年轮辨认难度而相对缺乏。利用树木年轮学方法研究该地区树木径向生长对气候和竞争的响应具有基础科学价值，并对于探索相关的森林管理措施有积极意义。

针对国内树木年轮学研究在亚热带地区的相对不足，中国科学院华南植物园生态及环境科学研究中心罗大为等研究生在导师黄建国的指导下，选取肇庆鼎湖山国家级自然保护区和英德石门台国家级自然保护区的主要树种——马尾松和木荷，采用树木年轮学方法比较研究其径向生长对于气候和竞争的响应。

研究表明，在中国亚热带森林，影响马尾松和木荷径向生长的气候因子主要是温度，而不同季节的温度对于树木径向生长的影响在尺度上和方向上都有差异，主要体现在夏季高温对树木径向生长的抑制和春季温度升高对树木径向生长的促进作用。树木的多年累积生长对竞争呈现出不同程度的响应，且竞争胁迫更多的来自大型树木，并在林龄较大的森林中更为明显。研究指出，该地区树木生长受到竞争的影响将随地区森林的低龄化趋势而减小，进而影响森林生产力的变化。

研究工作获得中国国家自然科学基金以及广东省自然科学基金支持，相关研究结果在线发表在Dendrochronologia上。（来源：中国科学院华南植物园）

Effect of climate and competition on radial growth of Pinus massoniana and Schima superba in China’s subtropical monsoon mixed forest

Abstract   Tree growth is affected by many exogenous and endogenous factors, especially climate and competition. To address the issue of how these factors influence tree growth under global warming, dendroclimatology combined with competition analysis was used to examine the radial growth response of two major species – Pinus massoniana and Schima superba in subtropical monsoon mixed forests in southern China. For growth-climate relationship analysis, residual and ARSTAN chronologies of these two species were compared for the response function analysis over the past several decades. In terms of competition analysis, annual basal area increment (BAI) over several time intervals was calculated and linear mixed model techniques were employed. Several distance-independent competition indices were measured, including density (N), basal area (BA), and sum of diameter at breast height (SDBH). For competition trees with greater diameter (GR) than the subject tree, NGR, BAGR, SDBHGR were also calculated. Growth-climate relationship analysis suggested that tree growth varied in response to climate and was mostly correlated with minimum, mean and maximum air temperature as indicated by the adjusted R2 value. Summer and winter temperatures had a negative effect on tree growth, while early spring temperature showed positive effects. Competition analysis suggested that subtropical trees had been affected by competition in varying degrees. Trees in the oldest forest had the most competition stress, while trees in younger forests were less affected by competition according to the adjusted R2 value. Given that subtropical forests in China have been found to have more smaller trees with recent warming, it is expected that these forests will experience a decreasing effect of competition in near future. This can have profound effects on forest productivity and carbon sequestration potentials in Chinese subtropical forests.

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