Abstract Mangroves throughout the world are threatened by environmental changes apart from anthropogenic disturbances. Many of these changes may inhibit the growth and survival of mangrove species. To understand and predict the effects of global change on mangrove forests, it is necessary to obtain insights on the growth dynamics of mangroves in relation to environmental factors. This study was conducted on Sonneratia apetala, a mangrove species which grows under a range of salinity conditions across the Sundarbans in Bangladesh. We studied trees growing under respectively high, medium, and low salinity conditions based on the influence of freshwater discharge. First, the periodicity of radial growth across the year was detected by applying cambial analyses. Based on tree-ring analyses, we calculated the growth response of S. apetala to monthly variation in precipitation and temperature as well as river discharge, as a proxy for salinity. We found the cambium of S. apetala being active during the monsoon and post-monsoon period whereas it was dormant in the pre-monsoon. This periodicity in radial growth leads to the formation of distinct annual rings with ring boundaries being marked by radially flattened fibres. S. apetala trees growing under low salinity conditions generally show higher growth rates indicating the positive impact of river discharge, i.e. freshwater input on mangrove growth. Wet and warm conditions during the monsoon period positively affected S. apetala growth, especially in the low salinity zone. Our results show that salinity is the primary driver of growth dynamics of S. apetala in the Sundarbans. A gradual or seasonal increase in salinity, e.g. as a consequence of sea-level rise may therefore importantly alter the growth of this species, possibly leading to changes in mangrove forest dynamics and zonation.

中文翻译：

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盐度驱动红树林Sonneratia apetala Buch 的生长动态。-火腿。孟加拉孙德尔本斯

摘要 除了人为干扰外，世界各地的红树林还受到环境变化的威胁。其中许多变化可能会抑制红树林物种的生长和生存。为了理解和预测全球变化对红树林的影响，有必要深入了解与环境因素相关的红树林生长动态。这项研究是对无瓣海桑属植物进行的，这是一种在孟加拉国孙德尔本斯的一系列盐度条件下生长的红树林物种。我们根据淡水排放的影响研究了分别在高、中和低盐度条件下生长的树木。首先，通过应用形成层分析检测了全年径向增长的周期性。基于年轮分析，我们计算了 S. 的生长响应。apetala 到降水和温度以及河流流量的月变化，作为盐度的代表。我们发现 S. apetala 的形成层在季风和季风后期活跃，而在季风前期则处于休眠状态。这种径向生长的周期性导致形成不同的年轮，年轮边界以径向扁平的纤维为标志。在低盐度条件下生长的 S. apetala 树通常表现出较高的生长率，表明河流排放的积极影响，即淡水输入对红树林生长的影响。季风期间潮湿和温暖的条件对 S. apetala 的生长产生了积极影响，尤其是在低盐度区。我们的结果表明，盐度是 Sundarbans 无瓣 S. apetala 生长动态的主要驱动因素。盐度逐渐或季节性增加，例如