ABSTRACT

Teak (Tectona grandis) is among the most valuable tropical hardwoods, but silvicultural guidelines are needed to improve the growth and quality of trees in teak plantations, particularly those owned by smallholders in Asia. We analyzed the diameter growth of individual trees to determine the effects of density control in the early stages of growth in a teak plantation in northern Thailand. Site water conditions estimated using the topographic index (TI) affected initial tree size at 10 years after planting, before the first thinning was conducted. Thinning comprised three levels: high, low, and none (control). Five years after thinning, we assessed the effects of thinning, diameter at thinning, TI, and neighborhood competition on tree diameter growth using generalized linear mixed models. We found two significant factors on diameter growth: negative effect of neighborhood competition and positive effect of initial diameter at thinning. We used two indices of neighborhood competition: size-asymmetric (one-sided) and symmetric (two-sided) competition. The two-sided competition model predicted diameter growth more accurately. The results indicate that inter-tree competition in even-aged teak plantations is size-symmetric or two-sided. In addition, the presence of size-symmetric competition implies that teak trees compete not only for light but also for below-ground resources, such as water and nutrients.

摘要

柚木（Tectona grandis）是最有价值的热带硬木之一，但需要进行造林指导，以改善柚木人工林，特别是亚洲小农拥有的人工林的生长和质量。我们分析了单个树木的直径生长情况，以确定在泰国北部柚木种植园生长早期阶段进行密度控制的效果。使用地形指数（TI）估算的现场水状况会影响种植后10年，首次进行间伐之前的初始树木大小。细化包括三个级别：高，低和无（控制）。间伐后五年，我们使用广义线性混合模型评估了间伐，间伐直径，TI和邻域竞争对树木直径增长的影响。我们发现了直径增长的两个重要因素：邻里竞争的负面影响和间伐时初始直径的积极影响。我们使用了邻里竞争的两个指标：规模不对称（单面）和对称（双面）竞争。双向竞争模型可以更准确地预测直径的增长。结果表明，在同龄的柚木人工林中树间竞争是大小对称的或两侧的。另外，大小对称竞争的存在意味着柚木树不仅竞争光，而且竞争地下资源，例如水和养分。结果表明，在同龄的柚木人工林中树间竞争是大小对称的或两侧的。另外，大小对称竞争的存在意味着柚木树不仅竞争光，而且竞争地下资源，例如水和养分。结果表明，在同龄的柚木人工林中树间竞争是大小对称的或两侧的。另外，大小对称竞争的存在意味着柚木树不仅竞争光，而且竞争地下资源，例如水和养分。