How do inter- or intra-specific differences in crown architecture, light absorption and light-use efficiency determine thinning responses and complementary effects in mixed-species forests?

生态学研究中关于树种多样性对生态系统功能影响的信息很少被转化为森林管理。由于缺乏资料，无法将案例研究的结果扩大到实际的森林，因为它们的立地条件和林分密度变化很大。混合物是否更有生产力取决于不同类型的相互作用的净效应，而这些相互作用是动态的，随着时间和空间的变化而变化。很少有研究审查资源可得性或气候条件的时空差异如何影响这些相互作用，而且似乎普遍认为，随着资源可得性的下降，混合物中的互补效应通常会增加。这通常是正确的，但大约30%的森林或人工林文献研究显示出相反的趋势，即随着资源可用性的增加或气候条件变得更加有利，特定物种组合的互补效应会增加，但没有研究实际测量驱动这种模式的过程。如果物种相互作用增加了光合有效辐射（APAR）的吸收或光利用效率（LUE），则互补性和生产力的提高可能会发生。随着生产力和林分叶面积的增加，对光的竞争也将增加，任何提高APAR或LUE的相互作用都将变得越来越有用。本研究将研究单物种和混合物种群落中单株树木的APAR和LUE，以及这是如何受到冠层结构和树冠结构种间或种内变异的影响的。林分密度对树木生长、APAR和LUE之间的关系有一定的影响。因此，在对植物生物多样性试验和混交林进行沿生产力梯度的分析时，将使用间伐试验的数据进行分析，也将使用生产力梯度的数据进行分析。这些结果将用于测试描述物种相互作用空间动态的新概念模型。

Very little of the information from ecological research on the effects of tree species diversity on ecosystem functioning has been translated into forest management. This has been hampered by the lack of information to scale up the results from case studies to real forests with their large variation in site conditions and stand densities. Whether or not mixtures are more productive depends on the net effects of different types of interactions, and these are dynamic, changing through space and time. Few studies have examined how spatial and temporal differences in resource availabilities or climatic conditions can influence these interactions, and there appears to be a general perception that complementary effects in mixtures usually increase as resource availability declines. This is often true, but about 30% of the studies in the forest or plantation literature show the opposite trend, where complementary effects for a given species combination increase as resource availability increases or climatic conditions become more favourable, but no studies have actually measured the processes that drive this pattern. Increasing complementarity with increasing productivity could occur if species interactions increase the absorption of photosynthetically active radiation (APAR) or light-use efficiency (LUE). As productivity and stand leaf area increase, competition for light will also increase and any interaction that improves APAR or LUE could become increasingly useful. This study will examine the APAR and LUE of individual trees in mono-specific and mixed-species neighbourhoods and how this is influenced by canopy structure and inter- or intra-specific variability in crown architecture. Relationships between tree growth, APAR and LUE will probably be influenced by stand density. Therefore analyses in planted biodiversity experiments and mixed-species forests along productivity gradients will be accompanied by analyses using data from thinning experiments, also along productivity gradients. These results will be used to test a new conceptual model describing the spatial dynamics of species interactions.