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?

关于树种多样性对生态系统功能的影响的生态学研究中，很少有信息被转化为森林管理。由于缺乏将案例研究的结果扩大到真实森林的信息，这一点受到了阻碍，因为这些森林的立地条件和林分密度差异很大。混合是否更有成效取决于不同类型的相互作用的净影响，而这些相互作用是动态的，随着空间和时间的变化。很少有研究研究资源可获得性或气候条件的空间和时间差异如何影响这些相互作用，而且似乎有一种普遍的看法，即随着资源可获得性的下降，混合物中的互补效应通常会增加。这通常是正确的，但森林或种植园文献中约30%的研究显示出相反的趋势，即特定物种组合的互补效应随着资源可获得性的增加或气候条件变得更有利而增加，但没有研究实际测量推动这种模式的过程。如果物种间的相互作用增加了对光合作用有效辐射(APAR)或光能利用效率(LUE)的吸收，就可能在提高生产力的同时增加互补性。随着生产力和林分叶面积的增加，对光的竞争也将增加，任何改善APAR或LUE的相互作用都可能变得越来越有用。这项研究将研究单一树种和混合树种社区中单个树木的APAR和LUE，以及树冠结构和树冠结构的种间或种内差异如何影响这一点。林木生长与APAR、LUE的关系可能受林分密度的影响。因此，种植生物多样性试验和混交林中沿生产力梯度的分析将伴随着使用间伐试验数据的分析，也将沿着生产力梯度进行。这些结果将用于测试一个新的概念模型，该模型描述了物种相互作用的空间动力学。

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.