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The horizontal distribution of stems, stand density and the differentiation of tree dimensions are among the most important aspects of stand structure. An increasing complexity of stand structure is often linked to a higher number of species and to greater ecological stability. For quantification, the Structural Complexity Index (SCI) describes structural complexity by means of an area ratio of the surface that is generated by connecting the tree tops of neighbouring trees to form triangles to the surface that is covered by all triangles if projected on a flat plane. Here, we propose two ecologically relevant modifications of the SCI: The degree of mingling of tree attributes, quantified by a vector ruggedness measure, and a stem density term. We investigate how these two modifications influence index values. Data come from forest inventory field plots sampled along a disturbance gradient from heavily disturbed shrub land, through secondary regrowth to mature montane rainforest stands in Mengsong, Xishuangbanna,Yunnan,China. An application is described linking structural complexity, as described by the SCI and its modified versions, to changes in species composition of insect communities. The results of this study show that the Enhanced Structural Complexity Index (ESCI) can serve as a valuable tool for forest managers and ecologists for describing the structural complexity of forest stands and is particularly valuable for natural forests with a high degree of structural
Avoiding potentially catastrophic global climate change is a moral imperative, demanding significant reductions in greenhouse gas emissions from all important transport sectors, including aviation. However, because passenger flights and freight traffic are increasing much faster than efficiency improvements, the aviation sector will not be able to reduce emissions, or even stabilize them at current levels, without direct, forceful action to reduce demand. This paper reviews the ethical principles and empirical realities supporting the case for reducing worldwide aviation traffic. It argues that most passenger air travel and air freight shipping represents unnecessary luxury consumption, which responsible moral agents should willingly reduce in order to mitigate global climate change. It considers several mechanisms for doing so, and contends that they may succeed, but only if combined with an explicit recognition and binding commitment that for the foreseeable future, aviation must be a slow-growth or no-growth sector of the world economy.