On the influence of stand spatial structure and species diversity on growth and recruitment of structurally complex forests: evaluating the role of distance-dependent and species-sensitive competition indices within the Acadian region of northeastern Nort

北半球许多地区的森林管理正在从传统的单一物种、平均树龄管理转向选择性采伐系统。这种做法的广泛采用超过了基础研究的速度，这些研究涉及选择系统的能力，以满足更复杂和多样化的森林结构的预期目标，确保更持续地提供生态系统产品和服务。通过模拟和预测长期的未来发展，森林生长和产量模型是克服这些缺陷的潜在手段。森林生长模拟器通常依赖于表达和量化局部邻域效应的竞争指数来分析树与树之间的相互作用和由此产生的林分动态。多项研究试图找到预测树木生长和林分产量的最佳竞争指数。然而，即使只比较某一类指数，例如与距离无关的指数，也没有从这些分析中得出明确的趋势。此外，大多数关注距离依赖竞争指数的分析都是在平均年龄的单一物种林分中进行的，重新测量的次数有限。在北美东北部的阿卡迪亚森林，向新管理程序的转变创造了前所未有的林分结构，对未来的森林发展和木材供应产生了未知的后果。然而，自20世纪60年代以来，一些具有永久地块系统的研究地点已经安装在森林林分上，这些林分已经被交替管理用于研究。现在，通过重新测量树木生长和补充以及收集茎图数据，可以对这些结构复杂的森林场址的生长和更新动态进行全面评价。此外，由于有更广泛的茎图永久测量样地和必要的计算技术来对竞争进行空间上明确的估计，现在有必要对这些混合物种和结构复杂的森林的竞争措施进行全面评估。本项目将分析构造林物种多样性和树木空间分布等特征的变化对不同竞争指数表现的影响。基于这些发现，将开发新的单株生长和长入（发生、频率、更新组成）方程，并将其插入目前正在开发的森林植被模拟器（FVS-ACD）的距离依赖阿卡迪亚变体中。因此，拟议的项目提供了回答有关树对树竞争的基本研究问题的机会，同时也解决了改进区域增长和产量模型的重要应用研究需求。

Forest management in many parts of the Northern hemisphere is moving away from the conventional single-species, even-aged management toward selection harvesting systems. The widespread adoption of such practices has outpaced fundamental research addressing the ability of selection systems to meet the intended objectives for more complex and diverse forest structures ensuring a more continuous provision of ecosystem goods and services. By simulating and predicting long-term future developments forest growth and yield models are a potential means to overcome these deficiencies. Forest growth simulators often rely on competition indices that express and quantify local neighborhood effects to analyze tree-to-tree interactions and the resulting stand dynamics. Multiple studies have attempted to find the best index of competition for predicting tree growth, and stand yield. No clear trends, however, have emerged from these analyses, even when just a certain class of indices, e.g. distance-independent indices, was compared. In addition, most analyses focusing on distance-dependent competition indices were conducted in even-aged, single species stands with limited remeasurements. In the Acadian Forest of northeastern North America the shift toward novel management procedures has created unprecedented stand structures with unknown consequences for the future forest development and timber supply. However, several study sites with a permanent plot system have been installed in forest stands that have been alternatively managed for research since the 1960s. Remeasurements of tree growth and recruitment as well as the collection of stem-mapped data now allow for the comprehensive evaluation of growth and regeneration dynamics in these structurally complex forest sites. Moreover, given the wider availability of stem-mapped permanent measurement plots and the necessary computing technology to make spatially explicit estimates of competition, a comprehensive assessment of competition measures is now warranted for these mixed-species and structurally complex forests. The proposed project will analyze how the variation of structural forest characteristics such as species diversity and tree spatial distribution influence the performance of different competition indices. Based on these findings, new individual tree growth and ingrowth (occurrence, frequency, composition of regeneration) equations will be developed and inserted into the distance dependent Acadian Variant of the Forest Vegetation Simulator (FVS-ACD) currently being developed. The proposed project therefore offers the opportunity to answer fundamental research questions regarding tree-to-tree competition, while also addressing an important applied research need for improved regional growth and yield models.