Disturbance is a central driver of forest development and ecosystem processes with variable effects within and across ecosystems. Despite the high levels of variation in disturbance severity often observed in forests following natural and anthropogenic disturbance, studies quantifying disturbance impacts often rely on categorical classifications, thus limiting opportunities to examine potential gradients in ecosystem response to a given disturbance or management regime. Given the potential increases in disturbance severity associated with global change, as well as shifts in management regimes related to procurement of biofuel feedstocks, there is an increasing need to quantitatively describe disturbance severity and associated responses of forest development, soil processes, and structural conditions. This study took advantage of two replicated large-scale studies of forest biomass harvesting in Populus tremuloides and Pinus bansksiana forests, respectively, to develop and test the utility of a continuous, quantitative, disturbance severity index (DSI) for describing postharvest response of plant communities and nutrient pools to different levels of biomass removal and legacy retention (i.e., live trees and coarse woody material). There was a high degree of variability in DSI within categorical treatments associated with different levels of legacy retention and regression models using DSI as a predictor explained a portion of the variation (>50%) for many of the ecosystem- and community-level responses to biomass harvesting examined. Nutrient losses associated with biomass harvesting were positively related to disturbance severity, particularly in P. tremuloides forests, with postharvest nutrient availability generally declining along the gradient of impacts. Consistent with expectations from ecological theory, species richness and diversity of woody plant communities were greatest at intermediate disturbance severities and regeneration densities of dominant trees species were most abundant at highest levels of disturbance. Although categorical benchmarks will continue to be the primary way through which management guidelines are conveyed to practitioners, evaluation of their effectiveness at sustaining ecosystem functioning should be through continuous analyses, such as the DSI approach used in this study, to allow for the more precise identification of thresholds that ensure a range of desirable outcomes exist across managed landscapes.

中文翻译：

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沿扰动严重度梯度评估生物质收获的生态影响。

干扰是森林发展​​和生态系统过程的主要驱动力，在生态系统内和生态系统之间产生不同的影响。尽管经常在自然和人为干扰后的森林中观察到干扰严重程度的高水平变化，但量化干扰影响的研究通常依赖于分类，因此限制了检查给定干扰或管理制度的生态系统响应中潜在梯度的机会。鉴于与全球变化相关的干扰严重程度潜在增加，以及与生物燃料原料采购相关的管理制度的变化，越来越需要定量描述干扰严重程度以及森林发展，土壤过程和结构条件的相关响应。这项研究分别利用了两个重复的大规模研究，即对杨树和松树森林的森林生物量收获进行了研究，以开发和测试连续，定量，干扰严重性指数（DSI）来描述植物群落收获后反应的效用。和营养池，以达到不同水平的生物质去除和传统保留（即，活树和粗木本材料）。使用DSI作为预测因子，与不同水平的遗留保留和回归模型相关联的分类处理中，DSI的高度可变性解释了许多生态系统和社区水平的响应变化的一部分（> 50％）检查了生物质收获。与生物量收集相关的营养损失与干扰的严重程度呈正相关，特别是在P. tremuloides森林中，收获后养分的可利用性通常随着影响梯度的增加而下降。符合生态学理论的期望，木本植物群落的物种丰富度和多样性在中度干扰严重度时最大，而优势树种的再生密度在最高干扰度时最丰富。尽管分类基准将继续是向管理者传达管理指南的主要方式，但应通过持续分析（例如本研究中使用的DSI方法）来评估其在维持生态系统功能方面的有效性，以进行更准确的识别确保在管理环境中存在一系列理想结果的阈值。收获后养分的可利用性通常随着影响梯度的降低而下降。符合生态学理论的期望，木本植物群落的物种丰富度和多样性在中度干扰严重度时最大，而优势树种的再生密度在最高干扰度时最丰富。尽管分类基准将继续是向管理者传达管理指南的主要方式，但应通过持续分析（例如本研究中使用的DSI方法）来评估其在维持生态系统功能方面的有效性，以进行更准确的识别确保在管理环境中存在一系列理想结果的阈值。收获后养分的可利用性通常随着影响梯度的增加而下降。符合生态学理论的期望，木本植物群落的物种丰富度和多样性在中度干扰严重度时最大，而优势树种的再生密度在最高干扰度时最丰富。尽管分类基准将继续是向管理者传达管理指南的主要方式，但应通过持续分析（例如本研究中使用的DSI方法）来评估其在维持生态系统功能方面的有效性，以进行更准确的识别确保在管理环境中存在一系列理想结果的阈值。