Wickham J, Neale A, Riitters K, Nash M, Dewitz J, Jin S, van Fossen M, Rosenbaum D
U.S. EPA, Center for Public Health and Environmental Assessment, Office of Research and Development, 109 T.W. Alexander Dr., Research Triangle Park, NC 27711, USA.
U.S. Department of Agriculture, Forest Service, Southern Research Station, Research Triangle Park, NC 27709, USA.
Ecol Indic. 2023 Feb;146:109756. doi: 10.1016/j.ecolind.2022.109756.
Droughts that are hotter, more frequent, and last longer; pest outbreaks that are more extensive and more common; and fires that are more frequent, more extensive, and perhaps more severe have raised concern that forests in the western United States may not return once disturbed by one or more of these agents. Numerous field-based studies have been undertaken to better understand forest response to these changing disturbance regimes. Meta-analyses of these studies provide broad guidelines on the biotic and abiotic factors that hinder forest recovery, but study-to-study differences in methods and objectives do not support estimation of the total extent of potentially impaired forest succession. In this research, we provide an estimate of the area of potentially impaired forest succession. The estimate was derived from modeling of an 18-year land cover and Normalized Difference Vegetation Index (NDVI) time series supported by an extensive ancillary dataset. We estimate an upper bound of approximately 3470 km of disturbed forest that may not return or reattain prior composition and structure. Based on the data used, fire appears to be the main disturbance agent of impaired forest succession, although climatic factors cannot be discounted. The numerous field studies routinely cite distal seed sources as a factor that hinders forest recovery, and we estimate that 20 % of the upper bound estimate has no forest cover within a 4.4-ha neighborhood. Our upper bound estimate is about 0.5 % of the 2001 mapped extent of western United States forests. The estimate is cognizant of measurement and modeling uncertainties (i.e., upper bound) and uncertainties related to successional rates and trajectories (i.e., potential).
干旱变得更炎热、更频繁且持续时间更长；虫害爆发范围更广且更常见；火灾更频繁、范围更广且可能更严重，这引发了人们对美国西部森林一旦受到这些因素中的一种或多种干扰后可能无法恢复的担忧。人们已经开展了大量实地研究，以更好地了解森林对这些不断变化的干扰模式的反应。对这些研究的荟萃分析提供了有关阻碍森林恢复的生物和非生物因素的广泛指导方针，但研究方法和目标在不同研究之间存在差异，这不利于对潜在受损森林演替的总体范围进行估计。在本研究中，我们对潜在受损森林演替的面积进行了估计。该估计是通过对一个18年的土地覆盖和归一化植被指数（NDVI）时间序列进行建模得出的，该建模得到了一个广泛的辅助数据集的支持。我们估计，约3470平方公里的受干扰森林可能无法恢复或重新达到先前的组成和结构，这是一个上限估计。基于所使用的数据，火灾似乎是受损森林演替的主要干扰因素，不过气候因素也不能忽视。众多实地研究经常将远距离种子源视为阻碍森林恢复的一个因素，我们估计，在上限估计范围内，有20%的区域在4.4公顷的邻域内没有森林覆盖。我们的上限估计约占2001年美国西部森林测绘范围的0.5%。该估计考虑到了测量和建模的不确定性（即上限）以及与演替速率和轨迹相关的不确定性（即潜力）。
