Collaborative Research; Understanding the Potential for a Climate Change-driven Critical Transition from Forest to Chaparral

在西部大部分地区，野火的频率和严重程度正在发生变化，影响了人类和森林生态系统服务以及野火后森林恢复的速度。这些变化的野火率和森林恢复模式可能迫使主要植被永久地从森林转向灌木。俄勒冈州和加利福尼亚州的2500万英亩（1000万公顷）的克拉马斯地区是一个特别值得关注的地区。从森林到灌木的转变将损害森林对人类有益的生态系统服务，损害克拉马斯地区无与伦比的植物多样性（例如，有29种针叶树支持其他植物和动物的相关组合），并在这些高碳固碳森林向低碳含量灌木-灌木林过渡时释放大量温室气体。从事该项目的科学家将评估克拉马斯森林向灌木过渡的潜力，并直接与美国林务局合作，确定面对气候变化的生态系统管理的有力战略。包括管理克拉马斯地区80%的林务局决策者的参与，将确保科学的透明度和可信度，从而增加其对环境结果的影响。该项目将测试一个普遍假设，即气候可能推动克拉马斯从高生物量针叶林主导地区向低生物量灌木-乔柏-硬木主导地区转变，因为火灾活动增加，森林恢复率下降。该项目将采用三管齐下的研究方法，量化气候引起的过渡的潜力和潜在机制：(1)建立一般数学模型，以广泛了解易发生火灾的过渡带中潜在临界阈值的动态，并确定在当地和景观水平上控制灌木-乔柏-硬木和成熟针叶林之间过渡的功能关系；(2)实地研究火灾后恢复的气候依赖特征，并对模型进行测试和参数化；(3)基于过程的本地、景观和区域动态模拟，以表征气候、火灾和管理在形成区域生态群落中的相互作用。面对气候变化，提高对关键转变的理解已被认为是生态学的一项基本挑战，具有全球相关性和紧迫性。加深对克拉马斯地区发生重大转变的可能性的了解，将为全世界易火森林的管理提供信息。

The frequency and severity of wildfires is changing throughout much of the West, impacting humans and forest ecosystem services and the rate of forest recovery after wildfires. These altered wildfire rates and forest recovery patterns may force the dominant vegetation permanently to shift from forests to shrubs. The 25-million acre (10 million hectare) Klamath region of Oregon and California is an area of particular concern. A shift from forest to shrub would impair the ecosystem services of the forest that benefit humans, impair unparalleled botanical diversity of the Klamath region (for example, there are 29 species of conifer trees that support associated assemblages of other plants and animals) and release massive amounts of greenhouse gasses as these high-carbon sequestering forests transition to low-carbon content shrub-chaparral. The scientists working on this project will evaluate the potential for a forest to shrub transition in the Klamath and collaborate directly with the U.S. Forest Service to identify robust strategies for ecosystem management in the face of climate change. Including the participation of Forest Service decision-makers, who manage 80% of the Klamath region, will ensure the transparency and credibility of the science, thereby increasing its impact on environmental outcomes.This project will test the general hypothesis that climate may drive a critical transition in the Klamath from a high-biomass conifer forest dominated region to a low-biomass shrub-chaparral-hardwood dominated region because of increased fire activity and decreased forest recovery rate. The project will quantify the potential for, and mechanisms underlying, a climate induced transition using a three-pronged research approach: (1) development of general mathematical models to gain a broad understanding of dynamics underlying critical thresholds in fire-prone ecotones and to identify the functional relationships that control transitions between shrub-chaparral-hardwood and mature conifer forest, at local and landscape levels; (2) field research to characterize the climate- dependence of post-fire recovery and to test and parameterize models; (3) process-based simulations of local, landscape, and regional dynamics to characterize the interactive roles of climate, fire, and management in shaping the region's ecological communities. Improving understanding of critical transitions has been recognized as a fundamental challenge in ecology with global relevance and urgency in the face of climate change. Increased understanding of the potential for a critical transition in the Klamath region will inform the management of fire-prone forests worldwide.