The role of tree species diversity in mitigating negative impacts of reduced water availability in boreal forests: Patterns and mechanisms

树种多样性在减轻北方森林可用水量减少的负面影响方面的作用：模式和机制

• 批准号: RGPIN-2019-05109
• 负责人: Chen, Han
• 金额: $ 4.01万
• 依托单位: Lakehead University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=715346
• 关键词: role; tree; species; diversity; mitigating

Biodiversity loss and climate change are two significant stressors on ecosystem productivity, element cycling, and other ecological processes. Observational studies have shown that tree mortality of Canadian boreal forests and elsewhere has increased in the past decades, accompanied by smaller or no increase or even decrease in growth, suggesting that reduced water available to trees induced by warming have negatively affected forest functions, particularly carbon sequestration. However, the direct evidence and mechanistic understanding of the impact of altered water availability on ecosystem function in natural forests is surprisingly limited. Moreover, we lack an understanding of whether, how and why species-rich forests help mitigate the negative impacts of altered water availability on forest functions. My past research program is centered on using observational approaches to understanding the consequences of biodiversity loss and climate change on productivity and element cycling at the ecosystem level including above- and belowground. This proposed research will examine the role of tree species diversity in mitigating negative impacts of reduced water availability in boreal forests. This work builds upon our recent discoveries from observational studies and relies upon a water alteration experiment in natural boreal forests. The experiment consists of three water treatments (ambient, 25% decrease and 25% increase of growing season precipitation (May to October) since 2016) in 10-year-old fire-origin pure jack pine, pure trembling aspen, and their even mixture, each replicated three times, with a total of 27 experimental units. Specifically, I will address: (1) the aboveground responses of growth, mortality, net biomass change, community structure, composition and diversity of all vegetation layers, (2) the responses of litterfall, coarse and fine roots, soil carbon, nutrients, microbial community, and respiration, (3) whether species mixture (diversity) help to mitigate adverse impacts of reduced water and enhance the positive impacts of increased water on processes assessed in objectives 1-2; (4) physiological mechanisms associated with the responses observed in objectives 1 to 3. The success of my research program is highly dependent upon the effective training HQP. As evidenced by the publication record and current positions of my previous lab members, I have been successful in my training efforts. I plan to carry forward with the HQP training momentum I have generated over the last 15 years. This proposed research aims at not only the patterns of but also mechanisms for the responses of natural forests to pulse and press water alteration. Our findings will help to develop strategies to cope with climate change in Canada's boreal forests, and shed mechanistic insights into the diversity effects on global change mitigation for natural systems.

生物多样性丧失和气候变化是生态系统生产力、元素循环和其他生态过程的两个重要压力因素。观测研究表明，过去几十年来，加拿大北方森林和其他地方的树木死亡率有所增加，但生长速度却较小或没有增加，甚至减少，这表明气候变暖导致树木可用水量减少对森林功能，特别是碳固存产生了负面影响。然而，关于水供应变化对天然林生态系统功能影响的直接证据和机制理解却非常有限。此外，我们不了解物种丰富的森林是否、如何以及为何有助于减轻水资源供应变化对森林功能的负面影响。我过去的研究项目主要是利用观测方法来了解生物多样性丧失和气候变化对生态系统层面（包括地上和地下）生产力和元素循环的影响。这项拟议的研究将探讨树种多样性在减轻北方森林可用水量减少的负面影响方面的作用。这项工作建立在我们最近的观察研究发现的基础上，并依赖于天然北方森林的水分变化实验。试验采用10年生火源纯短叶松、纯颤杨及其均匀混合物进行3次水处理（环境、2016年以来生长季降水量（5-10月）减少25%和增加25%），各重复3次，共27个试验单元。具体来说，我将讨论：（1）所有植被层的生长、死亡率、净生物量变化、群落结构、组成和多样性的地上响应，（2）凋落物、粗根和细根、土壤碳、养分、微生物群落和呼吸的响应，（3）物种混合（多样性）是否有助于减轻水减少的不利影响并增强水增加对评估过程的积极影响 目标 1-2； (4) 与目标 1 至 3 中观察到的反应相关的生理机制。我的研究计划的成功在很大程度上取决于有效的 HQP 训练。正如我以前的实验室成员的发表记录和当前职位所证明的那样，我的培训工作取得了成功。我计划发扬过去 15 年来所产生的 HQP 培训势头。这项拟议的研究不仅旨在研究天然林对脉冲和压力水变化的响应模式，而且还旨在研究其机制。我们的研究结果将有助于制定应对加拿大北方森林气候变化的战略，并为自然系统减缓全球变化的多样性影响提供机制见解。