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: 2019
• 资助国家: 加拿大
• 起止时间: 2019-01-01 至 2020-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=690639
• 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来源。观测研究表明，加拿大北方森林和其他地方的树木死亡率在过去几十年里有所增加，同时生长速度较小或没有增加，甚至减少，这表明气候变暖导致树木可用水减少，对森林功能产生了负面影响，特别是碳固存。然而，关于改变的水可获得性对天然林生态系统功能的影响的直接证据和机制理解令人惊讶地有限。此外，我们缺乏对物种丰富的森林是否、如何以及为什么有助于减轻水资源供应变化对森林功能的负面影响的理解。我过去的研究计划集中在使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水平(包括地上和地下)的生产力和元素循环的影响。这项拟议的研究将研究树种多样性在减轻北方森林水资源可获得性减少的负面影响方面的作用。这项工作建立在我们最近从观测研究中发现的基础上，并依赖于天然北方森林中的水变化实验。试验包括3个水分处理(自2016年5月至10月以来，生长季降水量分别减少25%和增加25%)，分别对10年生火生纯樟子松、纯颤杨及其均匀混交林进行3次重复，共27个试验单元。具体地说，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反应；(2)凋落物、粗根和细根、土壤碳、养分、微生物群落和呼吸的反应；(3)物种混合(多样性)是否有助于减轻减少水分的不利影响，并增强增加水分对目标1-2中评估的过程的积极影响；(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高度依赖于有效的培训HQP。我以前的实验室成员的出版记录和目前的职位证明，我的培训努力是成功的。我计划继续发扬我在过去15年中创造的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，而且还针对其响应机制。我们的发现将有助于制定应对加拿大北部森林气候变化的战略，并对自然系统的多样性对全球变化缓解的影响提供机械性的见解。