气候变化背景下岷江冷杉与红桦种间相互作用及菌根效应

Plant-plant interactions mainly include competition and facilitation, which are the core content of plant community ecology. Natural systems are being subjected to unprecedented rates of change and unique pressures from a combination of anthropogenic environmental change drivers. Alpine and subalpine species interactions will presumably become more important in the future as the impact of global warming on terrestrial ecosystems has been forecast to be greatest in arctic tundra and high mountain regions. So far, a number of studies have addressed competition and direct facilitation among plants in grassland species, whereas few studies have actually addressed this question experimentally in the alpine and subalpine species. In this study, Betula albo-sinensis and Abies faxoniana saplings, which are the dominant trees in the subalpine coniferous forests of Western Sichuan, are selected for our study. In the present study, photosynthesis physio-ecology, photosynthate allocation,resource uptake and use,phenotypic plasticity are measured under elevated CO2 and temperature to test whether there are different patterns of growth,morphology and physiological performance in Betula albo-sinensis and Abies faxoniana in the response to the climate change. Then a parallel experiment, in which saplings of Abies faxoniana and Betula albo-sinensis were grown in mono- and mixed cultures under elevated CO2 and temperature, is undertaken in phytotrons to evaluate whether climate change may modify species interactions. Additionally, resource allocation,space sequestration,resource acquisition per unit of resource investment, and nitrogen use strategy (nitrogen uptake, allocation, utilization and return) is investigated to elucidate the competitive strength of the two species under climate change. We subsequently use this information to characterize competitiveness for these two species. We further investigate the mediation of ectomycorrhizal fungi on plant-plant interactions under climate change. Our results through this project might lay a theoretical foundation for revealing the dynamic, structure, and stability of plant community and for the construction of ecological environment, sustainable development of forestry as well as for the restoration and rehabilitation of the degraded ecosystems in the southwest region of China.

种间互作是群落生态学的核心内容之一。然而，高山木本植物种间互作对气候变化的响应少有涉及。本项目选取对气候变化敏感的西南亚高山地区的代表性木本植物岷江冷杉与红桦为试验材料，利用封闭式生长室进行CO2浓度、温度升高及其交互实验，研究岷江冷杉/红桦不同树种对气候变化的响应差异；采用植物竞争的现代生态学理论和方法, 研究气候变化背景下共存植物资源分配、构建消耗、碳积累、氮利用策略（氮吸收、分配、利用和回归）的变化规律，明确影响植物竞争力的关键途径和因子，分析气候变化下种间关系的演变趋势；并以菌根真菌为切入点, 利用根箱分室法及多隔层法研究外生菌根真菌在气候变化背景下对种间互作的调控机理。本项目能在更深层次上推动和促进我国高山生态科学的发展，同时研究结果不仅为未来气候变化下高山植被组成和演替动态提供科学依据，还可为退化山地植被恢复与管理提供理论依据。

本研究以岷江冷杉（Abies faxoniana）与红桦（Betula albo-sinensis）幼树为研究材料，研究了CO2浓度升高、温度升高对岷江冷杉与红桦幼树的生理生化特征、生物量积累及其分配的影响，探究了气候变化对岷江冷杉与红桦种间关系的影响，检测了气候变化背景与互作条件下植物生长和养分吸收，探讨了外生菌根真菌对气候变化背景下种间关系的调节。主要结果如下：与对照相比，CO2 浓度升高、温度升高均显著促进了两树种幼树生长、净光合速率和生物量累积，且CO2 浓度升高对红桦生长的促进作用大于对岷江冷杉的正效应。在岷江冷杉、红桦种间互作模式下，研究了植物功能性状与植物竞争力的相关性。混栽与增温、CO2升高条件下红桦株高、总生物量和根生物量各指标分别相对于各自条件下的纯栽模式显著提高。CO2显著促进了单栽和混栽中红桦的分支数量而对单栽中的岷江冷杉的分枝无显著影响。增温与CO2升高条件下，种间竞争中的红桦表现出比岷江冷杉更高的根、叶、茎和总生物量，更低根茎比。红桦具有更高的净光合速率、更高的光合氮利用效率和光合磷利用效率。增温与CO2 升高条件下在混栽中红桦的竞争率始终大于岷江冷杉，但在高温下岷江冷杉对养分竞争能力大于红桦，同时发现植物功能性状的保守性是提高岷江冷杉耐热能力的关键。接种条件下CO2浓度和温度同时升高提高了岷江冷杉株高与基茎、光合作用，而对红桦影响不显著。在接种情况下，尤其在CO2与温度升高条件下外生菌根真菌降低了红桦对岷江冷杉的抑制作用，岷江冷杉的竞争力逐渐增强。该结果有利于深入认识亚高山针叶林优势树种对气候变化的响应机制。本项目按照计划要点完成了科研任务。依托本项目，撰写完成论文5篇，已发表4篇SCI论文(其中3篇均被SCI TOP 期刊收录)，1篇投稿在审(accept after minor revision)。另有2篇在撰写中。参与该项目的人员中有两人晋升为正高级职称，参与该项目已毕业研究生1名（1名博士），现有2名研究生（2名硕士生）在读。