Soil fertility impact on plant photosynthetic strategies: from global scale to Maple-dominated forests to Sugar Maple individuals

了解土壤肥力如何促进陆地生态系统的生产力目前正处于激烈的辩论之中。生态系统生产力取决于组成生态系统的功能战略以及它们在社区内的组合。在重要的策略中，植物交替利用水(H2O)或氮(N)资源以实现给定的叶片光合作用速率的能力，对预测生态系统生产力具有重要的理论影响。然而，随着土壤的空间梯度，将大部分H2O和N资源输送给植物的光合作用功能策略一直被忽视。此外，为了将功能策略与生态系统生产力联系起来，采用最优的光合作用策略(最大限度地增加树叶级别的碳收益)在多大程度上危及到物种在群落规模上的优势，这是必不可少的，但几乎没有人探索过。 我最近的研究表明，土壤pH在更经典的土壤肥力变量中是决定性的，以了解叶片营养和H2O利用的全球模式。然而，人们对这些空间格局背后的机制知之甚少。 在这项提案中，我计划确定土壤肥力如何通过其pH值来调节枫树为主的森林之间和内部的光合作用策略的分配。这一生态系统对北美东部具有重要的生态、文化和经济意义，但由于以前的酸性大气沉积而濒临灭绝。 首先，我们将定义土壤pH影响物种捕获、运输、利用N和H2O资源并最大化碳收益的功能特征最佳组合的机制。其次，我们将确定这种最优特征组合如何定义一个群落吸引点，哪个物种将向哪个物种汇聚以占据主导地位。然后，我们将确定土壤pH如何定义围绕这一吸引点的功能策略的变化。 土壤pH受气候的影响很大，在空间上对其进行解耦研究具有重要意义。我们将在三个相辅相成的尺度上开展工作：(I)使用全球特征数据集在全球尺度上开展工作；(Ii)在给定的气候和植被范围内，通过基础地质引起的自然土壤酸碱度梯度；(Iii)在个体树木层面上，通过在历史上酸化的土壤上进行长期的石灰处理。 结合功能生态学和群落生态学，我们将阐明土壤肥力在预测群落之间的最优功能策略、群落内功能策略的分布以及最终生态系统生产力方面的作用。作为该计划的核心，六名高素质的人员将学习专门的研究技术，并使用多学科方法来利用知识获取。

Understanding how soil fertility promotes the productivity of terrestrial ecosystems is currently under hot debate. Ecosystem productivity depends on the functional strategies that compose the ecosystem as well as their assembly within the community. Among important strategies, the ability of plants to alternatively use water (H2O) or nitrogen (N) resources for achieving a given leaf photosynthetic rate, has important theoretical impact to predict ecosystem productivity. However, photosynthetic functional strategies have been overlooked along spatial gradient of soils, which deliver most of the H2O and N resources to plants. In addition, the extent to which the adoption of an optimal photosynthetic strategy (maximizing carbon gain at the leaf scale) endangered confers dominance to species at the community scale, is essential but virtually unexplored in order to link functional strategies with ecosystem productivity. My recent research has demonstrated that soil pH is determinant over more classical soil fertility variables to understand the global patterns in leaf nutrition and H2O utilization. However, the mechanisms underlying these spatial patterns are poorly understood. In this proposal, I plan to determine how soil fertility, through its pH values, modulates the distribution of photosynthetic strategies between and within Maple-dominated forests. This ecosystem is of strong ecological, cultural and economic importance to Eastern North America but is endangered due to previous acidic atmospheric depositions. First we will define the mechanisms by which soil pH influences the optimal combination of functional traits that species adopt to capture, transport, use N and H2O resources and maximize carbon gain. Second we will determine how this optimal trait combination defines a community attractive point toward which species would converge in order to dominate. Then we will determine how soil pH defines the variance of functional strategies around this attractive point. Soil pH is strongly influenced by climate and it is important to spatially decouple its study. We will work at three complementary scales: (i) at the global scale using a global trait dataset; (ii) within a given climatic and vegetation envelope through a natural soil pH gradient caused by the underlying geology; (iii) at the individual tree level through a long-term liming treatment on a historically acidified soil. Coupling functional with community ecology, we will shed light on the role of soil fertility on the prediction of the optimal functional strategy between communities, the distribution of functional strategies within community and ultimately the ecosystem productivity. Central to this program, six highly qualified personnel will learn specialized research technologies, as well as using a multidisciplinary approach in order to leverage knowledge acquisition.