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是目前争论的热点。生态系统的生产力取决于组成生态系统的功能策略以及它们在群落中的组合。在重要的策略中，植物交替利用水（H2O）或氮(N)资源以达到给定叶片光合速率的能力，对预测生态系统生产力具有重要的理论影响。然而，光合功能策略在土壤空间梯度上被忽视，而光合功能策略是向植物输送大部分水和氮资源的途径。此外，为了将功能策略与生态系统生产力联系起来，采用最佳光合作用策略（在叶片尺度上最大化碳增益）在多大程度上使物种在群落尺度上处于优势地位是必不可少的，但实际上尚未被探索。***我最近的研究表明，土壤pH值是更多经典土壤肥力变量的决定因素，可以了解叶片营养和水分利用的全球格局。然而，人们对这些空间模式背后的机制知之甚少。***在这个提案中，我计划确定土壤肥力如何通过其pH值，调节枫树为主的森林之间和内部的光合策略分布。这个生态系统对北美东部具有很强的生态、文化和经济重要性，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值影响物种采用的功能性状的最佳组合的机制，以捕获、运输、利用N和H2O资源并最大化碳增益。其次，我们将确定这个最优性状组合如何定义一个群落吸引点，物种将向该点收敛以占据主导地位。然后，我们将确定土壤pH值如何定义这个吸引点周围功能策略的变化。***土壤pH受气候的强烈影响，对其空间解耦研究具有重要意义。我们将在三个互补的尺度上工作：(i)在全球尺度上使用全球特征数据集；（ii）在给定的气候和植被范围内，通过由底层地质造成的自然土壤pH梯度；（iii）通过对历史上酸化的土壤进行长期石灰化处理，在单个树的水平上。***将功能与群落生态学相结合，揭示土壤肥力对群落间最优功能策略的预测、群落内功能策略的分布以及最终对生态系统生产力的影响。该计划的核心是，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.**