Climatic Variability and Ecosystem Response: Precipitation Patterns, Soil Moisture Dynamics, and Productivity in Tallgrass Prairie

气候变异性是草原生态系统结构和功能的关键驱动因素，气候模型表明，由于全球气候变化，降雨量、温度和其他气候参数的变异性将增加。然而，未来的降雨模式存在不确定性，一些模型预测的雨量增加，另一些模型预测的生长季降雨量和土壤水分减少。降雨量或频率的任何变化都会改变降雨量的变异性，几条证据表明，变异性在调节高草草原净初级生产力方面可能与总降雨量一样重要。事实上，即使降雨量没有变化，降雨变异性的增加也会降低植物的表现和生产力，并可能导致高草草原群落组成的变化，因为植物跟踪和适应不同资源的能力不可避免地受到生理和形态上的限制。这项研究的目的是以塔尔草草原为模式系统，通过实验确定降雨模式的变异性对地上和地下草地生产力的影响。我们将通过16种不同数量和频率组合的试验灌溉，在含有普通高粱草原草和杂草的微型生态系统上施加降雨量输入变异性的减少和增加。测量的重点将是土壤水分动态、光合作用性能、树冠发育、根生长动态、植物繁殖以及地上和地下净第一性生产力。本实验验证的主要假设是，变异性是高草草原生产力的关键驱动因素，本实验将检验几个关于牧草和杂草的降雨量和频率与生产力之间关系的具体假设。这一知识将扩大我们对草原生产力调节的理解，并将对全球变化情景(降雨、温度和二氧化碳升高)下的生产力/多样性关系、火/牧民相互作用、陆地碳动态、大气/植被反馈以及气候要素之间的相互作用的研究产生影响。对这些问题的准确理解对于预测气候变化对草原的影响和为这些濒危系统制定积极的保护和管理计划至关重要。

Climatic variability is a key driver of ecosystem structure and function in grasslands, and climate models suggest that variability in rainfall, temperature, and other climatic parameters will increase because of global climate change. However, there is uncertainty about future rainfall patterns, with some models predicting increased, others decreased growing season rainfall and soil moisture. Any shifts in rainfall quantity or frequency will change rainfall variability, and several lines of evidence suggest that variability may as important as the total quantity of rainfall in regulating tallgrass prairie net primary productivity. Indeed, increases in rainfall variability, even with no change in rainfall quantity, have the capacity to reduce plant performance and productivity and may cause shifts in tallgrass prairie community composition, because of unavoidable physiological and morphological limitations on plant abilities to track and adjust to varying resources. The objective of the research described in this proposal is to experimentally determine the impact of variability in rainfall patterns on above- and belowground grassland productivity, using tallgrass prairie as a model system. We will impose decreases and increases in variability in rainfall inputs on microcosms containing common tallgrass prairie grasses and forbs, by experimental watering at sixteen different quantity and frequency combinations. Measurements will focus on soil moisture dynamics, photosynthetic performance, canopy development, root growth dynamics, plant reproduction, and above and belowground net primary productivity. The overarching hypothesis tested by this experiment is that variability is a key driver of tallgrass prairie productivity, and the experiment will examine several specific hypotheses about the relationships between rainfall quantity and frequency and productivity in grasses and forbs. This knowledge will broaden our understanding of the regulation of grassland productivity, and will have implications for research on productivity/diversity relationships, fire/grazer interactions, terrestrial carbon dynamics, atmosphere/vegetation feedbacks, and interactions among climatic elements in global change scenarios (rainfall, temperature, and elevated CO2). An accurate understanding of these issues is crucial to predicting climate change impacts on grasslands and developing proactive conservation and management plans for these endangered systems.