Collaborative Research: Rainfall variability and the axes of tree-grass niche differentiation

合作研究：降雨量变化和树草生态位分化的轴

• 批准号: 1928875
• 负责人: Jesse Nippert
• 金额: $ 24.07万
• 依托单位: Kansas State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-09-01 至 2024-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1928875&HistoricalAwards=false
• 关键词: Collaborative; Research; Rainfall; variability; axes

The savanna biome, in which a discontinuous tree layer coexists with a continuous grass layer, has a worldwide distribution. Increasingly, research suggests that the relative proportion of tree and grass biomass in savannas is strongly influenced by rainfall patterns, with higher rainfall leading to greater woody biomass. Despite mounting evidence for rainfall effects, however, it is unclear if more rainfall leads to greater tree biomass in savannas because of deeper water infiltration, changes in rainfall intensity, or because the length of the growing season increases with the amount of annual rainfall. This question is important because we cannot accurately predict future changes to the savanna biome without a detailed understanding of how tree and grass species respond to rainfall patterns. This project will seek answers to this and other questions using a South African savanna as a model system. North American savannas have been largely replaced by forests, and the reasons for this are not fully understood. Results from this project can be used to inform the restoration and maintenance of savannas in North America and elsewhere, as well as to predict with broad generality how the savanna biome might change in the future. The project will also introduce undergraduate students to the ecology of savannas through a multi-year field course and educate local communities about the role of rainfall variability on natural resource availability.The project will combine experimental, observational and modeling approaches to test alternative hypotheses about the relationship between rainfall and tree to grass ratios in savannas. The research has three specific aims: (1) identify the rainfall regimes that favor trees over grasses, (2) identify the functional traits and tradeoffs that differentiate savanna trees and grasses, and (3) develop and test a mechanistic model of tree and grass dynamics as a function of rainfall. The core element of the study will be a field experiment that will manipulate the timing, seasonality and depth distribution of rainfall, and monitor the response of a multi-species assemblage of known-age trees embedded in a grass matrix. In addition, the project will examine functional differences (e.g., drought tolerance, water use efficiency and functional rooting depth) between six tree and six grass species using greenhouse, growth chamber and field experiments. Finally, the project will use parameter estimates from this second component to develop and test a mechanistic model of tree growth and tree to grass ratios based on whole-plant traits, and validate the model under field conditions by comparing modeled and observed changes in tree to grass ratios to rainfall manipulations in the field experiment.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

Savanna Biome，其中不连续的树层与连续草层共存，具有全球分布。研究越来越多地表明，稀树草原中树木和草生物量的相对比例受降雨模式的强烈影响，降雨量较高，导致更大的木质生物量。尽管有证据表明降雨的影响，但尚不清楚更多的降雨量是否会导致稀树草原中更大的树木生物量，因为水渗透更深，降雨强度的变化，或者由于生长季节的长度随着年降雨量而增加。这个问题很重要，因为我们无法准确预测稀树草原生物群落的未来变化，而没有对树木和草物种如何应对降雨模式的详细了解。该项目将使用南非稀树草原作为模型系统寻求答案和其他问题。北美稀树草原已被森林取代，原因尚未完全理解。该项目的结果可用于告知北美和其他地方的稀树草原的恢复和维护，并以广泛的普遍性预测稀树草原生物群落如何在将来发生变化。该项目还将通过多年的野外课程向本科生介绍稀树草原的生态，并向当地社区进行降雨变异性在自然资源可用性中的作用。该项目将结合实验性，观察和建模方法，以测试有关Savannas中降雨与树对草率之间关系的替代假设。 这项研究具有三个特定的目的：（1）确定有利于树木而不是草的降雨状况，（2）确定区分稀树草原树木和草的功能性状和权衡，以及（3）开发和测试树木和草动力学的机械模型作为降雨的功能。该研究的核心要素将是一个现场实验，该实验将操纵降雨的时机，季节性和深度分布，并监测嵌入草基质中已知年龄树的多物种组合的响应。此外，该项目将使用温室，生长室和田间实验检查六棵树和六种草种之间的功能差异（例如，耐旱性，用水效率和功能生根深度）。最后，该项目将使用第二个组成部分的参数估计来开发和测试基于整个植物性状的树木生长和树与草率的机械模型，并通过比较田间条件下的模型和观察到的树木比率的变化和观察到的降雨比率的变化来验证该模型，并在现场实验中进行了临床奖励。 标准。