DISSERTATION RESEARCH: Do tradeoffs between water use efficiency and growth explain plant community response to nitrogen deposition?

论文研究：水分利用效率和生长之间的权衡是否可以解释植物群落对氮沉降的反应？

• 批准号: 1501110
• 负责人: Edith Allen
• 金额: $ 1.97万
• 依托单位: University of California-Riverside
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-07-01 至 2017-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1501110&HistoricalAwards=false
• 关键词: DISSERTATION; RESEARCH; Do; tradeoffs; between

Nitrogen is a largely unrecognized component of air pollution and can negatively impact ecosystems. Excess nitrogen in the air is eventually deposited in the soil. While more nitrogen in the soil may seem beneficial for plant growth, many plant species are adapted to lower nutrient levels. Indeed, previous studies have shown that nitrogen deposition can be detrimental to ecosystem health. Southern California, which is notorious for its nitrogen-containing smog, has high levels of nitrogen deposition in the soil and many invasive plant species that also reduce native biodiversity. Nitrogen deposition may magnify the impact of invasive species because it often promotes growth of invasive annual plants over native shrubs and wildflowers. One possible explanation for the loss of native species is that added nitrogen makes them grow faster and use water less efficiently, causing them to be more susceptible to drought. Invasive plants on the other hand, may be able to grow fast with added nitrogen and still use water efficiently. The purpose of this research is to compare growth and water use by native and invasive plants under different levels of nitrogen addition. This work will lead to a better understanding of the environmental effects of nitrogen deposition, especially in dry habitats with problematic invasive species.Identifying how trait differences between native and invasive plant species influence community composition over environmental gradients is critical to a mechanistic understanding of how ecosystems will respond to global change. Nitrogen deposition is reported as major driver of plant diversity loss, invasion and vegetation-type conversion in some areas of Europe and North America. In arid systems, nitrogen and water will have interactive effects on water-use efficiency and growth, and these responses may mediate survival. Trade-offs among plant traits, such as water-use efficiency and relative growth rate, are known to play an important role in community assembly and species coexistence. Native and invasive plants may differ in this trade-off, and added nitrogen may influence these dynamics. The use of stable isotopes (13C) for the estimation of integrated water-use efficiency in conjunction with a plant functional trait-based approach and community-level data will allow for exploration of this important tradeoff as a mechanism of invasion under N deposition. The researchers will address this hypothesis by measuring the growth and water-use efficiency of native and invasive plants along an experimental gradient in nitrogen deposition in the Santa Monica Mountains of southern California.

氮在很大程度上是空气污染中一种未被认识到的成分，可能会对生态系统产生负面影响。空气中多余的氮最终会沉积在土壤中。虽然土壤中更多的氮素似乎有利于植物的生长，但许多植物物种都适应了较低的营养水平。事实上，之前的研究已经表明，氮沉积可能对生态系统健康有害。南加州以其含氮烟雾而臭名昭著，土壤中的氮沉积水平很高，许多入侵植物物种也减少了当地的生物多样性。氮沉积可能会放大入侵物种的影响，因为它经常促进入侵的一年生植物在本土灌木和野花上的生长。本土物种减少的一个可能解释是，添加氮素会使它们生长得更快，利用水分的效率更低，导致它们更容易受到干旱的影响。另一方面，入侵植物可能能够在增加氮素的情况下快速生长，并仍然有效地利用水分。本研究的目的是比较不同氮素水平下原生植物和外来植物的生长和水分利用情况。这项工作将有助于更好地理解氮沉降的环境影响，特别是在有问题的入侵物种的干旱生境中。识别本地和入侵植物物种之间的特征差异如何影响环境梯度的群落组成，对于从机械上理解生态系统将如何响应全球变化至关重要。据报道，氮沉降是欧洲和北美一些地区植物多样性丧失、入侵和植被类型转变的主要驱动因素。在干旱系统中，氮和水会对水分利用效率和生长产生交互作用，这些反应可能调节生存。植物性状之间的权衡，如水分利用效率和相对生长速度，被认为在群落聚集和物种共存中起着重要作用。本地植物和外来植物在这种取舍上可能有所不同，而添加氮素可能会影响这些动态。使用稳定同位素(13C)结合基于植物功能特征的方法和群落水平的数据来估计综合水分利用效率，将允许探索这一重要的权衡作为氮沉积下入侵的机制。研究人员将通过测量南加州圣莫尼卡山脉原生植物和入侵植物沿氮沉积实验梯度的生长和水分利用效率来解决这一假设。