Data from: Short-term effects of elevated precipitation and nitrogen on soil fertility and plant growth in a Neotropical savanna

Increasing nitrogen (N) deposition and changing precipitation patterns in Neotropical savannas could alter plant growth, reproduction, and nutrients by altering soil nutrient and water availability. We examined the potential for simulated N deposition and increased dry season precipitation to have interactive effects on reproduction and growth of two abundant native Cerrado (Brazilian savanna) grasses – Loudetiopsis chrysothrix and Tristachya leiostachya – via feedbacks with soil nutrient status. Plant growth and reproduction responses consistently varied by species. Water addition led to more consistent increases in both growth and reproduction than nitrogen addition and the two treatments did have significant interactive effects. We expected that both treatments would affect plant growth and reproduction via positive effects on soil and plant N. Instead, we found that plant responses were linked to species-specific treatment effects on soil and foliar phosphorus (P). Structural equation models (SEM) confirmed that changes in soil P - rather than changes in soil N or increasing soil acidity - explained plant response to treatments. Our results imply that N deposition and precipitation change could impact Cerrado plant growth and reproduction via subtle effects on plant and soil phosphorus.

新热带稀树草原中不断加剧的氮（N）沉降与改变的降水格局，可通过调控土壤养分与水分有效性，进而改变植物的生长、繁殖过程及养分状态。本研究探讨了模拟氮沉降与旱季降水增加，是否会通过与土壤养分状态的反馈作用，对两种广布的塞拉多（巴西稀树草原）原生禾草——Loudetiopsis chrysothrix与Tristachya leiostachya——的生长与繁殖产生交互效应。植物的生长与繁殖响应因物种而异，且呈现出稳定的种间差异。与氮添加处理相比，增水处理对植物生长与繁殖的促进效应更为一致，且两种处理确实存在显著的交互效应。我们曾预期两种处理均可通过提升土壤与植物体内的氮含量，进而影响植物的生长与繁殖。但本研究结果显示，植物的响应反而与不同物种对土壤与叶片磷（P）的处理效应相关。结构方程模型（Structural equation models, SEM）证实，是土壤磷含量的变化——而非土壤氮变化或土壤酸度升高——解释了植物对实验处理的响应。本研究结果表明，氮沉降与降水变化或可通过调控植物与土壤磷的微妙变化，进而影响塞拉多地区植物的生长与繁殖。