Plant phosphorus use and acquisition strategies in the Amazon rainforest with relevance to vegetation models

The Amazon rainforest is the biggest tropical rainforest in the world and provides significant global climate regulation services. However, the future of the Amazon rainforest carbon sink under elevated CO₂ is uncertain. The potential fertilization effect of elevated CO₂ on the Amazon rainforest carbon sink may be constrained by phosphorus availability. Phosphorus is an essential element involved in all major plant processes and is considered to be the primary limiting nutrient in the Amazon rainforest. To cope with phosphorus limitation, plants have developed different strategies to increase the use efficiency, uptake, and availability of phosphorus. Vegetation models have identified phosphorus use and acquisition strategies as crucial to the projections of the future of the Amazon rainforest. Although some of the strategies are explicitly or implicitly represented in vegetation models, the mechanistic representations diverge due to the lack of empirical knowledge. Here, we synthesized the current understanding of the main strategies and how they may play out in the Amazon rainforest, namely, root phosphorus foraging, arbuscular mycorrhizal symbiosis, phosphatase and organic acids exudation, and leaf phosphorus resorption. We focus on mechanisms, drivers, and plasticity along soil phosphorus gradients of the named strategies, aiming to inform models and highlight important knowledge gaps, offering an opportunity to bring modeling and experimental research together.