Plants have evolved different strategies to withstand drought. In general, these strategies can be defined along a plant economics spectrum, which classifies plants depending on whether their growth rate is fast or slow, where fast growth is associated with high mortality, high water use, and high sensitivity to drought. Which strategy along this economy spectrum will be selected under different precipitation regimes is an open question. We address this question with a minimal soil–plant model in which a single plant economy trait related to growth rate characterizes the plant strategy. This generic and dimensionless trait influences both recruitment and mortality, but not background mortality. We explore the evolution of this trait by quantifying its effects on birth, mortality, and transpiration rates. Furthermore, we explore the influence of direct plant density dependence acting on recruitment and mortality, in addition to the indirect density dependence caused by plant feedback on soil water content.

We show that: (1) Increasingly fast-growing plants always evolve under increasing background mortality. (2) When soil water only depends on plant density and is independent of precipitation and abiotic water losses, the strategy minimizing soil water content is an evolutionarily stable strategy (ESS); i.e., the evolutionary outcome is a tragedy of the commons (Hardin, 1968). (3) When precipitation, abiotic water losses and trait dependent transpiration determine soil water content, the ESS lies between the strategy maximizing plant density and that minimizing soil water content; i.e., no tragedy of the commons occurs. (4) With a deterministic precipitation model and density dependence acting directly only on recruitment, higher precipitation promotes the evolution of faster plants. The opposite result is found when density dependence is acting directly only on mortality. (5) Similar trends in the economy trait are observed when forcing the model with stochastic precipitation events.

植物已经进化出不同的策略来抵抗干旱。通常，这些策略可以沿着植物经济学范围来定义，该经济学根据植物的生长速度是快还是慢来对植物进行分类，其中快速生长与高死亡率，高耗水量和对干旱的高度敏感性相关。在不同的降水机制下，将选择在该经济范围内选择哪种策略是一个悬而未决的问题。我们用最小的土壤-植物模型解决了这个问题，在该模型中，与生长率相关的单一植物经济性状表征了植物策略。这种通用和无量纲的特征会影响招募和死亡率，但不会影响本底死亡率。通过量化其对出生，死亡率和蒸腾速率的影响，我们探索了该性状的演变。此外，

我们证明：（1）越来越多的快速生长的植物总是在背景死亡率增加的情况下进化。（2）当土壤水分仅取决于植物密度并且与降水和非生物水分损失无关时，使土壤水分最小化的策略是一种进化稳定策略（ESS）；也就是说，进化的结果是公地的悲剧（Hardin，1968）。（3）当降水，非生物水分流失和性状相关的蒸腾作用决定了土壤含水量时，《环境与社会标准》就介于最大化植物密度和最小化土壤水分的策略之间；也就是说，不会发生公地悲剧。（4）具有确定性的降水模型和密度依赖性仅直接作用于募集，较高的降水量促进了较快植物的进化。当密度依赖性仅直接作用于死亡率时，发现相反的结果。（5）当模型具有随机降水事件时，观察到相似的经济特征趋势。