Plant–soil feedback (PSF) occurs when plants change the biota and physicochemical properties of the soil, and these changes affect future survival or growth of plants. PSF depends on several factors such as plant functional attributes (e.g., life cycle or photosynthetic metabolism) and the environment. PSF often turn positive under dry conditions because soil biota confers drought tolerance. Conspecifics and close relatives share pathogens and consume similar resources, exerting negative PSF on each other. These ideas have mostly been tested under controlled conditions, while field studies remain scarce. To reevaluate these findings in nature, we analyzed plant–soil feedbacks over a drought-stress gradient in a phosphorus-limited semiarid grassland. We planted seedlings of 17 species in plots where community composition had been monitored for six years. To determine PSF intensity, we measured how seedling longevity was affected by previous occupancy of conspecifics and heterospecifics. The previous occupancy–survival relationship (OSR) was used as a proxy for PSF. Evidence for OSRs was found in one-third of the species pairs, with inconclusive evidence for the rest suggesting weak feedbacks. This is in line with the expectation that PSFs in the field are weaker than under controlled conditions. As expected, positive PSFs were more frequent as drought stress increased. The strongest OSRs were caused in dry plots by C₄ perennial grasses, which had very positive OSRs on several C₃ annual forbs, but negative effects on each other. Well-documented differences between these two functional groups may explain this result: C₃ plants are more sensitive to drought, and thus may be favored by tolerance-conferring microbiota; in contrast, water-efficient C₄ perennial grasses compete for phosphorus strongly, perhaps driving strong negative PSFs between them. Finally, close relatives had more negative OSRs on each other than on distant relatives as expected, although only in dry plots. This pattern was mostly due to the negative effects of closely related C₄ grasses under dry conditions, and their positive effects on distantly related dicots. Our results highlight the importance of plant traits and of the environmental context in determining the direction and strength of PSFs under field conditions.

中文翻译：

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半干旱草原植物-土壤反馈取决于干旱胁迫、功能群和进化相关性

当植物改变土壤的生物群和理化特性时，就会发生植物 - 土壤反馈 (PSF)，这些变化会影响植物未来的生存或生长。PSF 取决于多种因素，例如植物功能属性（例如，生命周期或光合代谢）和环境。PSF 通常在干燥条件下变为阳性，因为土壤生物群赋予耐旱性。同种和近亲共享病原体并消耗相似的资源，对彼此产生负面的 PSF。这些想法大多在受控条件下进行了测试，而实地研究仍然很少。为了在自然界中重新评估这些发现，我们分析了磷限制的半干旱草原干旱 - 压力梯度上的植物 - 土壤反馈。我们在群落组成监测了六年的地块中种植了 17 个物种的幼苗。为了确定 PSF 强度，我们测量了幼苗寿命如何受到先前同种和异种占有率的影响。以前的居住-生存关系 (OSR) 被用作 PSF 的代理。在三分之一的物种对中发现了 OSR 的证据，其余的不确定证据表明反馈较弱。这符合现场 PSF 比受控条件下弱的预期。正如预期的那样，随着干旱压力的增加，阳性 PSF 更加频繁。最强的 OSR 是由 C 在干地块中引起的 以前的居住-生存关系 (OSR) 被用作 PSF 的代理。在三分之一的物种对中发现了 OSR 的证据，其余的不确定证据表明反馈较弱。这符合现场 PSF 比受控条件下弱的预期。正如预期的那样，随着干旱压力的增加，阳性 PSF 更加频繁。最强的 OSR 是由 C 在干地块中引起的 以前的居住-生存关系 (OSR) 被用作 PSF 的代理。在三分之一的物种对中发现了 OSR 的证据，其余的不确定证据表明反馈较弱。这符合现场 PSF 比受控条件下弱的预期。正如预期的那样，随着干旱压力的增加，阳性 PSF 更加频繁。最强的 OSR 是由 C 在干地块中引起的_{4 种}多年生草本，它们对几种 C ₃一年生杂草具有非常积极的 OSR ，但对彼此产生负面影响。这两个功能组之间有据可查的差异可以解释这一结果：C ₃植物对干旱更敏感，因此可能受到赋予耐受性的微生物群的青睐；相比之下，节水的 C ₄多年生草强烈地竞争磷，可能会导致它们之间产生强烈的负 PSF。最后，正如预期的那样，近亲对彼此的负 OSR 多于远亲，尽管只是在干燥的地块中。这种模式主要是由于密切相关的 C ₄的负面影响干燥条件下的草，以及它们对远缘双子叶植物的积极影响。我们的结果强调了植物性状和环境背景在确定田间条件下 PSF 的方向和强度方面的重要性。