Department of Ecology, University of Innsbruck, Innsbruck, Austria.
Department of Statistics, University of Innsbruck, Innsbruck, Austria.
Ecology. 2023 Feb;104(2):e3907. doi: 10.1002/ecy.3907. Epub 2023 Jan 3.
The ecological consequences of future droughts are difficult to predict due to a limited understanding of the nonlinear responses of plants to increasing drought intensity, which can change abruptly when critical thresholds of drought intensity are crossed. Drought responses are composed of resistance and postdrought recovery. Although it is well established that higher drought intensity increases the impact and, thus, reduces plant resistance, less is known about how drought intensity affects recovery and how resistance and recovery are related. In this study, we tested the hypothesis that resistance, recovery, and their relationship change abruptly upon crossing critical thresholds of drought intensity. We exposed mesocosms of two monospecific stands of the common grassland species Dactylis glomerata and Plantago lanceolata to a large gradient of drought intensity and quantified the resistance and recovery of multiple measures of plant productivity, including gross-primary productivity, vegetative height, Normalized Difference Vegetation Index, and aboveground biomass production. Drought intensity had nonlinear and contrasting effects on plant productivity during drought and recovery, which differed between the two species. Increasing drought intensity decreased the resistance of plant productivity and caused rapid compensatory growth during postdrought recovery, the degree of which was highly dependent on drought intensity. Across multiple response parameters two thresholds of drought intensity emerged, upon which we observed abrupt changes in plant resistance and recovery, as well as their relationship. We conclude that across gradients of drought intensity resistance and recovery are tightly coupled and that both the magnitude and the direction of drought effects on resistance and recovery can change abruptly upon specific thresholds of stress intensity. These findings highlight the urgent need to account for nonlinear responses of resistance and recovery to drought intensity as critical drivers of productivity in a changing climate.
由于对植物对干旱强度增加的非线性响应理解有限，未来干旱的生态后果难以预测，当干旱强度的关键阈值被越过时，这种响应可能会突然发生变化。干旱响应由抵抗力和干旱后恢复力组成。虽然已经证实较高的干旱强度会增加影响，从而降低植物的抵抗力，但对于干旱强度如何影响恢复力以及抵抗力和恢复力之间的关系知之甚少。在这项研究中，我们检验了这样一个假设，即当越过干旱强度的关键阈值时，抵抗力、恢复力及其关系会突然发生变化。我们将两种常见草原物种的单一种群的中生境培养箱暴露在一个大的干旱强度梯度中，并量化了植物生产力的多个指标的抵抗力和恢复力，包括总初级生产力、植物高度、归一化植被指数和地上生物量生产。干旱强度对干旱和恢复期间的植物生产力具有非线性和相反的影响，这在两种物种之间有所不同。随着干旱强度的增加，植物生产力的抵抗力降低，并在干旱后恢复期间导致快速的补偿性生长，其程度高度依赖于干旱强度。在多个响应参数中，出现了两个干旱强度阈值，我们观察到植物抵抗力和恢复力及其关系发生了突然变化。我们得出的结论是，在干旱强度的梯度上，抵抗力和恢复力紧密耦合，干旱对抵抗力和恢复力的影响的幅度和方向都可以在特定的压力强度阈值上突然发生变化。这些发现强调了迫切需要考虑抵抗力和恢复力对干旱强度的非线性响应，作为气候变化下生产力的关键驱动因素。
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