Urbina Ifigenia, Sardans Jordi, Beierkuhnlein Carl, Jentsch Anke, Backhaus Sabrina, Grant Kerstin, Kreyling Juergen, Peñuelas Josep
CSIC, Global Ecology Unit CREAF-CEAB-CSIC-UAB, 08913 Cerdanyola del Vallès, Catalonia, Spain.
CREAF, 08913 Cerdanyola del Vallès, Catalonia, Spain.
Environ Exp Bot. 2015 Mar;111:63-73. doi: 10.1016/j.envexpbot.2014.10.005. Epub 2014 Nov 4.
Diverse plant functions (e.g. growth, storage, defense and anti-stress mechanisms) use elements disproportionally. We hypothesized that plants growing under different abiotic and biotic conditions would shift their elemental compositions in response to a very severe drought. We tested this hypothesis by investigating the changes in foliar stoichiometry and species composition from a very severe drought. We also tested the effects of previous droughts (acclimation) on this response. Different species growing in the same community responded more similarly to a very severe drought than did individual species growing in different communities. The stoichiometric shifts were thus more community-dependent than species-dependent. The results also suggested that plants grown in monoculture were less stoichiometrically plastic during the drought than plants grown in a more diverse community. Previous exposure to long-term drought treatments in the same communities did not significantly affect the stoichiometric shifts during the new drought. Differential use of resources may have been responsible for these responses. Monocultured plants, which used the same resources in similar proportions, had more difficulty avoiding direct competition when the resources became scarcer. Moreover, each species tested had a particular elemental composition in all communities and climatic treatments. The differences in foliar elemental compositions were largest between plant functional groups (shrubs and grasses) and smallest among species within the same functional group. Global principal components analyses (PCAs) identified a general tendency for all species, independently of the community in which they grew, toward lower concentrations of K, N, P, Mg and S, and to higher concentrations of C and Fe as the drought advanced. This study has demonstrated the utility of analyses of differences and shifts in plant elemental composition for understanding the processes underlying the responses of plants to changes in biotic and abiotic environmental conditions.
多种植物功能（如生长、储存、防御和抗逆机制）对元素的利用不成比例。我们推测，在不同非生物和生物条件下生长的植物会因极端干旱而改变其元素组成。我们通过研究极端干旱下叶片化学计量和物种组成的变化来验证这一假设。我们还测试了先前干旱（适应性）对这种响应的影响。同一群落中生长的不同物种对极端干旱的响应比不同群落中生长的单个物种更为相似。因此，化学计量变化更多地取决于群落而非物种。结果还表明，与生长在多样性更高群落中的植物相比，单一栽培的植物在干旱期间化学计量可塑性较低。同一群落中先前经历长期干旱处理并未显著影响新干旱期间的化学计量变化。资源的差异利用可能是这些响应的原因。单一栽培的植物以相似比例利用相同资源，当资源变得稀缺时，更难避免直接竞争。此外，所测试的每个物种在所有群落和气候处理中都有特定的元素组成。叶片元素组成的差异在植物功能组（灌木和草本）之间最大，在同一功能组内的物种之间最小。全局主成分分析（PCA）表明，随着干旱加剧，所有物种无论生长在哪个群落中，都普遍呈现出K、N、P、Mg和S浓度降低，C和Fe浓度升高的趋势。这项研究证明了分析植物元素组成的差异和变化对于理解植物对生物和非生物环境条件变化响应背后的过程的实用性。
