Altered precipitation has asymmetric impacts on annual plant communities in warm and cool growing seasons
Altered precipitation has asymmetric impacts on annual plant communities in warm and cool growing seasons
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DOI：
10.1525/elementa.2021.00014
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发表时间：
2022
期刊：
影响因子：
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通讯作者：
M. Spasojevic;Peter M. Homyak;G. D. Jenerette;M. Goulden;Shane McFaul;Tesa Madsen-McQueen;Lisa Schauer;Miguel Solis
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文献类型：
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作者：
M. Spasojevic;Peter M. Homyak;G. D. Jenerette;M. Goulden;Shane McFaul;Tesa Madsen-McQueen;Lisa Schauer;Miguel Solis
虽然降水制度的改变可以极大地影响生物多样性和生态系统功能，但我们缺乏关于这些影响如何通过降水的季节性变化（即，一个季节相对于另一个季节是否降雨更多/更少）来调节的全面观点。在两年多的时间里，我们研究了季节降水变化如何影响一年生植物生物量和物种丰富度，辛普森多样性和一年生植物群落组成，在一个冬季和夏季都有降雨的旱地生态系统中，每个季节都有不同的一年生植物群落。利用降雨排除、收集和分配系统，我们在每个季节分别排除降水和加水，并与夏季和冬季环境降水的对照地块进行比较。在对照样地，植物年生物量是对照样地的5倍，物种数量是对照样地的2倍，冬季植物多样性是对照样地的2倍。增水仅增加了夏季的年生物量，夏季和冬季的丰富度和多样性均未发生变化，群落组成略有变化。排除任何季节的降水都会降低年植物生物量、丰富度和Simpson多样性。然而，在第二个冬季，在前一个夏季排除降水的样地，生物量更高，这表明夏季生产力降低可能促进冬季生物量的增加。研究结果表明，相对于冬季降水增加，夏季降水增加对年植物多样性和生态系统功能的短期影响更大。相比之下，降水减少在夏季和冬季对一年生植物都可能产生普遍的负面影响，但在随后的淡季可能导致生物量增加。这些模式表明，一年生植物群落和生态系统对季节降水变化的响应表现出不对称性，考虑降水的季节性对于预测降水制度变化的影响是重要的。
While altered precipitation regimes can greatly impact biodiversity and ecosystem functioning, we lack a comprehensive view of how these impacts are mediated by changes to the seasonality of precipitation (i.e., whether it rains more/less in one season relative to another). Over 2 years, we examined how altered seasonal precipitation influenced annual plant biomass and species richness, Simpson’s diversity, and community composition of annual plant communities in a dryland ecosystem that receives both winter and summer rainfall and has distinct annual plant communities in each season. Using a rainfall exclusion, collection, and distribution system, we excluded precipitation and added water during each season individually and compared responses to control plots which received ambient summer and winter precipitation. In control plots, we found five times greater annual plant biomass, twice as many species, and higher diversity in winter relative to summer. Adding water increased annual plant biomass in summer only, did not change richness or diversity in either summer or winter, and modestly shifted community composition. Excluding precipitation in either season reduced annual plant biomass, richness, and Simpson’s diversity. However, in the second winter season, biomass was higher in the plots where precipitation was excluded in the previous summer seasons suggesting that reduced productivity in the summer may facilitate biomass in the winter. Our results suggest that increased precipitation in summer may have stronger short-term impacts on annual plant biodiversity and ecosystem function relative to increased winter precipitation. In contrast, decreasing precipitation may have ubiquitous negative effects on annual plants across both summer and winter but may lead to increased biomass in the following off-seasons. These patterns suggest that annual plant communities exhibit asymmetries in their community and ecosystem responses to altered seasonal precipitation and that considering the seasonality of precipitation is important for predicting the effects of altered precipitation regimes.