Castillioni Karen, Wilcox Kevin, Jiang Lifen, Luo Yiqi, Jung Chang Gyo, Souza Lara
Oklahoma Biological Survey Department of Microbiology and Plant Biology University of Oklahoma Norman OK USA.
Ecosystem Science and Management University of Wyoming Laramie WY USA.
Ecol Evol. 2020 Jun 1;10(13):6702-6713. doi: 10.1002/ece3.6400. eCollection 2020 Jul.
Shifts in dominance and species reordering can occur in response to global change. However, it is not clear how altered precipitation and disturbance regimes interact to affect species composition and dominance.We explored community-level diversity and compositional similarity responses, both across and within years, to a manipulated precipitation gradient and annual clipping in a mixed-grass prairie in Oklahoma, USA. We imposed seven precipitation treatments (five water exclusion levels [-20%, -40%, -60%, -80%, and -100%], water addition [+50%], and control [0% change in precipitation]) year-round from 2016 to 2018 using fixed interception shelters. These treatments were crossed with annual clipping to mimic hay harvest.We found that community-level responses were influenced by precipitation across time. For instance, plant evenness was enhanced by extreme drought treatments, while plant richness was marginally promoted under increased precipitation.Clipping promoted species gain resulting in greater richness within each experimental year. Across years, clipping effects further reduced the precipitation effects on community-level responses (richness and evenness) at both extreme drought and added precipitation treatments. Our results highlight the importance of studying interactive drivers of change both within versus across time. For instance, clipping attenuated community-level responses to a gradient in precipitation, suggesting that management could buffer community-level responses to drought. However, precipitation effects were mild and likely to accentuate over time to produce further community change.
优势度的转变和物种重新排序可能会因全球变化而发生。然而，目前尚不清楚降水变化和干扰格局如何相互作用以影响物种组成和优势度。我们在美国俄克拉荷马州的一个混合草草原上，研究了群落水平的多样性和组成相似性对人工控制的降水梯度和年度刈割的响应，包括跨年度和年度内的响应。从2016年到2018年，我们使用固定的截留棚全年施加了七种降水处理（五种水分排除水平[-20%、-40%、-60%、-80%和-100%]、水分添加[+50%]以及对照[降水变化0%]）。这些处理与年度刈割交叉，以模拟干草收获。我们发现群落水平的响应随时间受到降水的影响。例如，极端干旱处理增强了植物均匀度，而降水增加时植物丰富度略有提高。刈割促进了物种增加，导致每个实验年份内的丰富度更高。跨年度来看，刈割效应进一步降低了极端干旱和降水增加处理下降水对群落水平响应（丰富度和均匀度）的影响。我们的结果强调了研究时间内和时间间变化的交互驱动因素的重要性。例如，刈割减弱了群落水平对降水梯度的响应，这表明管理措施可以缓冲群落水平对干旱的响应。然而，降水的影响较为轻微，且可能会随着时间加剧，从而导致群落进一步变化。
