Climate change alters plant biogeography in Mediterranean prairies along the West Coast, USA
Climate change alters plant biogeography in Mediterranean prairies along the West Coast, USA
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气候变化改变了美国西海岸地中海大草原的植物生物地理
DOI：
10.1111/gcb.13052
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发表时间：
2016
影响因子：
11.6
通讯作者：
Bart R. Johnson
中科院分区：
文献类型：
--
作者：
Laurel E. Pfeifer‐Meister;S. Bridgham;L. Reynolds;M. Goklany;H. Wilson;C. Little;Aryana Ferguson;Bart R. Johnson
预计气候变化将在未来几十年对植物群落组成和多样性产生广泛影响。然而，多地点，多因素的气候操纵研究，审查是否观察到的反应是区域一致的，是否多个气候扰动是相互依赖的是罕见的。使用这样的实验，我们量化了变暖和降水强度增加如何影响植物功能群和多样性在地中海大草原的广泛的气候梯度的相对优势。我们在美国太平洋西北部520 km纬度梯度的三个地点实施了一个完全因子气候操纵变暖（+2.5-3.0 °C）和雨季降水增加（+20%）。在所有地点用几乎相同的本地物种混合物播种后，我们测量了植物群落组成（即，覆盖，丰富度和多样性），温度和土壤水分3年。变暖和由此导致的土壤干燥改变了植物群落的组成，减少了本地的多样性，并增加了总覆盖，与温暖的北方社区变得更加相似的社区进一步南部。特别是，经过整整两年的变暖，年复盖率增加，杂类草覆盖率下降，在所有网站反映自然地理格局。这表明，现有的气候梯度增加热量和干旱的严重程度是负责的一个很大的一部分，在美国西海岸大草原，随着进一步向南移动，每年增加入侵观察到的地理模式。在雨季额外的降水并没有缓解干旱胁迫，并对植物群落组成的影响微乎其微。我们的研究结果表明，预计干旱严重程度的增加（即，在太平洋西北部草原，气候变化（例如，炎热、干燥的夏季）可能导致一年生植物入侵增加和杂类草的损失，类似于在加州中部和南部观察到的情况，导致新的物种组合和功能组成的变化，这反过来又可能改变生态系统的功能。
Projected changes in climate are expected to have widespread effects on plant community composition and diversity in coming decades. However, multisite, multifactor climate manipulation studies that have examined whether observed responses are regionally consistent and whether multiple climate perturbations are interdependent are rare. Using such an experiment, we quantified how warming and increased precipitation intensity affect the relative dominance of plant functional groups and diversity across a broad climate gradient of Mediterranean prairies. We implemented a fully factorial climate manipulation of warming (+2.5–3.0 °C) and increased wet‐season precipitation (+20%) at three sites across a 520‐km latitudinal gradient in the Pacific Northwest, USA. After seeding with a nearly identical mix of native species at all sites, we measured plant community composition (i.e., cover, richness, and diversity), temperature, and soil moisture for 3 years. Warming and the resultant drying of soils altered plant community composition, decreased native diversity, and increased total cover, with warmed northern communities becoming more similar to communities further south. In particular, after two full years of warming, annual cover increased and forb cover decreased at all sites mirroring the natural biogeographic pattern. This suggests that the extant climate gradient of increasing heat and drought severity is responsible for a large part of the observed biogeographic pattern of increasing annual invasion in US West Coast prairies as one moves further south. Additional precipitation during the rainy season did little to relieve drought stress and had minimal effects on plant community composition. Our results suggest that the projected increase in drought severity (i.e., hotter, drier summers) in Pacific Northwest prairies may lead to increased invasion by annuals and a loss of forbs, similar to what has been observed in central and southern California, resulting in novel species assemblages and shifts in functional composition, which in turn may alter ecosystem functions.