Co-ordinating Editor: Enrique Valencia Abstract Questions: Reordering of dominant species is an important mechanism of community response to global environmental change. We asked how wildfire (a pulse event) interacts with directional changes in climate (environmental presses) to affect plant community dynamics in a Chihuahuan Desert grassland. Location: Sevilleta National Wildlife Refuge, Socorro County, New Mexico, USA. Methods: Vegetation cover by species was measured twice each year from 1989 to 2019 along two permanently located 400-m long line intercept transects, one in Chihuahuan Desert grassland, and the second in the ecotone between Chihuahuan Desert and Great Plains grasslands. Trends in community structure were plotted over time, and climate sensitivity functions were used to predict how changes in the Pacific Decadal Oscillation (PDO) affected vegetation dynamics. Results: Community composition was undergoing gradual change in the absence of disturbance in the ecotone and desert grassland. These changes were related to the reordering of abundances between two foundation grasses, Bouteloua eriopoda and B. gracilis, that together account for >80% of above-ground primary production. However, reordering varied over time in response to wildfire (a pulse) and changes in the PDO (a press). Community dynamics were initially related to the warm and cool phases of the PDO, but in the ecotone these relationships changed following wildfire, which reset the system. Conclusion: Species reordering is an important component of community dynamics in response to ecological presses. However, reordering is a complex, non-linear process in response to ecological presses that may change over time and interact with pulse disturbances.

中文翻译：

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奇瓦环沙漠草原的压力-脉冲相互作用和长期群落动态

协调编辑：Enrique Valencia 摘要 问题：优势物种的重新排序是群落应对全球环境变化的重要机制。我们询问了野火（脉冲事件）如何与气候的定向变化（环境压力）相互作用以影响奇瓦瓦沙漠草原的植物群落动态。地点：美国新墨西哥州索科罗县塞维利亚国家野生动物保护区。方法：从 1989 年到 2019 年，每年两次沿两个永久定位的 400 米长线截断线测量物种植被覆盖度，一个在赤花环沙漠草原，第二个在赤花环沙漠和大平原草原之间的交错带。随着时间的推移绘制了社区结构的趋势，和气候敏感性函数用于预测太平洋年代际振荡 (PDO) 的变化如何影响植被动态。结果：在无干扰的交错带和荒漠草地群落组成逐渐发生变化。这些变化与两种基础草 Bouteloua eriopoda 和 B. gracilis 之间丰度的重新排序有关，它们共同占地上初级生产的 80% 以上。然而，重新排序会随着时间的推移而变化，以响应野火（脉冲）和 PDO（印刷机）的变化。社区动态最初与 PDO 的温暖和凉爽阶段有关，但在过渡带中，这些关系在野火后发生了变化，从而重置了系统。结论：物种重新排序是响应生态压力的群落动态的重要组成部分。