USDA-ARS-Jornada Experimental Range, New Mexico State University, Las Cruces, New Mexico, USA.
DEVCOM Army Research Laboratory, White Sands Missile Range, New Mexico, USA.
Ecology. 2023 Jul;104(7):e4065. doi: 10.1002/ecy.4065. Epub 2023 May 14.
Prediction of abrupt ecosystem transitions resulting from climatic change will be an essential element of adaptation strategies in the coming decades. In the arid southwest USA, the collapse and recovery of long-lived perennial grasses have important effects on ecosystem services, but the causes of these variations have been poorly understood. Here we use a quality-controlled vegetation monitoring dataset initiated in 1915 to show that grass cover dynamics during the 20th century were closely correlated to the Pacific decadal oscillation (PDO) index. The relationship out-performed models correlating grasses to yearly precipitation and drought indices, suggesting that ecosystem transitions attributed only to local disturbances were instead influenced by climate teleconnections. Shifts in PDO phase over time were associated with the persistent loss of core grass species and recovery of transient species, so recovery of grasses in aggregate concealed significant changes in species composition. However, the relationship between PDO and grass cover broke down after 1995; grass cover is consistently lower than PDO would predict. The decoupling of grass cover from the PDO suggests that a threshold had been crossed in which warming or land degradation overwhelmed the ability of any grass species to recover during favorable periods.
预测气候变化引起的生态系统突然转变将是未来几十年适应策略的重要组成部分。在美国干旱的西南部，长寿多年生草本植物的崩溃和恢复对生态系统服务有重要影响，但这些变化的原因还不太清楚。在这里，我们使用始于 1915 年的经过质量控制的植被监测数据集，表明 20 世纪草皮覆盖动态与太平洋年代际振荡（PDO）指数密切相关。该关系优于将草皮与年降水量和干旱指数相关联的模型，表明仅归因于局部干扰的生态系统转变反而受到气候远距离相关的影响。PDO 相位随时间的变化与核心草种的持续丧失和瞬时种的恢复有关，因此草类的总体恢复掩盖了物种组成的重大变化。然而，PDO 与草皮覆盖之间的关系在 1995 年后破裂；草皮覆盖始终低于 PDO 的预测值。草皮覆盖与 PDO 的解耦表明，已经越过了一个阈值，在这个阈值下，变暖或土地退化超过了任何草种在有利时期恢复的能力。
