Dryland ecosystems cover large regions of the Earth and have important impacts on global biogeochemistry and the carbon cycle. The plant species that occupy dryland environments have traits that enable them to withstand harsh environmental conditions, and some researchers have hypothesized that dryland vegetation may be comparatively resilient to changing climate, while others have pointed out that dryland vegetation often operates close to the physiological limits of many species, implying a possible vulnerability to warming. Here we use the Landsat archive to analyze vegetation dynamics for part of the Sonoran Desert and adjacent mountains in southern California. We show that large decreases in vegetation cover occurred over the last 34 years (1984–2017), especially across the xeric portions of our study region, where we observed a normalized difference vegetation index (NDVI) decline of 1.1 ± 0.3% yr⁻¹. Changes in precipitation explain most of the year-to-year variation but are unable to fully explain the observed long-term decline in NDVI. Statistical models that combined summer temperature and mean annual precipitation explained more of the spatial and temporal structure of NDVI trends and implicate climate warming as an important driver of declining vegetation cover. The impact of warming contributed to a change in the precipitation-vegetation relationship through time for this desert region, indicating a structural change in ecosystem function during the study period. These results suggest that recent climate change has already had significant impact on these drylands and highlight the potential for future warming to increase risks for dryland ecosystems in other regions.

中文翻译：

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气候变暖是加利福尼亚索诺兰沙漠植被损失的驱动因素

旱地生态系统覆盖地球的大片区域，对全球生物地球化学和碳循环具有重要影响。占据旱地环境的植物物种具有使它们能够承受恶劣环境条件的特​​性，一些研究人员假设旱地植被可能对气候变化具有相对弹性，而其他人则指出旱地植被通常接近于生理极限。许多物种，这意味着可能容易受到变暖的影响。在这里，我们使用 Landsat 档案来分析加利福尼亚南部索诺兰沙漠和邻近山脉的部分植被动态。我们表明，过去 34 年（1984-2017 年）植被覆盖率大幅下降，尤其是在我们研究区域的干旱部分，^-1。降水的变化可以解释大部分的逐年变化，但无法完全解释观察到的 NDVI 长期下降。结合夏季温度和年平均降水量的统计模型更多地解释了 NDVI 趋势的时空结构，并暗示气候变暖是植被覆盖率下降的重要驱动因素。变暖的影响导致了该沙漠地区降水-植被关系随时间的变化，表明研究期间生态系统功能发生了结构性变化。这些结果表明，最近的气候变化已经对这些旱地产生了重大影响，并强调了未来变暖可能会增加其他地区旱地生态系统的风险。