Cycles of plant growth, termed phenology, are tightly linked to environmental controls. The length of time spent growing, bounded by the start and end of season, is an important determinant of the global carbon, water, and energy balance. Much focus has been given to global warming and consequences for shifts in growing-season length in temperate regions. In conjunction with warming temperatures, altered precipitation regimes are another facet of climate change that have potentially larger consequences than temperature in dryland phenology globally. We experimentally manipulated incoming precipitation in a semiarid grassland for over a decade and recorded plant phenology at the daily scale for 7 years. We found precipitation to have a strong relationship with the timing of grass greenup and senescence but temperature had only a modest effect size on grass greenup. Pre-season drought strongly resulted in delayed grass greenup dates and shorter growing-season lengths. Spring and summer drought corresponded with earlier grass senescence, whereas higher precipitation accumulation over these seasons corresponded with delayed grass senescence. However, extremely wet conditions diluted this effect and caused a plateaued response. Deep-rooted woody shrubs showed few effects of variable precipitation or temperature on phenology and displayed consistent annual phenological timing compared with grasses. Whereas rising temperatures have already elicited phenological consequences and extended growing-season length for mid and high-latitude ecosystems, precipitation change will be the major driver of phenological change in drylands that cover 40% of the land surface with consequences for the global carbon, water, and energy balance.

中文翻译：

---

降水与温度作为旱地物候控制

植物生长周期，称为物候学，与环境控制密切相关。生长时间的长短受季节开始和结束的限制，是全球碳、水和能量平衡的重要决定因素。全球变暖及其对温带地区生长季节长度变化的影响已引起广泛关注。与变暖的温度相结合，改变的降水状况是气候变化的另一个方面，其对全球旱地物候的影响可能比温度更大。十多年来，我们通过实验控制了半干旱草原的降水量，并记录了 7 年的日尺度植物物候。我们发现降水与草地绿化和衰老的时间有很强的关系，但温度对草地绿化的影响不大。季前干旱严重导致草地绿化日期延迟和生长季节长度缩短。春季和夏季的干旱与较早的草衰老相对应，而这些季节较高的降水积累与延迟的草衰老相对应。然而，极端潮湿的条件削弱了这种影响并导致了稳定的反应。与草相比，深根木本灌木显示出变化的降水或温度对物候的影响很小，并且显示出一致的年度物候时间。鉴于气温上升已经引发了物候变化并延长了中高纬度生态系统的生长季节，