Increased climatic variability can impact tree physiological processes beyond what is predicted from changes in mean conditions. We assessed the sensitivity of conifer saplings to spatial and temporal variability in meteorological conditions, taking advantage of the end of California’s historic drought and the exceedingly wet winter of 2017. We sought to understand how very dry and very wet conditions constrain photosynthesis and growth in four regionally dominant conifers and whether sensitivity in these processes changes across a 500 m gradient in elevation. All species demonstrated phenotypic plasticity in response to temporal differences in precipitation on both inter-annual and seasonal timescales. Net photosynthesis in Pinus contorta decreased from an early season 2016 average of 12.4 to 6.89 μmol CO₂ m⁻² s⁻¹ later in the summer, but increased 14.1% between seasons in the wet year. By contrast, elevation had almost no effect on instantaneous photosynthetic gas exchange, CO₂ response curve parameters, or stem water potential in any of the years for any of the species. Effects of the heavy snow year (2017) on needle growth differed between elevations. Pinus contorta showed a 38.9% increase in average needle length at the lower two elevations but a 31.6% decrease at the highest site compared to the height of the drought. Despite these differences, biological variation was dampened compared to the physical variation between years, suggesting these trees can effectively withstand substantial meteorological variability. Our results show that these species demonstrated considerable ability to tolerate and recover from an extreme drought event.

气候变异性的增加会影响树木的生理过程，超出平均条件变化所能预测的范围。我们利用加利福尼亚州历史性干旱的结束和2017年极端潮湿的冬季，评估了针叶树苗对气象条件时空变化的敏感性。我们试图了解非常干燥和非常潮湿的条件如何限制了四个地区的光合作用和生长区域主要的针叶树，以及这些过程中的敏感性是否会在海拔500 m的梯度上变化。所有物种在年际和季节时间尺度上都响应于降水的时间差异表现出表型可塑性。松果的净光合作用从2016年初的平均季节12.4降至6.89μmolCO夏季晚些时候为₂ m ^-2  s ^-1，但在潮湿年份的季节之间增加了14.1％。相比之下，任何物种在任何年份中，海拔高度对瞬时光合气体交换，CO ₂响应曲线参数或茎水势几乎没有影响。不同海拔之间，大雪年（2017）对针叶生长的影响有所不同。松树与干旱高度相比，在较低的两个海拔高度处平均针长增加了38.9％，在最高位置减少了31.6％。尽管存在这些差异，但与多年间的物理差异相比，生物学差异得到了抑制，这表明这些树木可以有效承受较大的气象变异。我们的结果表明，这些物种具有极强的耐受能力，能够从极端干旱事件中恢复。