气候变化引发了人们对森林如何应对极端干旱的担忧,热浪,以及它们的共同发生。在这项温室研究中,我们测试了碳和水的关系如何与美国东北部树木在极端干旱期间和之后的幼苗生长和死亡率有关,变暖,干旱和变暖相结合。我们比较了我们的焦点物种红云杉(PicearubensSarg。)给普通合伙人(纸桦木,桦树.)和一个预计随着气候变化在该地区丰度增加的物种(北部红橡树,橡树L.)。我们追踪了增长和死亡率,光合作用,以及通过处理和恢复年对这些物种的216株幼苗的用水。将每个红云杉幼苗单独或与另一个幼苗一起种植在容器中,以模拟潜在的竞争,并将幼苗暴露于干旱的组合(灌溉,15天\'短\',或30天\'长\')和温度(环境温度或16天,每天最高+3.5°C)治疗。我们发现干旱减少光合作用的主要影响,中午水势,云杉和桦树的生长,但是橡树对干旱胁迫表现出相当大的抵抗力。一起种植幼苗的影响是中等的,可能是由于对有限水的竞争。尽管高温会降低所有物种的光合作用,这项研究中施加的变暖仅对恢复年的橡树的生长产生了微小的影响。总的来说,我们发现,在我们的研究中,该物种采用的不同用水策略与干旱胁迫后的生长和恢复有关。这项研究提供了生理证据来支持这一预测,即红云杉和纸桦树等该地区的本地物种易受未来极端气候的影响,这些极端气候可能有利于其他物种,如北方红橡树,导致气候变化对树木群落动态的潜在影响。
Climate change is raising concerns about how forests will respond to extreme droughts, heat waves, and their co-occurrence. In this greenhouse study, we tested how carbon and water relations relate to seedling growth and mortality of northeastern US trees during and after extreme drought, warming, and combined drought and warming. We compared the response of our focal species red spruce (Picea rubens Sarg.) to a common associate (paper birch, Betula papyrifera Marsh.) and a species expected to increase abundance in this region with climate change (northern red oak, Quercus rubra L.). We tracked growth and mortality, photosynthesis, and water use of 216 seedlings of these species through a treatment and a recovery year. Each red spruce seedling was planted in containers either alone or with another seedling to simulate potential competition and seedlings were exposed to combinations of drought (irrigated, 15-day \'short\', or 30-day \'long\') and temperature (ambient or 16 days at +3.5 °C daily maximum) treatments. We found dominant effects of the drought reducing photosynthesis, midday water potential, and growth of spruce and birch, but that oak showed considerable resistance to drought stress. The effects of planting seedlings together were moderate and likely due to competition for limited water. Despite high temperatures reducing photosynthesis for all species, the warming imposed in this study minorly impacted growth only for oak in the recovery year. Overall, we found that the diverse water-use strategies employed by the species in our study related to their growth and recovery following drought stress. This study provides physiological evidence to support the prediction that native species to this region like red spruce and paper birch are susceptible to future climate extremes that may favor other species like northern red oak, leading to potential impacts on tree community dynamics under climate change.