Columbia University, Department of Earth and Environmental Sciences, 5th Fl Schermerhorn Extension, 1200 Amsterdam Ave., New York, NY, USA.
Lamont-Doherty Earth Observatory, Columbia University, 61 Route 9W, Palisades, NY, USA.
Tree Physiol. 2018 Sep 1;38(9):1319-1332. doi: 10.1093/treephys/tpx176.
The forests of the northeastern US are globally, one of the fastest growing terrestrial carbon sinks due to historical declines in large-scale agriculture, timber harvesting and fire disturbance. However, shifting range distributions of tree species with warming air temperatures are altering forest community composition and carbon dynamics. Here, we focus on respiration, a physiological process that is strongly temperature and species dependent. We specifically examined the response of respiration (R; CO2 release) to temperature in 10 broadleaved and six conifer species, as well as the respiratory quotient (RQ; ratio of CO2 released to O2 consumed) of nine broadleaved species that co-occur in the Hudson Highlands Region of New York, USA. The relationships between these physiological measurements and associated leaf traits were also explored. The rates of respiration at 20 °C were 71% higher in northern-ranged broadleaved species when compared with both central- and southern-ranged species. In contrast, the rates of respiration at 20 °C in northern-ranged conifers were 12% lower than in central-ranged conifers. The RQ of broadleaved species increased by 14% as temperatures increased from 15 °C to 35 °C. When RQ values were pooled across temperature, northern-ranged broadleaved species had 12% and 9% lower RQ values than central, and southern-ranged species, respectively, suggesting a reliance on alternative (non-carbohydrate) substrates to fulfill respiratory demands. A Pearson correlation analysis of leaf traits and respiration revealed strong correlations between leaf nitrogen, leaf mass area and R for both broadleaved and conifer species. Our results elucidate leaf trait relationships with tree physiology and reveal the various form and function strategies for species from differing range distributions. Compounded with predicted range distribution shifts and species replacement, this may reduce the carbon storage potential of northeast forests.
美国东北部的森林是全球陆地碳汇增长最快的地区之一，这主要归因于大规模农业、木材采伐和火灾干扰活动的减少。然而，随着空气温度的升高，树种分布范围的变化正在改变森林群落的组成和碳动态。在这里，我们主要关注呼吸作用，这是一个强烈依赖于温度和物种的生理过程。我们特别研究了 10 种阔叶树和 6 种针叶树的呼吸作用（CO2 释放）对温度的响应，以及 9 种共同存在于美国纽约哈德逊高地地区的阔叶树种的呼吸商（CO2 释放与 O2 消耗的比率）。还探讨了这些生理测量值与相关叶片特征之间的关系。与中部和南部分布的物种相比，北部分布的阔叶树种在 20°C 时的呼吸速率要高出 71%。相比之下，北部分布的针叶树种在 20°C 时的呼吸速率比中部分布的低 12%。当温度从 15°C 升高到 35°C 时，阔叶树种的呼吸商增加了 14%。当将 RQ 值在整个温度范围内进行汇总时，与中部和南部分布的物种相比，北部分布的阔叶树种的 RQ 值分别低 12%和 9%，这表明它们依赖于替代（非碳水化合物）底物来满足呼吸需求。对叶片特征和呼吸作用的皮尔逊相关分析表明，无论是阔叶树还是针叶树，叶片氮、叶片质量面积和 R 之间都存在很强的相关性。我们的研究结果阐明了叶片特征与树木生理之间的关系，并揭示了不同分布范围的物种的各种形态和功能策略。加上预测的分布范围变化和物种更替，这可能会降低东北森林的碳储存潜力。
