Centre for Ecological Research and Forestry Applications, CREAF, c/o Universidad Autonoma de Barcelona, Edificio C, 08290, Cerdanyola, Barcelona, Spain.
Department of Agricultural and Food Sciences, University of Bologna, 40127, Bologna, Italy.
Sci Rep. 2020 Jul 24;10(1):12418. doi: 10.1038/s41598-020-67562-w.
Rising atmospheric CO (c) has been shown to increase forest carbon uptake. Yet, whether the c-fertilization effect on forests is modulated by changes in sulphur (S) and nitrogen (N) deposition and how N affects ecosystem N availability remains unclear. We explored spatial and temporal (over 30-years) changes in tree-ring δC-derived intrinsic water-use efficiency (iWUE), δO and δN for four species in twelve forests across climate and atmospheric deposition gradients in Britain. The increase in iWUE was not uniform across sites and species-specific underlying physiological mechanisms reflected the interactions between climate and atmospheric drivers (oak and Scots pine), but also an age effect (Sitka spruce). Most species showed no significant trends for tree-ring δN, suggesting no changes in N availability. Increase in iWUE was mostly associated with increase in temperature and decrease in moisture conditions across the South-North gradient and over 30-years. However, when excluding Sitka spruce (to account for age or stand development effects), variations in iWUE were significantly associated with changes in c and S. Our data suggest that overall climate had the prevailing effect on changes in iWUE across the investigated sites. Whereas, detection of N, S and c signals was partially confounded by structural changes during stand development.
大气中 CO（c）的增加已被证明会增加森林碳吸收。然而，c 施肥对森林的影响是否会受到硫（S）和氮（N）沉积变化的调节，以及 N 如何影响生态系统 N 有效性仍不清楚。我们在英国气候和大气沉积梯度的 12 个森林中，对四个物种的树木年轮 δC 衍生的内在水分利用效率（iWUE）、δO 和 δN 进行了 30 多年的时空变化研究。iWUE 的增加在不同地点并不均匀，物种特异性的潜在生理机制反映了气候和大气驱动因素（橡树和欧洲赤松）之间的相互作用，但也反映了年龄效应（欧洲云杉）。大多数物种的树木年轮 δN 没有明显的趋势，表明 N 有效性没有变化。在整个南-北梯度和 30 多年的时间里，iWUE 的增加主要与温度升高和水分条件减少有关。然而，当排除欧洲云杉（以解释年龄或林分发育效应）时，iWUE 的变化与 c 和 S 的变化显著相关。我们的数据表明，总体气候对研究地点的 iWUE 变化有主要影响。然而，N、S 和 c 信号的检测部分受到林分发育过程中结构变化的干扰。
