Climate and atmospheric deposition effects on forest water-use efficiency and nitrogen availability across Britain.

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.