Tree-scale carbon allocation dynamics in a mature mixed forest using long-term mass balance approach 

Abstract

<p>Mixed forests are typically more productive and are faster to recover from drought compared to monospecific forests. Disentangling the contribution of each species to the overall success of the forest requires observations at the individual tree level. In this study, we measured a complete set of carbon (C) pools and fluxes at the tree-level in five tree species, two conifers and three broadleaf, co-existing in a mature evergreen mixed Mediterranean forest. Our study period included a drought year, followed by an above-average year. Across species, C sinks of 38-91 kg tree<sup>-1</sup> year<sup>-1</sup> were 16-32% larger than C source of 27-77 kg tree<sup>-1</sup> year<sup>-1</sup> in the dry year, with larger belowground C investment of the shallow-rooted species. Overall, respiration was the largest sink across species and years, accounting for 26-62% of all assimilated C, followed by growth (16%) and root exudation (19%). Non-structural carbohydrates accumulation was similar between the wet and the dry year. These detailed tree-level observations expose large interspecific differences in C allocation among fluxes and tissues and specifically in response to varying water availability. These insights become useful for forest management under ongoing change.</p>