Tree canopy defoliation can reveal growth decline in mid-latitude temperate forests

Climate and weather fluctuations changes are the most important environmental drivers of tree canopy defoliation, an indicator forest health. We examined relationship between defoliation Basal Area Increment (BAI), a dimension growth related to wood biomass increment carbon sequestration therefore climate change mitigation potential forests. analysed data from mostly even-aged, single-species permanent monitoring plots in France over two growing periods (1995–2004: 47 plots, 2008 trees; 2000–2009: 63 3116 trees) for which precipitation deficit was identified as main driver defoliation. Trees ten different species were assessed annually measured periodically growth, we derived periodical (10-year) BAI (BAIperiod). investigated (i) direction significance defoliation-BAIperiod relationships (ii) occurrence, size deviation progressively defoliated trees proportion undefoliated (BAIrel). Analyses first carried out at level individual with results subsequently evaluated using meta-analysis further aggregated levels (all species, functional groups, species). BAIperiod resulted negatively significantly significant reduction detected already slight (15%) level. A generalized statistically BAIrel obvious, leading estimated 0.7–0.8% per 1% increase conifers 0.9% broadleaves. Considering observed distribution along range, our indicate overall ca. 42% comparison theoretical population trees. Shifts such can result into loss or gain turn may have cascading effects on land-climate interactions. In context Europe recent decades, suggest that even moderate variations had impact growth.