Stem Radial Growth Is Negatively Related to Tree Defoliation and Damage in Conifers, Northern Italy

Although several manipulative experiments provided evidence for a negative effect of defoliation on tree growth, results from observational studies were less univocal. This may be due to the ability observed reflect health status individual trees, influence site condition and amplitude time window used growth assessment. Here, we investigated relationship between two indicators (crown defoliation, damage symptoms) annual (measured by tree-ring width 69 Norway spruce trees) periodical (5-year 10-year diameter increments, 346 trees five coniferous species) growth. Data originated 14 (seven rings) ICP Forests Level I plots in Trentino, northern Italy. Diameter, measured 1997 2011 as part crown survey, while cores tree-rings collected sub-sample 2012. We carried out regression modeling combined with model selection one-step (periodical data) two-step (annual approaches, using moving averages data varying widths. Our indicated an overall correlation or stem The changes relation considered, becomes stronger when are aggregated over longer windows (>3 years), also occurrence symptoms plays significant role. aggregation is probably mechanisms behind defoliation-growth relationship, which change according causal factors involved. In particular, larger short-term fluctuations likely smoothed out, more general patterns emerge. concluded that radial significantly negatively related this supports use rapid indicator forest vitality.