Scars from human-tree interactions: pollarding, pathogens, body reserves, and long-term response by <i>Salix fragilis</i> L. (Salicaceae) in Scodovacca, Italy
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Arboriculture provides opportunities for assessing long-term tree-environment interactions. We assessed the surrounding context, scars, re-sprouts, and absolute width-growth of twenty-four <i>Salix fragilis</i> trees pollarded by the grandfather, father, and son of one family covering 120 years, quantifying the effects of cut, microorganism-infection, and body-accumulated photosynthate on the pollards’ resprout-and-growth. We determined pollard diameter, age, scars-number (C) and basal area (C<sub>AB</sub>), median times pruned (Cmn), putrid holes number (H), cumulative length (HL), and length-average (H<sub>AV</sub>), and two indicators of remaining photosynthate (Q, and Q<sub>AV</sub>). Response variables were number of re-sprouts (R<sub>N</sub>), re-sprout-basal area (R<sub>AB</sub>), and trunk’s Absolute Growth (AG; Classic (MLR), and Bayesian Multiple Linear Regressions (BMLR)). The pollards experienced similar incoming light, water, CO<sub>2</sub>, nutrients, and temperatures. Higher C-values for 40-year-old pollards produced higher H-values (Linear Regression, R<sup>2</sup> = 0.54, <i>p</i> = 0.02; Bayesian Linear Regression: BF10 = 3.79, <i>n</i> = 8) suggesting more infection when cutting. R<sub>N</sub> slightly changed in response to life-long accumulated C<sub>AB</sub>, Cmn, H, and H<sub>AV</sub> (BMLR, BF10 from 1.10 to 2.82, <i>n</i> = 24). R<sub>AB</sub> slightly changed responding to C, H, H<sub>AV</sub>, Q, and Q<sub>AV</sub> (BMLR, BF10 = 1.11; MLR: <i>p</i> < 0.05, <i>n</i> = 24). AG declined in response to Cmn (MLR, R2 = 0.38, <i>p</i> < 0.001, <i>n</i> = 24). Thus, under favourable conditions severely wounded-and-infected trees keep re-sprouting and growing, even if growth is reduced.
