Tree size and crown structure explain the presence of cavities required by wildlife in cool-temperate forests of South America

DUDINSZKY, N.; IPPI, S.; KITZBERGER, T.; CERÓN, G.; OJEDA, V.

FOREST ECOLOGY AND MANAGEMENT

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2021

0378-1127

Maintenance of tree cavity supply is a global conservation priority for forest wildlife,which requires understanding the ecology and population dynamics of cavity-bearingtrees. Explaining the occurrence of cavities in trees is particularly important inecosystems where most secondary cavity-users (SCUs) are critically dependent on theslow formation of cavities by wood-decay processes. Our main objectives were (1) toexplain the distribution of decay cavities in trees according to their individual attributesand, (2) to quantify the relative importance of each individual tree attribute to determinethe presence of decay cavities. We focused on medium and large decay cavities(smallest entrance dimension ≥ 5 cm), which can limit population of managementsensitiveSCUs. We measured forest attributes and inspected cavities in trees (n= 860)and snags (n= 93) in six 0.5 ha plots from old- and second-growth Nothofagusdombeyi forest stands. We used generalised linear mixed-effects models (GLMM) toanalyse the distribution of decay cavities in trees using data on theirpresence/absence, based on several tree individual attributes, across different sites.We applied an information-theoretical and multi-model inference approach to quantifythe strength of alternative sets of hypotheses/models. We used model averaging,which allows estimating coefficients and making inferences that account for model andparameter uncertainty. Diameter at breast height (DBH), crown damage and decay,crown ratio (crown length ? trunk length -1 ) and woodpecker foraging signs wereimportant to explain the presence/absence of decay cavities in trees. Diameter atbreast height, woodpecker foraging signs and a moderate-high crown damage anddecay were positively related with decay cavity presence. The presence of mediumand large decay cavities was also positively related with DBH, but trees with low crownratios had relatively low probabilities of presenting these cavities, even with DBHs>150 cm. Trees with DBHs smaller than 50 cm had very low probabilities (< 0.25-0.30)to present decay cavities, while the probability of trees presenting decay cavities ofmedium and large sizes was very low for trees with diameters < 100 cm, even for treeswith high crown ratios. Our results point out that conservation of large diameter treeswith high crown ratios is important to maintain the supply of decay cavities required bymanagement-sensitive SCUs in these forests. As these keystone structures areglobally threatened by climate change induced disturbances (e.g. fires, droughts), theyshould be maintained/restored through forest management (e.g. retention of keystonestructures) to achieve cavity-using wildlife habitat conservation in the long-term.