Meeting Abstract
Patterns of tree mortality determine how forest composition and structure change over time. Lightning directly and indirectly causes 70% of annual tree mortality in some forests, and interspecific differences in the electrical properties of trees likely influence the likelihood or severity of lightning damage. We hypothesized that the distribution of lightning damage is associated with specific tree characteristics (e.g., emergent status, slope position), and that biotic damage is associated with lightning damage. We also hypothesized that electrical resistivity differs among tree and vine species. We surveyed tree damage along 9 transects in old-growth forest in Michigan and classified damage on 309 focal trees. Although none of these trees exhibited evidence of lightning, associated meander surveys identified 14 cases of unambiguous lightning damage. We also measured the electrical resistivity of 8 tree species and 3 vine species. Lightning damage was more commonly associated with emergent stature (50% of struck trees) and higher rates of biotic damage (50%) than the surrounding tree community (22% emergent status and 21% incidence of biotic damage). Nearly all (93%) of the lightning damaged trees were conifers, suggesting that their interaction with lightning has a phylogenetic basis. Resistivity differed significantly among species and was ca. 200% higher in trees than vines. Accurate quantification of lightning-induced tree mortality will improve forest turnover models and improve predictions of future forest structure under conditions of increased lightning frequency.
