A CSR classification of tree life history strategies and implications for ice storm damage

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Differences in life history strategy influence the ecological roles of plant species, including their susceptibility to disturbance events. According to Grime’s CSR model, plants exhibit three primary strategies, which reflect tradeoffs between stress and disturbance. Here we classify eastern North American tree species into life history strategies on the basis of the CSR model. Then, using data on ice storm damage to trees, we investigate how the level of damage varied among the different CSR categories. We used tree damage data for almost 2000 individual trees representing 30 species collected during two ice storms in the Appalachian Mountains. We augmented the study with ice damage data gleaned from nine published ice-storm studies containing over 30 000 individuals representing 22 species. The trees we identified as stress-tolerators (S) consistently sustained less damage than the other species. This finding matches the stress-tolerant strategy: damageresistance is imperative for the persistence of trees that exhibit slow growth, low reproductive capacity and long lifespan. Our analyses also suggest that competitors (C) suffer widespread damage, particularly branch breakage, but experience low mortality. This pattern likely reflects features of the competitive strategy, such as wood strength and canopy form, which preclude resistance to damage but facilitate rapid recovery. The ice damage datasets did not contain trees that we classified as ruderals (R). Competitive ruderals (C-R) and stress-tolerant ruderals (S-R), however, sustained heavy damage and high mortality, consistent with low investment in tree defense and a prioritization of reproduction. Our analyses suggest the usefulness of the CSR model for interpreting forest dynamics and understanding the implications of tree life-history strategies for forest disturbance responses.