25 February 2009
Regional species–climate correlations are well documented, but little is knownabout the ecological processes responsible for generating these patterns. Using the data from over 690 000 individual trees I estimated five demographic rates—canopy growth, understorey growth, canopy lifespan, understorey lifespan and per capita reproduction—for 19 common eastern US tree species, within the core and the northern and southern boundaries, of the species range. Most species showed statistically significant boundary versus core differences in most rates at both boundary types. Differences in canopy and understorey growth were relatively small in magnitude but consistent among species, being lower at the northern (average -17%) and higher at the southern (average +12%) boundaries. Differences in lifespan were larger in magnitude but highly variable among species, except for a marked trend for reduced canopy lifespan at the northern boundary (average -49%). Differences in per capita reproduction were large and statistically significant for some species, but highly variable among species. The rate estimates were combined to calculate two performance indices: R0 (a measure of lifetime fitness in the absence of competition) was consistently lower at the northern boundary (average K86%) whereas Z*^ (a measure of competitive ability in closed forest) showed no sign of a consistent boundary–core difference at either boundary.
|Published in||Proceedings of the Royal Society Series B|
Drew Purves and Mark Vanderwel. (book chapter in press) Traits States and Rates: Understanding Coexistence in Forests , Cambridge University Press, 2012.
Raul Garcia-Valdes, Miguel A Zavala, Migueal B Araujo, and Drew W Purves. Chasing a moving target: projecting climate change-induced shifts in non-equilibrial tree species distributions, Journal of Ecology, British Ecological Society, January 2013.
Mark C Vanderwel, Vassily S Lyutsarev, and Drew W Purves. Climate-related variation in mortality and recruitment determine regional forest-type distributions, Global Ecology and Biogeography, Wiley, 4 June 2013.
Emily R Lines, David A Coomes, and Drew Purves. Influences of Forest Structure, Climate and Species Composition on Tree Mortality across the Eastern US, PLoS-One, PLoS, October 2010.
Mark C Vanderwel, David A Coomes, and Drew W Purves. Quantifying variation in forest disturbance, and its effects on aboveground biomass dynamics, across the eastern United States, Global Change Biology, Wiley, January 2013.