Disequilibrium between Tree Species Distributions and Regional Temperatures

by Cortland Henderson

Correlations between geographic distributions of plant species and the current climate have been identified, suggesting that species ranges will shift upwards if global temperatures rise. These links, however, are based on models that do not establish whether or not plant species are at equilibrium with the current climate, and are incapable of differentiating between naturally occurring shifts and climate-induced shifts. García-Valdés et al. (2013) examine the ten most common tree distributions throughout the Iberian Peninsula by creating a new species distribution model that relaxes built-in assumptions that tree species and climate are currently at equilibrium. Their model successfully removed previous biases and found that tree species are not at equilibrium Continue reading

Turnover versus Migration: Forest Responses to Climate Change

 

by Cortland Henderson

Studying fluctuations in biogeography–or the distribution of species and ecosystems–has been an effective alternative to viewing real life effects of climate change in short time scales. Although there is a large volume of research on the biogeography of animals, there is an inadequate amount of study into the change of forests despite vast amounts of data and the ability to check for age distributions, environmental effects or stressors. Zhu et al. (2014) assert that studying forest biogeography is important because species often fulfill different niches dependent on their life stage. Most models of species migration assume that juveniles and adults have the same environmental requirements, but by studying different life stages of trees, these models might prove inaccurate. One untested theory is that as temperature and precipitation increase, juvenile trees will develop rapid growth, increased mortality, and increased recruitment. This study found that forests in the Eastern United States have increased turnover rather than migrating North as a result of climate change suggesting that climate models need to be modified.

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