Climate remains an important driver of post-European vegetation change in the eastern United States

The influence of climate on forest change during the past century in the eastern United States was evaluated in a recent paper (Nowacki & Abrams, 2014) that centers on an increase in ‘highly competitive mesophytic hardwoods’ (Nowacki & Abrams, 2008) and a concomitant decrease in the more xerophytic Quercus species. Nowacki & Abrams (2014) concluded that climate change has not contributed significantly to observed changes in forest composition. However, the authors restrict their focus to a single element of climate: increasing temperature since the end of the Little Ice Age ca. 150 years ago. In their study, species were binned into four classifications (e.g., Acer saccharum – ‘cool-adapted’, Acer rubrum – ‘warm-adapted’) based on average annual temperature within each species range in the United States, reducing the multifaceted character of climate into a single, categorical measure. The broad temperature classes not only veil the many biologically relevant aspects of temperature (e.g., seasonal and extreme temperatures) but they may also mask other influences, both climatic (e.g., moisture sensitivity) and nonclimatic (e.g., competition).