Half-century evidence from western Canada shows forest dynamics are primarily driven by competition followed by climate

• DOI: 10.1073/pnas.1420844112
• Publication Date: 2015-03-17T02:56:33Z
• Authors: Jian Zhang; Shongming Huang; Fangliang He
• Keywords: Canada; Models, Statistical; Time Factors; Databases, Factual; Geography; Climate; Climate Change; Data Collection; Forests; 15. Life on land; Trees

Significance Forests worldwide have undergone rapid changes; however, understanding the causes of the changes has been a challenge. Climate on the regional scale has been overwhelmingly presumed to drive these changes, with little attention paid to the possible effects of competition. We compiled a long-term forest dataset from western Canada to study the relative importance of climate change and competition on tree growth, mortality, and recruitment. We showed that competition was the primary factor causing the long-term changes. Regional climate had a weaker yet significant effect on tree mortality, but no effect on tree growth and recruitment. This finding suggests that forest studies focused solely on the effects of climate may overlook the effect of other processes critical to forest dynamics.