Belgium (September 24, 2013) – An international team of researchers has found that forests with dense canopies create a microclimate that protects a variety of cold-adapted plant species from warming air temperatures. Research shows plants that favored cooler conditions fared better under dense canopies than in ones that were more open to the elements. They added that these conditions could be a “critical mechanism” in the conservation of forest plant diversity.
Around the globe, climate warming is increasing the dominance of warm-adapted species—a process described as “thermophilization.” However, thermophilization often lags behind warming of the climate itself, with some recent studies showing no response at all.
Using a unique database of more than 1,400 resurveyed vegetation plots in forests across Europe and North America, researchers document significant thermophilization of understory vegetation. However, the response to macroclimate warming was attenuated in forests whose canopies have become denser. In each plot, they compared the results from an original survey with a repeated survey that was, on average, carried out 34.5 years later.
The results showed that there had been a sizeable turnover, with about one-third of the species present in the original survey being replaced by other plants. This microclimatic effect likely reflects cooler forest-floor temperatures via increased shading during the growing season in denser forests. Because standing stocks of trees have increased in many temperate forests in recent decades, microclimate may commonly buffer understory plant responses to macroclimate warming.
“Microclimate moderates plant responses to macroclimate warming,” Proceedings of the National Academy of Sciences
“Trees ‘shield vulnerable species from climate change’,” BBC News