Plant response to temperature in Northern Alaska: Implications for predicting vegetation change

The response of plants to temperature has gained renewed interest as researchers speculate on the biotic response to climate change. It is of particular interest in the Arctic, due to recent warming trends and anticipated continued warming for the region. This long-term, multispecies study confirms that changes in temperature affect the functioning of plants in their natural environment. It also demonstrates that the influence of temperature should be considered in the context of natural variability within a given location. The study examined natural temperature gradients, interannual climate variation, and experimental warming at sites near Barrow (71 degrees 18' N, 156 degrees 40' W) and Atqasuk (70 degrees 29' N, 157 degrees 25' W) in northern Alaska, USA. At each of the four sites, 24 plots were experimentally warmed for 5-7 years with small, open-top chambers, and plant growth and phenology were monitored; an equal number of unmanipulated control plots were monitored. The response of seven traits from 32 plant species occurring in at least one site is reported when there were at least three years of recordings. Plants responded to temperature in 49% of the measured traits of a species in a site. The most common response to warming was earlier phenological development and increased growth and reproductive effort. However, the total response of a species, for all traits examined, was individualistic and varied among sites. In 14% of the documented responses, the plant trait was correlated with thawing degree-day totals from snowmelt (TDDsm), and temperature was considered the dominant factor. In 35% of the documented responses, the plant trait responded to warming, but the interannual variation in the trait was not correlated with TDDsm and temperature was considered subordinate to other factors. The abundance of temperature responses that were considered subordinate to other factors suggests that prediction of plant response to temperature that does not account for natural variability may overestimate the importance of temperature and lead to unrealistic projections of the rate of vegetation change due to climate warming.