These three temperture variables are among several ecological settings variables that collectively characterize the biophysical setting of each 30 m cell at a given point in time (McGarigal et al 2017). The temperature regime strongly affects species composition, as well as rates of ecological processes, such as nutrient cycling. We’ve chosen three variables to represent different aspects of temperature. All three variables have future versions that incorporate climate change via General Circulation Models (GCMs) (as described in the technical document on climate, McGarigal et al 2017). Growing season degree days integrates the total heat available throughout the season. In general, growth of plants and ectotherms can be roughly estimated by a degree-day model, thus the sum of degree-days over the season indicates which species may be within their northern range limits. Degree-days are the sum of daily mean temperatures above a lower threshold of 10 C. The Heat index, like growing season degree days, integrates heat throughout the season, but it focuses on high temperatures. It takes a sum of maximum daily temperatures above a lower threshold of 35 C, resulting in an index of likely heat stress to plants. This variable is an index to the southern range limits of many species. The Minimum winter temperature can determine the northern range limits for many species.
Environmental Sciences | Sustainability
McGarigal, Kevin; Compton, Brad; Plunkett, Ethan; DeLuca, Bill; and Grand, Joanna, "Designing Sustainable Landscapes: Growing season degree days, Heat index, and Minimum winter temperature settings variables" (2017). Data and Datasets. 13.