A bioclimatic model for the distribution of Sphagnum‐dominated peatlands in North America under present climatic conditions

Abstract

AbstractAimA model was developed that estimates the climatic and geographical distribution of Sphagnum‐dominated peatlands in western Canada and North America.LocationThe model is based on the abundance of Sphagnum species on 640 peatland sites located in proximity to permanent weather stations throughout western Canada.MethodsThe per cent cover of Sphagnum species was quantified for all possible combinations of mean annual temperature (MAT) and mean annual total precipitation (MATP) found in western Canada. Abundance values were expanded to include all climatic values in North America, by interpolating within the matrix of values for western Canada using distance‐weighted means. Because Sphagnum‐dominated peatlands do not occur in areas having summer moisture index (P–PET) values ≤ 6 cm, that value was also included in the model. The result produced a matrix of 3360 grid nodes in which each node was characterized by MAT, MATP and P–PET values and the presence of Sphagnum‐dominated peatlands. The climatic data in the model was then match merged with the MAT, MATP and P–PET values obtained from Leemans & Cramer (The IIASA Database for Mean Monthly Values of Temperature, Precipitation, and Cloudiness on a Global Terrestrial Grid. International Institute for Systems Analysis, Laxenberg, 1991), which is a global data set that also contains geographical data on a 0.5° latitude by longitude grid. The geographical distribution of Sphagnum‐dominated peatlands was then mapped for western Canada and North America. Those maps were compared with the observed distribution of bogs and poor fens for the same area.ResultsResults of the comparisons indicated that the model's estimations matched the southern distribution of Sphagnum‐dominated peatlands relatively closely. Results for the northern distribution, however, were not as accurate. The overall accuracy was c. 80%.Main conclusionsSome of the errors were caused by inaccurate climatic data which resulted from the lack of permanent weather stations in northern areas and the lack of definition of the northern limits of the actual distribution of bogs and poor fens. In areas where both the climatic data and the actual distribution of Sphagnum‐dominated peatlands are accurate, the model accuracy was c. 90%.