The utilization of bryophytes in bioclimatic modeling: Present distribution of peatlands in the Mackenzie River Basin, Canada

A model was developed that classified and projected the distribution of sev en different types of peatlands in the Mackenzie River Basin. The model was based an the relationships between bryophyte indicator species, the types of peatlands they characterize, and regional climate. The model used the pr esence, absence, and abundance of 15 bryophyte indicator species to classif y 81 peatlands in the study area into seven groups. Abundance values were c alculated for each of the indicator species along three climatic gradients- Mean Annual Temperature (MAT), Mean Annual Total Precipitation (MATP), and Length of the Growing Season (LGS). The percent cover of all species were t hen ascribed to appropriate combinations of MAP, MATP, and LGS. The result produced a matrix consisting of 4,560 grid nodes,where each node was identi fied by values for each of the three climatic variables and the types of pe atlands that could be found at that climate. An independent data set consis ting of climatic and ecological values and vegetation cover for 115 sites w as rued to test the ability and accuracy of the model to classify and proje ct the climatic distribution of the seven peatland groups. The model correc tly classified 106 of the 115 sites and of those, correctly projected the d istribution of all but five of the test sites. The model accuracy was great er than or equal to 70% for six of the seven groups, and > 90% for three of those. The accuracy for the remaining group was 50% and errors were mostly caused by the failure to project the distribution of three of the test sit es. Other errors include: the inability to classify lichen: dominated peatl ands; the inclusion of,wet lawns in bogs into one of the groups which cause d a southward extension of that group by approximately 200 km. The overall model accuracy was 88%.