P. Camill, How much do local factors matter for predicting transient ecosystem dynamics? Suggestions from permafrost formation in boreal peatlands, GL CHANGE B, 6(2), 2000, pp. 169-182
With rapid climate warming, ecosystems will probably exhibit complex dynami
cs because local factors and life history attributes of species mediate the
effects of regional climate change. To assess the relative importance of l
ocal vs. regional processes on permafrost formation in boreal peatlands, I
sampled for permafrost and factors affecting its formation in 38 collapse s
cars across a 4 degrees C mean annual temperature (MAT) gradient in the dis
continuous permafrost zone of northern Manitoba, Canada. Three complimentar
y approaches were used to model factors important to permafrost formation a
t both local and regional scales. In the first analysis, a mechanistic, spa
tial model of permafrost formation was developed as a function of Picea mar
iana size and proximity. In the second approach, permafrost formation was m
odelled as a function of two local factors, diameter of Picea mariana trees
and emergent organic matter depth, and the regional factor, mean annual te
mperature (MAT). Finally, published aerial photography data were used to de
termine whether the proportion of bogs with permafrost changes across a MAT
gradient. Results show that permafrost formation in boreal permafrost peat
lands is best described as a locally driven process within regional climati
c constraints. At local scales of 1-2 meters, the spatial and size distribu
tions of trees controlled the spatial distribution of permafrost. At region
al scales, tree size was a significantly better predictor than emergent org
anic matter or MAT. These results suggest that transient models of disconti
nuous permafrost based only on climate may poorly predict changes in vegeta
tion and permafrost.