Effects of hydrologic changes on aboveground production and surface water chemistry in two boreal peatlands in Alberta: Implications for global warming

Aboveground net primary production (NPP) and surface water chemistry variables were monitored in a lacustrine sedge fen and a bog for four years. There were no significant differences in precipitation, mean growing season annual temperature, and number of growing degree days from 1991 to 1994. The mean annual water levels in the lacustrine sedge fen differed significantly, whereas they were similar in the bog during these four years. We measured 15 surface water variables in the lacustrine sedge fen and the bog, and found that only two correlated significantly with water level fluctuations. In the lacustrine sedge fen, calcium correlated positively (r(2) = 0.56) and nitrate correlated negatively (r(2) = 0.20) with water levels. In the bog, potassium correlated positively (r(2) = 0.88) and total dissolved phosphorus correlated negatively (r(2) = 0.62) with water levels. The remaining chemical variables showed no significant correlations with water level fluctuations. Net primary production of the different vegetation strata appeared to respond to different environmental variables. In the lacustrine sedge fen, graminoid production was explained to a significant degree by water levels (r(2) = 0.53), whereas shrub production was explained to a significant degree by surface water chemistry variables, such as nitrate (r(2) = 0.74) and total phosphorus (r(2) = 0.22). In the bog, temperature was the only variable that explained moss production to a significant degree (r(2) = 0.71), whereas ammonium explained graminoid production (r(2) = 0.66) and soluble reactive phosphorus explained shrub production to significant degrees (r(2) = 0.71). There are few direct data on the impact of climatic warming in boreal wetlands, although paleoecological and 2xCO(2) model data have provided some indications of past and possibly future changes in vegetation composition, respectively. Our results suggest that the lacustrine sedge fen may succeed to a bog dominated by Sphagnum spp. and Picea mariana, whereas the bog may succeed to an upland-type forest ecosystem.