EFFECTS OF HYDROLOGIC CHANGES ON ABOVEGROUND PRODUCTION AND SURFACE-WATER CHEMISTRY IN 2 BOREAL PEATLANDS IN ALBERTA - IMPLICATIONS FOR GLOBAL WARMING

Aboveground net primary production (NPP) and surface water chemistry v ariables were monitored in a lacustrine sedge fen and a bog for four y ears. There were no significant differences in precipitation, mean gro wing season annual temperature, and number of growing degree days from 1991 to 1994. The mean annual water levels in the lacustrine sedge fe n differed significantly, whereas they were similar in the bog during these four years. We measured 15 surface water variables in the lacust rine sedge fen and the bog, and found that only two correlated signifi cantly with water level fluctuations. In the lacustrine sedge fen, cal cium correlated positively (r(2) = 0.56) and nitrate correlated negati vely (r(2) = 0.20) with water levels. In the bog, potassium correlated positively (r(2) = 0.88) and total dissolved phosphorus correlated ne gatively (r(2) = 0.62) with water levels. The remaining chemical varia bles 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 wa ter levels (r(2) = 0.53), whereas shrub production was explained to a significant degree by surface water chemistry variables, such as nitra te (r(2) = 0.74) and total phosphorus (r(2) = 0.22). In the bog, tempe rature was the only variable that explained moss production to a signi ficant degree (r(2) = 0.71), whereas ammonium explained graminoid prod uction (r(2) = 0.66) and soluble reactive phosphorus explained shrub p roduction to significant degrees (r(2) = 0.71). There are few direct d ata on the impact of climatic warming in boreal wetlands, although pal eoecological and 2xCO(2) model data have provided some indications of past and possibly future changes in vegetation composition, respective ly. 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.