Abstract
Study region: An abandoned drained peatland pasture undergoing natural revegetation and an adjacent natural bog in the Robinsons peatland complex, western Newfoundland, Canada. Study focus: Understanding how agricultural drainage affects ecosystem water use efficiency (WUE = gross primary productivity / evapotranspiration) is critical for managing water resources in cultivated peatlands. However, the relative roles of carbon uptake versus hydrological partitioning of water loss remain poorly quantified. This study compared a natural boreal bog with an adjacent drained peatland pasture using chamber-based flux measurements across plant functional types and microtopographic features. New hydrological insights: Equal date mixed model estimates of GPP were 0.49 mg CO2 m−2 s−1 (95% CI 0.43–0.55) at the abandoned pasture and 0.13 (0.07–0.19) at the natural bog. Estimated WUE was 0.03 mg CO2 mg−1 H2O (0.03–0.04) and 0.006 (0.004–0.009), respectively, corresponding to a site ratio of 5.38 (3.58–8.09). Mean adjusted ET did not differ clearly between the named sites (pasture minus bog = −2.02 mg H2O m−2 s−1, 95% CI −5.84–1.79), although ET trajectories differed by date. At the pasture, ET remained positively associated with photosynthetically active radiation. The environmental relationships were supported for a collar-sensitive positive association between deeper water tables and WUE. The chamber measured total water-vapour flux and did not partition evaporation from transpiration. These results provide site-specific, hypothesis generating evidence and require multisite, multiyear confirmation.