Harvested sites rarely return to functional ecosystems after abandonment because drainage and peat extraction lower the water table and expose relatively decomposed peat, which is hydrologically unsuitable for Sphagnum moss reestablishment. Some natural regeneration of Sphagnum has occurred in isolated pockets on traditionally harvested (block-cut) sites, for reasons that are poorly understood, but are related to natural functions that regulate runoff and evaporation. This study evaluates the water balance of a naturally regenerated cutover bog and compares it with a nearby natural bog of similar size and origin, near Riviere du Loup, Quebec. Water balance results indicated that evapotranspiration was the major water loss from the harvested bog, comprising 92 and 84% of total outputs (2.9 mm day(-1)) during the 1997 and 1998 seasons, respectively. Despite denser tree cover at the harvested site, evapotranspiration from the natural bog was similar, although less spatially variable. At the harvested site, evaporative losses ranged from 1.9 mm day(-1) on raised baulks and roads to 3.6 mm day(-1) from moist surfaces with Sphagnum. Although about half of the ditches were:inactive or operating at only a fraction of their original efficiency, runoff was still significant at 12 and 24% of precipitation during the 1997 and 1998 study seasons, respectively. This compares with negligible rates of runoff at the natural bog. Thus the cutover bog, although abandoned over 25 years ago, has not regained its hydrological function. This is both a cause and effect of its inability to support renewed Sphagnum regeneration. Without suitable management (e.g. blocking ditches), this site is not likely to improve for a very long time. Copyright (C) 2001 John Wiley & Sons, Ltd.
