Effects of chemical conditions in re-wetted peats on temporal variation in microbial biomass and acid phosphatase activity within the growing season

Possible effects of chemical alterations in peat following re-wetting on their microbial characteristics are insufficiently known. Microbial biomass carbon (C-mic), nitrogen (N-mic, phosphorus (P-mic) and acid phosphatase activity were investigated in re-wetted virtually undisturbed and differently degraded peatlands (Histosols) in northeast Germany to assess re-wetting effects on microbial biomass production and phosphorus (P) cycling in one growing season. The virtually undisturbed Eutri-Ombric Histosol had the largest content of microbial biomass (C-mic: 2132 mg/kg. N-mic: 309 mg/kg and P-mic: 48 mg/kg means of six sampling dates, upper 10cm). Increasingly lower contents of microbial biomass were observed in the more strongly degraded peats of two Ombri-Sapric Histosols. Furthermore, the proportions of P-mic as a percent of total P (P-t) were smallest in the strongly degraded Ombric-Sapric Histosol (1.6% of P-t) and gradually larger with better peat conservation (2.6% of P-t in the moderately degraded Ombri-Sapric Histosol and 3.0% of P-t in the virtually undisturbed Eutri-Ombric Histosol). The acid phosphatase activity was always greatest in May, irrespective of peat degradation, This maximum was lower for the Eutri-Ombric Histosol (2633 mug nitrophenol/(g h)) than for the two Ombri-Sapric Histosols (3963 and 3212 mug nitrophenol/(gh)). In the two degraded peats, the temporal variation in phosphatase activity was also more pronounced. Our results, in particular the higher peak phosphatase activity combined with an incorporation of P into microbial biomass, indicate that peat degradation may enhance the phosphate input to soil solution. Thus, it is concluded that modified biological P cycling could contribute to increased risks of P losses to adjacent surface water after re-wetting of degraded peats. (C) 2002 Elsevier Science B.V. All rights reserved.