Effect of water table drawdown on peatland nutrient dynamics: implications for climate change
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It is anticipated that a lowering of the water table and reduced soil moisture levels in peatlands may increase peat decomposition rates and consequently affect nutrient availability. However, it is not clear if patterns will be consistent across different peatland types or within peatlands given the natural range of ecohydrological conditions within these systems. We examined the effect of persistent drought on peatland nutrient dynamics by quantifying the effects of an experimentally lowered water table position (drained for a 10-year period) on peat KCl-extractable total inorganic nitrogen (ext-TIN), peat KCl-extractable nitrate (ext-NO3 −), and water-extractable ortho-phosphorus (ext-PO4 3−) concentrations and net phosphorus (P) and nitrogen (N) mineralization and nitrification rates at natural (control) and drained microforms (hummocks, lawns) of a bog and poor fen near Québec City, Canada. Drainage (water table drawdown) decreased net nitrification rates across the landscape and increased ext-NO3 − concentrations, but did not affect net N and P mineralization rates or ext-TIN and ext-PO4 3− concentrations. We suggest that the thick capillary fringe at the drained peatland likely maintained sufficient moisture above the water table to limit the effects of drainage on microbial activity, and a 20 cm lowering of the water table does not appear to have been sufficient to create a clear difference in nutrient dynamics in this peatland landscape. We found some evidence of differences in nutrient concentrations with microforms, where concentrations were greater in lawn than hummock microforms at control sites indicating some translocation of nutrients. In general, the same microtopographic differences were not observed at drained sites. The general spatial patterns in nutrient concentrations did not reflect net mineralization/immobilization rates measured at our control or drained peatlands. Rather, the spatial patterns in nutrient availability may be regulated by differences in vegetation (mainly Sphagnum moss) cover between control and drained sites and possibly differences in hydrologic connection between microforms. Our results suggest that microform distribution and composition within a peatland may be important for determining how peatland nutrient dynamics will respond to water table drawdown in northern peatlands, as some evidence of microtopographic differences in nutrient dynamics was found.
KeywordsPeatlands Nitrogen Phosphorus Drainage Water table drawdown Microtopography
We wish to thank Melissa Greenwood, Jason Cagampan, Claudia St-Arnaud, and Scott Ketcheson for field assistance, and Erin Harvey for assistance with statistical analyses. This project was supported by a McMaster postdoctoral fellowship to MLM through funding by a Premier’s Research Excellence Award to JMW. Additional funding was provided a Canadian Foundation for Climate and Atmospheric Science grant to JMW. We thank the Nirom Peat Moss company for access to the site.
- Binkley D, Hart SC (1989) The components of nitrogen availability assessments in forest soils. Adv Soil Sci 10:58–112Google Scholar
- De Mars H, Wassen MJ, Peeters W (1996) The effect of drainage and management on peat chemistry and nutrient deficiency in the former Jegrznia-floodplain (NE-Poland). Chemical and physical dynamics of fen hydrology. Nederlandse Geografische Studies 203:51–68Google Scholar
- Devito KJ, Hill AR (1997) Sulphate dynamics in relation to groundwater - surface water interactions in headwater wetlands of the southern Canadian Shield. Hydrol Proc 11(5):485–500. doi: 10.1002/(SICI)1099-1085(199704)11:5<485::AID-HYP455>3.3.CO;2-6 CrossRefGoogle Scholar
- Environment Canada (2003) National climate data archive [online]. http://www.msc-smc.ec.gc.ca/climate/daa-archives/. Accessed Dec 2003
- IPCC (2007) Climate change 2007: the physical science basis. In: Solomon S, Qin D, Manning M, Chen Z, Marquis M, Averyt KB, Tignor M, Miller HL (eds) Contribution of working group I to the fourth assessment report of the intergovernmental panel on climate change. Cambridge University Press, CambridgeGoogle Scholar
- Strack M, Waddington JM (2007) Response of peatland carbon dioxide and methane fluxes to a water table drawdown experiment. Global Biogeochem Cycles 21:GB1007. doi: 10.1029/2006GB002715
- Zimenko TG, Misnik AG (1970) Effect of groundwater level on ammonification and nitrification in peat bog soils. Mikrobiologia 39:522–526Google Scholar