Seasonal and Spatial Controls over Nutrient Cycling in a Pacific Northwest Prairie |
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Authors: | Laurel Pfeifer-Meister Scott D Bridgham |
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Affiliation: | (1) Center for Ecology and Evolutionary Biology, University of Oregon, Eugene, Oregon 97403, USA |
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Abstract: | West Coast prairies in the US are an endangered ecosystem, and effective conservation will require an understanding of how
changing climate will impact nutrient cycling and availability. We examined how seasonal patterns and micro-heterogeneity
in edaphic conditions (% moisture, total organic carbon, % clay, pH, and inorganic nitrogen and phosphorus) control carbon,
nitrogen, and phosphorus cycling in an upland prairie in western Oregon, USA. Across the prairie, we collected soils seasonally
and measured microbial respiration, net nitrogen mineralization, net nitrification, and phosphorus availability under field
conditions and under experimentally varied temperature and moisture treatments. The response variables differed in the degree
of temperature and moisture limitation within seasons and how these factors varied across sampling sites. In general, we found
that microbial respiration was limited by low soil moisture year-round and by low temperatures in the winter. Net nitrogen
mineralization and net nitrification were never limited by temperature, but both were limited by excessive soil moisture in
winter, and net nitrification was also inhibited by low soil moisture in the summer. Factors that enhanced microbial respiration
tended to decrease soil phosphorus availability. Edaphic factors explained 76% of the seasonal and spatial variation in microbial
respiration, 35% of the variation in phosphorus availability, and 29% of the variation in net nitrification. Much of the variation
in net nitrogen mineralization remained unexplained (R
2 = 0.19). This study, for the first time, demonstrates the complex seasonal controls over nutrient cycling in a Pacific Northwest
prairie. |
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Keywords: | microbial respiration moisture availability net nitrification net nitrogen mineralization Oregon phosphorous availability temperature |
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