Ungulate vs. landscape control of soil C and N processes in grasslands of Yellowstone National Park
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Authors: D. A. Frank, and P. M. Groffman
Date: 1998
Journal: Ecology
Volume: 79
Number: 7
Pages: 2229-2241
Summary of Methods: A year long study was conducted to examine how large herbivores and landscape factors affect soil C and N dynamics in grasslands of Yellowstone National Park. Results from the in situ experiment indicated that average net N mineralization among grazed plots (3.8 g N .m-2.yr-1) was double that of fenced, ungrazed plots (1.9 g N .m-2.yr-1) and dramatically increased between-site variation of that rate. Herbivores improved the organic matter quality of soil and reduced C respired/N mineralized ratios by an average of 21%. The greatest landscape influence on in situ net mineralization (2.2g N .m2.yr1) was similar to the average grazer impact on that rate (1.9 g N .m2.yr1). These results suggest that variation in net N mineralization among diverse sites is principally a function of differences in immobilization rates, while effects of grazers on net mineralization may be due to variation in gross mineralization. Findings indicate that the regulatory influences of herbivores on soil N dynamics may be underestimated, particularly for grasslands supporting large herds of ungulates.
Article Summary / Main Points: None
Vegetation Types:
MLRA Ecoregions:
Agrovoc Control Words: Riparian zones Rangelands Wildlife
Article Review Type: Refereed
Article Type: Experimental Research
Keywords: carbon, grazing, herbivory, grassland, elk, bison, nitrogen
Annotation: Study conducted on seven diverse sites including hilltop, slope, and slope bottom positions across a climatic gradient and represented among the driest and wettest grasslands on the northern winter range. Performed two experiments: (1) a 12 month in situ net N mineralization study and (2) a long-term (62) week laboratory incubation to measure potential N mineralization and microbial respiration. Grazing intensity defined as "ungrazed" and "grazed".
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