Submitted to: Soil Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/10/2010
Publication Date: 6/1/2010
Citation: Blank, R.R., Morgan, T.A. 2010. Influence of livestock grazing, floodplain position, and time on soil nutrient pools in a Sierra-Nevada montane meadow. Soil Science. 175:293-302.
Interpretive Summary: Limited data on the affect of season, floodplain location, and livestock grazing on nutrient availability in montane meadow ecosystems. Soil nutrient availability, as affected by season, grazing, and floodplain location, was quantified in a montane meadow of the Plumas National Forest, CA. Over the six years of the study, we did not measure a pulse of soil availability of N or P among floodplain locations, season, or grazing that would suggest decoupling of mineralization with root/microbial uptake. Overall the data suggest that the present grazing management plan does not greatly impact nutrient availability.
Technical Abstract: Limited data exist on quantification of soil nutrient pools in montane meadow ecosystems. Along Big Grizzly Creek in the Plumas National Forest, CA (June 1999-September 2005), soil nutrient pools were quantified by livestock grazing treatment (grazed, ungrazed), floodplain location (stream edge, midfloodplain, forest edge), and season using resin capsules (15-cm depth) and bulk soil samples (0- to 25-cm depths). Resin capsules integrated nutrient availability for three periods: overwinter, plant growth, and senescence. Bulk soil samples were collected immediately after snowmelt (pregrowth), during plant growth, and during plant senescence. During the study period, pulses of N or P did not occur, suggesting strong coupling of mineralization with root/microbial uptake. Soil availability of most nutrients was affected by sampling time and floodplain location; however, differences were small. Soil samples from grazed areas had significantly greater K and Na on clay exchange sites than soil from excluded areas possibly because of supplementation with salt blocks. A seasonal reciprocal relationship occurred for the proportional content of K and Na on clay exchange sites and on resin capsules: Na highest during the cold season, and K highest in the plant senescent period. This relationship may be important in retaining K in soil during snowmelt. Surprisingly, the robust pools of extractable Ca, Mg, K, and Na, and their proportional content on the exchanger differed significantly with time. Overall, the data suggest that the present grazing management plan does not greatly impact nutrient availability.