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Submitted to: Meeting Abstract
Publication Type: Proceedings Publication Acceptance Date: 4/15/2004 Publication Date: 6/1/2004 Citation: Blank, R.R. 2004. Nutrient availability in a montane riparian ecosystem: influence of livestock grazing, floodplain position, and season [abstract]. In: Proceedings of the Riparian Ecosystems and Buffers: Multi-scale Structure, Function, and Management, American Water Resources Association Summer Specially Conference. Olympic Valley, California. 2004 CDROM. Interpretive Summary: Montane meadows are important for livestock grazing, biotic diversity, fisheries and, as hydrologic buffers. If one is to maintain or increase health of these ecosystem, greater of soil nutrient availability is requisite. Soil nutrient availability was quantified in a three year study using mixed bed anion and cation exchange resin capsules. Livestock grazing minimally affected soil nutrient availability; compared to an excluded paddock, livestock grazing significantly (p'0.05) reduced Mn. Nutrient availability varied considerably by season of measurement. Potassium and phosphorus availability were least during winter and significantly higher in the spring-summer and summer-fall seasons. Nitrate availability was highest in the summer-fall season and significantly less in the spring-summer and winter seasons. High availability of nitrate and P during the summer-fall season is out of phase with native plant growth and suggests the potential for weed invasion. Overall, the data suggest plant growth and soil water content are major factors controlling soil nutrient availability. Technical Abstract: In montane meadows, greater understanding of soil nutrient availability and its interaction with grazing, floodplain position, and season could facilitate better management strategies. Soil nutrient availability was quantified in a three year study using mixed bed anion and cation exchange resin capsules (15 cm depth, 6 replications), by treatment (livestock exclusion, livestock grazing), floodplain position (stream edge, mid-floodplain, forest edge), and season (spring-summer growth period, summer-fall plant senescence, and winter). The only attribute affected by treatment was resin-extractable Mn; compared to the excluded paddock, livestock grazing significantly (p'0.05) reduced Mn (main effect). Potassium and P availability were least during winter and significantly higher in the spring-summer and summer-fall seasons. Nitrate availability was highest in the summer-fall season and significantly less in the spring-summer and winter seasons. A significant floodplain position by season interaction influenced availability of Ca, Mg, Fe, and Mn. Calcium and Mg availability were highest in the mid-floodplain position (wettest), but only during the spring-summer season. Likewise, Fe and Mn availability was greatest in the spring-summer season, but only in the mid-floodplain and forest edge positions. There was a pronounced asymptotic relationship between P and Fe availability, but it is dubious if the relationship is causal. High availability of nitrate and P during the summer-fall season is out of phase with native plant growth and suggests the potential for weed invasion. Overall, the data suggest plant growth and soil water content are major factors controlling soil nutrient availability. |
