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Helena, MT, United States

Norton J.B.,University of Wyoming | Jungst L.J.,Helena National Forest | Norton U.,University of Wyoming | Olsen H.R.,University of Wyoming | And 2 more authors.

Though typically limited in aerial extent, soils of high-elevation riparian wetlands have among the highest density of soil carbon (C) and nitrogen (N) of terrestrial ecosystems and therefore contribute disproportionally to ecosystem services such as water retention, forage production, wildlife habitat, and reactive N removal. Because much soil C and N is stored in labile forms in anaerobic conditions, management activities or environmental changes that lead to drying cause mineralization of labile soil organic matter, and loss of C and N. Meadows are focal points of human activities in mountain regions, often with incised stream channels from historically heavy grazing exacerbated by extreme runoff events. To quantify soil C and N stores in montane riparian meadows across hydrologic conditions, 17 meadows between 1950- and 2675-m elevation were selected in the central Sierra Nevada Range, California, that were classified using the proper functioning condition (PFC) system. Results indicate that C and N density in whole-solum soil cores were equivalent at forest edge positions of properly functioning, functioning at-risk, and nonfunctioning condition. Soils under more moist meadow positions in properly functioning meadows have at least twice the C, N, dissolved organic C, and dissolved organic N (DON) than those under nonfunctioning meadows. Densities of total N and DON, but not C, of functioning at-risk meadows are significantly lower (P < 0. 05) than those of properly functioning meadows at mid-slope and stream-bank positions, suggesting accelerated loss of N early in degradation processes. Though variable, the soil attributes measured correspond well to the PFC riparian wetland classification system. © 2011 Springer Science+Business Media, LLC. Source

Bahls L.,Montana Diatom Collection | Pierce J.,737 Locust | Apfelbeck R.,520 E. 6th Avenue | Olsen L.,Helena National Forest

Relict assemblages of arctic, sub-arctic, and boreal diatoms were found intact in two undisturbed floating-mat fens at 47o north latitude and 1,830 m elevation in the Rocky Mountains of western Montana, USA. The fens support Encyonema droseraphilum sp. nov. and several rare northern/alpine diatom species-including eleven apparent first records for the contiguous United States-and three species of vascular plants that are imperiled in Montana. For many of the diatoms and one of the vascular plants, the fens are at the southern limit of their known distributions in North America. Twentyseven of the 49 diatom taxa in the fens are considered at risk or declining in Germany, and similar ratings appear to be appropriate for these taxa in Montana, especially in light of global warming and human destruction of wetlands. A nearby wetland that has been disturbed by dam-building activities of beaver (Castor canadensis), but not by human landscape alterations, produced a diatom assemblage that contained three times more taxa than the fens but was dominated by common species, primarily Staurosirella pinnata. Our findings illustrate the effects of natural, intermediate disturbance on diatom species composition and underscore the importance of protecting undisturbed aquatic systems for the purpose of conserving rare species and for monitoring environmental change. © 2013 Magnolia Press. Source

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