3 research outputs found
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Classifying ecological types and evaluating site degradation
An analytical method for classifying ecological types was developed and tested for mountain meadows in central Nevada. Six ecological types were identified by plot sampling of vegetation and soil-site variables. Two-way indicator species analysis and canonical correspondence analysis were used to identify ecological types and to compare the discriminating abilities of different ecosystem components. Each ecological type was a characteristic combination of landform, soil, and vegetation. Changes in vegetation and soil conditions were assessed along a gradient of degradation within one ecological type—the dry graminoid/Cryoboroll/trough drainageway type. Direct gradient analysis was used to display changes in plant composition and indicators of site degradation. Plant and soil indicators of degradation were basal cover of vegetation, standing crop production of 3 key grass species, rates of infiltration, and soil compaction. Three states of range degradation were identified along the gradient. The grass-dominated state was the most desirable in terms of forage production, basal cover of vegetation and infiltration, while the grass/forb/shrub state represented the most degraded and least productive state.The Journal of Range Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform August 202
Vegetation and Water-Table Relationships in a Hydrologically Restored Riparian Meadow
We examined the relationship between water-table elevations and plant community distributions in a hydrologically restored riparian meadow. The meadow, adjacent to Bear Creek in northeastern California, experienced hydrologic modification due to “pond and plug” stream restoration. Plant species composition and cover were sampled within 128 plots, and a hydrologic model was used to simulate a three-year time series of water-table for each plot. TWINSPAN was used to classify the vegetation into four community types:Eleocharis macrostachya / Eleocharis acicularis, Downingia bacigalupii / Psilocarphus brevissimus, Carex nebrascensis / Juncus balticus, andPoa pratensis / Bromus japonicus. Nonmetric multidimensional scaling was utilized to investigate the relationships between community types and hydrologic variables. Community types were distributed along the hydrologic gradient at reasonably similar positions to those found in previous studies; howeverCarex nebrascensis, a species frequently used as an indicator of shallow water tables, occurred at greater water-table depths than reported in other studies. The range of water-table depths in this meadow was greater than previously observed, presumably due to the higher temporal resolution of water-table measurements, in addition to the intermittent nature of stream flow in Bear Creek. This study provides an increased understanding of the ecology of meadow communities, and can be utilized for improved design and objective setting in future restoration projects