Classifying ecological types and evaluating site degradation.

Abstract

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.