| Contemporary vegetation communities within subalpine and montane grasslands were described and compared with the historical communities of 86 years ago and with the potential natural communities (PNC) identified in the Terrestrial Ecosystem Survey (TES) of the Apache-Sitgreaves National Forests.; Eight TES grassland map units (MUs) were sampled using Daubenmire's cover methodology. Individual species' frequency, cover, and relative composition, bare ground, rock, litter, and vegetation cover were determined from 133 transects. NMDS and CS analyses compared contemporary grassland community composition and soil surface cover data with the same TES PNC variables. More transects displayed higher correlations with exposed soil surface area (≈74%) and litter cover (≈71%) than PNCs, while PNCs displayed higher correlations with rock (≈86%) and vegetation (≈54%) cover. CS analysis showed transect-to-PNC ratings of very low (≈17%), low (≈54%), moderate (≈24%) and high (≈5%). Explanations for these results include lack of contemporary successional theory in the development of PNCs, narrowly defined PNCs, and past management activities.; Based on analysis of similarity and non-metric multi-dimensional scaling (NMDS) ordination, the eight MUs were aggregated into four communities: mesic subalpine, mesic montane, xeric subalpine and xeric montane. All communities were dominated by C3, perennial, native species. Graminoids provided the greatest cover and composition, while forbs the greatest number of individuals.; Number of species, dominant species, life form, life span, origin, photosynthetic pathway, bare ground, rock, litter, and vegetation cover were compared with 1913--15 data. NMDS and Coefficient of similarity (CS) analyses showed mesic montane grasslands had the greatest vegetation composition variability and the lowest species compositional rating (≈28%). Xeric subalpine grasslands had the least vegetation composition variability and the highest species compositional rating (≈61%).; Independent sample t tests indicated significant declines in vegetation and litter cover with a significant increase in bare ground across all communities since 1913--15. Multivariate analysis of variance determined annual precipitation, annual wild fires suppressed, estimated elk populations, livestock levels, and/or their interactions to be significant. By itself, precipitation was not significant. Ungulate grazing, independently or interacting with each other and/or the other independent variables was more significant than either precipitation or fire suppression to changes in the dependent variables. |
