Multivariate Analysis of Rangeland Vegetation and Soil Organic Carbon Describes Degradation, Informs Restoration and Conservation

Abstract

Agricultural expansion has eliminated a high proportion of native land cover and severely degraded remaining native vegetation. Managers must determine where degradation is severe enough to merit restoration action, and what action, if any, is necessary. We report on grassland degraded by multiple factors, including grazing, soil disturbance, and exotic plant species introduced in response to agriculture management. We use a multivariate method to categorize plant communities by degradation state based on floristic and biophysical degradation associated with historical land use. The variables we associate with degradation include abundance of the invasive cool-season grass, tall fescue (Schedonorus phoenix (Scop.) Holub); soil organic carbon (SOC); and heavy livestock grazing. Using a series of multivariate analyses (ordination, hierarchical clustering, and multiple regression), we identify patterns in plant community composition and describe floristic degradation states. We found vegetation states to be described largely by vegetation composition associated primarily with tall fescue and secondarily by severe grazing, but not soil organic carbon. Categorizing grasslands by vegetation states helps

Exotic-Dominated Grasslands Show Signs of Recovery with Cattle Grazing and Fire

“…Sites were therefore distributed among treatments nonrandomly, so that each treatment contained a range of land use histories [47]. These land use histories are discussed in detail in McGranahan et al [48]. Sites were categorized as either native-dominated tallgrass prairie remnants (used as reference only) or degraded pastures based on proportion of native plant canopy cover in 2007 (Table 1).…”

“…Prior to the experiment, all degraded sites appeared to have experienced extended periods of intense grazing, applications of chemical fertilizer (likely N-based), and seeding of exotic forage species in the past (M. Moe, personal communication). Further details on the land use history at these sites can be found in Debinski et al [43] and McGranahan et al [48]. We perceive the diversity of land-use histories as a benefit to our analysis in this study because this provides a greater representation of degraded grasslands on the landscape and because the difficulty of detecting trends in less controlled studies makes a significant result more robust.…”

Analysis of Vegetation Phytosociological Characteristics and Soil Physico-Chemical Conditions in Harishin Rangelands of Eastern Ethiopia

“…This could be attributable to their broad ecological amplitude and greater adaptability against biotic influences. In relation to this, McGranahan et al [42] noted that grazing might be associated with variation in community composition within vegetation states. Vegetation structure and composition may be influenced by novel factors such as fire, herbivore, topography and past management practices that interact in a complex way to determine plant community architecture [43][44][45].…”

Connecting Soil Organic Carbon and Root Biomass with Land-Use and Vegetation in Temperate Grassland

“…For plant community data we used the 2006 pretreatment vegetation survey [37] and used the Canberra distance metric. As applied here, the constrained ordination first describes variation in plant community composition along defined axes—in this case, the composite variables of soil/root data represented by the PCs—then proceeds to explain remaining variation via unconstrained ordination.…”