Main Results Summary

Eight parameters, within all three National Research Council (NRC) principle criteria for rangeland health, were found to be altered by plant community seral stage. Soil bulk density, soil mechanical resistance at 4.5 cm depth, total soil C at 0 - 7.5 cm and 7.5 - 15 cm depths, total soil N at 0 - 7.5 cm depth, total aboveground living biomass, litter biomass, and rough fescue plant density were all affected by plant community seral stage. For the purposes of this study, plant community seral stage is assumed to be an index of long-term cattle grazing (i.e., an early seral stage indicates improper long-term grazing).

Table 1. Soil bulk density, soil mechanical resistance at 4.5 cm depth, total soil C at 0 - 7.5 cm and 7.5 - 15 cm depths, total soil N at 0 - 7.5 cm depth, total aboveground living biomass, litter biomass, and rough fescue plant density (mean ± SE) at 18 rough fescue grassland treatment units in southern interior BC. Twenty-four potential indicators were screened for their ability to predict rough fescue grassland health as defined by NRC’s three principal criteria. The top five indicators based on cost-effectiveness and strength of relationship (R2) with health criteria are: percent exposed mineral soil, percent litter cover, percent Sandberg’s bluegrass cover, percent Junegrass cover, and percent rough fescue cover. Two of these five indicators (percent litter cover and percent Sandberg’s bluegrass cover) showed redundant function with percent exposed mineral soil suggesting that they do not contribute unique information to an assessment of health. Percent litter and percent exposed mineral soil were consistently related to Principle Criteria no. 1 (degree of soil stability and watershed function) and Principle Criteria no. 2 (integrity of nutrient cycles and energy flows). Percent litter always had the inverse relationship to percent exposed mineral soil for the same health criteria. Litter was always associated with better ecosystem health, while exposed soil was always associated with poor health. Because of this, it may not be necessary to include both indicators when determining rangeland health. Percent cover of rough fescue stands apart from the other indicators because it was the only reliable predictor of Principle Criteria no. 3 (the presence of functioning recovery mechanisms). The presence of functioning recovery mechanisms, as defined by key bunchgrass plant density and bunchgrass seed head density, requires the assessment of rough fescue cover. It should be noted, however, that the measurement of bunchgrass plant density and bunchgrass seed head density is not much more difficult to determine directly than percent rough fescue cover. Rough fescue was the only reliable indicator of aboveground and litter biomass (Principle Criteria no. 2). Junegrass and Sandberg’s bluegrass had negative associations with rangeland health, because they are known to increase with grazing. These two grass species become more common at earlier seral stages. Although they both often showed similar relationships to the same set of Principle Criteria, they appear to contribute in different ways. Sandberg’s bluegrass is common on sites in poor health, but did not occur on many of the sites in better health. Junegrass tended to be more evenly distributed across the sites. Junegrass may prove to be a useful early indicator of poor grazing practices, while Sandberg’s bluegrass may be useful in differentiating among the poorest sites. Table 2. Summary of indicators examined and their associations with the three principal criteria for determination of rangeland health as outlined by NRC (1994) at 20 rough fescue grassland treatment units in southern interior BC.

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Last Modified: 2008 April 29. Ministry contact: Reg Newman. Webmaster: For.Prodres@gov.bc.ca