|DE Soyza, Amrita - NEW MEXICO STATE UNIV|
|VAN ZEE, JUSTIN|
Submitted to: Environmental Monitoring and Assessment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 1, 1998
Publication Date: N/A
Interpretive Summary: We measured vegetational, soil and animal-based characteristics of rangeland sites with long, well documented records of human and naturally caused vegetational change. The factors measured included the sizes of unvegetated bare soil patches, vegetational cover and species composition, surface soil stability and abundance and species composition of birds and ants. Several indicators including bare patch index, cover by long-lived grasses, a palatability index and soil surface stability index. However, some indicators such as the bird and ant based indicators were not useful because they were not sufficiently sensitive or their interpretation was ambiguous. The variability of indicators underlines the importance of always using combinations of indicators when determining ecosystem health.
Technical Abstract: We studied indicators of rangeland health on benchmark sites with long, well documented records of protection from stress by domestic livestock or histories of environmental stress and vegetation change. We measured ecosystem properties (metrics) that were clearly linked to ecosystem processes. We focused on conservation of soil and water as key processes in nhealthy ecosystems and on maintenance of biodiversity and productivity as important functions of healthy ecosystems. Measurements from which indicators of rangeland health were derived included: sizes of unvegetated patches, cover and species composition of perennial grasses, cover and species composition of shrubs and herbaceous perennials, soil slaking and abundance and species composition of the bird fauna. Indicators that provided an interpretable range of values over the gradient from irreversibly degraded sites to healthy sites included: bare patch index, cover of long-lived grasses, palatability index and weighted soil surface stability index. Indicators for which values above a threshold may serve as an indicator of rangeland health include: cover of plant species toxic to livestock, cover of exotic species and cover of increaser species. Several other indicator metrics were judged not sensitive nor interpretable. Examples of application of rangeland health indicators to evaluate the success of various restoration efforts supported the contention that a suite of indicators are required to assess rangeland health. Bird species diversity and ant species diversity were not related to the status of the sample site and were judged inadequate as indicators of maintenance of biodiversity.