Phytomass is the mass of plants, including dead attached parts, per unit area at a given time. Phytomass is commonly measured in units of kilograms per hectare (or pounds per acre). It is a direct measure of biomass production, carbon storage, energy availability, and available forage for potential grazers and users of rangelands. It also serves as a fuel source for rangeland fire. Phytomass is not to be confused with the next indicator, primary productivity, which describes rates of biomass accumulation. Spatially explicit maps of biomass and standing dead material are becoming extremely useful for providing inputs into wildfire behavior models.

Aboveground biomass (i.e., annual production) is an indicator of the energy captured by plants and its availability for secondary consumers in an ecosystem given current weather conditions. Production potential will change with communities or ecological sites, biological diversity, and with latitude. Annual production of the area of interest is compared to the site potential from the rangeland ecological site description and/or the ecological reference area(s).

Native rangeland shrubs and grasses provide habitat to many native species and are adapted to climatic and fire conditions. Change in the density and occurrence of shrubs and grasses may indicate climatic, land-use, invasive species, or other disturbances/threats to the native plant cover.

This indicator measures the extent and condition of riparian plant communities along rivers and streams on rangelands. The status or condition may be evaluated on a quantitative basis using a numeric value. Possible numeric values could include a metric similar to the Index of Biotic Integrity (IBI), a hydrogeomorphic (HGM) index, or a qualitative evaluation with a descriptor such as “fair condition”.

Functional/structural groups are a suite of species that because of similar shoot (height and volume) or root (fibrous vs. tap) structure, photosynthetic pathways, nitrogen fixing ability, or life cycle are grouped together on an ecological site basis. factors that change ecosystem composition, such as invasion by novel organisms, nitrogen deposition, disturbance frequency, fragmentation, predator decimation, species removal, and alternative management practices can have a strong effect on ecosystem processes.

This indicator, “Integrity of Natural Fire Regimes,” spatially and temporally quantifies acres of rangeland burned annually. Fire is a key ecological driver in many rangeland ecosystems, facilitating nutrient cycling, promoting recruitment of native grasses and forbs, and limiting encroachment of woody species. For many rangeland ecosystems, the introduction of domestic grazers, invasive species, conversion of rangeland to cropland, urbanization, fire suppression, and fragmentation of rangeland have significantly altered the natural fire regimes as well as landscape composition and structure. Because fire is such a dramatic disturbance, changes in its frequency or intensity results in significant changes in nutrient cycling, species richness, ecological integrity, and carbon stocks. Monitoring the integrity of fire regimes promises to significantly inform evaluations of rangeland health.

The indicator relates to abundance of wetlands in the rangeland landscape. Wetlands for this indicator include depression (e.g., vernal pools) and slope wetlands but do not include riverine or floodplain wetlands that are covered under the “Extent and Condition of Riparian Systems” indicator. This indicator measures the number and total area of wetlands within all or portions of the rangeland system. The metric may be either a) numbers of individually identifiable wetlands and acreage for a particular region, or for the entire rangeland region, or b) numbers and percent of landscape occupied by wetlands.

Rangeland vegetation can respond to changing climatic conditions, over-grazing, weed invasion, and other influences.

Native perennial plants are important in rangelands, providing forage, habitat, and soil stabilization. Diverse assemblages of perennial plants are more likely to provide these services across wider ranges of habitat and climatic conditions.

The proportion of dead or decadent (e.g., moribund, dying) to young or mature plants in the community relative to that expected for the site, under normal disturbance regimes, is an indicator of the population dynamics of the stand. If recruitment is not occurring and existing plants are either dying or dead, the integrity of the stand would be expected to decline and other undesirable plants (e.g., weeds or invasives) may increase. A healthy range has a mixture of many age classes of plants relative to site potential and climatic conditions.