Multi-layered canopies and ground cover contribute to habitat quality and cover for cryptic animal species, and indicate a healthy forest, though one with potentially low rates of severe disturbance.
Very large/thick trees take a long time to grow (centuries), depending on the species and ambient conditions. Very large trees are sometimes the only habitat suitable for certain species and store very large amounts of carbon.
Dead standing trees provide habitat for various birds, insects, and mammals. These benefits increase with the size of the trees and to some degree the number of dead trees in an area. Dead standing trees store carbon, but will gradually release it to the soil after falling, or more rapidly during a fire.
Most forests have naturally-occurring openings among stems. Sometimes this is caused by localized disturbance (fire, disease). Openings provide habitat for species tolerant of openings and edges and reduce habitat for species preferring the cover of closed forests. Logging tends to create more openings (thinning), or larger openings (clear-cutting).
The distribution of tree stems will help to determine horizontal forest structure. Depending on scale, the more heterogeneous the distribution, the more likely the provision of habitat for a wide range of species. Natural disturbance will tend to maximize heterogeneity because many random forces may come into play. Logging and re-planting strategies may make the distribution homogeneous, depending on how it is carried out.
The total biomass of woody vegetation is a measure of the carbon storage and net production, and is one indication of the amount of structure that could be present on a site.
Forests encompass a wide variety of environments (from inland to coast, to alpine) and a range of natural disturbances (for example fire regimes). (California’s) forests are vitally important for maintaining watershed health, biodiversity, and social values and services. This indicator measures the amount of forest of each of the diverse types.
This indicator is defined as the breaking up or loss of connectivity of rangeland or of a rangeland cover type. Fragmentation has been shown to impact plant and animal species and ecosystem function in western ecosystems. While fragmentation studies have a long history in forested ecosystems, recent research has also described fragmentation as an interruptive process affecting the sustainability of rangeland ecosystems. Fragmentation of rangelands affects wildlife and some plant populations, hydrological and biogeochemical processes, and even social and economic systems associated with rangelands. Fragmentation measures the size of contiguous areas, spatial organization, and community type dispersion.
The height to diameter (at breast height, dbh) ratio is an important measure of stand condition. In crowded stands, the ratio will tend to be higher than in open stands and the ratio for trees with suppressed growth (usually in crowded stands) will be higher than the ratio for dominant trees and trees with less competition.
Biomass is the organic mass of something. Forest biomass is the total organic mass of an area. Net increase in biomass will increase with plant growth, as long as growth exceeds loss of material due to oxidation (e.g., during fire) and extraction. Many animals and plants depend on forest biomass as sources of food and habitat structure.
