Indicator framework for stand level evaluation and monitoring of environmentally sustainable forest management

Area of Focus
General Frameworks

The framework aims to assess the effects of forest management on forest composition, structure and functioning. It consists of seven principles and 19 criteria, to which 157 potential indicators, selected from literature, were assigned; 40 of these were considered as suitable by an expert panel, based on 10 operational selection criteria. All indicators were quantitative variables measurable in the field. After elaboration of a measurement protocol, the indicator framework was validated in 115 forest stands, distributed over the three main forest types of Flanders. The new indicator framework exhibited greater sensitivity to forest management practices and demonstrated better discriminating power than the method that is currently used by the Flemish forest administration to estimate the naturalness and environmental quality of a forest stand. Following a detailed cost calculation of each indicator and based on the sensitivity of each indicator to forest management practices, the indicator framework was further reduced to a final set of 29 indicators.

Related Links
Forest Management Indicator Framework

Indicators

  • Forest structure: Height differentiation index of Von Gadow
    Stand structure can be defined as the horizontal and vertical spatial distribution of trees of different diameters and heights in a forest ecosystem. The height differentiation index takes into account variations in tree heights in a forest area. Stand structure heterogeneity (horizontal and vertical) leads to a higher number of species and contributes to higher stability and forest integrity.
  • Forest structure: Leaf Area Index (LAI)
    This is green-leaf area (one side of leaves) per unit area of ground. For conifers, the leaf area is half of the surface area per needle. The LAI can be used to predict primary productivity.
  • Forest structure: Number of large, dead standing and fallen trees per hectare
    This indicator is a measure of the large snag production of an area. Large standing and fallen dead trees are critical habitat for birds and mammalian predators, store carbon, and contribute eventually to soil carbon and nutrient cycling.
  • Forest structure: Number of thick trees per hectare
    Thick (or large) trees provide cover, habitat, carbon storage, high carbon sequestration rates (per tree) and aesthetic benefits. The number of thick (large) trees per acre will naturally vary by species, geomorphic/soil conditions, natural disturbance, and climate conditions.
  • Forest structure: Number of vegetation layers
    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.
  • Forest structure: Number of very thick trees per hectare
    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.
  • Forest structure: Percentage of surface area consisting of dead standing trees
    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.
  • Forest structure: Percentage open spaces
    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).
  • Forest structure: Stem distribution
    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.
  • Forest structure: Total above ground biomass of the woody vegetation
    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.
  • Improvement of biodiversity: Fagers‚ NMS index of diversity
    This index is also called the evenness index and compares calculated and maximum biodiversity (evenness = (calculated diversity - minimum diversity)/(maximum diversity - minimum diversity)).
  • Improvement of biodiversity: Number of native non-woody vascular plants
    Herbaceous plants on the forest floor and in rangelands are habitat an forage for many animal species. They are light/shade-sensitive, usually lost during fire, and recover quickly from disturbance, assuming climatic conditions and seeds are available. Their presence, abundance and diversity indicate a healthy forest or rangeland.
  • Improvement of biodiversity: Number of native woody species
    In some areas, one would expect to find a wide range of woody species, in other areas, less diversity might be expected. The number of observed species relative to expected is a common measure of ecosystem condition.
  • Improvement of biodiversity: Number of red listed non-woody plant species
    The IUCN "Red List" includes plants and animals that are threatened with further endangerment or extinction. Presence on this list is an indication of serious rarity or threats to a species.
  • Improvement of biodiversity: Percentage of surface area with native species
    Ideally, 100% of a forest or rangeland area would be covered with native species. As weeds invade, the area covered by native species may decline, resulting in simplification of plant communities, loss of habitat, and change in ecosystem structure and function.
  • Improvement of biotic processes: Cover and abundance of the natural regeneration per species
    Artificial and natural disturbance can eliminate plants form an area. Natural regeneration occurs when seeds, or remaining root masses sprout and create new plant cover. This will vary with species due to variation in number of propagules, rate of regeneration, climatic conditions, severity of disturbance, and competition with other species.
  • Improvement of biotic processes: Coverage of pest species
    Invasive, non-native plant species can change the structure an function of ecosystems. As they invade, they will increase their cover of forest and rangeland ground.
  • Improvement of biotic processes: Health condition of forest crowns
    Tree crowns are both sites of primary production and habitat for arboreal species. Crowns may be damaged by human activity and pollution (e.g., ozone), as well as disease, insects, storms and fire.
  • Improvement of biotic processes: Height/diameter ratio
    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.
  • Improvement of biotic processes: Number of naturally regenerating native woody species
    Artificial and natural disturbance is usually followed by regeneration of species removed by the disturbance. Ideally the number of regernating native woody species will be close to expected, after disturbance.