EXTRACT FROM :

    Marcot, B. G., M. A. Castellano, J. A. Christy, L. K. Croft, J. F. Lehmkuhl, R. H. Naney, K. Nelson, C. G. Niwa, R. E. Rosentreter, R. E. Sandquist, B. C. Wales, and E. Zieroth.  1997.  Terrestrial ecology assessment.  Pp. 1497-1713 in:  T. M. Quigley and S. J. Arbelbide, ed.  An assessment of ecosystem components in the interior Columbia Basin and portions of the Klamath and Great Basins.  Volume III.  USDA Forest Service General Technical Report PNW-GTR-405.  USDA Forest Service Pacific Northwest Research Station, Portland, OR.  1713 pp.

Studying invertebrates provides many advantages for assessing ecosystem health (Samways 1993), including their functioning as easily-monitored indicators of ecosystem health.

Ginsberg (1993) believes that invertebrates are appropriate study organisms for better understanding population ecology and ecosystem health, because:

• Most global biodiversity consists of invertebrates.  Insects and other invertebrates constitute the bulk of the biosphere faunal biomass.
• Invertebrates are important in the production and processing of energy and essential materials and in recycling and processing of nutrients in ecosystems.
• Invertebrates are ideal study organisms for research, assessment, or monitoring because of the short generation times and rapid population growth capabilities of many species.
• Short generation times and high reproductive potential also make invertebrates excellent indicator and "early warning" organisms.
• Invertebrate populations play important roles in soil development, pollination and fruit set of crops and wildland plants; as natural enemies of important pest species; as major food items (for example, shrimp, lobsters, crabs); and as agricultural and health pests.
• Invertebrates serve as vectors and reservoir hosts for diseases that have major impacts on the health of human populations.

...the soil food web has been suggested as a prime indicator of ecosystem health.  Measurement of disrupted soil processes; decreased bacterial or fungal activity; inappropriate change in the ratio of fungal to bacterial biomass; decreased number or diversity of protozoa; and altered nematode numbers, nematode community structures, or maturity indices can indicate problems long before the natural vegetation appears to be affected.

Butterflies are an example of a forest herbivore group that would make a good indicator of total ecosystem diversity (Hammond 1994a).  They are relatively conspicuous and easy to observe in the field, and their functional role is well known.  Their abundance and diversity relates directly to the presence of their host plants as they are generally monophagous.  Butterflies, in turn, support a rich diversity of generalist predators including arthropod predators and parasites, passerine birds, bats, rodents, and other small mammals.  Other invertebrate herbivore groups may offer similar opportunities to act as indexes to important ecosystem functions or to total ecosystem diversity.
 

On use of vertebrates as bioindicators:

Many vertebrate species rely on invertebrate or other vertebrate abundance for prey, others represent the condition of aquatic systems, and some are indicators (presence or absence) of degraded environments.

Ultimately, the distribution and health of large carnivore populations of the assessment area can be thought of as an index of the status and distribution of wild areas in the Western United States.  These species are sensitive indicators of the degree of human-caused change of wild lands.  From a human perspective, they also play critical roles in American Indian Tribal lore and religion and are living embodiments of places that are felt to be still truly wild.

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EXTRACT FROM :

Marcot, B. G., L. K. Croft, J. F. Lehmkuhl, R. H. Naney, C. G. Niwa, W. R. Owen, and R. E. Sandquist.  1999.  Macroecology, paleoecology, and ecological integrity of terrestrial species and communities of the interior Columbia River Basin and portions of the Klamath and Great Basins.  General Technical Report PNW-GTR-XXX.   USDA Forest Service.  XXX pp.

On use of plants and allies as bioindicators:

Indicators--Plants and allies can serve as bioindicators of environmental conditions and ecosystem health.  The concept is far from new, beginning perhaps with Clemment's (1920) usage of plant indicators to denote vegetation communities.  Others have extended the concept in various directions.  For example, Nygaard (1949) indexed the trophic health and degree of eutrophication of water bodies by calculating the ratio in number of algae species of different taxonomic groups.  Westveld (1954) used plants to index site quality.  And Anderson (1986) (and many others) identified plant indicators of range condition.

The Plant Task Group of SIT identified a number of lichen, bryophyte, and vascular plant groups and vascular plant species that can serve to index specific environmental conditions of the CRB assessment area.  Such environmental conditions include:  air quality, carbonate levels, water flow levels (low, high), high nitrogen conditions, metal-rich rock conditions, old-growth forest conditions, soil temperature (low, high), and soil texture (coarse, fine).  Specific groups and their indicator values are listed in Table 8.

Overall, a number of lichens can be used to index air quality (Fig. 22, Table 8), a function already finding utility in management of a wide variety of forests and other geographic areas (for example, Geiser and others 1994, Stolte and others 1993).  Lichen groups along with bryophyte groups also can be used to index most of the other categories of environmental conditions listed above (Fig. 22, Table 8).  In addition, vascular plant groups and rare or potentially rare vascular plant species can be used as bioindicators of alkaline (carbonate) soil conditions, overgrazing, metal-rich rock conditions, old growth, low soil temperature, coarse soil textures, and other conditions (Fig. 22; Tables 8, 9).

Nonvascular plant indicators of old-growth forest conditions may be of particular interest to managers.  Tibell (1992) identified crustose lichens as indicators of temporal continuity of old boreal conifer forests.  The term temporal continuity refers to the degree to which specific kinds of habitats -- in this case, old boreal conifer forests -- continuously occupy a local geographic area over time.  Some studies outside the CRB assessment area have indicated that interrupting the temporal continuity of old forests has led to loss of sensitive species closely associated with such habitats, because there was insufficient time or lack of sources for recolonization.

Lichens have also been identified by others that indicate forest stand temporal continuity in northern boreal forests (Selva 1994, Esseen and others 1996, Nilsson and others 1995).  Pike and others (1975) identified epiphytic lichens and bryophytes associated with old-growth forests of western Oregon.  S?derstr?m and Jonsson (1992) identified bryophytes that indicate fragmentation of old-forests, that is, loss of old-growth bryophyte species in the more isolated forest fragments.  In the current study, we have identified 15 lichen groups and 9 bryophyte groups that may indicate old-growth forest conditions in the CRB assessment area (Tables 8, 9).  The rotten log and tree base lichen group in particular indicates ecological continuity of old growth.

Many of the bioindicator species and groups identified here, including those of old-growth forests, can be of use to managers interested in quickly surveying potential environmental conditions without investing in long-term ecological research studies.  Such indicators can serve to track effects of alternative management activities, such as variations in grazing, timber harvesting, or restoration regimes.

Bioindicators of Terrestrial Ecosystem Health

In this report, we have further explored the potential use of lichens as bioindicators of a variety of environmental situations, including old-growth forests, air quality, metal accumulation in soils, degree of soil acidity or alkalinity, fire and grazing regimes, and other conditions.  As we discussed previously (Marcot and others 1996), invertebrates can also serve as excellent early-warning signals of existing or impending changes in environmental conditions.  Sampling a very small part of the invertebrate fauna, too, can help to index diversity of the entire invertebrate fauna.  For example, Oliver and Beattie (1996) discovered that monitoring and assessment of terrestrial invertebrate biodiversity in Australian forests can be done by careful use of invertebrate morphospecies (species of the same morphologies) -- principally ants, beetles, and spiders.  Their results also suggested which invertebrate taxa to use, as well as sampling methods and sampling periods to yield the most consistent and reliable monitoring.  In another study in the southern Appalachians, Hollifield and Dimmick (1995) censused arthropod availability and abundance, and they inferred from that suitability of logging roads, clearcuts, and mature hardwood forests for ruffed grouse (Bonasa umbellus).  Other tests of plant or invertebrate indicators were presented by Nilsson and others (1995), and Murtaugh (1996) discussed statistical analyses of indicators.

Although major surveys and systematics studies are needed on invertebrates in the CRB assessment area, we feel
that such bioindicator approaches hold great promise for rapid field evaluations of environmental conditions and of
biodiversity in this region as well.

On use of amphibians:

One point of good news is that there is no evidence that acid precipitation is a major problem for wildlife in the CRB assessment area as it is in other parts of the continent.  Recent studies by Vertucci and Corn (1996) suggested that high-elevation aquatic amphibians -- organisms most highly sensitive to, and excellent indicators of, acid precipitation and degradation of water quality -- do not seem to be incurring this problem in the Rocky Mountains.  But this does not mean that populations of native amphibians are necessarily stable; some indeed are declining for a variety of other reasons.  Beyond the assessment area, amphibian declines and disappearances have been linked to quite a list of environmental woes including chemical pollution, acid precipitation, increased ultraviolet radiation, introduction of exotic species, pathogens, harvesting by humans, and natural population fluctuations (Blaustein and others 1994), as well as increasingly dessicating climates (Pounds and Crump 1994) and depletion of atmospheric ozone (Hileman 1994).  We may consider amphibians as crucial indicators of conditions to come, and use this list of environmental assailants to check our progress over time.  More localized current conditions and future changes also can be heralded by heeding the health of selected lichen, plant, and invertebrate populations.