Ecological Indicators for the Nation (2000) / Chapter Skim
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5 Local and Regional Indicators
5 Local and Regional Indicators
Pages 116-130
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From page 116... ...
In addition, most policy and management decisions are made at scales defined by laws and regulations established by political entities, such as local municipalities, counties, states, and the federal government. Although the committee focused its attention on the national-level ecological indicators recommended in Chapter 4, the methods used to select and formulate those indicators are equally applicable to indicators designed for use at smaller spatial scales.
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From page 117... ...
Forest Service form the basis of monitoring various aspects of forest structure and productivity. These inventory programs are positioned to take advantage of the existing theoretical base provided by individualtree simulation models (Shugart 1984~.
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From page 118... ...
Based on this review, we then recommend specific indicators of the status of forests, focusing on how these indicators relate to current inventory programs and ecosystem models. Current Forest Inventory Programs The U.S.
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From page 119... ...
For example, although the FIA plots in Minnesota are distributed across all ownership types, there are few FIA plots on national forest land in other states, particularly in the Pacific Northwest. Current Simulation Models of Forest Ecosystems The raw field data collected by the FHMP and FIA programs can be imported into individual tree-based ecosystem models (Shugart 1984)
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From page 120... ...
Productivity and tree species diversity form the basis of the forest food web; this web is sustained by the ability of soils to provide water and nutrients and by the ability of the crown to capture light. The FHMP and FIA programs already collect the data required to assess the status and trends of productivity and tree species diversity.
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From page 121... ...
The latter characteristics translate into less carbon being available for defense against insects and pathogens and repair of damage caused by biotic or abiotic agents; energy reserves are critical in surviving periods of stress. Trends in damage and crown condition are usually accurate indicators of trends in productivity and mortality.
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From page 122... ...
Useful measurements of crown condition are crown ratios (percentage of tree height that supports live foliage) , crown diameters, density, transparency, and dieback (progressive mortality of branches proceeding from branch tips inward)
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From page 123... ...
Local assessment of species diversity presents a new problem, because simple counts of species diversity have at least five weaknesses that make them unreliable. · Diversity counts are biased by sample size (Fisher et al.
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From page 124... ...
1998, Colwell and Coddington 1994~. Our recommended local and regional indicators assume the use of these methods, and they also correct for the other deficiencies of simple counts.
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From page 125... ...
It might appear that the more species housed in a reserve, the better its condition, but this is not necessarily true. As Chapter 4 showed, the form of the species-area curve means that an adjusted species density reveals more than raw species densities, Si/Ai.
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From page 126... ...
The city itself is mostly a vast suburb with expanses of vegetation supported by urban irrigation. As a result of extensive watering, the total abundance and biomass of all bird species has risen more than 26-fold, but most of the individuals belong to a few commensal and exotic species, mostly house sparrows, house finches, doves, starlings, and mockingbirds.
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From page 127... ...
Individuals/100 acres Species Desert City Gambel's quail 0.3 White-winged dove 0.5 140 Mourning dove 1.9 30 Inca dove 230 Roadrunner 0.5 Black-chinned hummingbird 6 Gilded flicker 1.9 Gila woodpecker 0.3 14 Ash-throated flycatcher 0.8 2 Verdin 2.5 14 Cactus wren 6.8 2 Curve-billed thrasher 6.9 5 Bendire's thrasher 0.2 Mockingbird 0.3 45 Black-tailed gnatcatcher 1.6 Starling 35 Loggerhead shrike 0.1 Brown-headed cowbird 0.4 1 Hooded oriole 0.6 House sparrow 520 Cardinal 1 7 Pyrrhuloxia 0.6 House finch 0.3 170 Brown towhee 1.2 Black-throated sparrow 16.5 Rufus-winged sparrow 2.5 tolerant species are likely to succeed exuberantly, whereas the intolerant ones become confined to nature reserves. One reason why so many Old World species have moved in and exploded in suburban environments to the detriment of natives may be that they have had more time to adjust to humans.
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From page 128... ...
Because Gi measures native species density, it makes a better index of local diversity and gives a truer picture of the value of a place in supporting diversity. The complement of Gi is an indicator of true deficiency in diversity, labeled U to signify unnaturalness: Ui = [cAZ _ Si n]
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From page 129... ...
Other nonnative species, such as guppies in Oregon, survive only in very specific environments, in this case, hot springs. Conversely, introduced trout cannot survive the hot summers in most lowland waters of the eastern United States, but they thrive in cool tailwaters below dams.
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From page 130... ...
For example, Ohio has developed an extensive set of IBIs that vary by ecoregion, drainage area, and stream habitat (Ohio EPA 1987~. As mentioned above, the statistical properties of additive indices make it unrealistic to add or average scores across spatial scales to create a national indicator (Norris 1995, Gerritsen 1995~.
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