ALBERT — All Library Books, journals and Electronic Records Telegrafenberg

1

Electronic Resource

Diagnostic variables as predictors of ecological risk (1988)

Johnson, Alan R.

Springer

Environmental management 12 (1988), S. 515-523

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ISSN: 1432-1009

Keywords: Diagnostic variables ; Risk ; Error rates ; Cost-benefit ; Multiple regression ; Discriminant analysis

Source: Springer Online Journal Archives 1860-2000

Topics: Energy, Environment Protection, Nuclear Power Engineering

Notes: Abstract The state of an ecosystem may be represented by a multidemensional state vector,x. The goal of ecosystem management is to insure that the ecosystem remains within some setX of acceptable states, such thatx ∈X. Since ecosystem management decisions must be based on limited knowledge, a small number of diagnostic variables must be found which accurately reflect ecosystem state. If the vector of diagnostic variables, ω, is found to be within a specified set Ω, the state vectorx is predicted to be withinX. The selection and use of such diagnostic variables is examined in the context of an aquatic ecosystem simulation model. Techniques used in searching for diagnostic criteria include multiple linear regression, discriminant analysis, and visual inspection of graphical data displays. The adequacy of a diagnostic criterion as a predictor of ecological risk is demonstrated to be a function of the associated rates of type I and type II statistical errors. A simple cost-benefit analysis is undertaken to illustrate one approach for choosing an optimal balance between these error rates.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF01873264

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2

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A Growth Cone Collapsing Activity in Chicken Gray Matter (1991)

KEYNES, ROGER J. ; JOHNSON, ALAN R. ; PICART, CAROLINE J. ; [et al.]

Oxford, UK : Blackwell Publishing Ltd

Annals of the New York Academy of Sciences 633 (1991), S. 0

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ISSN: 1749-6632

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Natural Sciences in General

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1749-6632.1991.tb15661.x

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3

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Temporal and spatial variation in dispersal in the greater flamingo (Phoenicopterus ruber roseus) (1996)

Nager, Ruedi G. ; Johnson, Alan R. ; Boy, Vincent ; [et al.]

Springer

Oecologia 107 (1996), S. 204-211

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ISSN: 1432-1939

Keywords: Greater flamingo ; Phoenicopterus ruber roseus ; Philopatry ; Dispersal ; Competition

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract We studied movements of individually marked greater flamingos (Phoenicopterus ruber roseus) born in the Camargue, southern France, between their two most important breeding colonies in the western Mediterranean (Camargue and Fuente de Piedra, Spain) from 1986 to 1992. The two sites differ in the frequency with which they offer suitable conditions for breeding. Flamingos have bred each year in the Camargue since 1974, but in only 12 of the past 22 years at Fuente de Piedra. Higher colony fidelity is thus expected in the less variable environment (Camargue), but if dispersal occurs competition might be an important factor causing this dispersal. Following years during which breeding birds in the Camrgue were disturbed (1988 and 1990) a higher proportion of adults changed colonies between breeding attempts (= breeding dispersal, 12.4%), while only 0.4% of flamingos breeding in the Camargue dispersed in the other years. As expected, flamingos breeding at Fuente de Piedra showed a higher rate of breeding dispersal (8.14%). No differences were observed between males and females. The importance of breeding failure as a factor causing breeding dispersal in flamingos was also confirmed by the movements of individual birds. The proportion of young flamingos that moved from their natal colony to start breeding at Fuente de Piedra (= natal dispersal) was independent of sex and age, but increased when breeding access to the Camargue colony was more difficult. However, natal dispersal was also higher in 1988 and 1990 (40.5%) than in the remaining years (1.2%), as was breeding dispersal. We discuss possible ways in which the increased natal dispersal among inexperienced birds could be linked with the increased breeding dispersal of adults in the same year.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00327904

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4

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Transmutation and functional representation of heterogeneous landscapes (1991)

King, Anthony W. ; Johnson, Alan R. ; O'Neill, Robert V.

Springer

Landscape ecology 5 (1991), S. 239-253

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ISSN: 1572-9761

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract Models of local small-scale ecological processes can be used to describe related processes at larger spatial scales if the influences of increased scale and heterogeneity are carefully considered. In this paper we consider the changes in the functional representation of an ecological process that can occur as one moves from a local small-scale model to a model of the aggregate expression of that process for a larger spatial extent. We call these changes “spatial transmutation”. We specifically examine landscape heterogeneity as a cause of transmutation. Spatial transmutation as a consequence of landscape heterogeneity is a source of error in the prediction of aggregate landscape behavior from smaller scale models. However, we also demonstrate a procedure for taking advantage of spatial transmutation to develop appropriately scaled landscape functions. First a mathematical function describing the process of interest as a local function of local variables is defined. The spatial heterogeneity of the local variables is described by their statistical distribution in the landscape. The aggregate landscape expression of the local process is then predicted by calculating the expected value of the local function, explicitly integrating landscape heterogeneity. Monte Carlo simulation is used to repeat the local-to-landscape extrapolation for a variety of landscape patterns. Finally, the extrapolated landscape results are regressed on landscape variables to define response functions that explain a useful fraction of the total variation in landscape behavior. The response functions are hypotheses about the functional representation of the local process at the larger spatial scale.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00141438

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5

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Assessing and Monitoring the Health of Western Rangeland Watersheds (2000)

Desoyza, Amrita G. ; Whitford, Walter G. ; Turner, Sandra J. ; [et al.]

Springer

Environmental monitoring and assessment 64 (2000), S. 153-166

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ISSN: 1573-2959

Keywords: Soil and water retention ; bare patch size ; percent bare soil ; grass ; shrub ; remote sensing

Source: Springer Online Journal Archives 1860-2000

Topics: Energy, Environment Protection, Nuclear Power Engineering

Notes: Abstract The most important function of watersheds in the western U.S. is the capacity to retain soil and water, thereby providing stability in hydrologic head and minimizing stream sediment loads. Long-term soil and water retention varies directly with vegetation cover. Data on ground cover and plant species composition were collected from 129 sites in the Rio Grande drainage of south-central New Mexico. This area was previously assessed by classification of Advanced Very High Resolution Radiometry (AVHRR) imagery. The classification of irreversibly degraded sites failed to identify most of the severely degraded sites based on size of bare patches and 35% of the sites classified as degraded were healthy based on mean bare patch size and vegetation cover. Previous research showed that an index of unvegetated soil (bare patch size and percent of ground without vegetative cover) was the most robust indicator of the soil and water retention function. Although the regression of mean bare patch size on percent bare ground was significant (p 〈 0.001), percent bare ground accounted for only 11% of the variability in bare patch size. Therefore bare patch size cannot be estimated from data on percent bare ground derived from remote sensing. At sites with less than 25% grass cover, and on sites with more than 15% shrub cover, there were significant relationships between percent bare soil and mean bare patch size (p 〈 0.05). Several other indicators of ecosystem health were related to mean bare patch size: perennial plant species richness (r = 0.6, p 〈 0.0001), percent cover of increaser species (r = 0.5, p 〈 0.0001) and percent cover of forage useable by livestock (r = 0.62, p 〈 0.0001). There was no relationship between bare patch size and cover of species that are toxic to livestock. In order to assess the ability of western rangeland watersheds to retain soil and water using remote sensing, it will be necessary to detect and estimate sizes of bare patches ranging between at least 0.5 m in diameter to several meters in diameter.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1006423708707

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6

Electronic Resource

Contact inhibition in the failure of mammalian CNS axonal regeneration (1993)

Johnson, Alan R.

New York, NY : Wiley-Blackwell

BioEssays 15 (1993), S. 807-813

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ISSN: 0265-9247

Keywords: Life and Medical Sciences ; Cell & Developmental Biology

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Biology , Medicine

Notes: Anamniote animals, such as fish and amphibians, are able to regenerate damaged CNS nerves following injury, but regeneration in the mammalian CNS tracts, such as the optic nerve, does not occur. However, severed adult mammalian retinal axons can regenerate into peripheral nerve segments grafted into the brain and this finding has emphasized the importance of the environment in explaining regenerative failure in the adult mammalian CNS. Following lesions, regenerating axons encounter the glial cells, oligodendrocytes and astro-cytes, and their derivatives, respectively myelin and the astrocytic scar. Experiments to investigate the influence of these components on axon growth in culture have revealed cell-surface and extracellular matrix molecules that inhibit axon extension and growth cone motility. Structural and functional characterization of these ligands and their receptors is underway, and may solve the interesting neurobiological conundrum posed by the failure of mammalian CNS regeneration. Simultaneously, this might allow new possibilities for treatment of the severe clinical disabilities resulting from injury to the brain and spinal cord.

Additional Material: 3 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/bies.950151206

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