摘要:

When pressing national environmental problems must be solved, and serve as the justification for large infusions of public funds, mechanisms must be found to assure that the requisite research and assessment are performed. Large, managed programs seem to offer a way to direct energies in the needed directions, but individual creativity and intellectual curiosity must also be fostered through investigator—initiated studies. Research results cannot be achieved to meet imposed deadlines, and assessment in the face of uncertainty must be given due attention. This paper introduces five subsequent papers, four of which present perspectives on the National Acid Precipitation Assessment Program, as a model for coordinated research and assessment programs, and one that presents plans for a national and international research effort on biodiversity.

ISSN:1051-0761    

DOI:10.2307/1941764

出版商:Ecological Society of America    

年代:1992

数据来源: WILEY

摘要:

NAPAP was an institutional innovation of great benefit in bringing the United States to a decision on acid precipitation control. The nation's return from the $600 000 000 investment in NAPAP will be greater still if the lessons learned in the course of its existence are put to proper use in the future. This essay concentrates on the lessons learned about the interface between science and public policy as experienced in NAPAP.

ISSN:1051-0761    

DOI:10.2307/1941765

出版商:Ecological Society of America    

年代:1992

数据来源: WILEY

摘要:

This paper reviews the performance of the National Acid Precipitation Assessment Program during its initial 10 yr. Special emphasis is given to contributions to science, to public decision—making, and to lessons for future environmental and ecological research.

ISSN:1051-0761    

DOI:10.2307/1941766

出版商:Ecological Society of America    

年代:1992

数据来源: WILEY

摘要:

The Forest Response Program (FRP), a major component of the National Acid Precipitation Assessment Program (NAPAP), was established only after NAPAP had been underway for five years. Thus, it benefitted from a more sophisticated understanding of the essential policy questions that the research on forests would be required to answer, in comparison to the earlier aquatic studies. The "gradient studies" of the Eastern Hardwoods Research Cooperative were planned as 5—yr projects to determine whether there was any epidemiological pattern in forest responses corresponding to measures of pollutant dose (acidic deposition or oxidants). The NAPAP "Assessment" was written after only 3 yr of the research, and its findings differ in important ways from the 5—yr findings of the gradient studies. The FRP had the potential to be a model study of how applied research can be designed to solve major resource policy questions, but it is perceived to have failed for reasons of multiple non—congruences between planning and reporting. Potential still exists for a positive outcome.

ISSN:1051-0761    

DOI:10.2307/1941767

出版商:Ecological Society of America    

年代:1992

数据来源: WILEY

摘要:

Despite widespread political interference with programs and confusion of science and policy, the NAPAP program has produced a number of sound, if not outstanding, publications documenting the effects of acidic deposition. NAPAP's outstanding strengths in aquatic science are in paleoecology and spatial surveys of chemistry. NAPAP has severe shortcomings in documentation of temporal trends, in deducing biological responses to acidification by organisms other than fish, in considering the effects of nitrogen deposition, and in considering results from countries other than the USA. Summaries of the NAPAP program in 1987 and 1990 underrepresent the extent of damage caused by acidification, as documented elsewhere in NAPAP's publications and by the peer—reviewed literature at large. Overall, it represents a mediocre return for a large amount of investment, and is a poor model for future large, multidisciplinary science projects.

ISSN:1051-0761    

DOI:10.2307/1941768

出版商:Ecological Society of America    

年代:1992

数据来源: WILEY

摘要:

A planning workshop was called by IUBS (the International Union of Biological Sciences) at the Harvard Forest to develop an international research program in biodiversity, including the inventorying and monitoring of the world's biological diversity. Workshop participants were asked to develop research hypotheses that answer aspects of the question "What is the importance of biodiversity for the proper functioning of biological systems, from populations to ecosystems?" The hypotheses developed dealt with the changes that might be expected in biodiversity as a result of anthropogenic activity and also the complementary issue of how changes in biodiversity will affect the functioning of biological systems. Habitat fragmentation, loss and addition of species, changes in the functional and structural attributes of ecosystems, and the ability of depauperate ecosystems to respond to climatic and other changes, were addressed. Two issues emerged from the workshop as needing serious investigation. The first is the degree to which each species of plants and animals is unique. Many species are similar in appearance; many more perform similar ecological functions (primary producers, herbivores, decomposers, etc.). However, no two species are alike in their genetic structure or in all functional features. A very fundamental question for managers and decision—makers is the degree to which a species can substitute for another in an ecosystem, that is, how much is ecosystem function impaired when a species is lost or gained? Since human activities are resulting in both losses and introductions, a careful and precise answer to this question is essential. The second issue concerns habitat fragmentation. Human activity is creating an unprecedented fragmentation of natural habitats and ecosystems all over the world. Habitat fragmentation disrupts gene flow and propagule dispersal, but can result in increased speciation and differentiation of populations. Much more information is needed before it will be possible to predict the effects of habitat fragmentation. Without this information precise management of natural and artificial ecosystems is not possible. It is one of the issues tagged by the workshop as of crucial importance for future research. The workshop pointed out once more the serious problem that the decline in taxonomic activity is creating. There is a serious shortage of trained systematists all over the world, but particularly in tropical countries where most of the world's diversity is located. A strong recommendation from the workshop is that support for training and research in systematics be increased, that systematic collections be upgraded and supported, and that more employment opportunities for systematists be created.

ISSN:1051-0761    

DOI:10.2307/1941769

出版商:Ecological Society of America    

年代:1992

数据来源: WILEY

摘要:

The effect of foliage feeding by the serpentine leafminer, Liriomyza trifolii (Burgess), on seed production and germination by male—sterile marigolds (Tagetes erecta L.) was examined over two cropping seasons in commercial production greenhouses. Five components of T. erecta relative fitness (the number of flowers, ovules, and germinations per plant, seed mass, and plant height) were compared in plants grown under four different control strategies representing three different intensities of L. trifolii herbivory: no control (high herbivory), biological or chemical control (intermediate herbivory), and insect—free (low herbivory). In both years of the study, significant between—treatment differences in number of viable seeds per plant were detected but no significant differences were found in the other four relative fitness measures. The number of viable seeds was highest with high herbivory (no—control treatments) and lowest with comparatively low herbivory (chemical and insect—free treatments). L. trifolii damage may reduce photosynthate availability, which may slow seed development and increase the length of time in which ovule physiological and morphological conditions are suitable for successful fertilization. Because all plants within each year received an equal number of pollinations occurring at the same time relative to plant growth, ovules within plants in the high—damage treatments may have had a greater probability of being fertilized, resulting in an increase in production of viable seeds.

ISSN:1051-0761    

DOI:10.2307/1941770

出版商:Ecological Society of America    

年代:1992

数据来源: WILEY

摘要:

Phenylpropanoids, a class of common phenolic compounds in plants, may potentially be useful as pest repellents. We investigated the relationship between the chemical structure of coniferyl benzoate and its repellency to birds by comparing coniferyl benzoate to two analogous natural esters, corresponding alcohols, and benzoic acid. The absolute and relative feeding repellency of these compounds were assessed in choice (two—cup) and no—choice (one—cup) tests using European Starlings (Sturnus vulgaris). In addition, benzoin Siam (= gum benzoin Siam) was compared to coniferyl benzoate to ascertain if phenolics that naturally occur with coniferyl benzoate in benzoin Siam enhance its repellency. Two—cup tests suggested that coniferyl alcohol was the most repellent compound followed by 3,4—dimethoxycinnamyl alcohol, 3,4—dimethoxycinnamyl benzoate, cinnamyl alcohol, cinnamyl benzoate, coniferyl benzoate, and benzoic acid. The repellency of most alcohols relative to their corresponding ester reversed in the one—cup tests. One—cup tests suggested that 3,4—dimethoxycinnamyl benzoate was the most repellent substance followed by cinnamyl benzoate, benzoin Siam, 3,4—dimethoxycinnamylalcohol, cinnamyl alcohol, coniferyl alcohol, coniferyl benzoate, and benzoic acid. Three conclusions on structure—activity relationships were inferred from these data. First, benzoate esters are more repellent than their corresponding alcohols.Second, repellency is increased by electron—donating groups. Third, acidic functions decrease repellency. We suggest that one function of naturally occurring coniferyl and cinnamyl derivatives may be chemical defense. Genetically engineering agricultural crops to produce analogs of coniferyl alcohol, as an inherent defense against pests and pathogens, may be possible.

ISSN:1051-0761    

DOI:10.2307/1941771

出版商:Ecological Society of America    

年代:1992

数据来源: WILEY

摘要:

We examined the 30—yr cumulative effects of prescribed fires at intervals of 1, 2, 3, and 4 yr in a loblolly and longleaf pine forest in the Coastal Plain of South Carolina. The fine fraction of the forest floor (Oe + Oa horizons) contained much more carbon and nitrogen per unit area in the control plots (1.7 and 0.05 kg/m2, respectively) than in the 1—yr burn interval plots (0.4 and 0.007 kg/m2, respectively). Mineral soils (0—0.2 m depth) were highly variable in chemistry, and showed only slight differences across the burning treatments for nitrogen and sulfur. No trends were apparent for phosphorus in the forest floor or mineral soil; differences in acidity and extractable cations were also slight. The nutrient content of foliage was generally low, with no differences across burning intervals. Our results are consistent with earlier studies that showed the biogeochemical effects of repeated surface fires in southern pine forests are generally limited to the forest floor, with the possible exception of overall reductions in nitrogen cycling.

ISSN:1051-0761    

DOI:10.2307/1941772

出版商:Ecological Society of America    

年代:1992

数据来源: WILEY

摘要:

The abundance and distribution of natural populations can be strongly influenced by the types and arrangement of habitat patches within a landscape. The impact of landscape changes on population dynamics is difficult to study using conventional population models and field techniques. Spatially explicit simulation models provide a powerful method for modelling landscape and population changes at large spatial scales and may prove useful as a management tool for mobile animal populations. As an example of this approach, we present a model designed to elucidate the effects of landscape—level variation in habitat dispersion on the size and extinction probability of avian populations in a region managed for timber production. In the model, habitat suitability and availability within the landscape change annually as a function of timber harvest and management strategies. The model incorporates life history characteristics of Bachman's Sparrow (Aimophila aestivalis), a species of management concern in the southeastern United States, and the landscape characteristics of the Savannah River Site, South Carolina, an area managed for timber production where the sparrow is relatively common. Life history characteristics used in the model include dispersal, survivorship, and reproductive success information reported for Bachman's Sparrow at this site or elsewhere in its range. Results of the simulations suggest that variation in demographic variables affects population size more than variation in dispersal ability. Changes in adult and juvenile survivorship have especially large impacts on the probability of population extinction. The presence of habitat types that serve as permanent sources of dispersers increases the total population size in the landscape, and lowers the probability of extinction. Results of models such as BACHMAP can suggest modifications to current management plans that would increase the probability of population persistence for species of special concern in managed landscapes.

ISSN:1051-0761    

DOI:10.2307/1941773

出版商:Ecological Society of America    

年代:1992

数据来源: WILEY