SOME SIMPLE MODELS FOR CONTINUOUS VARIATE TIME SERIES1

ABSTRACT: A survey is given of recently developed models for continuous variate non–Gaussian time series. The emphasis is on marginally specific models with given correlation structure. Exponential, Gamma, Weibull, Laplace, Beta and Mixed Exponential models are considered for the marginal distributions of the stationary time series. Most of the models are random coefficient, additive linear models. Some discussion of the meaning of autoregression and linearity is given, as well as suggestions for higher–order linear residual analysis for non–Gaussian models.     

Corallum morphology and composition of crustacean cryptofauna of the hermatypic coralMadracis mirabilis

The motile crustacean cryptofauna of the hermatypic coralMadracis mirabilis (Duchassaing and Michelotti) was examined from three sites on reefs along the west coast of Barbados in 1985. In addition to site differences in degree of eutrophication, two distinct with-in-corallum habitats were recognized, based on differences in the growth form of the coral host. One form grows in isolated, hemispherical heads, with short, robust, widely separated branches covered by 50 to 80% live tissue. The second form occurs within large continuous beds of long, thin, tightly spaced branches tipped by 20 to 30% live tissue. Coral habitats consisting of small isolated heads support a crustacean fauna of high decapod and amphipod diversity, with numerous rare and site endemic species and an abundance of relatively large decapods and amphipods. The continuous beds favour a community of lower decapod and amphipod diversity, fewer rare and site endemic species and with an abundance of smaller sized isopods and copepods. It is suggested that spatial separation of branches and colonies as well as food availability associated with corallum morphology are factors influencing the variation in species abundance and faunal composition of the two habitats.     

An economist's remarks on landscaping

These costs and benefits may be more easily noticed or precisely defined by different persons. Some are seen by the landscape architect but not by the economist, and the other way round. This implies that a reasonably adequate enumeration of the benefits and costs, each considered in a very wide sense, can be achieved only if a proposal is viewed from the standpoints of different disciplines.

It may very well be that the mere enumeration of these costs and benefits will either convince the economist that the proposed scheme is ‘on’ or convince the landscape architect that it is ‘off’. In the latter case the landscape architect may say that while it would be wonderful to proceed with the scheme he can see that it would, in the wide ‘opportunity’ sense of the phrase, cost too much. But there may come a stage where the enumeration of costs and benefits leaves the landscape man wanting Scheme A and the social scientist wanting Scheme B. It is here that, first of all, adjustment must be tried. But if it fails then compromise may be needed, in which one side or the other, or both, reluctantly sacrifices some feature of his favoured scheme. If agreement cannot be reached, then the difference of opinion ought to be put to the client, who can reach his own decision.     

A multi-hazard history of Antigua*

Antigua experiences earthquakes, droughts and hurricanes. To isolate for study each of these as they occur, would be to over simplify the inter-relationships between the aftereffects of one and the occurrence and the effects of the next. Moreover, there will be conditions arising from factors outside the natural disaster spectrum which bear upon, and are themselves affected by, all of these phenomena. This interplay of events and conditions is readily illustrated in the case of island countries, which have a natural and clearly defined containment. Such interrelationships suggest a complex human-ecological system which must be recognized if environmental balance and compatability are to be maintained - particularly in respect of hazards. This documentary analysis of the colonial era in Antigua, has to conclude for the time being with questions concerning the environmental effectiveness of imported systems of administration which, with no knowledge of comparable natural hazards, assumed sectoral separation.     

Source apportionment of Phoenix PM2.5 aerosol with the Unmix receptor model

The multivariate receptor model Unmix has been used to analyze a 3-yr PM2.5 ambient aerosol data set collected in Phoenix, AZ, beginning in 1995. The analysis generated source profiles and overall average percentage source contribution estimates (SCEs) for five source categories:gasoline engines (33 +/- 4%), diesel engines (16 +/- 2%), secondary SO4(2-) (19 +/- 2%), crustal/soil (22 +/- 2%), and vegetative burning (10 +/- 2%). The Unmix analysis was supplemented with scanning electron microscopy (SEM) of a limited number of filter samples for information on possible additional low-strength sources. Except for the diesel engine source category, the Unmix SCEs were generally consistent with an earlier multivariate receptor analysis of essentially the same data using the Positive Matrix Factorization (PMF) model. This article provides the first demonstration for an urban area of the capability of the Unmix receptor model.     

Factors regulating annual mating success and reproductive success in spotted sandpipers (Actitis macularia)

Summary We investigated factors affecting annual mating success (MS) and reproductive success (RS) of spotted sandpipers (Actitis macularia) from 13 years of a 17-year study at Little Pelican Island, Leech Lake, Minnesota. Analyses were restricted to ages 1–3. Mean annual female MS varied from 1.3 to 2.7 mates, and the MS pattern was indistinguishable from random. However, female MS increased with age and was affected by arrival date, territory size, and beach size. Female RS also increased with age, and number of mates and year effects were the most significant explanatory variables in each age. Older female RS was increased by priority on a territory and presence of a previous mate. Territory size and beach size varied with population density and did not predictably affect RS. The strong year affect on RS was associated with annual variation in sex ratio and predation. Males produce only one successful clutch per year, so MS greater than one is a result of nest loss and does not increase RS. Neither male MS nor RS changed with age. Male reproductive failure rate varied by year. Given that a male produced young, the degree of RS was affected by year, arrival date, priority on a territory, territory size, and beach size. In years with early-season predation, late arrivals had higher RS; territory and beach size effects varied by year. Neither the presence, nor degree, of female care was associated with male RS. Male RS was more subject to annual environmental variability than was female RS, probably because of relatively low annual potential RS among males.Offprint requests to: L.W. Oring at the current address     

Projected change in climate thresholds in the Northeastern U.S.: implications for crops, pests, livestock, and farmers

Most prior climate change assessments for U.S. agriculture have focused on major world food crops such as wheat and maize. While useful from a national and global perspective, these results are not particularly relevant to the Northeastern U.S. agriculture economy, which is dominated by dairy milk production, and high-value horticultural crops such as apples (Malus domestica), grapes (Vitis vinifera), sweet corn (Zea mays var. rugosa), cabbage (Brassica oleracea var. capitata), and maple syrup (sugar maple, Acer saccharum). We used statistically downscaled climate projections generated by the HadCM3 atmosphere–ocean general circulation model, run with Intergovernmental Panel on Climate Change future emissions scenarios A1fi (higher) and B1 (lower), to evaluate several climate thresholds of direct relevance to agriculture in the region. A longer (frost-free) growing season could create new opportunities for farmers with enough capital to take risks on new crops (assuming a market for new crops can be developed). However, our results indicate that many crops will have yield losses associated with increased frequency of high temperature stress, inadequate winter chill period for optimum fruiting in spring, increased pressure from marginally over-wintering and/or invasive weeds, insects, or disease, or other factors. Weeds are likely to benefit more than cash crops from increasing atmospheric carbon dioxide. Projections of thermal heat index values for dairy cows indicate a substantial potential negative impact on milk production. At the higher compared to lower emissions scenario, negative climate change effects will occur sooner, and impact a larger geographic area within the region. Farmer adaptations to climate change will not be cost- or risk-free, and the impact on individual farm families and rural communities will depend on commodity produced, available capital, and timely, accurate climate projections.     

Using envirodaemon to search the internet for environmental information and building custom search engines

The Internet holds vast stores of information pertaining to pollution prevention and environmental issues, and with each day more is added. Yet, as this storehouse grows, the difficulty of finding specific information increases. This article details how EnviroDaemon was built to ease the task of finding this information and knowledge base. It automatically builds and updates a catalog of objects at pre-selected Internet sites that are related to pollution prevention. Users search for information by submitting keywords. Searches can be restricted to small subsets of the indexed sites by choosing one of five search criteria, or the entire catalog can be searched. The results are returned rapidly and are embedded in several lines of text to provide context. If the text looks promising, the user can click on a hyperlink to access the full article. Since its release in March, EnviroDaemon has seen increasing use, especially following its demonstration at the National Pollution Prevention Roundtable Conference. The authors also discuss the process of building this search engine to show interested readers how to create other environmental custom search engines.