Nonlinear regression and ARIMA models for precipitation chemistry in East Central Florida from 1978 to 1997

Continuous monitoring of precipitation in East Central Florida has occurred since 1978 at a sampling site located on the University of Central Florida (UCF) campus. Monthly volume-weighted average (VWA) concentration for several major analytes that are present in precipitation samples was calculated from samples collected daily. Monthly VWA concentration and wet deposition of H(+), NH(4)(+), Ca(2+), Mg(2+), NO(3)(-), Cl(-) and SO(4)(2-) were evaluated by a nonlinear regression (NLR) model that considered 10-year data (from 1978 to 1987) and 20-year data (from 1978 to 1997). Little change in the NLR parameter estimates was indicated among the 10-year and 20-year evaluations except for general decreases in the predicted trends from the 10-year to the 20-year fits. Box-Jenkins autoregressive integrated moving average (ARIMA) models with linear trend were considered as an alternative to the NLR models for these data. The NLR and ARIMA model forecasts for 1998 were compared to the actual 1998 data. For monthly VWA concentration values, the two models gave similar results. For the wet deposition values, the ARIMA models performed considerably better.     

Modeling the impact of potential wetlands on phosphorus retention in a Swedish catchment

In southern Sweden, wetlands are constructed to remove nitrogen (N) in agricultural catchments. The possible effects of such wetlands on riverine phosphorus (P) were also estimated using input-output data from three well-monitored wetlands. This was done to formulate a simple model for removal of P that is dependent on inflow characteristics. Next, the N- and P-reducing effects of wetlands were modeled on a catchment scale (1900 km2) using the HBV-NP model and various assumptions about the wetland area and location. All three wetlands functioned as sinks for total P (tot-P) and for total suspended solids (TSS) with a removal of 10% to 31% and 28% to 50%, respectively. Mean P-removal rates of 17-49 kg ha(-1) yr(-1) were well simulated with the model. Catchment scale simulations indicated that wetlands were more efficient (in percentage of load) as traps for P than for N and that this may motivate the construction of wetlands for P removal far upstream from the catchment outlet.     

Farm cooperation to improve sustainability

In this paper, it is demonstrated that partnership arrangements between farmers might be a way to secure the economic viability of their farms as well as to increase profitability. The article discusses empirical analyses of three different forms of collaboration, with an emphasis on the environmental improvements associated with collaboration. Collaboration between a dairy farm and a crop farm is analyzed in the first case. The results show that potential gains from improved diversification and crop rotation are substantial, and even larger when the collaboration also involves machinery. The second analysis considers external integration between farrowing and finishing-pig operations. Gains from collaboration originate from biological and technical factors, such as improved growth rate of the pigs and better utilization of buildings. Finally, an evaluation of a group of collaborating crop farmers is performed. In this case, the benefits that arise are mainly due to reduced machinery costs and/or gains due to other factors, such as improved crop rotation and managerial/marketing strategies.     

Description of the early development of the halibut Hippoglossus hippoglossus and attempts to rear the larvae past first feeding

Rearing experiments on the halibut Hippoglossus hippoglossus (L.) were carried out using gametes from parents caught at a depth of 600 to 700 m off the Norwegian coast in February 1980. After fertilization, the average egg diameter was 3.08 mm, average dry weight 1 038 μg and neutral buoyancy was at 36.5‰ S. The eggs hatched after 20 d at 4.7°C, 18 d at 5°C and 13 d at 7°C. Survival to hatching was better when antibiotics were used. At hatching the larvae were 6.4 mm long, there were no functional eyes or mouth, but prominent neuromast organs were present. Resorption of yolk lasted 50 d at 5.3°C; the eyes and mouth were then functioning and the larva was about 11.5 mm long. The larvae were offered zooplankton as food, but with little success in initial feeding. A few larvae fed and grew in 2 500-litre plastic bags, one reaching a length of 24 mm after 90 d.     

Simulating correlated count data

In this study we compare two techniques for simulating count-valued random n-vectors Y with specified mean and correlation structure. The first technique is to use a lognormal-Poisson hierarchy (L-P method). A vector of correlated normals Z is generated and transformed to a vector of lognormals X. Then, Y is generated as conditionally independent Poissons with means X _i . The L-P method is simple, fast, and familiar to many researchers. However, the method requires each Y _i to be overdispersed (i.e., σ² > μ), and only low correlations are possible with this method when the variables have small means. We develop a second technique to generate the elements of Y as overlapping sums (OS) of independent X _j ’s (OS method). For example, suppose X, X ₁, and X ₂ are independent. If Y ₁ = X + X ₁ and Y ₂ = X + X ₂, then Y ₁ and Y ₂ are correlated because they share the common component X. A generalized version of the OS method for simulating n-vectors of two-parameter count-valued distributions is presented. The OS method is shown to address some of the shortcomings of the L-P method. In particular, underdispersed random variables can be simulated, and high correlations are feasible even when the means are small. However, negative correlations cannot be simulated with the OS method, and when n > 3, the OS method is more complicated to implement than the L-P method.     

Local Participation in Natural Resource Monitoring: a Characterization of Approaches

Abstract: The monitoring of trends in the status of species or habitats is routine in developed countries, where it is funded by the state or large nongovernmental organizations and often involves large numbers of skilled amateur volunteers. Far less monitoring of natural resources takes place in developing countries, where state agencies have small budgets, there are fewer skilled professionals or amateurs, and socioeconomic conditions prevent development of a culture of volunteerism. The resulting lack of knowledge about trends in species and habitats presents a serious challenge for detecting, understanding, and reversing declines in natural resource values. International environmental agreements require signatories undertake systematic monitoring of their natural resources, but no system exists to guide the development and expansion of monitoring schemes. To help develop such a protocol, we suggest a typology of monitoring categories, defined by their degree of local participation, ranging from no local involvement with monitoring undertaken by professional researchers to an entirely local effort with monitoring undertaken by local people. We assessed the strengths and weaknesses of each monitoring category and the potential of each to be sustainable in developed or developing countries. Locally based monitoring is particularly relevant in developing countries, where it can lead to rapid decisions to solve the key threats affecting natural resources, can empower local communities to better manage their resources, and can refine sustainable‐use strategies to improve local livelihoods. Nevertheless, we recognize that the accuracy and precision of the monitoring undertaken by local communities in different situations needs further study and field protocols need to be further developed to get the best from the unrealized potential of this approach. A challenge to conservation biologists is to identify and establish the monitoring system most relevant to a particular situation and to develop methods to integrate outputs from across the spectrum of monitoring schemes to produce wider indices of natural resources that capture the strengths of each.     

Feeding current characteristics of three morphologically different bivalve suspension feeders, Crassostrea gigas, Mytilus edulis and Cerastoderma edule, in relation to food competition

Introduced Pacific oysters (Crassostrea gigas) have shown rapid expansion in the Oosterschelde estuary, while stocks of native bivalves declined slightly or remained stable. This indicates that they might have an advantage over native bivalve filter feeders. Hence, at the scale of individual bivalves, we studied whether this advantage occurs in optimizing food intake over native bivalves. We investigated feeding current characteristics, in which potential differences may ultimately lead to a differential food intake. We compared feeding currents of the invasive epibenthic non-siphonate Pacific oyster to those of two native bivalve suspension feeders: the epibenthic siphonate blue mussel Mytilus edulis and the endobenthic siphonate common cockle Cerastoderma edule. Inhalant flow fields were studied empirically using digital particle image velocimetry and particle tracking velocimetry. Exhalant jet speeds were modelled for a range of exhalant-aperture cross-sectional areas as determined in the laboratory and a range of filtration rates derived from literature. Significant differences were found in inhalant and exhalant current velocities and properties of the inhalant flow field (acceleration and distance of influence). At comparable body weight, inhalant current velocities were lower in C. gigas than in the other species. Modelled exhalant jets were higher in C. gigas, but oriented horizontally instead of vertically as in the other species. Despite these significant differences and apparent morphological differences between the three species, absolute differences in feeding current characteristics were small and are not expected to lead to significant differences in feeding efficiency.     

Female and male behavioral response to advertisement calls of graded complexity in túngara frogs, <Emphasis Type="Italic">Physalaemus pustulosus</Emphasis>

We investigated the natural dynamics in a sexual signal that combines different call components and explored the role of call complexity in sexual selection using a neotropical frog. Male túngara frogs, Physalaemus pustulosus, facultatively add up to seven short, multi-harmonic components (chucks) to the simple form of their calls (whines). Female túngara frogs are preferentially attracted to whines with chucks over whines without chucks, and males also call more in response to calls containing chucks. Because acoustic predators prefer complex calls, in the context of simple (no chucks) versus complex (any number of chucks) calls, the variably complex call appears to have evolved in response to the opposing selective forces of natural and sexual selection. There is no evidence, however, for the function of increasing the number of chucks within complex calls. We tested two aspects of increasing call complexity: natural patterns of use of call types in males and how both sexes respond to variation in multi-chuck calls. Males incrementally change call complexity by the addition or subtraction of a single chuck and usually do not produce more than two chucks. Variation in call complexity, for calls with at least one chuck, does not influence response calling in males or phonotaxis in females. Our results suggest that one reason for not increasing call complexity beyond a single chuck is the diminishing effectiveness on the responses of both sexes. This is a posthumous publication for A. Stanley Rand     

Completely disjunct mitochondrial DNA haplotype distribution without a phylogeographic break in a planktonic developing gastropod

Planktonic developing organisms are generally assumed to be good dispersers showing little genetic structuring in neutral markers. At first glance, this also applies to the planktonic developing periwinkle Tectarius striatus, an endemic gastropod from Macaronesia (i.e. Azores, Madeira, Canary Islands and Cape Verde Islands), where the only sign of genetic structuring hitherto is provided by a non-significant allozyme/RAPD heterogeneity between the Cape Verde Islands and the other archipelagos. However, partial sequences of the mitochondrial cytochrome b and cytochrome oxidase I genes now show that the Cape Verde Islands and the three other archipelagos have no haplotypes in common, whereas the latter three do share several haplotypes. Nevertheless, this highly disjunct haplotype distribution does not entail a phylogeographic break separating the haplotypes of both areas in two reciprocally monophyletic groups. This remarkable geographic and phylogenetic structuring may be explained by assuming that T. striatus colonized the Macaronesian archipelagos in periods when sea levels were lower (and/or volcanic activity was higher), so that seamounts peaked above sea level and could act as stepping-stones. Yet, after the last glacial period seamounts submerged, thus preventing further stepping-stones mediated dispersal of T. striatus between the Cape Verde Islands and the other archipelagos, while not affecting dispersal among the latter because of their closer proximity and connectivity. Hence, these contrasting patterns of neutral genetic variation in T. striatus show that genetic structuring in planktonic developing species may be far more complex than is usually assumed.     

Understanding consistencies and gaps between desired forest futures: An analysis of visions from stakeholder groups in Sweden

Conflicting perspectives on forests has for a long time challenged forest policy development in Sweden. Disagreements about forest futures create intractable deadlocks when stakeholders talk past each other. The purpose of this study is to move beyond this situation through the application of participatory backcasting. By comparing visions of the future forest among stakeholder groups, we highlight contemporary trajectories and identify changes that were conceived as desirable. We worked with four groups: the Biomass and Bioenergy group, the Conservation group, the Sami Livelihood group and the Recreation and Rural Development group; in total representatives from 40 organizations participated in workshops articulating the groups’ visions. Our results show well-known tensions such as intrinsic versus instrumental values but also new ones concerning forests’ social values. Identified synergies include prioritization of rural development, new valued-added forest products and diversified forest management. The results may feed directly into forest policy processes facilitating the process and break current deadlocks.