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Support Models (support + models)

Distribution by Scientific Domains
Life Sciences50%

Selected Abstracts

The Aquatic Conservation Strategy of the Northwest Forest Plan

CONSERVATION BIOLOGY, Issue 2 2006
GORDON H. REEVES
gestión de ecosistemas; gestión ribereña; modelos de soporte de decisiones; terrenos públicos Abstract:,Implemented in 1994, the Aquatic Conservation Strategy of the Northwest Forest Plan was designed to restore and maintain ecological processes for aquatic and riparian area conservation on federal lands in the western portion of the Pacific Northwest. We used decision support models to quantitatively evaluate changes in the condition of selected watersheds. In the approximately 10 years since strategy implementation, watershed condition scores changed modestly, but conditions improved in 64% of 250 sampled watersheds, declined in 28%, and remained relatively the same in 7%. Watersheds that had the largest declines included some where wildfires burned 30,60% of their area. The overall statistical distribution of the condition scores did not change significantly, however. Much of the increase in watershed condition was related to improved riparian conditions. The number of large trees (>51 cm diameter at breast height) increased 2,4%, and there were substantial reductions in tree harvest and other disturbances along streams. Whether such changes will translate into longer-term improvements in aquatic ecosystems across broader landscapes remains to be seen. Resumen:,Implementada en 1994, la Estrategia de Conservación Acuática del Plan Forestal del Noroeste fue diseñada para restaurar y mantener procesos ecológicos para la conservación de áreas acuáticas y ribereñas en terrenos federales en la porción occidental del Pacífico Noroeste (E.U.A.). Utilizamos modelos de soporte de decisiones para evaluar cuantitativamente los cambios en la condición de cuencas seleccionadas. En los casi 10 años desde la implementación de la estrategia, los valores de la condición de las cuencas cambiaron someramente, pero las condiciones mejoraron en 64% de las 250 cuencas muestreadas, declinaron en 28% y permanecieron relativamente iguales en 7%. Las cuencas con las mayores declinaciones incluyeron algunas en las que 30-60% de su superficie fue quemada por fuegos sin control. Sin embargo, la distribución espacial total de los valores no cambió significativamente. Buena parte del incremento en las condiciones de la cuenca se relacionó con el mejoramiento de las condiciones ribereñas. El número de árboles grandes (>51 cm diámetro a la altura del pecho) aumentó 2-4%, y hubo reducciones sustanciales en la cosecha de árboles y otras perturbaciones a lo largo de arroyos. Aun habrá que ver si tales cambios se traducirán en mejoramientos a largo plazo en los ecosistemas acuáticos en paisajes más extensos. [source]

Nutrient fluxes at the river basin scale.

HYDROLOGICAL PROCESSES, Issue 5 2001
II: the balance between data availability, model complexity
Abstract In order to model complex environmental systems, one needs to find a balance between the model complexity and the quality of the data available needed to run and validate the model. This paper describes a method to find this balance. Four models of different complexity were applied to describe the transfer of nitrogen and phosphorus from pollution sources to river outlets in two large European river basins (Rhine and Elbe). A comparison of the predictive capability of these four models tells us something about the added value of the added model complexity. We also quantified the errors in the data that were used to run and validate the models and analysed to what extent the model validation errors could be attributed to data errors, and to what extent to shortcomings of the model. We conclude that although the addition of more process description is interesting from a theoretical point of view, it does not necessarily improve the predictive capability. Although our analysis is based on an extensive pollution-sources,river-load database it appeared that the information content of this database was sufficient only to support models of a limited complexity. Our analysis also illustrates that for a proper justification of a model's degree of complexity one should compare the model to simplified versions of the model. Copyright © 2001 John Wiley & Sons, Ltd. [source]

A meta-analysis of serotonin metabolite 5-HIAA and antisocial behavior

AGGRESSIVE BEHAVIOR, Issue 4 2002
Todd M. Moore
Abstract During the past 25 years, researchers have examined the relationship between neurochemical variables and antisocial behavior in human adults, but none has been studied more intensely than the serotonin metabolite 5-hydroxyindoleacetic acid (5-HIAA). The goal of the current study was to employ meta-analytic procedures to quantitatively evaluate selected evidence on the relationship between 5-HIAA and antisocial behavior. It was expected that antisocial groups would show reduced cerebrospinal fluid 5-HIAA compared with non,antisocial groups. This study also aimed to assess moderators that could influence the relationship between 5-HIAA and antisociality. An electronic search and strict inclusion criteria identified 20 reports used in this meta-analysis. Results showed a significant overall mean effect size (ES = ,.45, P < .05) in the direction of lowered 5-HIAA in antisocial vs. non,antisocial groups. A significant moderating effect for age indicated that groups comprised of antisocial individuals younger than 30 years exhibited larger negative effect sizes (ES = ,1.37, P < .05) than groups with older subjects (ES = ,.31, P < .05). There were no moderating effects for gender, target of violence, history of suicide, and alcoholism. Age effects may help explain age-related declines in crime. The fact that effects did not differ based on other moderating variables supports models of reduced serotonin in antisocial individuals, regardless of type of crime or psychiatric problems. Aggr. Behav. 28:299,316, 2002. © 2002 Wiley-Liss, Inc. [source]

Genomic islands of speciation or genomic islands and speciation?

MOLECULAR ECOLOGY, Issue 5 2010
THOMAS L. TURNER
Populations of the malaria mosquito, Anopheles gambiae, are comprised of at least two reproductively isolated, sympatric populations. In this issue, White et al. (2010) use extensive sampling, high-density tiling microarrays, and an updated reference genome to clarify and expand our knowledge of genomic differentiation between these populations. It is now clear that DNA near the centromeres of all three chromosomes are in near-perfect disequilibrium with each other. This is in stark contrast to the remaining 97% of the assembled genome, where fixed differences between populations have not been found, and many polymorphisms are shared. This pattern, coupled with direct evidence of hybridization in nature, supports models of "mosaic" speciation, where ongoing hybridization homogenizes variation in most of the genome while loci under strong selection remain in disequilibrium with each other. However, unambiguously demonstrating that selection maintains the association of these pericentric "speciation islands" in the face of gene flow is difficult. Low recombination at all three loci complicates the issue, and increases the probability that selection unrelated to the speciation process alters patterns of variation in these loci. Here, we discuss these different scenarios in light of this new data. [source]