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501.
We modeled a fishery's system with two types of fishermen, commercial and subsistence fishermen, who exploit the fish stock at the Amazonian floodplain lakes. In the first model, we combined the Lotka-Volterra equations with Verhulst's Logistic model, by inserting hydrological cycle oscillations. The second model was based on the equations proposed by Berryman, which reflect the predator's functional response in relation to the prey's population behavior, taking into account the hydrological cycle. In both models, commercial fishermen and local direct consumers (called riverside dwellers - riverines - in the model), were considered the only predators acting upon fishing stocks. Primary data were collected in 48 riverside homes throughout 2006. The total number of interviewees corresponds to 69.6% of the universe of homes in the community defined as study area. The riverines were the predators that showed capacity to eliminate the opponent predators (commercial fishermen). The best scenery obtained regarding the number of prey, was the one that showed only commercial fishermen in the region. On the other hand, the simulations show that the coexistence is possible among predators, and between predators and their prey. The seasonal model with functional response provides a better response in relation to the system's current situation and to the established modeling conditions than the Lotka-Volterra seasonal model. The seasonal model with functional response also showed a better response pattern in all scenarios, with oscillations taking place more gradually, both for variations associated with the flooding pulse and for relations between predators and prey. 相似文献
502.
Atmospheric polycyclic aromatic hydrocarbons in remote European and Atlantic sites located above the boundary mixing layer 总被引:1,自引:1,他引:0
Barend Leendert Van Drooge Pilar Fernández Joan O. Grimalt Evzen Stuchlík Carlos J. Torres García Emilio Cuevas 《Environmental science and pollution research international》2010,17(6):1207-1216
Background, aim and scope
Ambient air concentrations of polycyclic aromatic hydrocarbons (PAH) were determined at five elevated mountain sites on the European continent and the Atlantic Ocean. All sites can be considered remote background areas since they are situated above the timberline and they lack local emission sources of these compounds. 相似文献503.
Connecting today's climates to future climate analogs to facilitate movement of species under climate change
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Caitlin E. Littlefield Brad H. McRae Julia L. Michalak Joshua J. Lawler Carlos Carroll 《Conservation biology》2017,31(6):1397-1408
Increasing connectivity is an important strategy for facilitating species range shifts and maintaining biodiversity in the face of climate change. To date, however, few researchers have included future climate projections in efforts to prioritize areas for increasing connectivity. We identified key areas likely to facilitate climate‐induced species’ movement across western North America. Using historical climate data sets and future climate projections, we mapped potential species’ movement routes that link current climate conditions to analogous climate conditions in the future (i.e., future climate analogs) with a novel moving‐window analysis based on electrical circuit theory. In addition to tracing shifting climates, the approach accounted for landscape permeability and empirically derived species’ dispersal capabilities. We compared connectivity maps generated with our climate‐change‐informed approach with maps of connectivity based solely on the degree of human modification of the landscape. Including future climate projections in connectivity models substantially shifted and constrained priority areas for movement to a smaller proportion of the landscape than when climate projections were not considered. Potential movement, measured as current flow, decreased in all ecoregions when climate projections were included, particularly when dispersal was limited, which made climate analogs inaccessible. Many areas emerged as important for connectivity only when climate change was modeled in 2 time steps rather than in a single time step. Our results illustrate that movement routes needed to track changing climatic conditions may differ from those that connect present‐day landscapes. Incorporating future climate projections into connectivity modeling is an important step toward facilitating successful species movement and population persistence in a changing climate. 相似文献
504.
Sadia E. Ahmed Carlos M. Souza Jr. Júlia Riberio Robert M. Ewers 《Regional Environmental Change》2013,13(5):927-937
The Brazilian Amazon is a globally important ecosystem that is undergoing rapid development and land-use change. Roads are a key spatial determinant of land-use conversion and strongly influence the rates and patterns of habitat loss and represent a key component of models that attempt to predict the spatio-temporal patterns of Amazonian land-use change and the consequences of such changes. However, the spatio-temporal patterns of road network development are poorly understood and seldom quantified. Here, we used manually digitised satellite imagery at multiple temporal and spatial scales across the Brazilian Amazon to quantify and model the rate at which road networks are proliferating. We found that the road network grew by almost 17,000 km per year between 2004 and 2007. There was large spatial variation in road network density, with some municipalities having road densities as high as 0.5 km/km2, and road network growth rates were highest in municipalities with an intermediate road network density. Simulations indicated that road network development within municipalities follows a logistic growth pattern through time, with most of the development occurring within a 39-year time period. This time period is similar to those of other boom and bust development dynamics observed in the Brazilian Amazon. Understanding the temporal patterns of road development will aid the development of better predictive land-use change models for the Amazon, given the key importance of roads as a predictor of deforestation in many existing models. 相似文献
505.
506.
Juan Carlos Alonso Luis M. Bautista Javier A. Alonso 《Behavioral ecology and sociobiology》1997,40(6):401-408
We studied the behavior of 13 radiotagged cranes dispersing from a communal roost over days when they changed their main
daily foraging area between consecutive days during two winter seasons. Individuals went to a new foraging zone when on the
previous day their morning food intake had fallen below their mean morning food intake measured over the whole winter. Food
intake on the day before a change in foraging area was positively correlated with dominance rank. Dominant cranes changed
to new zones with higher numbers of birds and food density, while subordinate cranes went to new zones with lower numbers
of birds. As a result, all birds increased their food intake over that of the previous day. Dominant cranes remained more
faithful to their most preferred foraging zone, where they spent 69% of the mornings, while subordinate birds were more mobile,
switching among zones frequently. Dominant birds left the roost later than subordinate birds on the days they changed to a
new zone, which could be used to track the main departing flows. The results suggest that the dynamics that led to a truncated
phenotype-limited distribution were determined by social dominance and food abundance, with dominant cranes shifting to a
new zone to maintain their high intake levels and subordinates changing more frequently whenever their daily intake did not
reach the minimum metabolic requirements.
Received: 16 December 1996 / Accepted after revision: 22 February 1997 相似文献
507.
Carlos Molinet Edwin Niklitschek Carlos A. Moreno Alejandra Arévalo 《Marine Biology》2008,153(5):779-787
The transport of marine invertebrate larvae is strongly influenced by their distribution in the water column, which could
be affected by the biological features of the larvae and environmental variables. Larvae can modify their swimming behavior
throughout their planktonic cycle, thereby changing the observed distributional patterns. This ability, coupled with oceanographic
features, could induce landward or seaward transport. We studied the vertical distribution of C. concholepas larval stages in two differently stratified systems in Chilean inland seas; Refugio Channel (a strongly stratified channel,
where previously has been described as a frontal system) and Guaitecas (a gently stratified system). Combinations of 12–24 h
larval collection experiments were done simultaneously with fixed temperature and salinity profiles; meteorological data were
also obtained. The results suggest that both salinity and day period influence the C. concholepas distributional patterns in the water column. Early veliger and competent larvae are concentrated in different parts of the
water column, probably related to their transport capacities. The upper layer of the water column at the Refugio site, unlike
the Guaitecas site, showed a stratified regime, which could affect larval density and larval length between the two sites.
Finally, our results suggest that Refugio may be a sink habitat for C. concholepas. 相似文献
508.
509.
The Arribes del Duero area, in western Spain, at the border with Portugal, is suffering a drastic change in the landscape, as a response of the diminution of population. Traditional tasks related to agriculture have been abandoned, and heavy sheep farming on the area is provoking the impoverishment of soils. The effect derived from these actions is the disintegration of the terraces, which are one of the major attractions for tourists visiting the region. We propose that incentives for local people could help to develop those traditional labours to recover the landscape, together with the promotion of immigration of families with school-age children, could bring back the economy to the area. 相似文献
510.
Richard G. Allen Boyd Burnett William Kramber Justin Huntington Jeppe Kjaersgaard Ayse Kilic Carlos Kelly Ricardo Trezza 《Journal of the American Water Resources Association》2013,49(3):563-576
A remaining challenge to applying satellite‐based energy‐balance algorithms for operational estimation of evapotranspiration (ET) is the calibration of the energy‐balance model. Customized calibration for each image date is generally required to overcome biases associated with radiometric accuracy of the image, uncertainties in aerodynamic features of the landscape, background thermal conditions, and model assumptions. The CIMEC process (calibration using inverse modeling at extreme conditions) is an endpoint calibration procedure where near extreme conditions in the image are identified where the ET can be estimated and assigned. In the Mapping EvapoTranspiration at high Resolution with Internalized Calibration (METRIC?) energy‐balance model, two endpoints represent the dry and wet ends of the ET spectrum. Generally, user‐intervention is required to select locations in the image to produce best accuracy. To bring the METRIC and similar processes into the domain of less experienced operators, a consistent, reproducible, and dependable statistics‐based procedure is introduced where relationships between vegetation amount and surface temperature are used to identify a subpopulation of locations (pixels) in an image that may best represent the calibration endpoints. This article describes the background and logic for the statistical approach, how the statistics were developed, area of interest requirements and assumptions, adjustment for dry conditions in desert climates, and implementation in a common image processing environment (ERDAS Imagine). 相似文献