Search results for "Spatial Ecology"
showing 10 items of 191 documents
Noise Induced Phenomena in Lotka-Volterra Systems
2003
We study the time evolution of two ecosystems in the presence of external noise and climatic periodical forcing by a generalized Lotka-Volterra (LV) model. In the first ecosystem, composed by two competing species, we find noise induced phenomena such as: (i) quasi deterministic oscillations, (ii) stochastic resonance, (iii) noise delayed extinction and (iv) spatial patterns. In the second ecosystem, composed by three interacting species (one predator and two preys), using a discrete model of the LV equations we find that the time evolution of the spatial patterns is strongly dependent on the initial conditions of the three species.
The implications of stand composition, age and spatial patterns of forest regions with different ownership type for management optimisation in northe…
2015
Abstract Forests with different ownership type often form complex mosaics of stands, thus adding new challenges to the spatial planning of sustainable management in forested landscapes. This study attempted to analyse the spatial patterns and age structures of forest regions with different ownership type and to formulate suggestions for the optimisation of tactical planning of forest management planning by addressing ecological functionality at the landscape level. We hypothesised that structure of forests of various ownership groups differs significantly. National forest inventory data from 2011 was used in this study to compare spatial patterns of forest stands and clearcuts, as well as f…
Linking seed dispersal and genetic structure of trees: a biogeographical approach
2009
Aim Natural and human-induced differences in frugivore assemblages can influence the seed dispersal distances of trees. An important issue in seed dispersal systems is to understand whether differences in seed dispersal distances also affect the genetic structure of mature trees. One possible approach to test for a relationship between seed dispersal and the genetic structure of mature trees is to compare the genetic structure of two closely related tree species between two biogeographical regions that differ in frugivore assemblages and seed dispersal distances. Previous studies on two Commiphora species revealed that Commiphora guillauminii in Madagascar has a much lower seed dispersal d…
Morphology and genetics reveal an intriguing pattern of differentiation at a very small geographic scale in a bird species, the forest thrush Turdus …
2014
12 pages; International audience; Mobile organisms are expected to show population differentiation only over fairly large geographical distances. However, there is growing evidence of discrepancy between dispersal potential and realized gene flow. Here we report an intriguing pattern of differentiation at a very small spatial scale in the forest thrush (Turdus lherminieri), a bird species endemic to the Lesser Antilles. Analysis of 331 individuals from 17 sampling sites distributed over three islands revealed a clear morphological and genetic differentiation between these islands isolated by 40-50 km. More surprisingly, we found that the phenotypic divergence between the two geographic zone…
Spatial Patterns of Regional Income Inequality Then and Now
2018
In this chapter an important element characteristic of territorial inequality is examined: the presence of geographical patterns, that is, the grouping of neighbouring regions into clusters of wealth or poverty. The descriptive evidence provided by the maps is supplemented with spatial autocorrelation statistics to test for the presence of spatial clustering. The analysis aims to identify when exactly the geographical patterns that characterize regional inequality in Spain today took shape. Then some hypotheses as to the causes are established. Finally, the chapter analyses whether the clusters of poor or rich regions continue uninterrupted beyond national borders to include regions of Port…
Assessment of inputs to land surface processes models derived from hyperspectral multiangular data
2002
Global Models of the Earth - Atmosphere System describe the role of the terrestrial biosphere using increasingly complex Land Surface Models (LSM). These models mimic the exchange of energy, water and carbon between the land and the atmosphere, with emphasis on the role of terrestrial vegetation. Literature shows a clear trend towards fully interactive LSM-s, i.e. accounting for the dynamic response of vegetation to weather and climate. The latter may not be limited to biomass accumulation and address slower changes in vegetation type and composition. Improving the performance of such models require addressing two broad questions: Can we measure vegetation properties with the accuracy requi…
ASSESSMENT OF ECOSYSTEM SERVICES FOR PLANNING OF GREEN INFRASTRUCTURE AT THE REGIONAL LEVEL
2019
Ecosystem services (ES) are defined as the benefits that human beings derive from ecosystem functions. Assessment and mapping of these benefits are crucial for sustainable environmental planning and future natural capital. Green infrastructure (GI) is natural or semi-natural territories that provide wide range of ES. Human affected ecosystems tend to fail to provide certain sets of ES due to the trade-offs among those services, which could be mitigated through implementation of GI. Mapping of ES, as well as assessing the interactions among various ES and analysing their supply potential’s cold/hot spots considerably enhances and substantiates the planning process of GI, particularly at the …
Spatial autocorrelation and the selection of simultaneous autoregressive models
2007
Aim Spatial autocorrelation is a frequent phenomenon in ecological data and can affect estimates of model coefficients and inference from statistical models. Here, we test the performance of three different simultaneous autoregressive (SAR) model types (spatial error = SAR err , lagged = SAR lag and mixed = SAR mix ) and common ordinary least squares (OLS) regression when accounting for spatial autocorrelation in species distribution data using four artificial data sets with known (but different) spatial autocorrelation structures. Methods We evaluate the performance of SAR models by examining spatial patterns in model residuals (with correlograms and residual maps), by comparing model para…
Scale-related patterns in the spatial and environmental components of stream macroinvertebrate assemblage variation
2007
Aim We examined the relative contributions of spatial gradients and local environmental conditions to macroinvertebrate assemblages of boreal headwater streams at three hierarchical extents: bioregion, ecoregion and drainage system. We also aimed to identify the environmental variables most strongly related to assemblage structure at each study scale, and to assess how the importance of these variables is related to regional context and spatial structuring at different scales. Location Northern Finland (62–68° N, 25–32° E). Methods Variation in macroinvertebrate data was partitioned using partial canonical correspondence analysis into components explained by spatial variables (nine terms…
Poor prenatal care in an urban area: a geographic analysis.
2009
Abstract Poor prenatal care increases the risk of having a premature or low-birth-weight infant. Rates of poor prenatal care vary spatially, influenced not only by individual mothers’ characteristics but also by social neighborhood context and proximity to healthcare services. The aim of this article is to identify and map the spatial patterns of prenatal care and to analyze the spatial and social origins of such inequalities. Our study concerns 30,338 individuals who received antenatal care in a highly urbanized French district: Seine-Saint-Denis. The geographical distribution of poor prenatal care is revealed by exploratory spatial data analysis tools. This spatial clustering is related t…