Search results for "Spatial heterogeneity"
showing 10 items of 71 documents
Proximal-sensing-powered modelling of energy-water fluxes in a vineyard: A spatial resolution analysis
2021
Spatial resolution is a key parameter in energy–water surface flux modelling. In this research, scale effects are analyzed on fluxes modelled with the FEST-EWB model, by upscaling both its inputs and outputs separately. The main questions are: (a) if high-resolution remote sensing images are necessary to accurately model a heterogeneous area; and (b) whether and to what extent low-resolution modelling provides worse/better results than the upscaled results of high-resolution modelling. The study area is an experimental vineyard field where proximal sensing images were obtained by an airborne platform and verification fluxes were measured via a flux tower. Modelled fluxes are in line with th…
Determinants of the distribution of nitrogen-cycling microbial communities at the landscape-scale
2010
Little information is available regarding the landscape-scale distribution of microbial communities and its environmental determinants. However, a landscape perspective is needed to understand the relative importance of local and regional factors and land management for the microbial communities. In this manuscript, we investigated the distribution of functional microbial communities involved in N-cycling and of the total bacterial and crenarchaeal communities over 107 sites using a grid with a 16 km lag distance within Burgundy, a 31 500 km2 region in France. After quantifying the abundances of the total bacterial, crenarchaeal, nitrate-reducing, denitrifying and ammonia-oxidizing communit…
Plankton Ecology and Diversity
2010
In this chapter we describe plankton responses induced by fluctuating hydrology and eutrophication process in the semi-arid TDNP wetland. We have followed the planktonic community since 1992, at seasonal and interannual scales, covering as well the spatial heterogeneity of the wetland. The studied planktonic components were bacterioplankton, autotrophic picoplankton, nano and microphytoplankton and zooplankton, including ciliates. Plankton has been studied in terms of species composition (diversity), functional groups, spatial heterogeneity, population dynamics. The present data from this wetland allow us to determine which factors (resources and conditions) are relevant for each group and …
Competition for breeding sites and site-dependent population regulation in a highly colonial seabird, the common guillemot Uria aalge
2004
Summary 1. The hypothesis of site-dependent population regulation predicts that birds utilize available nesting sites in a pre-emptive (ideal despotic) manner, leading to density dependence in heterogeneous habitats as poorer sites are used at higher population densities. At small population sizes adaptive site choice protects populations against fluctuations (the buffer effect). 2. Common guillemots Uria aalge (Pontoppidan) breed at high density on sea-cliffs. The population breeding on the Isle of May, Scotland increased by 60% between 1981 and 2000. A good nest-site is a prerequisite for successful breeding and there is much competition for the best sites. Throughout this period, site us…
Population genetic structure of aposematic alpine wood tiger moths (Parasemia plantaginis)
2012
Alpine landscape with natural fragmentation restricts gene flow among populations and causes spatio-genetic structuring (high genetic differentiation) in species living there. Consequently, alpine habitat fragmentation and dispersal barriers should make isolated populations such as wood tiger moth (Parasemia plantaginis) populations prone to lose genetic diversity by local adaptation and fixation of fittest phenotype in each local population. This species is also known to be aposematic. Yellow colour on the males’ hind wings in wood tiger moth is presumed to work more efficiently against visual hunting predators due to increased conspicuousness. In addition, in field experiments with wood t…
Effect of restoration on zooplankton community in a permanent interdunal pond
2013
Restoration projects in wetlands are becoming increasingly frequent to recover or to create new aquatic ecosystems, after the significant impact and high degradation they have undergone. In the present study, we focused on the changes in the zooplankton community in a permanent peridunal pond where a restoration was carried out in order to increase its surface as a main objective. For this purpose, the community was compared before and after the restoration (15 years before, the year after and between 3 and 6 years later). Significant changes in environmental variables were observed after pond restoration: chlorophyll a concentration decreased and dissolved oxygen increased. Substantial mod…
Land surface temperature representativeness in a heterogeneous area through a distributed energy-water balance model and remote sensing data
2010
Land surface temperature is the link between soil-vegetation-atmosphere fluxes and soil water content through the energy water balance. This paper analyses the representativeness of land surface temperature (LST) for a distributed hydrological water balance model (FEST-EWB) using LST from AHS (airborne hyperspectral scanner), with a spatial resolution between 2–4 m, LST from MODIS, with a spatial resolution of 1000 m, and thermal infrared radiometric ground measurements that are compared with the representative equilibrium temperature that closes the energy balance equation in the distributed hydrological model. <br><br> Diurnal and nocturnal images are analyzed due to the non s…
The role of regional competitiveness in shaping the heterogeneous impact of the Great Recession
2020
This paper assesses the employment resilience of 202 European regions to the Great Recession by investigating the role of regional competitiveness. By using the regional shift component derived from a multiple bases shift–share analysis of employment change as a measure of regional endogenous employment growth, we show that pre‐crisis regional competitiveness determinants are associated with positive performances during the crisis period. However, the variables considered explain well the different vulnerability of the economies, but less convincingly the ability to recover. Taking into account the spatial interactions among regions, results are confirmed and allow us to identify spillover …
Hétérogénéité spatiale : principes et méthodes
2004
Spatial Heterogeneity : Principles and Methods This article has a dual purpose . First , it describes the main econometric specifications which can be used to represent spatial heterogeneity , reflected in an instability of parameters in space and / or a heteroscedasticity of error terms . Only the specifications valid in cross-section are examined . Second , it explains the links between spatial heterogeneity and autocorrelation , the other major feature of localised data , defined by the absence of independence between geographical observations . In particular , we look at the extent to which traditional tests of heteroscedasticity or instability need to be amended to take account of spat…
The importance of phytoplankton production for carbon budgets in a semiarid floodplain wetland
2011
Phytoplankton production (PP) in wetlands is not measured as often as that of macrophytes. A three year-study during a period of sustained high flooding was undertaken in a central Spanish floodplain wetland (Las Tablas de Daimiel National Park) to determine net PP, its spatial heterogeneity and controlling factors, and compare it with primary production in macrophyte communities. This enabled us to estimate carbon budgets for each community. All PP variables showed high spatial and temporal variability among sites, resulting in low coherence even when flooding connected all sites. Net PP corresponded to 25- 36% of submerged plant production and 3-10% of helophyte production. Net PP was con…