Effects of landscape context on herbivory and parasitism at different spatial scales

Local community structure and interactions have been shown to depend partly on landscape context. In this paper we tested the hypothesis that the spatial scale experienced by an organism depends on its trophic level. We analyzed plant-herbivore and herbivore-parasitoid interactions in 15 agricultural landscapes differing in structural complexity using the rape pollen beetle (Meligethes aeneus), an important pest on oilseed rape (Brassica napus), and its parasitoids. In the very center of each landscape a patch of potted rape plants was placed in a grassy field margin strip for standardized measurement. Percent non-crop area of landscapes was negatively related to plant damage caused by herbivory and positively to the herbivores’ larval mortality resulting from parasitism. In a geographic scale analysis, we quantified the structure of the 15 landscapes for eight circular sectors ranging from 0.5 to 6 km diameter. Correlations between parasitism and non-crop areas as well as between herbivory and non-crop area were strongest at a scale of 1.5 km, thereby not supporting the view that higher trophic levels experience the world at a larger spatial scale. However, the predictive power of non-crop area changed only slightly for herbivory, but greatly with respect to parasitism as scales from 0.5 to 1.5 km and from 1.5 to 6 km diameter increased. Furthermore, the effect of non-crop area tended to be stronger in parasitism than herbivory suggesting a greater effect of changes in landscape context on parasitoids. This is in support of the general idea that higher trophic levels should be more susceptible to disturbance. (Thies, C., Steffan-Dewenter, I. and Tscharntke, T. 2003. Effects of landscape context on herbivory and parasitism at different spatial scales. – Oikos 101: 18–25.

Flood-plain research at different spatial scales

This paper presents the main philosophy, aims and some preliminary results of the joint Rumanian—Hungarian ecological project carricd out in the terrestrial habitats of River Murc$/Maros flood plains. The studies, scoping different spatial scalcs from the microcosms to the regions, have revealed the specificities of plant communities in very small patches (ant mounds), the role of an ant supercolony in structuring spatial pattern of the whole ant community, the differential effect of exogenous factors on the habitat selection of plant and different invertebrate assemblages, the restricted potential corridor function of the terrestrial habitats along River Mure?/Maros, and the scale-dependence of the faunal and community similarities

Estimating productivity of water at different spatial scales using simulation modeling

Water resources / Productivity / Simulation models / Water scarcity / Water supply / Water balance / Performance indexes / Indicators / River basins / Cropping systems / Crop yield / Cotton / Hydrology / Economic analysis

The fractal dimension of star-forming regions at different spatial scales in M33

We study the distribution of stars, HII regions, molecular gas, and individual giant molecular clouds in M33 over a wide range of spatial scales. The clustering strength of these components is systematically estimated through the fractal dimension. We find scale-free behavior at small spatial scales and a transition to a larger correlation dimension (consistent with a nearly uniform distribution) at larger scales. The transition region lies in the range 500-1000 pc. This transition defines a characteristic size that separates the regime of small-scale turbulent motion from that of large-scale galactic dynamics. At small spatial scales, bright young stars and molecular gas are distributed with nearly the same three-dimensional fractal dimension (Df <= 1.9), whereas fainter stars and HII regions exhibit higher values (Df = 2.2-2.5). Our results indicate that the interstellar medium in M33 is on average more fragmented and irregular than in the Milky Way.Comment: 18 pages including 4 figures. Accepted for publication in Ap

Valuation of environmental public goods and services at different spatial scales: a review

To manage environmental problems in an adequate way, it is essential to take different spatial scales into consideration. As a tool for decision making, it would be beneficial if valuation methods take spatial scales into account as well. In this article, we review the valuation literature with regard to the spatial scales of environmental public goods and services to which the contingent valuation method, hedonic pricing method, and travel cost method have been applied in the past. We classified 117 environmental case studies to the local, landscape/watershed, regional, and global scales. These case studies cover a broad range of environmental goods and services, such as green space in a city, air quality, rivers, natural areas, and a stable climate system. Additionally, we took into account the year of publication of the case studies. Our results show that the majority of the environmental case studies are related to the local and landscape/watershed scales. However, the number of case studies on the regional and global scales has been increasing in recent years. This article argues that such a change in spatial scale calls for a debate on scaling issues in the field of environmental valuation.

Exploring occupants\u27 impact at different spatial scales

Buildings\u27 users have widely been accepted as a source of uncertainty in building energy performance predictions. However, it is not evident that the diversity of occupants\u27 presence and behavior at the building level is as important as at the room level. The questions are: How should occupants be modeled at different spatial scales? At the various scales of interest, how much difference does it make if: (1) industry standard assumptions or a dynamic occupant modeling approach is used in a simulation-based analysis, and (2) probabilistic or deterministic models are used for the dynamic modeling of occupants? This paper explores the reliability of building energy predictions and the ability to quantify uncertainty associated with occupant modeling at different scales. To this end, the impacts of occupancy and occupants\u27 use of lighting and window shades on the predicted building lighting energy performance at the room and building level are studied. The simulation results showed that the inter-occupant variation at larger scales is not as important as at the room level. At larger scales (about 100 offices), the rule-base model, custom schedule model, and stochastic lighting use model compared closely for predicting mean annual lighting energy use

Dispersal and population structure at different spatial scales in the subterranean rodent Ctenomys australis

This study was funded by grants from Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET, PIP5838), Agencia de Promoción Científica y Tecnológica de la Argentina (PICTO1-423, BID-1728/OC-AR), and the programme ECOS-Sud France/Argentina (A05B01).Background: The population genetic structure of subterranean rodent species is strongly affected by demographic (e.g. rates of dispersal and social structure) and stochastic factors (e.g. random genetic drift among subpopulations and habitat fragmentation). In particular, gene flow estimates at different spatial scales are essential to understand genetic differentiation among populations of a species living in a highly fragmented landscape. Ctenomys australis (the sand dune tuco-tuco) is a territorial subterranean rodent that inhabits a relatively secure, permanently sealed burrow system, occurring in sand dune habitats on the coastal landscape in the south-east of Buenos Aires province, Argentina. Currently, this habitat is threatened by urban development and forestry and, therefore, the survival of this endemic species is at risk. Here, we assess population genetic structure and patterns of dispersal among individuals of this species at different spatial scales using 8 polymorphic microsatellite loci. Furthermore, we evaluate the relative importance of sex and habitat configuration in modulating the dispersal patterns at these geographical scales. Results: Our results show that dispersal in C. australis is not restricted at regional spatial scales (similar to 4 km). Assignment tests revealed significant population substructure within the study area, providing support for the presence of two subpopulations from three original sampling sites. Finally, male-biased dispersal was found in the Western side of our study area, but in the Eastern side no apparent philopatric pattern was found, suggesting that in a more continuous habitat males might move longer distances than females. Conclusions: Overall, the assignment-based approaches were able to detect population substructure at fine geographical scales. Additionally, the maintenance of a significant genetic structure at regional (similar to 4 km) and small (less than 1 km) spatial scales despite apparently moderate to high levels of gene flow between local sampling sites could not be explained simply by the linear distance among them. On the whole, our results support the hypothesis that males disperse more frequently than females; however they do not provide support for strict philopatry within females.Publisher PDFPeer reviewe

Arthropods as surrogates of diversity at different spatial scales

Copyright © 2010 Elsevier Ltd. All rights reserved.This study evaluates the effectiveness of taxonomic, colonization and trophic groups of arthropods from native forests of the Azores archipelago as surrogates of the diversity of other arthropod groups and of the remaining arthropods. Consistency in the performance of surrogates was tested across three spatial scales and using two measures of diversity. Pitfall and beating samples from 109 transects, 18 forest fragments and seven islands were analysed. The results showed that Araneae, Hemiptera and small orders taxonomic groups; native, endemic and introduced colonization groups; and the herbivores trophic group were consistent surrogates of the remaining diversity across the three spatial scales analysed, for both alpha and dissimilarity diversities. However, none of the subsets considered was significantly related with all of the other subsets at any of the three spatial scales. The effectiveness of surrogacy was dependent on the spatial level considered, and groups behaved inconsistently depending on the measure of diversity used. The value of a group as a diversity surrogate should be evaluated for a study area for a given spatial scale and diversity measure, in accordance with the scale and measure that will be used for biodiversity assessments and monitoring programs in that area

Arthropods as surrogates of diversity at different spatial scales

Copyright © 2010 Elsevier Ltd. All rights reserved.This study evaluates the effectiveness of taxonomic, colonization and trophic groups of arthropods from native forests of the Azores archipelago as surrogates of the diversity of other arthropod groups and of the remaining arthropods. Consistency in the performance of surrogates was tested across three spatial scales and using two measures of diversity. Pitfall and beating samples from 109 transects, 18 forest fragments and seven islands were analysed. The results showed that Araneae, Hemiptera and small orders taxonomic groups; native, endemic and introduced colonization groups; and the herbivores trophic group were consistent surrogates of the remaining diversity across the three spatial scales analysed, for both alpha and dissimilarity diversities. However, none of the subsets considered was significantly related with all of the other subsets at any of the three spatial scales. The effectiveness of surrogacy was dependent on the spatial level considered, and groups behaved inconsistently depending on the measure of diversity used. The value of a group as a diversity surrogate should be evaluated for a study area for a given spatial scale and diversity measure, in accordance with the scale and measure that will be used for biodiversity assessments and monitoring programs in that area

Species' responses along environmental gradients on different spatial scales

The abundance of species on Earth varies greatly - while some occur all over the globe, others can only exist in very distinct regions. Trying to explain the reasoning behind the temporal and spatial variation in the commonness and rarity of species has a long history in ecology and yet, many pieces are still missing to complete the puzzle. This thesis investigates species' responses to changing environmental gradients and asks in how far niche characteristics can be used to predict species' range sizes at different spatial scales. We worked with herbaceous species from semi-natural grasslands as well as deciduous forests, focusing especially on their reactions to abiotic conditions (soil pH, nutrients and light). We could show that the breadth of resources used by species (especially regarding soil pH), as well as their tolerance limits, are reliable predictors for their rarity and commonness across different spatial scales. Furthermore, we believe that niche properties can provide guidelines for conservation decisions, especially concerning the selection of suitable habitats for the reintroduction of species. This is a particularly important task to preserve the worldâ s biodiversity in todayâ s ever changing environments