| 1. |
- Öckinger, Erik, et al.
(författare)
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Landscape matrix modifies richness of plants and insects in grassland fragments
- 2012
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Ingår i: Ecography. - : Wiley. - 0906-7590 .- 1600-0587. ; 35:3, s. 259-267
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Tidskriftsartikel (refereegranskat)abstract
- There is an increasing awareness that not only area and isolation, but also the characteristics of the landscape surrounding habitat patches influence population persistence and species diversity in fragmented landscapes. In this study, we examine the effects of grassland fragmentation and land use in the landscape matrix (on a 2 km scale) on species richness of plants, butterflies, bees and hoverflies. These organisms were studied in replicated remnant patches of different sizes and isolation, embedded in landscapes dominated either by forest, arable land or a mix of these. We found positive effects of patch area on species richness of the three insect taxa, but not of plants. Isolation had a negative effect only on hoverflies. Matrix type had contrasting effects on the studied taxa. Species richness of plants and butterflies was lowest in patches in landscapes dominated by arable land and highest in forest-dominated landscapes. For hoverflies, the negative effect of small patch area was strongest in forest-dominated landscapes, and there was a similar non-significant trend for bees. Our study shows the importance of considering matrix characteristics when studying responses to habitat fragmentation. Differences in matrix response among organism groups probably impinge on differing mechanisms. A forest matrix is likely to provide additional resources for butterflies but either constitute a barrier to dispersal or deprive resources as compared to an arable matrix for hoverflies. Enhanced plant diversity in grassland patches embedded in forested landscapes can be explained by habitat generalists more easily invading these patches, or by an unpaid extinction debt in these landscapes.
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| 2. |
- Andersson, Erik, et al.
(författare)
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A social-ecological analysis of ecosystem services in two different farming systems
- 2015
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Ingår i: Ambio. - : Springer Science and Business Media LLC. - 0044-7447 .- 1654-7209. ; 44, s. 102-112
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Tidskriftsartikel (refereegranskat)abstract
- In this exploratory study we use existing in situ qualitative and quantitative data on biophysical and social indicators to compare two contrasting Swedish farming systems (low intensity and high intensity) with regard to ecosystem service supply and demand of a broad suite of services. We show that the value (demand) placed on a service is not necessarily connected to the quantity (supply) of the service, most clearly shown for the services recreation, biodiversity, esthetic experience, identity, and cultural heritage. To better capture this complexity we argue for the need to develop portfolios of indicators for different ecosystem services and to further investigate the different aspects of supply and demand. The study indicates that available data are often ill-suited to answer questions about local delivery of services. If ecosystem services are to be included in policy, planning, and management, census data need to be formatted and scaled appropriately.
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| 3. |
- Andersson, Erik, et al.
(författare)
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Species Richness and Assemblages in Landscapes of Different Farming Intensity - Time to Revise Conservation Strategies?
- 2014
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 9:10, s. e109816-
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Tidskriftsartikel (refereegranskat)abstract
- Worldwide conservation goals to protect biodiversity emphasize the need to rethink which objectives are most suitable for different landscapes. Comparing two different Swedish farming landscapes, we used survey data on birds and vascular plants to test whether landscapes with large, intensively managed farms had lower richness and diversity of the two taxa than landscapes with less intensively managed small farms, and if they differed in species composition. Landscapes with large intensively managed farms did not have lower richness than smaller low intensively managed farms. The landscape types were also similar in that they had few red listed species, normally targeted in conservation. Differences in species composition demonstrate that by having both types of agricultural landscapes regional diversity is increased, which is seldom captured in the objectives for agro-environmental policies. Thus we argue that focus on species richness or red listed species would miss the actual diversity found in the two landscape types. Biodiversity conservation, especially in production landscapes, would therefore benefit from a hierarchy of local to regional objectives with explicit targets in terms of which aspects of biodiversity to focus on.
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| 4. |
- Augier, Pierre, et al.
(författare)
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A New Formulation of the Spectral Energy Budget of the Atmosphere, with Application to Two High-Resolution General Circulation Models
- 2013
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Ingår i: Journal of the Atmospheric Sciences. - 0022-4928 .- 1520-0469. ; 70:7, s. 2293-2308
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Tidskriftsartikel (refereegranskat)abstract
- A new formulation of the spectral energy budget of kinetic and available potential energies of the atmosphere is derived, with spherical harmonics as base functions. Compared to previous formulations, there are three main improvements: (i) the topography is taken into account, (ii) the exact three-dimensional advection terms are considered, and (iii) the vertical flux is separated from the energy transfer between different spherical harmonics. Using this formulation, results from two different high-resolution GCMs are analyzed: the Atmospheric GCM for the Earth Simulator (AFES) T639L24 and the European Centre for Medium-Range Weather Forecasts (ECMWF) Integrated Forecast System (IFS) T1279L91. The spectral fluxes show that the AFES, which reproduces quite realistic horizontal spectra with a k(-5/3) inertial range at the mesoscales, simulates a strong downscale energy cascade. In contrast, neither the k(-5/3) vertically integrated spectra nor the downscale energy cascade are produced by the ECMWF IFS.
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| 5. |
- Augier, Pierre, et al.
(författare)
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Shallow water wave turbulence
- 2019
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Ingår i: Journal of Fluid Mechanics. - : Cambridge University Press. - 0022-1120 .- 1469-7645. ; 874, s. 1169-1196
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Tidskriftsartikel (refereegranskat)abstract
- The dynamics of irrotational shallow water wave turbulence forced in large scales and dissipated at small scales is investigated. First, we derive the shallow water analogue of the `four-fifths law' of Kolmogorov turbulence for a third order structure function involving velocity and displacement increments. Using this relation and assuming that the flow is dominated by shocks we develop a simple model predicting that the shock amplitude scales as (ϵd)1/3, where ϵ is the mean dissipation rate and d the mean distance between the shocks, and that the pth order displacement and velocity structure functions scale as (ϵd)p/3r/d, where r is the separation. Then we carry out a series of forced simulations with resolutions up to 76802, varying the Froude number, Ff=ϵ1/3/ckf1/3, where kf is the forcing wave number and c is the wave speed. In all simulations a stationary state is reached in which there is a constant spectral energy flux and equipartition between kinetic and potential energy in the constant flux range. The third order structure function relation is satisfied with a high degree of accuracy. Mean energy is found to scale as E∼√(ϵc/kf), and is also dependent on resolution, indicating that shallow water wave turbulence does not fit into the paradigm of a Richardson-Kolmogorov cascade. In all simulations shocks develop, displayed as long thin bands of negative divergence in flow visualisations. The mean distance between the shocks is found to scale as d∼Ff1/2/kf. Structure functions of second and higher order are found to scale in good agreement with the model. We conclude that in the weak limit, Ff→0, shocks will become denser and weaker and finally disappear for a finite Reynolds number. On the other hand, for a given Ff, no matter how small, shocks will prevail if the Reynolds number is sufficiently large.
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| 6. |
- Bommarco, Riccardo, et al.
(författare)
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Extinction debt for plants and flower-visiting insects in landscapes with contrasting land use history
- 2014
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Ingår i: Diversity & distributions. - : Wiley. - 1366-9516 .- 1472-4642. ; 20:5, s. 591-599
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Tidskriftsartikel (refereegranskat)abstract
- Aim Species are lost world-wide because of habitat destruction and fragmentation. Impacted communities can exhibit transient dynamics in response to such environmental changes, where slow extinctions and immigration delay the arrival to a new equilibrium. Life history traits such as generation time, resource use and dispersal capacity, as well as landscape history can be expected to affect possible extinction debt, but few have examined this for multiple taxa in the same study and particularly so for arthropods. The aim was to assess under which current and historical land use circumstances an extinction debt occurs for vascular plants and three insect taxa. Location South-eastern Sweden. Method We sampled current species richness of habitat specialist and generalist butterflies, bees, hoverflies, and vascular plants in 45 dry to mesic semi-natural grassland fragments of various size and degree of connectivity, and situated in landscapes with contrasting land use conversion history. Habitat loss was estimated in each landscape by comparing modern maps to ~45year old digitized aerial photographs. An extinction debt can be assumed if historical habitat size and connectivity better explain current species distribution than current habitat variables do. Results Bees responded rapidly to habitat loss possibly as a result of their primary nesting resource being destroyed. Interestingly, species richness of specialist plants was best explained by historical habitat connectivity, richness of hoverflies by historical habitat area, and richness of butterflies by both historical habitat area and connectivity, indicating extinction debt for these taxa. Habitat generalist butterflies and hoverflies, but not plants and bees, exhibited extinction debt mainly in relation to habitat area. No effect of landscape type was found on the observed extinction debt. Main conclusions Slow extinctions of persistent and long-lived plants might explain extinction debt for both plants and herbivorous insects linked to these plants.
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| 7. |
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| 8. |
- Brethouwer, Gert, et al.
(författare)
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Numerical simulations of particle dispersion in stratified flows
- 2009
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Ingår i: ADVANCES IN TURBULENCE XII. - Berlin, Heidelberg : Springer Berlin Heidelberg. ; , s. 51-55
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Konferensbidrag (refereegranskat)abstract
- Several researchers have examined the vertical dispersion of fluid particles in stratified flows to obtain a better understanding of mixing in geophysical flows. Pearson et al. [5] used a Langevin model to predict that the mean square of vertical fluid particle displacements reaches a plateau with in stationary stratified flows. Here, w is the vertical velocity fluctuation and N is the Brunt-Väisälä frequency. At long times, they predict that, when molecular diffusion alters the particle density. Venayagamoorthy and Stretch [6] examined the role of the changing particle density on vertical dispersion in DNS of decaying stratified turbulence and observed that after one eddy turnover time diabatic dispersion dominated. Van Aartrijk et al. [1] studied particle dispersion in DNS of stationary strat-ified turbulence and observed a plateau with. However, some of the DNS showed that at long times caused by density changes of fluid particles by molecular diffusion.
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| 9. |
- Brethouwer, Geert, et al.
(författare)
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Numerical study of vertical dispersion by stratified turbulence
- 2009
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Ingår i: Journal of Fluid Mechanics. - 0022-1120 .- 1469-7645. ; 631, s. 149-163
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Tidskriftsartikel (refereegranskat)abstract
- Numerical simulations are carried Out to investigate vertical fluid particle dispersion in uniformly stratified stationary turbulent flows. The results are compared with the analysis of Lindborg & Brethouwer (J. Fluid Mech., vol. 614, 2008, pp. 303-314), who derived long- and short-time relations for the mean square vertical displacement of fluid particles. Several direct numerical simulations (DNSs) with different degrees of stratification and different buoyancy Reynolds numbers are carried out to test the long-time relation = 2 epsilon(P)t/N-2. Here, epsilon(P) is the mean dissipation of turbulent potential energy; N is the Brunt-Vaisala frequency; and t is time. The DNSs show good agreement with this relation, with a weak dependence on the buoyancy Reynolds number. Simulations with hyperviscosity are carried out to test the relation = (1 + pi C-PL)2 epsilon(P)t/N-2, which should be valid for shorter time scales in the range N-1 << t << T, where T is the turbulent eddy turnover time. The results of the hyperviscosity simulations come closer to this prediction with C-PL about 3 with increasing stratification. However, even in the simulation with the strongest stratification the growth of is somewhat slower than linear in this regime. Based on the simulation results it is argued that the time scale determining the evolution Of is the eddy turnover time, T, rather than the buoyancy time scale N-1, as suggested in previous studies. The simulation results are also consistent with the prediction of Lindborg & Brethouwer (2008) that the nearly flat plateau Of observed at t similar to T should scale as 4E(P)/N-2, where E-P is the mean turbulent potential energy.
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| 10. |
- Brethouwer, Geert, et al.
(författare)
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Particle Diffusion in Stably Stratified Flows
- 2010
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Ingår i: PROGRESS IN TURBULENCE III. - Berlin, Heidelberg : Springer Berlin Heidelberg. - 9783642022241 ; , s. 163-166
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Konferensbidrag (refereegranskat)abstract
- Numerical simulations are used to study the vertical dispersion of fluid particles in homogeneous turbulent flows with a stable stratification. The results of direct numerical simulations are in good agreement with the relation for the long time fluid particle dispersion, = 2 epsilon(P)t / N-2, derived by [6], though with a small dependence on the buoyancy Reynolds number. Here, is the mean square vertical particle displacement, epsilon p is the dissipation of potential energy, t is time and N is the Brunt-Vaisala frequency. A simulation with hyperviscosicity is performed to verify the relation = (1 + pi C-PL)2 epsilon(P)t / N-2 for shorter times, also derived by [6]. The agreement is reasonable and we find that C-PL similar to 3. The onset of a plateau in is observed in the simulations at t similar to E-P / epsilon(P) which scales as 4E(P) / N-2, where E-P is the potential energy.
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