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- Adams, David A., et al.
(författare)
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Forest Composition and Structure onGlade-forming Limestones in Middle Tennessee
- 2012
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Ingår i: Castanea. - : Southern Appalachian Botanical Society. - 0008-7475 .- 1938-4386. ; 77:4, s. 335-347
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Tidskriftsartikel (refereegranskat)abstract
- Within a successional context, the vegetation associated with the cedar gladeecosystem in middle Tennessee develops from bare limestone bedrock to subclimax redcedar,preclimax oak-hickory, and climax mixed hardwood forests. Studies on the composition andstructure of forests associated with cedar glade–forming limestones (Lebanon, Ridley) are rare.We sampled the canopy and understory of six forest stands in middle Tennessee on theselimestones. Observed number of canopy species was 14–24 across stands; estimated richnesswas greater by 1–3 species (bootstrap) or 3–6 species (first-order jackknife) than observedrichness. With the exception of Ailanthus altissima in one stand, all other canopy species werenative. Juniperus virginiana, Fraxinus americana, Carya ovata, and Quercus muehlenbergii wereprimary canopy components in 4 or 6 stands, and C. glabra, Q. shumardii, Ulmus alata, F.quadrangulata, Q. alba, and Q. velutina in 2–3 stands. When we included stands from apreviously published study (most on the non-glade Carters Limestone) with our data, aprincipal components analysis identified three groups with the axes approximating a moisturebedrockgradient and a time-successional gradient. An examination of regeneration in ourstands predicts that (1) mesophytes and/or fire-sensitive species (Acer saccharum, Fraxinus spp.,Celtis spp.) will increase and (2) xerophytes and/or fire-adapted species (Quercus spp., Caryaspp.) will decrease. Altogether, our results strongly suggest that the oak-hickory stage shown insuccessional outlines of vegetation development associated with the cedar glade ecosystem maynot occur in its current state in the future.
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| 2. |
- Andersson, K., et al.
(författare)
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High-accuracy sampling of saproxylic diversity indicators at regional scales with pheromones : The case of Elater ferrugineus (Coleoptera, Elateridae)
- 2014
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Ingår i: Biological Conservation. - : Elsevier BV. - 0006-3207 .- 1873-2917. ; 171, s. 156-166
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Tidskriftsartikel (refereegranskat)abstract
- The rare beetle Elater ferrugineus was sampled at 47 sites in the county of Östergötland, Sweden by means of pheromone-baited traps to assess its value as an indicator species for hollow oak stands rich in rare saproxylic beetle species. In addition, Osmoderma eremita was also sampled with pheromone baits. These data were then compared against species survey data collected at the same sites by pitfall and window traps. Both species co-occur with many Red Listed saproxylic beetles, with E. ferrugineus being a somewhat better indicator for the rarest species. The conservation value of a site (measured as Red List points or number of Red Listed species) increased with the number of specimens of E. ferrugineus and O. eremita caught. Accuracy of sampling by means of pheromone trapping turned out to be radically different for the two model species. E. ferrugineus traps put out during July obtained full accuracy after only 6. days, whereas O. eremita traps needed to be out from early July to mid-August in order to obtain full accuracy with one trap per site. By using E. ferrugineus, or preferably both species, as indicator species, accuracy would increase and costs decrease for saproxylic biodiversity sampling, monitoring and identification of hotspots. © 2014 Elsevier Ltd.
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| 6. |
- Andersson, Marie, et al.
(författare)
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Low pre-death growth rates of oak (Quercus robur L.)-Is oak death a long-term process induced by dry years?
- 2011
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Ingår i: ANNALS OF FOREST SCIENCE. - : EDP Sciences. - 1286-4560 .- 1297-966X. ; 68:1, s. 159-168
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Tidskriftsartikel (refereegranskat)abstract
- Background and purpose A complex interplay between biotic and abiotic factors is believed to be responsible for several oak declines in pedunculate oak (Quercus robur L.). This study aims to clarify the temporal process of oak declines, as well as identifying individual tree and environmental variables that affects growth rate and that may increase the risk of mortality. The study was performed in southern Sweden at three sites. Findings Cross-dating revealed that most trees had died during the last decade and that the growth rates of the dead oaks were affected long before death. Averaged growth chronologies of dead and control trees reaching 150 years back in time illustrated an excellent match up until around 1992, when a severe drought occurred after which the dead trees started to express reduced growth. Precipitation the previous year during August-September and during March-June this current year was of significant importance for oak growth. Site-specific results that showed that dead trees: included fewer small-sized trees, grew on non-clay soils, were more likely to have shelf fungus and cavities and were exposed to less sunshine. Conclusion The results support the theories that oak mortality is a long process that may be induced decades before the actual death.
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| 8. |
- Auffret, Alistair
(författare)
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The role of past and present management in the seed dispersal of grassland plants in the rural landscape
- 2010
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The destruction and fragmentation of semi-natural grasslands due toagricultural industrialisation during the past 150 years has had seriousconsequences for biodiversity in the rural landscape. Currently, plantcommunities are usually better explained by historical than by presentday landscape configurations, and the ability for plant species todisperse in space and in time, within and between remaining habitatfragments or to restoration sites will be an important factor in thefuture diversity in the landscape. Here, I present a landscape scaleseed bank and seed rain experiment covering semi-natural grasslands,pastures on former arable fields, abandoned grasslands and smallremnant habitats. The results suggest that in addition to grasslandspecialists remaining in the field layer of abandoned grasslands,remnant seed banks have the potential to be important contributors tothe future diversity of the rural landscape. However, unsuitablegrazing intensities in current pastures are limiting the potential fordispersal of target species across the landscape. Despite large changesin agricultural practice, there still exists the opportunity for human-mediated seed dispersal to increase functional connectivity infragmented landscapes, and I also present a review article in which Iassess past and present human-mediated seed dispersal vectors, andgive recommendations for management and further research.
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| 9. |
- Bergman, Karl-Olof, et al.
(författare)
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How much and at what scale? Multiscale analyses as decision support for conservation of saproxylic oak beetles
- 2012
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Ingår i: Forest Ecology and Management. - : Elsevier. - 0378-1127 .- 1872-7042. ; 265, s. 133-141
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Tidskriftsartikel (refereegranskat)abstract
- A key aspect for understanding species distributions is how they respond to habitat factors at different spatial scales. In this study we used a dataset mapping 33,000 large/hollow oaks, habitat for a guild of saproxylic beetles specialised on oaks at an extent of 10,000 km2. A total of 16 oak-dependent saproxylic species, out of 35, showed a clear relationship with substrate density at scales ranging from 52 m to ⩾5200 m. The characteristic scale of response for species richness of oak specialist species was 2284 m. At this scale, there was a tendency for richness to plateau at about 0.15 oaks ha−1, in which case about 250 hollow or large (circumference 310 cm) oaks would be needed in an area of 1600 ha to ensure a rich saproxylic oak fauna. The main general conclusions were: (i) a multi-scale approach is especially valuable to identify the characteristic scale of response; and that assuming a joint, single scale for all species may result in very poor decision support. (ii) The variation in species’ responses to substrate density at different scales means that habitat loss and fragmentation as well as management and restoration may have very different effects upon different species. (iii) Some species respond both to local and landscape scales, indicating that species occurrences in fragmented oak landscapes are affected both by short-term dynamics of the beetles and long term dynamics of the oak substrate. (iv) Maps, useful as decision support, can be constructed based on resource availability (in our case oak density) and characteristic scales.
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| 10. |
- Bodin, Hristina, et al.
(författare)
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Influence of residence time analyses on estimates of wetland hydraulics and pollutant removal
- 2013
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Ingår i: Journal of Hydrology. - : Elsevier. - 0022-1694 .- 1879-2707. ; 501, s. 1-12
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Tidskriftsartikel (refereegranskat)abstract
- Hydraulic tracer studies are frequently used to estimate wetland residence time distributions (RTDs) and ultimately pollutant removal. However, there is no consensus on how to analyse these data. We set out to (i) review the different methods used and (ii) use simulations to explore how the data analysis method influences the quantification of wetland hydraulics and pollutant removal. The results showed that the method influences the water dispersion (N) most strongly and the removal least strongly. The influence increased with decreasing effective volume ratio (e) and N, indicating a greater effect of the method in wetlands with low effective volume and high dispersion. The method of moments with RTD truncation at 3 times the theoretical residence time (t(n)) and tracer background concentration produced the most dissimilar parameters. The most similar parameters values were those for gamma modelling and the method of moments with RTD truncation at tracer background concentration. For correct removal estimates, e was more important than N. However, the results from the literature review and simulations indicated that previously published articles may contain overestimated e and underestimated N values as a result of frequent RTD truncations at 3t(n), when using the method of moments. As a result, the removal rates may also be overestimated by as much as 14% compared to other truncation methods or modelling. Thus, it is recommended that wetland hydraulic tracer studies should use the same method, specifically, RTD truncation. We conclude that the choice of tracer data analysis method can greatly influence the quantifications of wetland hydraulics and removal rate.
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