| 333721. |
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| 333722. |
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| 333723. |
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| 333724. |
- Sandström, Jennie, et al.
(författare)
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Impacts of dead-wood manipulation on the biodiversity of temperate and boreal forests - A systematic review
- 2019
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Ingår i: Journal of Applied Ecology. - : Wiley. - 0021-8901 .- 1365-2664. ; 56:7, s. 1770-1781
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Dead wood (DW) provides critical habitat for thousands of species in forests, but its amount, quality and diversity have been heavily reduced by forestry. Therefore, interventions aiming to increase DW might be necessary to support its associated biodiversity, even in protected forests, which may be former production forests. Our aim was to synthesize the current state of knowledge drawn from replicated experimental studies into solid quantitative evidence of the effects of DW manipulation on forest biodiversity, with a focus on protected forests.We conducted a full systematic review of effects of DW manipulation on forest biodiversity in boreal and temperate regions. We included three intervention types: creation of DW from live trees at the site, addition of DW from outside the site and prescribed burning. Outcomes included abundance and species richness of saproxylic insects, ground insects, wood-inhabiting fungi, lichens, reptiles and cavity-nesting birds. In total, we included 91 studies, 37 of which were used in meta-analyses. Although meta-analysis outcomes were heterogeneous, they showed that increasing the amount of DW (“DW enrichment”) has positive effects on the abundance and richness of saproxylic insects and fungi. The positive effect on saproxylic pest insect abundance tended to be less than that on saproxylic insects in general. No significant effects were found for ground insects or cavity-nesting birds.Although reviewed studies were mainly short term, our results support that management that increases DW amounts has the potential to increase the abundance of DW-dependent species and, in most cases, also their species richness. Studies of burning showed positive effects on the abundance of saproxylic insects similar to those of other interventions, even though burning on average resulted in a smaller enrichment of DW amounts.Policy implications. The findings of the review suggest that manipulating dead wood (DW) can be an effective part of conservation management to support biodiversity in protected areas. The findings also indicate that the diversity of DW types is important, a mix of DW qualities should be favoured. Burning seems to be an effective method to increase biodiversity but to benefit cavity-nesting birds, snag losses need to be minimized.
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| 333725. |
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| 333726. |
- Sandström, Jennie
(författare)
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Old-Growth Forests in the High Coast Region in Sweden and Active Management in Forest Set-Asides
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In today´s intensively managed landscape, very few forests with old-growth characteristics and little human impact exist. One of the rare exceptions is pine forests on rocky soils, a forest type which has probably escaped extensive human use because of its low productivity. Our objective was to investigate the structure, dynamics, and history as well as the abundance and richness of wood-inhabiting fungi in these types of forest. We chose rocky pine forests situated in the High Coast Region to exemplify this forest type since the regional County Administration had already made surveys of the conservation value in 26 rocky pine forest stands in this region. We investigated the forests by recording tree species and measuring tree size and age in eight of the stands that were ranked with the highest conservation value. We also sampled dead wood to examine time since death and we sampled living and dead trees with fire scars to date fires. In addition, we made an inventory of wood-inhabiting fruiting bodies and took woodchip samples from logs to learn (by DNA analysis) whether five rare wood inhabiting fungi species were present as mycelia in logs.We found that rocky pine forests in the High Coast Region have a multi-sizedand multi-aged structure and old pine trees (approximately 13 ha-1 older than 300 years) are present. Fire has been common (an average of 42 years betweenfires) but they were likely to have been low-intense and small. Although the amount of dead wood is relatively low (4.4 m3 ha-1 on average) compared to many other boreal forests with old-growth characteristics, the share of deadwood of the total tree basal area (18%) was in line with other pine forests with low levels of human impact. The low dead wood volume is therefore likely to be an effect of the low productivity rather than dead wood extraction by humans. We also discovered that dead wood can be present for a really longtime without totally decomposing; we found logs and snags that had been dead for 500 years. This continuity of dead wood might be important for organisms dependent on dead wood as a substrate and even though we found that the species richness of wood-inhabiting fungi was somewhat low, we did find some rare species. Cinereomyces lenis and Hyphodontia halonata were present as fruiting bodies and we also found Antrodia albobrunnea, Antrodiainfirma, Crustoderma corneum and Anomoporia kamtschatica present as myceliain logs.The second part of this thesis reports two systematic reviews studying the effects of active management on the biodiversity in boreal and temperate forests. A systematic review follows certain guidelines and aims to compile the evidence base in well-defined topics, so that managers, researchers and policymakers can gain access to a high-quality compilation of current research. In our systematic map, we found almost 800 relevant papers but the set of papers turned out to be too heterogenic (many intervention types, e.g. thinning, burning, grazing and many types of outcomes) to allow any quantitative analysis. However, this map identified knowledge gaps and several detailed research questions that had sufficient data to provide aquantitative statistical analysis.One of these questions was: What is the impact of dead wood creation or addition on dead wood-dependent species? We focused on three types of interventions: creation of dead wood, addition of dead wood from elsewhere and prescribed burning. The selected outcomes were: saproxylic insects (rareand pest species), saproxylic fungi (rare species), ground-living insects and cavity-nesting birds. There was no significant negative effect on any of the investigated species groups but a positive effect on the abundance and richness of saproxylic insects and fungi. We also found that, although the amount of dead wood created was much less (50%) with prescribed burning, the abundance and richness of saproxylic insects showed similar positive effects to those of other intervention methods. A likely explanation for this is that burning results in a diversity of dead wood of various levels of quality (e.g. dense and/or charred wood), which creates a heterogeneity of dead woodtypes having a positive effect on the diversity of species dependent on deadwood. In summary, active management generally has a positive effect on biodiversity but the choice of management type should always be made carefully, and in consideration of the effect you want to achieve. In addition, there is a need for more long-term primary studies and more species groups in more geographical areas need to be incorporated so that the systematic reviews in this field will be even more informative in the future.
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| 333727. |
- Sandström, Jennie
(författare)
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Phytoplankton response to a changing climate in lakes in northern Sweden
- 2013
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In a climate change perspective, increased air temperatures are already a reality and are expected to increase even more in the future, especially in areas at high latitudes. The present thesis therefore addresses the influence of climate change on the physical properties and the phytoplankton communities of typical small and oligotrophic lakes in northern Sweden (62-64˚N). In the first part of the study, we found a significant trend (10 lakes from 1916 to 2010) of ice break-ups occurring increasingly earlier. The timing of ice break-up was strongly influenced by the April air temperature indicating that expected increases in air temperature in the future will also result in an earlier ice break-up. We also used concentrations of chlorophyll a (chl a) as estimations of phytoplankton biomass and discovered a positive relationship between surface water temperature and concentrations of chl a in Lake Remmaren (from 1991 to 2008). The second part of the thesis focuses on climatic conditions and cyanobacteria abundance in three small, oligotrophic lakes in northern Sweden; Lake Remmaren, Lake S. Bergsjön and Lake Gransjön. The concentration and relative abundance of cyanobacteria differ between 2011 and 2012, with different climatic conditions. The "warm" year of 2011 had higher concentrations and relative abundance of cyanobacteria than the "cold" year of 2012. Trends in increasing surface water temperatures as well as increasing abundance of cyanobacteria in August were found in Lake Remmaren (from 1988 to 2011). The direct or indirect effects of warming had a positive effect on the cyanobacteria abundance, since nutrients (Tot N and Tot P) did not display an increasing trend in Lake Remmaren. An analysis on the composition of phytoplankton species in Lake Remmaren, Lake S. Bergsjön and Lake Gransjön revealed that the cyanobacteria Merismopedia sp. was more common in 2011 than 2012. If different cyanobacteria become more common in oligotrophic lakes in the future, the functioning of lake ecosystems may be impacted. Small zooplankton eats small phytoplankton and if smaller phytoplankton species, e.g. cyanobacteria, increase at the expense of other phytoplankton groups, an extra step in the food chain might be added. Less energy might be transferred to the upper levels because many cyanobacteria contain toxic compounds and are less edible than other phytoplankton groups. An increase of toxic containing cyanobacteria in lakes can also make lakes less attractive for recreational purposes in the future.
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| 333728. |
- Sandström, Johan, et al.
(författare)
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Reliability analysis with VMEA of a rack and pinion mechanism in a wave energy gravity accumulator
- 2018
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The method Variation and Mode Effect Analysis (VMEA) is successfully implemented for the AGMA based gear design of the rack pinion mechanism. The rack and pinion is a feature in Ocean Harvesting Technologies (OHT) gravity accumulator device. The purpose of it is to make the electrical power output to the grid more uniform. This is a novel technology where previous experience in designing is absent. The VMEA method is there for useful for incorporating all known uncertainties to estimate the uncertainty and reliability of the technology. This allows for adequate safety factors to be set so the desired reliability can be achieved.The uncertainty and reliability analysis is performed for different OHT designs and methods where the reliability is calculated. This calculation can be used as basis for further analysis when more design details are determined and modifications are made, thus allowing for more optimized and reliable design to be made.
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| 333729. |
- Sandström, Johan
(författare)
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Simulation and calibration of rubber materials for seals
- 2018
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Finite element (FE) simulations of how rubber materials for seals behave over time isperformed. The application is seals for nuclear power plants where seals are exposed toelevated levels of ionizing radiation and temperature.A major challenge for the simulations is to find an appropriate material model for the rubbermaterials and how to calibrate it to experiments. Here is a material model proposed that caninclude effects like creep, permanent set, and temperature dependence. Calibration of materialmodels for relaxation tests on EPDM rubber is performed and presented with good results.Further modelling to include more effects in the material and to simulate leak and tightness ofseals are proposed.
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| 333730. |
- Sandström, Johan
(författare)
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Simulation of rubber materials for seals in use in nuclear power plants
- 2019
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Finite element (FE) simulations of how rubber materials for seals behave over time is performed. The application is seals for nuclear power plants where seals are exposed to elevated levels of ionizing radiation and temperature.A major challenge for the simulations is to find an appropriate material model for the rubber materials and how to calibrate it to experiments. Here is a material model proposed that can include effects like creep, permanent set, and temperature dependence. Calibration of material models for relaxation tests on EPDM rubber is performed and presented with good results. Simulations of leak and tightness of seals are evaluated and some initial observations on the effects temperature and ageing on the tightness are made.
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