Department of Plant and Environmental Sciences / Institutionen för växt- och miljövetenskaper (-2011)
https://hdl.handle.net/2077/17608
2024-03-29T10:42:13ZThe influence of climate on ozone risk for vegetation
https://hdl.handle.net/2077/25120
The influence of climate on ozone risk for vegetation
Klingberg, Jenny
Ground-level ozone (O3) is a harmful air pollutant causing reduced crop yield and quality, reduced forest growth and negative effects on human health in large parts of the world. O3 is generally seen as a regional scale air pollution problem, but O3 concentration ([O3]) variation on a smaller geographical scale can be considerable. Knowledge of the size of this local scale variation and the underlying causes is important in environmental monitoring and assessments of O3 exposure. The local scale variation in [O3] in Sweden was investigated and described in relation to local climate and site characteristics such as altitude, topography, vicinity to the coast and local NO emissions based on measurements of [O3] and meteorology with a mobile monitoring station. In addition, [O3] and [NO2] were measured with passive diffusion samplers and [O3] data from permanent monitoring stations were analysed. The strength of nocturnal temperature inversions was found to be crucial in determining the differences in average [O3] and diurnal [O3] range (DOR) at rural sites in southern Sweden. Inland low sites experienced stronger nocturnal temperature inversions, lower average [O3] and larger DOR compared to inland high and coastal sites. In addition, the underlying surface (important for the deposition rate), advection of O3-rich marine air and local NO emissions also influence the local scale variation of [O3]. The negative effects of O3 on vegetation are more closely related to the plant uptake of O3 through the stomata than to the [O3] in the ambient air. Environmental factors such as humidity, temperature and light, influence the degree of stomatal opening and thus the stomatal O3 flux into the leaf interior. The flux-based PODY-index (phytotoxic O3 dose above a flux threshold Y) was used to assess the O3 risk for vegetation. It allows modification of O3 uptake by climatic conditions to be incorporated in O3 risk assessment for vegetation. A large part of the local scale variation in [O3] in southern Sweden occurs during night-time. At night the stomatal O3 uptake by vegetation is low and the risk of O3 damage is therefore not greatly influenced. Thus, plant stomatal O3 uptake and O3 risk for vegetation are less influenced by the site position in the landscape than 24-hour average [O3]. At the coastal sites the [O3] were higher also during daytime, which implies an increased risk of negative effects of O3 on vegetation compared to inland sites. The influence of potential future climate change on the flux-based risk of negative effects of O3 on vegetation in Europe was investigated with modelled future [O3] from the chemistry transport model MATCH and meteorology from the regional climate model RCA3. The future plant O3 uptake and risk of O3 damage to vegetation was predicted to remain unchanged or decrease in Europe, despite substantially increased modelled [O3] in Central and Southern Europe. The expected reduction in stomatal conductance with rising atmospheric [CO2] is of large importance for this result. However, the magnitude of the CO2 effect is uncertain, especially for trees. If the CO2 effect will turn out to be small, future climate change has the potential to dramatically increase the flux-based O3 risk for vegetation in Northern and Central Europe.
2011-05-11T00:00:00ZManagement of urban woodlands - effects on bird communities and recreational values
https://hdl.handle.net/2077/25327
Management of urban woodlands - effects on bird communities and recreational values
Heyman, Erik
The ongoing urbanisation increases the pressure on urban nature. Urban woodlands
are receiving growing attention as they provide valuable ecosystem services to urban
citizens, mainly by providing areas for recreation but also through improving air
quality and reducing noise. There is an increasing demand for knowledge of how
urban woodlands should be managed to combine several functions, such as
recreational values and biodiversity conservation. There are, however, few field
experiments that evaluate the effects of forest management.
The work in this thesis is based on the results of large-scale, replicated field
experiments in urban woodlands in southern Sweden. Management by clearance of
woody understory (bushes and small trees) was conducted at five sites in oakdominated
forest stands on the fringe of three midsize cities. Two different types of
clearance were applied: 90% removal of understory and 50% removal in regular
50x50 meter patches. Control plots of equal size were left unmanaged. Bird
communities were surveyed before and after management, and the impact of bird
predation on arthropods in bush and tree canopies were evaluated with exclosure
experiments. Bird communities were affected by understory clearance and a decrease
in bird abundance was observed in the stands with 90% removal of understory. Patchy
clearance had no negative effects on bird abundance. Bird predation had strong effects
on arthropods in the understory, which suggests that an important food resource for
birds is removed when the understory is cleared. Arthropods were affected by bird
predation in the tree canopies too, but the effects of bird predation were weaker in the
managed areas, which further stresses the negative impact on birds by extensive
clearance of understory.
The recreational values in relation to understory density were evaluated in a photo
survey where pictures from the managed areas were shown to panels of students.
Open forests were considered most attractive for recreation but 75% of the
respondents claimed that they preferred a mix of open and closed forest. In a field
study, the participants used cameras to take photos of liked and disliked places along
a forest trail in an urban forest. The analysis of photo contents showed that both open
and dense forest landscapes were appreciated while visible human impact was usually
perceived negatively. Implications for management are that clearance of understory
can enhance recreational values but should be conducted in a small scale pattern to
promote visual variation and minimise the negative effects on birds. Visible impact
from recreational facilities and forest management should be minimised as far as
possible. Openness is often affected by management and was found to be useful as a
key-variable to analyse management trade-offs between social and ecological values.
2011-05-07T00:00:00ZEnvironmental and health hazards of chemicals in plastic polymers and products
https://hdl.handle.net/2077/24978
Environmental and health hazards of chemicals in plastic polymers and products
Lithner, Delilah
Plastics are extremely diverse in terms of chemical composition, properties and possible applications, and are widely distributed in the society and the environment. In the last 15 years the global annual production has doubled, reaching 245 million tons in 2008. Several of the chemicals used to produce
plastics are hazardous for human health and the environment. These, and their degradation products, may be released during the life cycle of a plastic product. The plastic polymers are not considered as toxic, but in plastic products there may be non-bound residual monomers, polymerisation chemicals,
degradation products, and additives which have toxic properties.
The overall aim of this thesis, which is based on five papers [I-V], was to study the
environmental and health hazards of chemicals in plastic polymers and products. Leaching tests, toxicity tests and Toxicity Identification Evaluations (TIEs) were made on plastic products [I, II], synthetic textiles [III], and discarded electronic products [IV]. A hazard ranking model was developed and used to rank plastic polymers based on monomer composition and environmental and health hazard classifications [V]. Also other hazardous substances needed to produce each polymer were identified [V].
Substances causing acute toxicity to Daphnia magna (water flee) leached from one third of all 83 plastic products/textiles even during short term (1-3 d) leaching in deionised water [I-III]. The toxic leachates came mainly from products that were soft to semi-soft, i.e. plasticised PVC (11/13) and polyurethane (3/4), and from epoxy products (5/5), and from synthetic textiles made of various
plastic fibres [I-III]. The electronic product leachates that were acutely toxic came from mixed material and metal components, and not from plastics components. TIEs, performed on some leachates, indicated that the major toxicants were hydrophobic organics for the plastic product and synthetic textile leachates [I-III], and metals for the electronic product leachates [IV].
The polymers ranked as most hazardous are made of monomers classified as mutagenic and/or carcinogenic (category 1A or 1B). These belong to the polymer families of polyurethanes, polyacrylonitriles, PVC, epoxy resins, and styrenic copolymers (ABS, SAN and HIPS), and have a large global production (1-37 million tons/year). A considerable number of polymers, 31 out of 55, are made of monomers that belong to the two highest of the ranking model’s five hazard levels [V].
Examples of such polymers, with a large global production (1-5 million tons/year), are phenol
formaldehyde resins, unsaturated polyesters, polycarbonate, polymethyl methacrylate, and ureaformaldehyde resins [V].
The ranking model was useful for identifying and comparing hazardous substances, and the
results from the hazard identification can be used for further hazard and risk assessment for decisions on the need for risk reduction measures, substitution or phase out.
In conclusion, considering the extensive dispersion in the society and the environment, the growing production, and the release and use of many hazardous chemicals, it is important to further assess the risks of chemicals associated with plastic polymers and products.
2011-04-15T00:00:00ZReproductive Biology and Population Genetics of Common Ash (Fraxinus excelsior L.)
https://hdl.handle.net/2077/24970
Reproductive Biology and Population Genetics of Common Ash (Fraxinus excelsior L.)
Bochenek, Grazyna
Common Ash, Fraxinus excelsior L. (Oleaceae) is a wind-pollinated, wind-dispersed, deciduous tree, commonly occurring throughout Central and Northern Europe. The thesis addresses several questions concerning reproductive biology and factors influencing the genetic richness of ash stands. The breeding system is characterised in morphological terms as polygamous. However, individuals can be described as male, or seed producing hermaphrodites and females. The gender-related differences in vegetative growth were investigated on the branch level using dendrochronological techniques. The radial growth of male and female individuals turned out to be similar in a long-term perspective, but males invested more in building up their crown biomass. Genders responded also to different climatic variables. To determine the conditions for male gametophyte competition, a series of controlled pollinations were conducted and the pollen tube growth in naturally pollinated pistils was observed. As many other temperate trees, fertilization is delayed in Fraxinus and the pollen tube growth is arrested in the style. The results showed that the trait does not play any role in prezygotic selection in this species. The order of pollen grain arrival and, thus, flowering phenology was more important for paternity success than pollen tube growth performance. Furthermore, the functional breeding system of F. excelsior was examined. Hermaphrodite individuals were shown to have very low male fecundity and so could be classified as functionally female.
To test the effect of maternal flowering phenology on mating distances and genetic variability of their progeny nuclear microsatellite markers were employed on early and late flowering individuals. Additionally the influence of genetic population structure on the level of biparental inbreeding was discussed. Microsatellite markers were used also to examine the level of inbreeding and allelic richness in the commercial stock of ash seed available for reforestation. Results from both works confirmed that neutral genetic variation in Fraxinus excelsior is high and that the level of inbreeding is very low the allelic diversity of an individual seed family may vary depending on flowering synchrony of neighbouring trees. Collection of seed from limited number of trees should be avoided; also the genetic diversity and structure of seed sources should be assessed when obtaining planting material for forest restoration
2011-03-17T00:00:00Z