No abstract

The effect of elevated UV-B radiation on CO 2 exchange of a natural flark fen was studied in open-field conditions during [2003][2004][2005]. The experimental site was located in Sodankylä in northern Finland (67122 0 N, 26138 0 E, 179 m a.s.l.). Altogether 30 study plots, each 120 cm  120 cm in size, were randomly distributed between three treatments (n 5 10): ambient control, UV-A control and UV-B treatment. The UV-B-treated plots were exposed to elevated UV-B radiation level for three growing seasons. The instantaneous net ecosystem CO 2 exchange (NEE) and dark respiration (R TOT ) were measured during the growing season using a closed chamber method. The wintertime CO 2 emissions were estimated using a gradient technique by analyzing the CO 2 concentration in the snow pack. In addition to the instantaneous CO 2 exchange, the seasonal CO 2 balances during the growing seasons were modeled using environmental data measured at the site. In general, the instantaneous NEE at light saturation was slightly higher in the UV-B treatment compared with the ambient control, but the gross photosynthesis was unaffected by the exposure. The R TOT was significantly lower under elevated UV-B in the third study year. The modeled seasonal (June-September) CO 2 balance varied between the years depending on the ground water level and temperature conditions. During the driest year, the seasonal CO 2 balance was negative (net release of CO 2 ) in the ambient control and the UV-B treatment was CO 2 neutral. During the third year, the seasonal CO 2 uptake was 43 AE 36 g CO 2 -C m À2 in the ambient control and 79 AE 45 g CO 2 -C m À2 in the UV-B treatment. The results suggest that the long-term exposure to high UV-B radiation levels may slightly increase the CO 2 accumulation to fens resulting from a decrease in microbial activity in peat. However, it is unlikely that the predicted development of the level of UV-B radiation would significantly affect the CO 2 balance of fen ecosystems in future.

The effects of elevated ultraviolet-B (UV-B) radiation on methane dynamics was studied in a natural fen in Northern Finland for three growing seasons (2003)(2004)(2005). This is the first in situ study on the effects of elevated UV-B radiation on methane dynamics in a natural fen. The experimental setup consisted of 30 study plots (120 9 120 cm) that were randomly divided into three treatments: ambient control, UV-A control and elevated UV-B. The UV-B enhancements were 63, 37 and 21% above ambient during the growing seasons 2003, 2004 and 2005, respectively. Elevated UV-B did not affect net methane emission. Stable isotope composition of methane indicated that methane was produced by the acetate fermentation. Under elevated UV-B there was a slight increase in the concentrations of acetate and propionate but decrease in the oxalate concentration suggesting UV-B-induced changes in the belowground processes. The results emphasize the need for long-term field studies under moderately enhanced exposures to estimate whether the function and feedbacks of mire ecosystems change under increased UV-B radiation.

The aim of this work was to test our hypothesis that pine needles protect themselves against UV-B radiation via anatomical changes in the epidermal layer. This could lead to needle growth reductions if large quantities of assimilates are allocated for the epidermal protective mechanisms at the expense of photosynthetic area. Effects of enhanced UV-B radiation on the needle ontogeny of mature Scots pines (Pinus sylvestris L.) were studied during the second season of a field experiment. Depending on the season and the time of the year (1996)(1997), the enhanced UV-B irradiance varied from 0.92 to 5.09 kJ m -2 day -1 UV-B BE compared to 0.54-2.44 kJ m -2 day -1 UV-B BE of ambient radiation. It was found that UV-B treatment accelerated the early development of needles. In 6-day-old enhanced UV-Btreated needles, mesophyll and hypodermic cells were fully differentiated, whereas in ambient-treated needles, no lobate mesophyll cells were seen and hypodermic cells had not yet developed. In fully grown needles, no accelerated differentiation was seen, except that the epidermal cross-sectional area was smaller. The continuation of the experiment will show if such a significant difference only occurs irregularly and incidentally or if it is of consistent significance for needles.

The changes the polar regions face are too complex to be tackled by single scientific disciplines and in isolation from societal actors. Therefore, the call for polar research projects that engage with stakeholders outside academia increases. The ideal set-up of these projects is envisioned as an inclusive and action-oriented process that brings scientists and stakeholders together to identify pressing issues of societal and scientific relevance and to develop research projects that produce practical outcomes. However, working across disciplines and knowledge systems can be challenging. To better understand stakeholders’ motivation for engaging in polar science projects, to learn what stages of a project they are interested in and what their preferred modes of engagement are, stakeholders were surveyed as part of the EU-funded project EU-PolarNet. The results suggest that while most academic survey participants are eager to participate from problem definition to dissemination of results, most non-academic survey participants preferred interaction at the stages when results were disseminated and used for informed decision-making. The survey results have their limitations, yet they provide a basis for important future approaches to stakeholder engagement in polar research projects. They show that stakeholders prefer to engage in different stages of a research project depending on their specific needs and interests, while also acknowledging that additional support may be required to enable meaningful engagement throughout the research process.