Minor long-term effects of ultraviolet-B radiation on methane dynamics of a subarctic fen in Northern Finland

189

137

In this assessment we summarise advances in our knowledge of how UV-B radiation (280-315 nm), together with other climate change factors, influence terrestrial organisms and ecosystems. We identify key uncertainties and knowledge gaps that limit our ability to fully evaluate the interactive effects of ozone depletion and climate change on these systems. We also evaluate the biological consequences of the way in which stratospheric ozone depletion has contributed to climate change in the Southern Hemisphere. Since the last assessment, several new findings or insights have emerged or been strengthened. These include: (1) the increasing recognition that UV-B radiation has specific regulatory roles in plant growth and development that in turn can have beneficial consequences for plant productivity via effects on plant hardiness, enhanced plant resistance to herbivores and pathogens, and improved quality of agricultural products with subsequent implications for food security; (2) UV-B radiation together with UV-A (315-400 nm) and visible (400-700 nm) radiation are significant drivers of decomposition of plant litter in globally important arid and semi-arid ecosystems, such as grasslands and deserts. This occurs through the process of photodegradation, which has implications for nutrient cycling and carbon storage, although considerable uncertainty exists in quantifying its regional and global biogeochemical significance; (3) UV radiation can contribute to climate change via its stimulation of volatile organic compounds from plants, plant litter and soils, although the magnitude, rates and spatial patterns of these emissions remain highly uncertain at present. UV-induced release of carbon from plant litter and soils may also contribute to global warming; and (4) depletion of ozone in the Southern Hemisphere modifies climate directly via effects on seasonal weather patterns (precipitation and wind) and these in turn have been linked to changes in the growth of plants across the Southern Hemisphere. Such research has broadened our understanding of the linkages that exist between the effects of ozone depletion, UV-B radiation and climate change on terrestrial ecosystems.

Section: Fertiliser Application and Nitrogen Depositionmentioning

confidence: 99%

Solar ultraviolet radiation and ozone depletion-driven climate change: effects on terrestrial ecosystems

Bornman

Barnes

Robinson

et al. 2014

189

137

“…The alteration in the contents of these LMWOAs was considered an important factor that was responsible for changes in the production and emissions of CH 4 in the marsh induced by enhanced UV-B radiation. 42 UV-B radiation decreased the distribution of carbohydrates into the roots of reeds (Phragmites australis) at the end of summer, which was thought to be the major reason why UV-B radiation inhibited CH 4 emissions in wetlands. 43 The present study revealed that enhanced UV-B radiation induced increases in the contents of both oxalic acid and succinic acid in root exudates, and that the content of oxalic acid had a highly significant positive correlation with CH 4 emissions in paddy fields.…”

Section: Effects Of Enhanced Uv-b Radiation On Methane Emissions In P...mentioning

confidence: 99%

Effect of enhanced UV-B radiation on methane emission in a paddy field and rice root exudation of low-molecular-weight organic acids

Zhan

et al. 2016

A local rice variety, "Baijiaolaojing", was grown in a paddy field in the Yuanyang rice terraces under ambient and supplemental levels of ultraviolet-B (UV-B, 280-315 nm) radiation. The effects of enhanced UV-B radiation (5 and 10 kJ m(-2) d(-1)) on methane emissions in the paddy field were evaluated using a closed-chamber gas chromatography-based system, and the contents of low-molecular-weight organic acids (LMWOAs) in root exudates were determined by high-performance liquid chromatography (HPLC). Peaks in methane emissions in the paddy field were detected at 60, 80 and 100 days after rice transplantation. The highest level of cumulative methane emissions occurred at the tillering stage, followed by the jointing-booting and maturity stages. The lowest level was found at the flowering stage. The enhanced UV-B radiation did not change the seasonal variation in methane emissions in the paddy field; however, it induced a significant increase in the flux of methane emissions at the jointing-booting and maturity stages, as well as a significant increase in the cumulative flux of methane emissions throughout the growth period. In addition, the enhanced UV-B radiation caused an increase in the contents of oxalic acid and succinic acid and a decrease in the contents of tartaric acid and malic acid in rice root exudates. Furthermore, a significant positive correlation (r = 0.725, p < 0.01) was found between the content of oxalic acid and the methane emissions in the paddy field. The results indicated that enhanced UV-B radiation promoted methane emissions in the paddy field, which was closely associated with its impact on the exudation of LMWOAs by rice roots.

“…169 These emerging technologies allow quantification and evaluation of the wild-fire production of atmospheric methane, an increasing source due to the climate related increased occurrence of wildfires. 170,171 UV radiation plays a critical role in the atmospheric chemistry of methane as well as modulating its production in soils and other components of the terrestrial biosphere, 172,173 although Morsky et al 174 found its role in methane production in a subarctic fen was more modest. The release of methane to the atmosphere from land surfaces is dependent upon climate change in the terrestrial biosphere as well as heat and UV supply to specific methane reservoirs such as permafrost regions.…”

Section: Methanementioning

confidence: 99%

Effects of stratospheric ozone depletion, solar UV radiation, and climate change on biogeochemical cycling: interactions and feedbacks

Erickson

Sulzberger

Zepp

et al. 2014

Climate change modulates the effects of solar UV radiation on biogeochemical cycles in terrestrial and aquatic ecosystems, particularly for carbon cycling, resulting in UV-mediated positive or negative feedbacks on climate. Possible positive feedbacks discussed in this assessment include: (i) enhanced UV-induced mineralisation of above ground litter due to aridification; (ii) enhanced UV-induced mineralisation of photoreactive dissolved organic matter (DOM) in aquatic ecosystems due to changes in continental runoff and ice melting; (iii) reduced efficiency of the biological pump due to UV-induced bleaching of coloured dissolved organic matter (CDOM) in stratified aquatic ecosystems, where CDOM protects phytoplankton from the damaging solar UV-B radiation. Mineralisation of organic matter results in the production and release of CO2, whereas the biological pump is the main biological process for CO2 removal by aquatic ecosystems. This paper also assesses the interactive effects of solar UV radiation and climate change on the biogeochemical cycling of aerosols and trace gases other than CO2, as well as of chemical and biological contaminants. Interacting effects of solar UV radiation and climate change on biogeochemical cycles are particularly pronounced at terrestrial-aquatic interfaces.