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The soil nematode fauna can give important insights into soil development and other habitat changes that occur during primary succession. We investigated the generic composition, density, distribution and community structure of nematodes 50 years after the formation of a pristine volcanic island, Surtsey, Iceland. Part of the island has received additional nutrient inputs from seagulls breeding there since 1985, while the reminder has been much less affected and is at present found at a different successional sere. In total, 25 genera of nematodes were identified, of which 14 were reported on Surtsey for the first time. Nematode communities were more diverse in the more infertile area outside the gull colony, where 24 genera were found, compared to 18 inside. The trophic structure of the nematode communities showed relatively higher abundance of fungal feeders in the infertile areas, but relatively more bacterial- and plant-feeders inside the colony. Nematode abundance in surface soil was, however, significantly higher within the gull colony, with 16.7 ind. cm-2 compared to 3.6 ind. cm-2 outside. A multivariate analysis indicated that the nematode abundance and distribution on Surtsey were most strongly related to the soil C:N ratio, soil acidity, plant cover and biomass, soil temperature and soil depth. [ABSTRACT FROM AUTHOR]

Colonisation of life on Surtsey has been observed systematically since the formation of the island 50 years ago. Although the first colonisers were prokaryotes, such as bacteria and blue-green algae, most studies have been focusing on settlement of plants and animals but less on microbial succession. To explore microbial colonization in diverse soils and the influence of associate vegetation and birds on numbers of environmental bacteria, we collected 45 samples from different soils types on the surface of the island. Total viable bacterial counts were performed with plate count at 22, 30 and 37°C for all soils samples and the amount of organic matter and nitrogen (N) was measured. Selected samples were also tested for coliforms, faecal coliforms aerobic and anaerobic bacteria. The deep subsurface biosphere was investigated by collecting liquid subsurface samples from a 182 m borehole with a special sampler. Diversity analysis of uncultivated biota in samples was performed by 16S rRNA gene sequences analysis and cultivation. Correlation was observed between N deficits and the number of microorganisms in surface soils samples. The lowest number of bacteria (1 x 104 - 1 x 105 g-1) was detected in almost pure pumice but the count was significant higher (1 x 106 - 1 x 109 g-1) in vegetated soil or pumice with bird droppings. The number of faecal bacteria correlated also to the total number of bacteria and type of soil. Bacteria belonging to Enterobacteriaceae were only detected in vegetated and samples containing bird droppings. The human pathogens Salmonella, Campylobacter and Listeria were not in any sample. Both thermophilic bacteria and archaea 16S rDNA sequences were found in the subsurface samples collected at 145 m and 172 m depth at 80°C and 54°C, respectively, but no growth was observed in enrichments. The microbiota sequences generally showed low affiliation to any known 16S rRNA gene sequences. [ABSTRACT FROM AUTHOR]

This study reports on three years (2004-2006) of measurements of net ecosystem exchange (NEE) over a young Siberian larch plantation in Iceland established on previously grazed heathland pasture that had been scarified prior to planting. The study evaluated the variation of NEE and its component fluxes, gross primary production (GPP) and ecosystem respiration (Re), with the aim to clarify how climatic factors controlled the site's carbon balance. The young plantation acted as a relatively strong sink for CO2 during all of the three years, with an annual net sequestration of -102, -154, and -67 gCm-2 for 2004, 2005, and 2006, respectively. This variation was more related to variation in carbon efflux (Re) than carbon uptake (GPP). The abiotic factors that showed the strongest correlation to Re were air temperature during the growing season and soil water potential. The GPP mostly followed the seasonal pattern in irradiance, except in 2005, when the plantation experienced severe spring frost damage that set the GPP back to zero. It was not expected that the rather slow-growing Siberian larch plantation would be such a strong sink for atmospheric CO2 only twelve years after site preparation and afforestation. [ABSTRACT FROM AUTHOR]

The main goal of this research was to determine the short-term effects of forest management practices (precommercial thinning and fertilization) on carbon efflux of a young black cottonwood (Populus trichocarpa) plantation in southern Iceland. Changes in leaf area index, tree growth, soil and air temperature were also monitored. Traditional precommercial thinning (50%) had little effect on soil temperature, but heavy thinning (80%) led to higher soil temperatures in spring and summer, but not much difference in winter. Thinning did not change foliage nutrient content or tree growth in the first treatment year. Effects on soil respiration were surprising; even if soil temperature was slightly higher and all organic material was left at site after precommercial thinning, soil respiration in the thinned stands was significantly lowered. Fertilization increased foliage nutrient content, but did not significantly change tree growth during the first growing season following spring application. It did however significantly increase soil respiration rate in the first treatment year. These results may be important when the effects of early forest management on carbon fluxes are modeled. [ABSTRACT FROM AUTHOR]

Since its birth in 1963 by volcanic eruption in the North Atlantic Ocean off Iceland, Surtsey has been a unique natural laboratory on how organisms colonize volcanic islands and form ecosystems with contrasting structure and function. In July, 2004, ecosystem respiration rate, soil properties and surface cover of vascular plants were measured on 21 plots distributed among the main plant communities found 40 years after the primary succession started. The plots could be divided into two groups, inside and outside seagull (Larus sp.) colonies found on the island. Vegetation cover of the plots was strongly related to the density of seagull nests within and around them. The occurrence of seagull nests and increased vegetation also coincided with significant increase in ecosystem respiration, soil carbon and nitrogen, and with significantly lower soil pH and soil temperatures. The ecosystem respiration was high inside the gull colonies, similar to the highest fluxes measured in drained wetlands or agricultural fields in Iceland. The most important factor for vegetation succession and ecosystem function on Surtsey seems to be the amount of nitrogen, which was mainly brought in by the seagulls. [ABSTRACT FROM AUTHOR]

This study reports 3-year measurements (2004-2006) of net ecosystem exchange (NEE) over a 12-14 year old Siberian larch forest in Iceland established on previously grazed heath land pasture that had been site-prepared prior to planting. The study evaluated interannual and seasonal variation of NEE and its component fluxes, gross primary production (GPP) and ecosystem respiration (Re), with the aim to clarify how climatic factors controlled the site's carbon balance. The young plantation acted as a relatively strong sink for CO2 during all of the three years, with a net sequestration of -375, -566 and -245 g CO2 m>-2 for years 2004, 2005 and 2006, respectively. The annual carbon balance was strongly influenced by climatic factors leading to a high inter-annual variability in NEE. This variation was more related to variation in carbon efflux (Re) than carbon uptake (GPP). The abiotic factors that showed the strongest correlation to Re were air temperature during the growing season and soil water potential. The GPP mostly followed the seasonal pattern in irradiance, except in 2005, 15 when the plantation experienced severe spring frost damage that set the GPP back to zero. It was not expected that the rather slow-growing Siberian larch plantation would be such a strong sink for atmospheric CO2 only twelve years after site preparation and afforestation. [ABSTRACT FROM AUTHOR]

This article provides an overview of the effects of land-use on the fluxes of methane (CH4), nitrous oxide (N2O) and carbon dioxide (CO2) of peatlands in the Nordic countries presented in about 100 studies. In addition, the article identifies the gaps in the present knowledge on the greenhouse gas (GHG) balances associated with the land-use of these northern ecosystems. Northern peatlands have accumulated, as peat, a vast amount of carbon from the atmosphere since the last glaciation. However, past land-use and the present climate have evidently changed their GHG balance. The mean annual GHG balances of undisturbed ombrotrophic and minerotrophic peatlands were surprisingly positive (net sources) of 140 and 380 gCO2 eqm-2, respectively, even if the former was a sink of 63 gCO2 eqm-2 when only the CO2 balance was considered. Drainage of such peatlands for agriculture resulted in the most disadvantageous land-use option for the atmosphere, with the net annual GHG balance increasing to 2190, 2280 and 3140 gCO2 eqm-2 for areas drained for grass swards, 15 cereals or those left fallow, respectively. Even after ceasing of the cultivation practices, N2O emissions remained high and together with the other GHGs resulted in net emissions of 1570 and 500 gCO2eqm-2, in abandoned and afforested peatlands, respectively. Peat extraction sites were also net sources, 730 g CO2 eqm-2. The cultivation of reed canary grass turned the site to net sink of -330 gCO2eqm-2 but restoration did not (source of 470 gCO2 eqm-2). Data for afforested extraction sites is lacking. Peat soils originally drained for forestry may act as net sinks of 780 gCO2eqm-2, and when those sites were restored the sink was 190 gCO2 eq m-2. However, more data is needed to confirm this point. Peat soils submerged under water reservoirs had a mean annual emission of 240 gCO2 eq m-2. In general, there is a lack of studies where all 25 three GHGs have been measured at an ecosystem level, especially in the forested peatlands. [ABSTRACT FROM AUTHOR]