Effects of elevated CO2 and N deposition on CH4 emissions from European mires

[1] Methane fluxes were measured at five sites representing oligotrophic peatlands along a European transect. Five study plots were subjected to elevated CO2 concentration (560 ppm), and five plots to NH4NO3 (3 or 5 g N yr(-1)). The CH4 emissions from the control plots correlated in most cases with the soil temperatures. The depth of the water table, the pH, and the DOC, N and SO4 concentrations were only weakly correlated with the CH4 emissions. The elevated CO2 treatment gave nonsignificantly higher CH4 emissions at three sites and lower at two sites. The N treatment resulted in higher methane emissions at three sites (nonsignificant). At one site, the CH4 fluxes of the N-treatment plots were significantly lower than those of the control plots. These results were not in agreement with our hypotheses, nor with the results obtained in some earlier studies. However, the results are consistent with the results of the vegetation analyses, which showed no significant treatment effects on species relationships or biomass production

Problems in managing a slow-growing pikeperch (

Local fishery managers in Lake Sahajärvi tried to increase pikeperch yields by increasing the minimum allowed mesh size from 45 to 60 mm and size limit from 37 to 40 cm. However, due to the slow growth of pikeperch these measures may not be reasonable. Here, pikeperch yields were modelled with an age and size-structured yield-per-recruit model as a function of mesh size. Besides yields, also the proportion of minimum landing size and immature pikeperch caught with a different mesh size were evaluated. The results showed that maximum yields per recruit can be obtained with a 44 mm mesh size corresponding to yields of about 180 kg per 1000 age 2 pikeperch while with 60 mm mesh size the estimated yields are only 46 kg. The share of immature pikeperch is only 0.4% in 44 mm mesh size nets due to very small average size at maturity (24.8 cm TL) of both sexes. Because the observed growth is slow (k = 0.11 and L∞ = 65.28 cm TL) and the density of pikeperch (BPUE in NORDIC nettings = 1200 g·net-1) is high, the most reasonable management measure to improve growth and average size could be to radically decrease population density

Revised vegetation types in poor Picea abies mires (swamp forests) of Finland: ecological and geographical aspects

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