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Abstract: We present novel findings highlighting the early effects of inoculation of downy birch (Betula pubescens Ehrh.) seedlings with factorial combinations of beneficial soil fungi, namely, ectomycorrhizal and insect pathogenic fungi, on Otiorhynchus spp. larval root herbivory under Icelandic field conditions. Birch seedlings were pre-treated with (1) a mixture of four ectomycorrhizal fungal species: Paxillus involutus (Batsch: Fr.) Fr., Telephora terrestris Ehrh.: Fr., Phialophora finlandia Wang & Wilcox. and Hebeloma sp., (2) the insect pathogenic fungus Metarhizium anisopliae (Metschnikoff) Sorokin or (3) a combined inoculum that included the four ectomycorrhizal fungal species and M. anisopliae. Non-inoculated seedlings served as untreated controls. Inoculated and control seedlings were transplanted into soils at three different sites representing eroded land, birch woodland and heathland. Assessment following the first growing season indicated that the effects on Otiorhynchus spp. larval root herbivory and seedling productivity of pre-inoculation with the ectomycorrhizal fungal species mixture and the insect pathogenic fungus, M. anisopliae, were highly dependent on site and treatment. Inoculation with ectomycorrhizal fungi and M. anisopliae significantly reduced root herbivory in both the birch woodland and, in particular, the eroded land sites. In the heathland site, no or even negative effects on root herbivory were observed. However, potential synergistic effects of combined inoculation with both ectomycorrhizal fungi and M. anisopliae were not identified under these experimental conditions. Accumulated seedling mortality ascribed to root herbivory after three growing seasons showed a significant site dependent response, but no significant treatment effect was detected. The effects of ectomycorrhizal and insect pathogenic fungi on root herbivory are discussed and we conclude that significant, although mostly unidentified, interactions between the inoculated fungi and the naturally occurring soil microorganisms may explain these findings. Such interactions require further detailed investigation in order to develop an efficient strategy for soil inoculation with beneficial fungi. [Copyright &y& Elsevier]

• The afforested drained peatland was a C-sink, with an average NEE of 714 g C m−2 yr−1. • The dormant-season CO 2 emissions were low, due to high groundwater level. • Only 0.5% of the total NEE was lost through lateral DOC and POC transport. • 92% of NEP could be explained by biomass increment of trees and ground vegetation. • Around 66% of the measured precipitation was estimated to have evaporated back to the atmosphere. Drainage of peatlands increases the depth of the oxic peat layer and can turn them into a carbon (C) source to the atmosphere. Afforestation of drained peatlands could help to reverse this process since the trees may enhance C sequestration. We followed the C and water dynamics of an afforested drained peatland in S-Iceland during a 2 year period, during which the Black Cottonwood (Populus balsamifera ssp. trichocarpa) plantation was 23–25 year old. Net ecosystem exchange (NEE) of carbon dioxide (CO 2) was measured with the eddy covariance method and C pools of trees and ground vegetation were measured using the stock change method. Lateral losses of dissolved and particulated organic C (DOC, POC) were estimated from weekly water-runoff samples. Unexpectedly, the afforested drained peatland was a strong sink of carbon during the two years, with an average NEE value of 714 g C m−2 yr−1. Only 0.5% of the total NEE was lost through lateral DOC and POC transport, leaving 710 g C m−2 yr−1 as the total net ecosystem production (NEP). Ca. 91% of the observed NEP could be explained by the annual biomass increment of the Black Cottonwood trees and 1.3% by the ground vegetation. This means that the remaining 7.5% of the total NEP most likely accumulated in peat soil and litter, contributing to the soil C stocks. The dormant-season CO 2 emissions were unexpectedly low, which was explained by a high groundwater level at this drained site outside the ca. 5 months of the active growing season. On average, 66% of the annual measured precipitation was estimated to have evaporated back to the atmosphere. This left 416 mm for potential runoff, which was somewhat lower value than the measured runoff (662 mm). These results indicate that during the age span of ca. 20–25 years, afforestation was a valid method to reverse the expected negative C-balance of this drained grassland pasture in Iceland. Although the site is currently a soil C sink, simulation studies with process models are needed to test whether such sites could remain C sinks when managed for forestry over several tree-stand rotations. [ABSTRACT FROM AUTHOR]