Impact of Populus Plantations on Water and Soil Quality

Trees of genus Populus (in our context primarily poplars) are predominantly grown in Sweden in small plantations on arable land in southern and central parts of the country to produce biomass for energy and other purposes. This study evaluated the effects (i) of poplar plantations on groundwater quality, by determining differences in leaching of nitrogen and phosphorus to groundwater, and (ii) of poplar and hybrid aspen plantations on soil quality in terms of carbon in the top- and subsoil. The study was conducted comparing Populus plantations in Sweden with adjacent fields with cereals and grasslands. The experiment concerning the groundwater leaching was conducted in eight poplar plantations along three growing seasons (2012–2015). For the soil carbon experiments, 19 poplar and two hybrid aspen plantations and the respective reference fields were sampled. NO3-N leaching from poplar plantations was significantly lower than that from reference fields with cereals, but not when compared with grasslands. Spring NO3-N leaching was significantly lower in poplars than in the reference fields, whereas leaching of NO3-N in autumn did not differ. Concentrations of PO4-P in the groundwater of poplar plantations were lower compared to the respective ones of the reference fields. There were no clear trends observed when comparing carbon concentrations in the topsoil of the poplar and hybrid aspen plantations compared to the respective adjacent reference fields. For the subsoil, the average carbon concentrations in the poplar and hybrid aspen plantations were equal to the respective ones of cereals, but were higher when compared to grassland.publishedVersio

Barriers and opportunities for bioenergy expansion in Chinese rural areas

Bioenergy can contribute to the development of a more sustainable environmental friendly alternative in rural areas in China. The perceptions, preferences and awareness concerning bioenergy among farmers are assessed in a systematic study of 594 Chinese farmers in 33 towns in the province of Shaanxi, using a generalized mixed model approach. In addition to the farmer's background and socio-economic variables, the spatial varia-tion in the perceptions is addressed by mapping the residual between-county variation. The overall awareness of bioenergy as a viable alternative is still low (N = 80). Education and preferences on centralized heating sys-tems play the most important role to explain the willingness to use biomass for domestic use or bioenergy from power plants. Users of large amounts of coal and electricity for heating increase the willingness to pay for bioenergy; users of firewood and raw residues are less prone to change their current energy uses. Nearly 75 % of farmers see bioenergy as a promising alternative to current consumption and production patterns of energy. The results show that not only the farmer's profile but the local context concerning energy mix, land uses and socio-economic factors are influencing their views, presenting defined spatial patterns and reflecting local geog-raphies. Over one-third of respondents provide spontaneous recommendations to develop bioenergy markets. The results contribute to a better understanding of farmers' motivations, perceptions and views concerning en-ergy uses, and can be used as an empirical basis for local energy planning towards a more sustainable energy transition in rural areas. (c) 2022 The Authors. Published by Elsevier Inc. on behalf of International Energy Initiative. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)

Positioning the biofuel policy in the bioeconomy of the BioEast macro-region

This study outlines and reviews the concerted biofuels' policy for transport of eleven countries in central and eastern Europe (BioEast macro-region). Policy preferences collected from relevant government representatives of the region are analyzed using choice architecture and fuzzy Analytical Hierarchy Process. The experts' preferences concerning criteria related to land use, decarbonization and development of a national market are ranked with similar importance, with a slight preference for the latter. The results demonstrate a great variation in the priorities for forming and implementing biofuel policies in the region, strongly related to national realities (e.g. available land for biofuel production, target fulfilment). Countries delaying in their biofuel targets aim at policies that fulfil internal demands without considering other criteria related to land use issues and own sources. The results show a general agreement (95% consensus) of having about 66% of renewable energy in transport covered from biofuels resulting from domestic biomass supply. Yet, there are differing preferences in the policy options at country level, which makes a single consensus policy for the macro-region challenging. Finally, the results highlight the different degrees of policy intervention that are implicit in the policy preferences of the national decision makers

Large-scale deployment of grass in crop rotations as a multifunctional climate mitigation strategy

The agriculture sector can contribute to climate change mitigation by reducing its own greenhouse gas (GHG) emissions, sequestering carbon in vegetation and soils, and providing biomass to substitute for fossil fuels and other GHG-intensive products. The sector also needs to address water, soil, and biodiversity impacts caused by historic and current practices. Emerging EU policies create incentives for cultivation of perennial plants that provide biomass along with environmental benefits. One such option, common in northern Europe, is to include grass in rotations with annual crops to provide biomass while remediating soil organic carbon (SOC) losses and other environmental impacts. Here, we apply a spatially explicit model on >81,000 sub-watersheds in EU27 + UK (Europe) to explore the effects of widespread deployment of such systems. Based on current accumulated SOC losses in individual sub-watersheds, the model identifies and quantifies suitable areas for increased grass cultivation and corresponding biomass- and protein supply, SOC sequestration, and reductions in nitrogen emissions to water as well as wind and water erosion. The model also provides information about possible flood mitigation. The results indicate a substantial climate mitigation potential, with combined annual GHG savings from soil-carbon sequestration and displacement of natural gas with biogas from grass-based biorefineries, equivalent to 13%–48% of current GHG emissions from agriculture in Europe. The environmental co-benefits are also notable, in some cases exceeding the estimated mitigation needs. Yield increases for annual crops in modified rotations mitigate the displacement effect of increasing grass cultivation. If the grass is used as feedstock in lieu of annual crops, the displacement effect can\ua0even be negative, that is, a reduced need for annual crop production elsewhere. Incentivizing widespread deployment will require supportive policy measures as well as new uses of grass biomass, for example, as feedstock for green biorefineries producing protein concentrate, biofuels, and other bio-based products

Predicting understory maximum shrubs cover using altitude and overstory basal area in different Mediterranean forests

In some areas of the Mediterranean basin where the understory stratum represents a critical fire hazard, managing the canopy cover to control the understory shrubby vegetation is an ecological alternative to the current mechanical management techniques. In this study, we determine the relationship between the overstory basal area and the cover of the understory shrubby vegetation for different dominant canopy species (Pinaceae and Fagaceae species) along a wide altitudinal gradient in the province of Catalonia (Spain). Analyses were conducted using data from the Spanish National Forest Inventory. At the regional scale, when all stands are analysed together, a strong negative relationship between mean shrub cover and site elevation was found. Among the Pinaceae species, we found fairly good relationships between stand basal area and the maximum development of the shrub stratum for species located at intermediate elevations (Pinus nigra, Pinus sylvestris). However, at the extremes of the elevationclimatic gradient (Pinus halepensis and Pinus uncinata stands), stand basal area explained very little of the shrub cover variation probably because microsite and topographic factors override its effect. Among the Fagaceae species, a negative relationship between basal area and the maximum development of the shrub stratum was found in Quercus humilis and Fagus sylvatica dominated stands but not in Quercus ilex. This can be due to the particular canopy structure and management history of Q. ilex stands. In conclusion, our study revealed a marked effect of the tree layer composition and the environment on the relationship between the development of the understory and overstory tree structure. More fine-grained studies are needed to provide forest managers with more detailed information about the relationship between these two forest strata