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Changes in the composition, structure, and altitudinal distribution of low forests at the upper limit of their growth over the past 50 years have been studied in the Tylaisko-Konzhakovsko-Serebryanskii Massif (the Northern Urals). The qualitative and quantitative assessment of these changes has been made on the basis of descriptions, photographs, and maps made in 1956 and 2005. The results show that the upper boundary of low forests on the majority of slopes has ascended. Considerable changes have occurred in the composition, density, and height of the tree layer in the communities that formed the upper low-forest boundary in 1956. Among a fairly large number of tree species growing in the subgoltzy belt (Picea obovata, Larix sibirica, Pinus sibirica, and Abies sibirica), the birch Betula tortuosa has expanded most actively, whereas the proportions of P. obovata and especially L. sibirica in low forests have decreased. These changes are explained by climate warming and increasing humidity.

Bioenergy crops are well known for their ability to reduce greenhouse gas emissions and increase the soil carbon stock. Although such crops are often held to be in competition with food crops and thus raise the question of current and future food security, at the same time mitigation measures are required to tackle climate change and sustain local farming communities and crop production. However, in some cases the actions envisaged for specific pedo-climatic conditions are not always economically sustainable by farmers. In this frame, energy crops with high environmental adaptability and yields, such as giant reed (Arundo donax L.), may represent an opportunity to improve farm incomes, making marginal areas not suitable for food production once again productive. In so doing, three of the 17 Sustainable Development Goals (SDGs) of the United Nations would be met, namely SDG 2 on food security and sustainable agriculture, SDG 7 on reliable, sustainable and modern energy, and SDG 13 on action to combat climate change and its impacts. In this work, the response of giant reed in the marginal areas of an agricultural district of southern Italy (Destra Sele) and expected farm incomes under climate change (2021-2050) are evaluated. The normalized water productivity index of giant reed was determined (WP; 30.1gm-2) by means of a SWAP agro-hydrological model, calibrated and validated on two years of a long-term field experiment. The model was used to estimate giant reed response (biomass yield) in marginal areas under climate change, and economic evaluation was performed to determine expected farm incomes (woodchips and chopped forage). The results show that woodchip production represents the most profitable option for farmers, yielding a gross margin 50% lower than ordinary high-input maize cultivation across the study area.

Decreasing nutrient losses from excessive synthetic fertilizer inputs is the direct and valid way to address low nutrient use efficiency and the related environmental consequences. Here, we established a comprehensive database of nitrogen (N), phosphorus (P), and carbon (C) losses from rice paddy fields in China, which we used to evaluate fertilization-induced losses and the impact of environmental factors, and to mitigate losses by adopting alternative fertilization options and setting input thresholds. Our results showed that most N-loss pathways had exponential increases with additional N input. In average, 23.8% of the N applied was lost via NH3 (16.1%), N2O (0.3%), leaching (4.8%), and runoff (2.6%). Total P loss was approximately 2.7% of the input, composed of leaching (1.3%) and runoff (1.4%). C lost as CH4 accounted for 4.9% of the organic C input. A relative importance analysis indicated that climate or soil variation rather than fertilizer rate was the dominant factor driving N and P leaching, and CH4 emissions. Based on the sensitivity of multiple N-loss pathways to N fertilization, we propose upper thresholds for N inputs of 142–191 kg N ha−1 across four rice types, which would avoid dramatic increases in N losses. Compared to conventional chemical fertilization, alternative fertilization options had diverse performances: enhanced-efficiency N fertilizer reduced N loss rate by 7.8 percent points and the global warming potential (GWP, considering N2O and CH4 emissions) by 28.8%; combined manure and chemical N fertilizer reduced N loss rate by 9.0 percent points but increased the GWP by 56.9%; straw return had no effect on total N loss but almost doubled the GWP. Using nutrient sources most appropriate to site-specific conditions is demonstrated as a robust way to decrease nutrient losses. Setting nutrient input thresholds would also contribute to the mitigation of environmental pollution, especially in regions with poor fertilization recommendation systems.

Better prediction of turbulent airflow around urban trees is necessary because it impacts urban pollutant dispersion, outdoor thermal comfort, energy efficiency, pedestrian-level comfort and urban heat island mitigation. A major challenge is how to obtain an accurate numerical model of the turbulent flow field around trees and an improved parameterization of the turbulent momentum deficit using the drag coefficient (Cd). To address this challenge, we use wind tunnel tests and real trees to measure Cd for four common subtropical tree species: Ficus microcarpa, Mangifera indica, Michelia alba and Bauhinia blakeana. The results show that the Cd of the four trees ranges from 0.523 to 0.932, and that the negative relationship between Cd and wind speed (U) can be expressed by the exponential formula Cd=a*U−b. A three-dimensional model of wind modification by trees is proposed, and its accuracy is verified with wind tunnel measurements. With precise Cd and model, the predictability of the influence of trees on urban wind in subtropical areas is enhanced (root mean square error RMSE ranging from 2.89 m/s to 0.45 m/s). Future development and applications of the numerical model will help provide useful guidelines for urban landscape management and sustainable urban planning in terms of urban ventilation.

Developing bioenergy from plant feedstocks is considered an opportunity to reduce greenhouse gas emissions and secure biofuel supply. This study is an assessment of the availability of field crop residues for bioenergy feedstocks in northwest China (NWC) and southwest China (SWC). The amount of field crop residues was calculated by analyzing statistical data on crop acreages and yields at the provincial and county levels in the NWC and SWC regions. Total residue mass varied from 58.1 to 62.0 million tons (Mt) in NWC and from 92.8 to 97.2 Mt in SWC from 2008 to 2010. Field residues accounted for 86 % in NWC and 94 % in SWC of the total residue mass; the process residue mass accounted for 14 and 6 % of the total residue mass in the NWC and SWC, respectively. In the NWC region, wheat, maize, and cotton were the main crops, providing 17.0, 14.0, and 8.1 Mt of the field residue mass, respectively. In the SWCregion, rice, maize, and canola provided 30.6, 15.2, and 9.7 Mt of the total residue mass, respectively. In NWC, maize cob (1.98 Mt) and cotton seed hull (1.93Mt) formed the majority of the process residues. In SWC, rice hull (5.9 Mt), maize cob (3.7 Mt), and sugarcane bagasse (3.2 Mt) were the main contributors. Most crop residues became available from August to September in the NWC region, whereas harvesting was spread over the whole year in the SWC region. Converted to standard coal equivalent (SCE), total residues in the NWC region amounted to 32.6–34.1 Mt SCE, with 30.7 Mt of field residues and 2.7 Mt of process residue mass. In the SWC region, the total residue mass was equivalent to 48.7–50.8 Mt SCE, including 42.5 Mt of field residues and 7.2 Mt of process residues. Total crop residue availability for biofuels amounted to 16.9 and 28.1 Mt of field residues in NWC and SWC, respectively. Considering transport conditions, surplus amounts, residue densities, and harvest timings, Chongqing Municipality and Shaanxi province showed the best conditions for producing biofuel feedstocks.

A variety of palaeoclimatic records show a shift towards cooler, wetter and windier conditions in Europe around 2800 cal a BP. The shift broadly coincides with an increase of the atmospheric C-14 concentration, suggesting a connection between solar activity variations and climate change. Here we investigate a peat record from Undarsmosse in southern Sweden. In a previous study, based on a low-resolution chronology, this record showed increased aeolian sand influx and Sphagnum spore content around 2800 cal a BP, indicating high storm activity and wetter conditions. We applied the C-14 wiggle-match dating technique on the same record to construct a robust chronology to evaluate the temporal relationship to solar forcing. In addition, we performed plant macrofossil analysis to determine local vegetation changes. Based on the new chronology, a shift to a Sphagnum-dominated bog, representing wetter conditions, and the onset of a period with increased storminess occurred around 2700 cal a BP. These changes are, within age model uncertainties, synchronous with climatic changes inferred from other sites in Europe, suggesting a shift in the larger scale atmospheric circulation, possibly triggered by decreased solar activity. (Less)

We modelled the effects of past and expected future changes in climate (temperature, precipitation), CO2 concentration, nitrogen deposition (N) and ozone (O3) exposure (phytotoxic ozone dose, POD) on carbon (C) sequestration by European forest ecosystems for the period 1900-2050. Tree C sequestration was assessed by using empirical response functions, while soil C sequestration was simulated with the process-based model VSD, combined with the RothC model. We evaluated two empirical growth responses to N deposition (linear and non-linear) and two O3 exposure relationships (linear function with total biomass or net annual increment). We further investigated an 'interactive model' with interactions between drivers and a 'multiplicative model', in which the combined effect is the product of individual drivers. A single deposition and climate scenario was used for the period 1900-2050. Contrary to expectations, growth observations at European level for the period 1950-2010 compared better with predictions by the multiplicative model than with the interactive model. This coincides with the fact that carbon responses in kgCha-1yr-1 per unit change in drivers, i.e. per °C, ppm CO2, kgNha-1yr-1 and mmolm-2yr-1 POD, are more in line with literature data when using the multiplicative model. Compared to 1900, the estimated European average total C sequestration in both forests and forest soils between 1950 and 2000 increased by 21% in the interactive model and by 41% in the multiplicative model, but observed changes were even higher. This growth increase is expected to decline between 2000 and 2050. The simulated changes between 1950 and 2000 were mainly due to the increase in both N deposition and CO2, while the predicted increases between 2000 and 2050 were mainly caused by the increase in CO2 and temperature, and to lesser extent a decrease in POD, counteracted by reduced N deposition.

Novel methods for enhancing collaboration and interactions are required to ensure that stakeholders and governments are able to develop a shared vision that supports sustainable watershed governance. Particular attention must be placed on integrating stakeholders who would otherwise have limited decision-making power. By crossing professional, ideological and jurisdictional boundaries, stakeholders' perspectives are more likely to change than when staying within those boundaries. This process, known as boundary crossing, requires boundary objects; either artifacts, people, or institutions that play a bridging role between different boundary spaces. For this study, serious games powered by scientific models are identified as potentially effective boundary objects. A serious game simulation called Aqua Republica was used to organize game simulation events allowing stakeholders to connect in an in-person, informal and novel setting. This exploratory research aims to study the role and impact of serious games as boundary objects to enhancing collaboration and knowledge co-creation. The following research questions are addressed: (1) Do interactions increase over the course of a game simulation event? (2) Does the quality of interactions change over the course of a game simulation event? (3) Are the quantity and quality of interactions affected by pre-existing relationships? And if so, how? (4) How does the relationship between participants change over the course of a game simulation event? As part of this study, four game simulation events were organized that included students, professionals and diverse stakeholder groups working in watershed management contexts across Eastern Canada with 40 participants in total. Participants were divided into teams of 3-5 members and were surveyed and their interactions recorded. An interaction and social network analysis of the audiovisual recordings of each game simulation event indicates that interactions between participants increase in both quantity and quality as the game progresses. The analysis shows that serious game simulations provide an intervention platform not only to facilitate cross-boundary interactions, but also to strengthen relationships between diverse stakeholders, as expressed by an increase in mutual trust and empathy, as well as an improved understanding among the participants of the watershed system and the complex issues at stake.