The impact of carbon revenue on the profitability of agroforestry systems in comparison to monocultures is unexplored in regard to Sub-Saharan Africa. This study creates a multivariate model to evaluate the impact of carbon revenue on the profitability of agroforestry relative to the dominant monocultures in Ethiopia by using stylized plots. Yields and carbon stock changes of eight agroforestry systems were modeled based on data from agroforestry plots in the Ethiopian Central Rift Valley. According to our model, agroforestry was, on average, four times more profitable than the main monoculture systems (wheat, barley, maize, teff, sorghum, sugarcane and lentil) even when carbon revenues were excluded, primarily due to the higher prices of fruit produce. Carbon revenues were estimated using a plausible carbon price ranging from US$8/tCO2e to $40/tCO2e and carbon sequestration rates of 0.59 to 17.2 Mg C ha−1 year−1. The possibility of receiving carbon revenue increased the profitability of agroforestry by 0.5% when using the lowest utilized carbon price and carbon sequestration rate, by 20% when using the carbon price of $20 and the average carbon sequestration rate, and by 70% when using the highest price and highest sequestration rate of carbon. On average, carbon revenue increased the profitability of agroforestry by 150% in comparison to monoculture farming. We conclude that carbon income may have significant potential to motivate smallholders to convert to agroforestry when there is a proper management system, a sufficiently high carbon price and effective institutional support to mitigate the transition and transaction costs.

In order to achieve the goals of carbon (C) neutrality within next 20 year, municipalities worldwide need to increasingly apply negative emission technologies. We focus on the main principles of urban demonstration areas using biochars for C sequestration and explore the lessons learned from a co-creation process of one such park, Hyvantoivonpuisto in Helsinki, Finland. Demonstration sites of urban C sinks in public parks must be safe, visible and scientifically sound for reliable and cost-effective verification of carbon sequestration. We find that different interests can be arbitrated and that synergy that emerges from co-creation of urban C sink parks between stakeholders (scientists, city officials, companies, and citizens) can result in demo areas with maximized potential for impact, dissemination and consideration of principles of scientific experimentation.

We study the economics of carbon storage using a model that includes forest size structure and determines the choice between rotation forestry and continuous cover forestry. Optimal harvests may rely solely on thinning, implying infinite rotation and continuous cover forestry, or both thinning and clearcuts, implying finite rotation periods. Given several carbon prices and interest rates, we optimize the timing and intensity of thinnings along with the choice of management regime. In addition to the carbon storage in living trees, we include the carbon dynamics of dead trees and timber products. Forest growth is specified by an empirically validated transition matrix model for Norway spruce (Picea abies (L.) Karst.). The optimization problem is solved in its general dynamic form by applying bilevel optimization with gradient-based interior point methods and a genetic algorithm. Carbon pricing postpones thinnings, increases stand density by directing harvests to larger trees, and typically yields a regime shift from rotation forestry to continuous cover forestry. In continuous cover solutions, the steady-state harvesting interval and the diameter distribution of standing and harvested trees are sensitive to carbon price, implying that carbon pricing increases the sawlog ratio of timber yields. Additionally, we obtain relatively inexpensive stand-level marginal costs of carbon storage.

Purpose Currently, no clear guidance exists for ISO and EN standards of calculating, verifying, and reporting the climate impacts of plants, mulches, and soils used in landscape design and construction. In order to optimise the potential of ecosystem services in the mitigation of greenhouse gas emissions in the built environment, we unequivocally propose their inclusion when assessing sustainability. Methods We analysed the life cycle phases of plants, soils, and mulches from the viewpoint of compiling standard-based Environmental Product Declarations. In comparison to other construction products, the differences of both mass and carbon flows were identified in these products. Results Living and organic products of green infrastructure require an LCA approach of their own. Most importantly, if conventional life cycle guidance for Environmental Product Declarations were to be followed, over time, the asymmetric mass and carbon flows would lead to skewed conclusions. Moreover, the ability of plants to reproduce raises additional questions for allocating environmental impacts. Conclusions We present a set of recommendations that are required for compiling Environmental Product Declarations for the studied products of green infrastructure. In order to enable the quantification of the climate change mitigation potential of these products, it is essential that work for further development of LCA guidance be mandated.

In Vietnam, fast-growing Acacia hybrid dominates commercial smallholdings and is largely managed in short rotations for pulpwood. However, increasing demand for logwood implies growing Acacia hybrid in longer rotations. One way of encouraging smallholders to prolong the rotation would be payments for aboveground carbon storage. Thus, this study evaluated the financial attractiveness of shifting from pulpwood to logwood production, with and without hypothetical carbon payments of $5, $10 and $20 tCO(2)e ha(-1). The data were drawn from smallholder interviews, a plantation inventory and a market study. The growth models for a 5-year pulpwood regime and various logwood regimes used for financial modelling were developed in CO2FIX simulation software. With a financially optimal rotation length of 9-10 years, the study finds that growing Acacia hybrid for logwood is much more profitable than growing it for pulpwood. However, due to thinning in logwood regime, a financially optimal logwood regime stores only 15-16% more carbon than a 5-year pulpwood regime. Consequently, carbon payments at any of the three price levels would not shift the financially optimal rotation length. The study concluded that carbon payments alone are unlikely to be an effective means to encourage smallholders in central Vietnam to prolong the rotation.

The boreal forest is an important global carbon (C) sink. Since low soil nitrogen (N) availability is commonly a key constraint on forest productivity, the prevalent view is that increased N input enhances its C sink-strength. This understanding however relies primarily on observations of increased aboveground tree biomass and soil C stock following N fertilization, whereas empirical data evaluating the effects on the whole ecosystem-scale C balance are lacking. Here we use a unique long-term experiment consisting of paired forest stands with eddy covariance measurements to explore the effect of ecosystem-scale N fertilization on the C balance of a managed boreal pine forest. We find that the annual C uptake (i.e. net ecosystem production, NEP) at the fertilized stand was 16 +/- 2% greater relative to the control stand by the end of the first decade of N addition. Subsequently, the ratio of NEP between the fertilized and control stand remained at a stable level during the following five years with an average NEP to N response of 7 & PLUSMN; 1 g C per g N. Our study reveals that this non-linear response of NEP to long-term N fertilization was the result of a cross-seasonal feedback between the N-induced increases in both growing-season C uptake and subsequent winter C emission. We further find that one decade of N addition altered the sensitivity of ecosystem C fluxes to key environmental drivers resulting in divergent responses to weather patterns. Thus, our study highlights the need to account for ecosystem-scale responses to perturbations to improve our understanding of nitrogen-carbon-climate feedbacks in boreal forests.

During the last decade it has been increasingly acknowledged that carbon (C) contained in root exudates can accelerate decomposition of soil organic matter (SOM), a phenomenon known as rhizosphere priming effect (RPE). However, the controlling factors and the role of different soil microorganisms in RPE are not yet well understood. There are some indications that the response of the soil microbial decomposers to labile C input in the rhizosphere depends on microbial demand of nutrients for growth and maintenance, especially that of C and nitrogen (N). To test this hypothesis, we assessed SOM decomposition induced by 13C-glucose additions during one week in forest soils with different C:N ratios (11.5–22.2). We estimated SOM respiration, the potential activity (concentration) of a range of extracellular enzymes, and incorporation of 13C and deuterium (D) in microbial phospholipid fatty acids (PLFAs). Glucose additions induced positive priming (a 12–52% increase in SOM respiration) in all soil types, but there was no linear relationship between priming and the soil C:N ratio. Instead, priming of SOM respiration was positively linked to the C:N imbalance, where a higher C:N imbalance implies stronger microbial N limitation. The total oxidative enzyme activity and the ratio between the activities of C and N acquiring enzymes were lower in soil with higher C:N ratios, but these findings could not be quantitatively linked to the observed priming rates. It appears as if glucose addition resulted in priming by stimulating the activity rather than the concentration of oxidative enzymes. Microbial incorporation of D and 13C into in PLFAs demonstrated that glucose additions stimulated both fungal and bacterial growth. The increased growth was mainly supported by glucose assimilation in fungi, while the increase in bacterial growth partly was a result of increased availability of C or N released from SOM. Taken together, the findings suggest that the soil C:N ratio is a poor predictor of priming and that priming is more dependent on the C:N imbalance, which reflects both microbial nutrient demand and nutrient provision.

Mollisols are globally distributed in grain-producing regions, and soil organic carbon (SOC) dynamics in mollisol regions are closely related to food security. Regional climate, land use and cover, and field management practice have massively changed since the 1980s in mollisol region in Northeast China, however, the dynamics of topsoil and profile SOC stocks and their distribution have not updated. To explore the dynamics of SOC stocks and their horizontal and vertical distributions in the 1980s-2010s, we took the mollisol region in Northeast China as an example location to conduct profile-scale soil surveys. The in situ surveys indicated that the topsoil SOC stock (0-20 cm) remained relatively stable throughout the 1980s, 2000s, and 2010s, and was 57.3 +/- 5.5, 58.2 +/- 3.3, and 57.4 +/- 4.4 t C ha(-1), respectively. The average profile SOC stock (1 m) increased from 148.9 +/- 18.5 t C ha(-1) in the 1980s to 162.0 +/- 14.0 t C ha(-1) in the 2010s. A slowdown in land reclamation and implementation of conservation tillage helped maintain and restore SOC stocks. Although the overall SOC stock tended to accumulate, the study area suffered an increasingly unbalanced redistribution of SOC related to severe soil erosion. Soil particles and SOC at erosional positions such as backslope were stripped from the soil surface, leading to attenuated soil thickness and SOC stock; SOC-rich sediment accumulated and was buried at depositional positions, especially at the foot-slope, increasing the soil thickness and SOC stock. These results confirmed that not only the total SOC stock, but also changes in SOC spatial distribution deserve great attention. This study provides a platform to examine and modify the simulation effectiveness of carbon-cycling models, as well as solid foundations for optimal global mollisols management. (C) 2021 The Authors. Published by Elsevier B.V.