The boreal biome exchanges large amounts of carbon (C) and greenhouse gases (GHGs) with the atmosphere and thus significantly affects the global climate. A managed boreal landscape consists of various sinks and sources of carbon dioxide (CO2), methane (CH4), and dissolved organic and inorganic carbon (DOC and DIC) across forests, mires, lakes, and streams. Due to the spatial heterogeneity, large uncertainties exist regarding the net landscape carbon balance (NLCB). In this study, we compiled terrestrial and aquatic fluxes of CO2, CH4, DOC, DIC, and harvested C obtained from tall‐tower eddy covariance measurements, stream monitoring, and remote sensing of biomass stocks for an entire boreal catchment (~68 km2) in Sweden to estimate the NLCB across the land–water–atmosphere continuum. Our results showed that this managed boreal forest landscape was a net C sink (NLCB = 39 g C m?2 year?1) with the landscape–atmosphere CO2 exchange being the dominant component, followed by the C export via harvest and streams. Accounting for the global warming potential of CH4, the landscape was a GHG sink of 237 g CO2‐eq m?2 year?1, thus providing a climate‐cooling effect. The CH4 flux contribution to the annual GHG budget increased from 0.6% during spring to 3.2% during winter. The aquatic C loss was most significant during spring contributing 8% to the annual NLCB. We further found that abiotic controls (e.g., air temperature and incoming radiation) regulated the temporal variability of the NLCB whereas land cover types (e.g., mire vs. forest) and management practices (e.g., clear‐cutting) determined their spatial variability. Our study advocates the need for integrating terrestrial and aquatic fluxes at the landscape scale based on tall‐tower eddy covariance measurements combined with biomass stock and stream monitoring to develop a holistic understanding of the NLCB of managed boreal forest landscapes and to better evaluate their potential for mitigating climate change. 相似文献
There is growing international interest in better managing soils to increase soil organic carbon (SOC) content to contribute to climate change mitigation, to enhance resilience to climate change and to underpin food security, through initiatives such as international ‘4p1000’ initiative and the FAO's Global assessment of SOC sequestration potential (GSOCseq) programme. Since SOC content of soils cannot be easily measured, a key barrier to implementing programmes to increase SOC at large scale, is the need for credible and reliable measurement/monitoring, reporting and verification (MRV) platforms, both for national reporting and for emissions trading. Without such platforms, investments could be considered risky. In this paper, we review methods and challenges of measuring SOC change directly in soils, before examining some recent novel developments that show promise for quantifying SOC. We describe how repeat soil surveys are used to estimate changes in SOC over time, and how long‐term experiments and space‐for‐time substitution sites can serve as sources of knowledge and can be used to test models, and as potential benchmark sites in global frameworks to estimate SOC change. We briefly consider models that can be used to simulate and project change in SOC and examine the MRV platforms for SOC change already in use in various countries/regions. In the final section, we bring together the various components described in this review, to describe a new vision for a global framework for MRV of SOC change, to support national and international initiatives seeking to effect change in the way we manage our soils. 相似文献
Fire is a primary disturbance in boreal forests and generates both positive and negative climate forcings. The influence of fire on surface albedo is a predominantly negative forcing in boreal forests, and one of the strongest overall, due to increased snow exposure in the winter and spring months. Albedo forcings are spatially and temporally heterogeneous and depend on a variety of factors related to soils, topography, climate, land cover/vegetation type, successional dynamics, time since fire, season, and fire severity. However, how these variables interact to influence albedo is not well understood, and quantifying these relationships and predicting postfire albedo becomes increasingly important as the climate changes and management frameworks evolve to consider climate impacts. Here we developed a MODIS‐derived ‘blue sky’ albedo product and a novel machine learning modeling framework to predict fire‐driven changes in albedo under historical and future climate scenarios across boreal North America. Converted to radiative forcing (RF), we estimated that fires generate an annual mean cooling of ?1.77 ± 1.35 W/m2 from albedo under historical climate conditions (1971–2000) integrated over 70 years postfire. Increasing postfire albedo along a south–north climatic gradient was offset by a nearly opposite gradient in solar insolation, such that large‐scale spatial patterns in RF were minimal. Our models suggest that climate change will lead to decreases in mean annual postfire albedo, and hence a decreasing strength of the negative RF, a trend dominated by decreased snow cover in spring months. Considering the range of future climate scenarios and model uncertainties, we estimate that for fires burning in the current era (2016) the cooling effect from long‐term postfire albedo will be reduced by 15%–28% due to climate change. 相似文献
Obsolescence, as premature end of use, increases the overall number of products produced and consumed, and thereby can increase the environmental impact. Measures to decrease the effects of obsolescence by altering the product or service design have the potential to increase use time (defined as the realized active service life) of devices, but can themselves have (environmental) drawbacks, for example, because the amount of material required for production increases. As such, paying special attention to methodological choices when assessing such measures and strategies using life cycle assessment (LCA) needs is crucial.
Methods
Open questions and key aspects of obsolescence, including the analysis of its effects and preventative measures, are discussed against the backdrop of the principles and framework for LCA given in ISO 14040/44, which includes guidance on how to define a useful functional unit and reference flow in the context of real-life use time.
Results and discussion
The open and foundational requirements of ISO 14040/14044 already form an excellent basis for analysis of the phenomenon obsolescence and its environmental impact in product comparisons. However, any analysis presumes clear definition of the goal and scope phase with special attention paid to aspects relevant to obsolescence: the target product and user group needs to be placed into context with the analysed “anti-obsolescence” measures. The reference flow needs to reflect a realized use time (and not solely a technical lifetime when not relevant for the product under study). System boundaries and types of data need to be chosen also in context of the anti-obsolescence measure to include, for example, the production of spare parts to reflect repairable design and/or manufacturer-specific yields to reflect high-quality manufacturing.
Conclusions
Understanding the relevant obsolescence conditions for the product system under study and how these may differ across the market segment or user types is crucial for a fair and useful comparison and the evaluation of anti-obsolescence measures.
The International Journal of Life Cycle Assessment - Since 2013, the European Commission (EC) is developing and testing the Product Environmental Footprint (PEF)—a product evaluation method,... 相似文献
In oxygenic photosynthetic organisms, excluding angiosperms, flavodiiron proteins (FDPs) catalyze light‐dependent reduction of O2 to H2O. This alleviates electron pressure on the photosynthetic apparatus and protects it from photodamage. In Synechocystis sp. PCC 6803, four FDP isoforms function as hetero‐oligomers of Flv1 and Flv3 and/or Flv2 and Flv4. An alternative electron transport pathway mediated by the NAD(P)H dehydrogenase‐like complex (NDH‐1) also contributes to redox hemostasis and the photoprotection of photosynthesis. Four NDH‐1 types have been characterized in cyanobacteria: NDH‐11 and NDH‐12, which function in respiration; and NDH‐13 and NDH‐14, which function in CO2 uptake. All four types are involved in cyclic electron transport. Along with single FDP mutants (?flv1 and Δflv3) and the double NDH‐1 mutants (?d1d2, which is deficient in NDH‐11,2 and ?d3d4, which is deficient in NDH‐13,4), we studied triple mutants lacking one of Flv1 or Flv3, and NDH‐11,2 or NDH‐13,4. We show that the presence of either Flv1/3 or NDH‐11,2, but not NDH‐13,4, is indispensable for survival during changes in growth conditions from high CO2/moderate light to low CO2/high light. Our results show functional redundancy between FDPs and NDH‐11,2 under the studied conditions. We suggest that ferredoxin probably functions as a primary electron donor to both Flv1/3 and NDH‐11,2, allowing their functions to be dynamically coordinated for efficient oxidation of photosystem I and for photoprotection under variable CO2 and light availability. 相似文献