Estimating crop net primary production using national inventory data and MODIS-derived parameters

National estimates of spatially-resolved cropland net primary production (NPP) are needed for diagnostic and prognostic modeling of carbon sources, sinks, and net carbon flux between land and atmosphere. Cropland NPP estimates that correspond with existing cropland cover maps are needed to drive biogeochemical models at the local scale as well as national and continental scales. Existing satellite-based NPP products tend to underestimate NPP on croplands. An Agricultural Inventory-based Light Use Efficiency (AgI-LUE) framework was developed to estimate individual crop biophysical parameters for use in estimating crop-specific NPP over large multi-state regions. The method is documented here and evaluated for corn (Zea mays L.) and soybean (Glycine max L. Merr.) in Iowa and Illinois in 2006 and 2007. The method includes a crop-specific Enhanced Vegetation Index (EVI), shortwave radiation data estimated using the Mountain Climate Simulator (MTCLIM) algorithm, and crop-specific LUE per county. The combined aforementioned variables were used to generate spatially-resolved, crop-specific NPP that corresponds to the Cropland Data Layer (CDL) land cover product. Results from the modeling framework captured the spatial NPP gradient across croplands of Iowa and Illinois, and also represented the difference in NPP between years 2006 and 2007. Average corn and soybean NPP from AgI-LUE was 917 g C m⁻² yr⁻¹ and 409 g C m⁻² yr⁻¹, respectively. This was 2.4 and 1.1 times higher, respectively, for corn and soybean compared to the MOD17A3 NPP product. Site comparisons with flux tower data show AgI-LUE NPP in close agreement with tower-derived NPP, lower than inventory-based NPP, and higher than MOD17A3 NPP. The combination of new inputs and improved datasets enabled the development of spatially explicit and reliable NPP estimates for individual crops over large regional extents.     

A global comparison of carbon-water-food nexus based on dietary consumption

Exploring the environmental impact of dietary consumption has become increasingly important to understand the carbon-water-food nexus, vital to achieving UN sustainable development goals. However, the research on diet-based nexus assessment is still lacking. Here, we developed an Environmentally Extended Multi-Regional Input-Output (EE-MRIO) model with compiling a global MRIO table based on the latest Global Trade Analysis Project (GTAP) 10 database, where we specifically constructed a water withdrawal account and matched it to each economy at the sectoral level. The regional heterogeneity and synergy of carbon-water nexus affected by dietary patterns in nine countries was explored. The results show that: (1) Dietary consumption is the main use of water withdrawal for each country; Japan, the US, South Korea, and India have a high per capita dietary water footprint. Mainly due to consumption of processed rice, Japan has the highest per capita value of 488 M³/year, accounting for 63.4% of the total water footprint. (2) The total dietary carbon footprints in China, India, and the US are high, which is mainly caused by the high consumption of animal products (including dairy) either due to the large population (China, India) or animal-based diet (the US). Americans have the highest per capita dietary carbon footprint, reaching 755.4 kg/year, 2.76 times that of the global average. (3) Generally, imported/foreign footprints account for a greater share in dietary water and carbon footprints of developed countries with an animal-based diet. (4) In the nexus analysis, the US, Japan, and South Korea are key-nexus countries, vegetables, fruit and nuts, tobacco and beverages, and other food products are selected as key-nexus sectors with relatively high dietary water and carbon footprint. Furthermore, dietary consumption choices lead to different environmental impacts. It is particularly important to find a sustainable dietary route adapted to each country considering that heterogeneity and synergism exist in key-nexus sectors to achieve the relevant Sustainable Development Goals.     

The Synergism between Methanogens and Methanotrophs and the Nature of their Contributions to the Seasonal Variation of Methane Fluxes in a Wetland: The Case of Dajiuhu Subalpine Peatland

Wetland ecosystems are the most important natural methane (CH₄) sources, whose fluxes periodically fluctuate. Methanogens (methane producers) and methanotrophs (methane consumers) are considered key factors affecting CH₄ fluxes in wetlands. However, the symbiotic relationship between methanogens and methanotrophs remains unclear. To help close this research gap, we collected and analyzed samples from four soil depths in the Dajiuhu subalpine peatland in January, April, July, and October 2019 and acquired seasonal methane flux data from an eddy covariance (EC) system, and investigated relationships. A phylogenetic molecular ecological networks (pMENs) analysis was used to identify keystone species and the seasonal variations of the co-occurrence patterns of methanogenic and methanotrophic communities. The results indicate that the seasonal variations of the interactions between methanogenic and methanotrophic communities contributed to CH₄ emissions in wetlands. The keystone species discerned by the network analysis also showed their importance in mediating CH₄ fluxes. Methane (CH₄) emissions in wetlands were lowest in spring; during this period, the most complex interactions between microbes were observed, with intense competition among methanogens while methanotrophs demonstrated better cooperation. Reverse patterns manifested themselves in summer when the highest CH₄ flux was observed. Methanoregula formicica was negatively correlated with CH₄ fluxes and occupied the largest ecological niches in the spring network. In contrast, both Methanocella arvoryzae and Methylocystaceae demonstrated positive correlations with CH₄ fluxes and were better adapted to the microbial community in the summer. In addition, soil temperature and nitrogen were regarded as significant environmental factors to CH₄ fluxes. This study was successful in explaining the seasonal patterns and microbial driving mechanisms of CH₄ emissions in wetlands.     

Interpretation of IPCC AR6 on buildings北大核心CSCD

IPCC于2022年4月正式发布了第六次评估报告(AR6)第三工作组(WGⅢ)报告《气候变化2022:减缓气候变化》,该报告以已发布的第一和第二工作组报告作为基础,评估了各领域减缓气候变化的进展。报告的第九章建筑章节系统全面地评估了全球建筑领域的温室气体排放现状、趋势和驱动因素,综述并评估了建筑减缓气候变化的措施、潜力、成本和政策。报告主要结论认为,全球建筑领域有可能在2050年实现温室气体净零排放,但如果政策措施执行不力,将有可能在建筑领域形成长达几十年的高碳锁定效应。报告的主要结论将成为全球建筑领域应对气候变化行动的重要参考,对于我国建筑领域实现碳达峰、碳中和目标也有非常重要的借鉴意义。     

Seeking a handle on climate change: Examining the comparative effectiveness of energy efficiency improvement and renewable energy production in the United States

This study examines the comparative effectiveness of two important proposed solutions to climate change—energy efficiency improvement and the development and use of renewable energy sources. We focus specifically on their impacts on carbon dioxide emissions by conducting fixed effects regression analysis of panel data pertaining to U.S. states. The analysis reveals a negative relationship between both remedies and carbon dioxide emissions. Although the effects of these potential solutions are statistically equivalent, renewable energy production has a slight edge. Reflecting upon these findings and the larger environmental problem, we caution against exclusive reliance on efficiency improvement and renewable energy to the neglect of other important actions, such as lifestyle modifications. A broad range of social changes, which incorporate the remedies investigated in this paper, are needed to limit long-term global temperature increases to the desired level.     

Negative-emissions technology portfolios to meet the 1.5 °C target

Our carbon-intensive economy has led to an average temperature rise of 1 °C since pre-industrial times. As a consequence, the world has seen increasing droughts, significant shrinking of the polar ice caps, and steady sea-level rise. To stall these issues’ worsening further, we must limit global warming to 1.5 °C. In addition to the economy’s decarbonization, this endeavour requires the use of negative-emissions technologies (NETs) that remove the main greenhouse gas, carbon dioxide, from the atmosphere. While techno-economic feasibility alone has driven the definition of negative-emissions solutions, NETs’ diverse, far-reaching implications demand a more holistic assessment. Here, we present a comprehensive framework, integrating NETs’ critical performance aspects of feasibility, effectiveness, and side impacts, to define the optimal technology mix within realistic outlooks. The resulting technology portfolios provide a useful new benchmark to compare carbon avoidance and removal measures and deliberately choose the best path to solve the climate emergency.     

河口沉积物孔隙水营养盐分布特征及扩散通量

通过2010年夏季在李村河口潮滩区3个站位的采样分析,研究了孔隙水营养盐的分布特征,并利用Fick第一定律估算了沉积物-水界面间营养盐的扩散通量。结果表明,孔隙水营养盐在不同站位间质量浓度不同,呈现出自河口上游向下游逐渐降低的分布趋势。NH₄⁺-N质量浓度为26.21~53.10 mg/L,是孔隙水中营养盐的主要组分。沉积物中有机物的降解反应主要在还原状态下进行,营养盐质量浓度在垂向上的变化受有机质含量及沉积物氧化还原环境改变的综合影响。除NO₃^--N外其他营养盐均由沉积物向上覆水体扩散,沉积物是底层水体营养盐的重要来源。     

碳纤维布加固钢筋混凝土梁的现场实荷加载试验

通过对某工程中的钢筋混凝土梁采取粘贴碳纤维布的方式进行加固,并现场抽取试验梁进行了现场堆载实荷加载试验,对试验梁的挠度、裂缝开展情况和承载能力进行了全面分析,对该加固工程的效果进行了评价,供同行参考。     

A comprehensive survey of lignin geochemistry in the sedimentary organic matter along the Kapuas River (West Kalimantan, Indonesia)

In this first study of lignin geochemistry in the world’s longest river on an island, surface sediments were collected along the Kapuas River, three lakes in the upper river, a tributary in the lower river and a separate river during June-July 2007 and December 2007-January 2008. The samples were analyzed for lignin-derived phenols and bulk elemental and stable carbon isotope compositions. Λ values (the sum of eight lignin phenols, expressed as mg/100 mg organic carbon (OC)) ranged from 0.13 to 3.70. Ratios of syringyl/vanillyl (S/V) and cinnamyl/vanillyl (C/V) ranged from 0.34 to 1.18 and 0.28 to 1.40, respectively, indicating the presence of non-woody angiosperm tissues. The high vanillic acid to vanillin (Ad/Al)v (0.71-2.01) and syringic acid to syringaldehyde (Ad/Al)s (0.72-2.12) ratios indicate highly degraded lignin materials. In the upper Kapuas River, highly degraded soil materials discharged from lands that were barren as a result of deforestation activities were detected in the locations directly in those vicinities. The middle Kapuas River showed rapid organic matter degradation, probably due to the presence of fresh terrestrial and phytoplankton organic matter fueling the biogeochemical cycling. The Kapuas Kecil River, one of the two branches in the lower reach of the Kapuas River, showed higher levels and diagenesis of sedimentary organic matter due to input from anthropogenic sources and increased marine organic matter near the mouth. This study shows that different stretches along the river exhibit different levels and composition of sedimentary organic matter, as well as different carbon dynamics, which is directly attributable to the varying landscapes and quality of organic matter.     

Soil Organic Carbon mapping of partially vegetated agricultural fields with imaging spectroscopy

Soil Organic Carbon (SOC) is one of the key soil properties, but the large spatial variation makes continuous mapping a complex task. Imaging spectroscopy has proven to be an useful technique for mapping of soil properties, but the applicability decreases rapidly when fields are partially covered with vegetation. In this paper we show that with only a few percent fractional maize cover the accuracy of a Partial Least Square Regression (PLSR) based SOC prediction model drops dramatically. However, this problem can be solved with the use of spectral unmixing techniques. First, the fractional maize cover is determined with linear spectral unmixing, taking the illumination and observation angles into account. In a next step the influence of maize is filtered out from the spectral signal by a new procedure termed Residual Spectral Unmixing (RSU). The residual soil spectra resulting from this procedure are used for mapping of SOC using PLSR, which could be done with accuracies comparable to studies performed on bare soil surfaces (Root Mean Standard Error of Calibration = 1.34 g/kg and Root Mean Standard Error of Prediction = 1.65 g/kg). With the presented RSU approach it is possible to filter out the influence of maize from the mixed spectra, and the residual soil spectra contain enough information for mapping of the SOC distribution within agricultural fields. This can improve the applicability of airborne imaging spectroscopy for soil studies in temperate climates, since the use of the RSU approach can extend the flight-window which is often constrained by the presence of vegetation.