Small Sink Research Articles

Carbon uptake in Eurasian boreal forests dominates the high-latitude net ecosystem carbon budget.

Arctic-boreal landscapes are experiencing profound warming, along with changes in ecosystem moisture status and disturbance from fire. This region is of global importance in terms of carbon feedbacks to climate, yet the sign (sink or source) and magnitude of the Arctic-boreal carbon budget within recent years remains highly uncertain. Here, we provide new estimates of recent (2003-2015) vegetation gross primary productivity (GPP), ecosystem respiration (Reco ), net ecosystem CO2 exchange (NEE; Reco - GPP), and terrestrial methane (CH4 ) emissions for the Arctic-boreal zone using a satellite data-driven process-model for northern ecosystems (TCFM-Arctic), calibrated and evaluated using measurements from >60 tower eddy covariance (EC) sites. We used TCFM-Arctic to obtain daily 1-km2 flux estimates and annual carbon budgets for the pan-Arctic-boreal region. Across the domain, the model indicated an overall average NEE sink of -850 Tg CO2 -C year-1 . Eurasian boreal zones, especially those in Siberia, contributed to a majority of the net sink. In contrast, the tundra biome was relatively carbon neutral (ranging from small sink to source). Regional CH4 emissions from tundra and boreal wetlands (not accounting for aquatic CH4 ) were estimated at 35 TgCH4 -C year-1 . Accounting for additional emissions from open water aquatic bodies and from fire, using available estimates from the literature, reduced the total regional NEE sink by 21% and shifted many far northern tundra landscapes, and some boreal forests, to a net carbon source. This assessment, based on in situ observations and models, improves our understanding of the high-latitude carbon status and also indicates a continued need for integrated site-to-regional assessments to monitor the vulnerability of these ecosystems to climate change.

Influence of gypsum and cover crop on greenhouse gas emissions in soybean cropping systems

Agriculture has the opportunity to mitigate anthropogenic contributions to global change by increasing soil sequestration of greenhouse gases (GHG) and by reducing efflux through management. Common agricultural management practices include crop rotation and use of cover crops. Interest in the use of gypsum in agricultural systems has also increased in recent years. However, little is known regarding how combining gypsum with other management practices impact GHG emissions in soybean (<i>Glycine max</i> [L.] Merr.)-based cropping systems. A study was implemented at three locations (i.e., east-central Indiana, northwest Ohio, and east-central Alabama) to evaluate the influence of gypsum and cover cropping within a continuous soybean and a corn (<i>Zea mays</i> L.)–soybean rotation on crop yield and soil properties. Within this study, carbon dioxide (CO₂), nitrous oxide (N₂O), and methane (CH₄) were also monitored periodically following soybean seeding through harvest from 2012 to 2016. The combined gas data were then used to calculate a global warming potential (GWP). Overall, few differences in GHG emissions were observed across sites and years, and no consistent patterns were noted, likely due to large variabilities in gas efflux measurements and limited influence of treatments on trace gases. However, treatment differences were observed for one or more GHG within specific years and at specific sites. Comparison across sites revealed the warmer/wetter climate in Alabama resulted in greater CO₂ efflux, while climate and soil factors at the northern sites led to greater N₂O efflux. At all locations, CH₄ emissions were generally low and sites tended to be small net sinks. Given that GHG emissions drive GWP, it also showed few treatment responses and no consistent patterns. It can be concluded from this study that contributions of gypsum and cover crop to GHG emissions from soil in soybean cropping systems will likely have little influence on contributions to global climate change.

Directional polymer crystallisation with a fast-moving sink.

It has previously been shown that non-isothermal directional polymer crystallisation driven by local melting (Zone Annealing), has a close analogy with an equivalent isothermal crystallisation protocol. This surprising analogy is due to the low thermal conductivity of polymers-because they are poor thermal conductors, crystallisation occurs over a relatively narrow spatial domain while the thermal gradient spans a much wider scale. This separation of scales, which occurs in the limit of small sink velocity, allows replacing the crystallinity profile with a step and the temperature at the step acts as an effective isothermal crystallisation temperature. In this paper, we study directional polymer crystallisation under faster moving sinks using both numerical simulations and analytical theory. While, only partial crystallisation occurs, regardless, a steady state exists. At large velocity, the sink quickly moves ahead of a region that is still crystallizing; since polymers are poor thermal conductors, the latent heat dissipation to the sink becomes inefficient, eventually resulting in the temperature increasing back to the melting point thereby resulting in incomplete crystallization. This transition occurs when the two length scales measuring the sink-interface distance and the width of the crystallizing interface become comparable. For steady state and in the limit of large sink velocity, regular perturbation solutions of the differential equations governing heat transport and crystallization in the region between the heat sink and the solid-melt interface are in good agreement with numerical results.

Siberian carbon sink reduced by forest disturbances

Siberian forests are generally thought to have acted as an important carbon sink over recent decades, but exposure to severe droughts and fire disturbances may have impacted their carbon dynamics. Limited available forest inventories mean the carbon balance remains uncertain. Here we analyse annual live and dead above-ground carbon changes derived from low-frequency passive microwave observations from 2010 to 2019. We find that during this period, the carbon balance of Siberian forests was close to neutral, with the forests acting as a small carbon sink of $$+ 0.02_{ + 0.01}^{ + 0.03}$$ PgC yr−1. Carbon storage in dead wood increased, but this was largely offset by a decrease in live biomass. Substantial losses of live above-ground carbon are attributed to fire and drought, such as the widespread fires in northern Siberia in 2012 and extreme drought in eastern Siberia in 2015. These live above-ground carbon losses contrast with ‘greening’ trends seen in leaf area index over the same period, a decoupling explained by faster post-disturbance recovery of leaf area than live above-ground carbon. Our study highlights the vulnerability of large forest carbon stores in Siberia to climate-induced disturbances, challenging the persistence of the carbon sink in this region of the globe. Carbon sequestration by Siberian forests has been low over the past decade due to disturbances that have decreased live biomass and increased dead wood, according to passive microwave observations.

Implications of tropical cyclones on damage and potential recovery and restoration of logged forests in Vietnam.

Many natural forests in Southeast Asia are degraded following decades of logging. Restoration of these forests is delayed by ongoing logging and tropical cyclones, but the implications for recovery are largely uncertain. We analysed meteorological, satellite and forest inventory plot data to assess the effect of Typhoon Doksuri, a major tropical cyclone, on the forest landscapes of central Vietnam consisting of natural forests and plantations. We estimated the return period for a cyclone of this intensity to be 40 years. Plantations were almost twice as likely to suffer cyclone damage compared to natural forests. Logged natural forests (9-12 years after cessation of government-licensed logging) were surveyed before and after the storm with 2 years between measurements and remained a small biomass carbon sink (0.1 ± 0.3 Mg C ha-1 yr-1) over this period. The cyclone reduced the carbon sink of recovering natural forests by an average of 0.85 Mg C ha-1 yr-1, less than the carbon loss due to ongoing unlicensed logging. Restoration of forest landscapes in Southeast Asia requires a reduction in unlicensed logging and prevention of further conversion of degraded natural forests to plantations, particularly in landscapes prone to tropical cyclones where natural forests provide a resilient carbon sink. This article is part of the theme issue 'Understanding forest landscape restoration: reinforcing scientific foundations for the UN Decade on Ecosystem Restoration'.

Microbial mechanisms for methane source-to-sink transition after wetland conversion to cropland

Wetland conversion to cropland substantially reduces methane (CH4) emission, turning a source into a sink on many occasions; how various microbial processes contribute to this source-to-sink transition remains elusive. We addressed this issue by examining the net CH4 flux, CH4 production potential, CH4 oxidation potential, and functional genes associated with methanogenesis and methanotrophy in a pristine wetland and a 23-year cultivated cropland in the Sanjiang Plain, China. The study confirmed that wetland conversion to cropland turned a CH4 source of 44.93 ± 10.17 g CH4·m−2·yr−1 to a small CH4 sink of −0.056 ± 0.051 g·CH4 m−2·yr−1. The proportion of total CH4-related genes, methanogenesis genes, as well as the CH4 production marker genes – mcr were significantly decreased by 24.14 %, 32.10 %, and 97.89 %, respectively in cropland. The proportions of methanotrophic marker genes, pMMO, and the sum of sMMO and pMMO were significantly increased by 48.74 % and 22.79 % after wetland cultivation. The 23-year cultivation yielded suppressing impacts on methanogenesis and mcr genes throughout the four seasons while stimulating effects on the functional genes of sMMO, pMMO, and MMO in spring and summer. The proportions of CH4-related genes decreased along soil depth in wetland and cropland, while pMMO and MMO slightly increased in the depth of 20–60 cm in cropland. A global synthesis supported this microbial mechanism for the CH4 source-to-sink transition, indicating the strong methanogenesis suppression and slight methanotrophy enhancement in explaining the source-to-sink transition after wetland conversion to cropland. This mechanism should be incorporated into CH4 models to predict CH4 dynamics under land-use change.

CO2 and CH4 exchanges between moist moss tundra and atmosphere on Kapp Linné, Svalbard

Abstract. We measured CO2 and CH4 fluxes using chambers and eddy covariance (only CO2) from a moist moss tundra in Svalbard. The average net ecosystem exchange (NEE) during the summer (9 June–31 August) was negative (sink), with −0.139 ± 0.032 µmol m−2 s−1 corresponding to −11.8 g C m−2 for the whole summer. The cumulated NEE over the whole growing season (day no. 160 to 284) was −2.5 g C m−2. The CH4 flux during the summer period showed a large spatial and temporal variability. The mean value of all 214 samples was 0.000511 ± 0.000315 µmol m−2 s−1, which corresponds to a growing season estimate of 0.04 to 0.16 g CH4 m−2. Thus, we find that this moss tundra ecosystem is closely in balance with the atmosphere during the growing season when regarding exchanges of CO2 and CH4. The sink of CO2 and the source of CH4 are small in comparison with other tundra ecosystems in the high Arctic. Air temperature, soil moisture and the greenness index contributed significantly to explaining the variation in ecosystem respiration (Reco), while active layer depth, soil moisture and the greenness index were the variables that best explained CH4 emissions. An estimate of temperature sensitivity of Reco and gross primary productivity (GPP) showed that the sensitivity is slightly higher for GPP than for Reco in the interval 0–4.5 ∘C; thereafter, the difference is small up to about 6 ∘C and then begins to rise rapidly for Reco. The consequence of this, for a small increase in air temperature of 1∘ (all other variables assumed unchanged), was that the respiration increased more than photosynthesis turning the small sink into a small source (4.5 g C m−2) during the growing season. Thus, we cannot rule out that the reason why the moss tundra is close to balance today is an effect of the warming that has already taken place in Svalbard.

Emissions of Greenhouse Gases and NO from Rice Fields and a Peach Orchard as Affected by N Input and Land-Use Conversion

Nitrogen (N) inputs and land-use conversion are management practices that affect soil greenhouse gas (GHG) and nitric oxide (NO) emissions. Here, we measured soil methane (CH4), nitrous oxide (N2O), and NO fluxes from rice fields and a peach orchard that converted from paddies to assess the impacts of nitrogen (N) inputs and land-use conversion on their emissions. Treatments included four paddy field treatments (PN0, PN160, PN220, and PN280) and one peach orchard treatment (ON280) with number indicating the N-input rate of kg N ha−1. The results showed that cumulative emissions of CH4, N2O and NO ranged from 28.6 to 85.3 kg C ha−1, 0.5 to 4.0 kg N ha−1 and 0.2 to 0.3 kg N ha−1 during the rice-growing season, respectively. In terms of greenhouse gas intensity, the PN280 treatment is the recommended N application rate. Land-use conversion significantly reduced the global warming potential from croplands. The conversion shifted soils from an essential source of CH4 to a small net sink. In addition, N2O emissions from the rice–wheat rotation system were 1.8 times higher than from the orchard, mainly due to the difference in the N application rate. In summary, to reduce agriculture-induced GHG emissions, future research needs to focus on the effects of N inputs on rice-upland crop rotation systems.

Coordinating maize source and sink relationship to achieve yield potential of 22.5 Mg ha-1

Coordination between source and sink is vital for the final maize grain yield planted under high density. To clarify the source and sink characteristics of high yield potential (22.5 Mg ha-1), a four-year field experiment was conducted at Qitai Farm in Xinjiang, China. At silking, the maximum leaf area indexes were 5.8, 7.5, and 6.2 for cultivars of high yield level-1 (H1), high yield level-2 (H2), and high yield level-3 (H3) with yield increase of H1 < H2 < H3, which were 2.2, 4.6, and 3.9 at maturity, respectively. The H3 biomass was significantly higher than those of H1 and H2 during post-silking, and the H2 and H3 total kernel numbers were significantly higher than H1’s, although H2 had a significantly higher harvest ear number. While H3’s kernel size was not the largest of the three levels, H3 had a significantly higher thousand kernel weight. The grain filling analysis showed that H1 and H3 had shorter lag period durations (D1) than H2, and H3 had a longer maturation drying period duration (D3) than the other groups did. However, H1 and H3 had significantly higher grain filling rates than H2 in the lag period (D1), and H3’s was the lowest in the maturation drying period (D3). Also, H3’s maximum grain filling rate was significantly higher than H2’s, and H3 had significantly higher biomass/kernel number and kernel weight/leaf area ratios than H1 and H2 did. Based on our findings, three high yield levels were classified into three source-sink types: (1) H1: small source and weak productivity, small sink and short maturation drying period duration (D3); (2) H2: large source but weak productivity, large sink but slow grain filling start, and low maximum grain filling rate; (3) H3: small source but strong productivity, large sink, fast grain filling start, long maturation drying period duration (D3), and high maximum grain filling rate. We achieved an actual high yield of 22.4 Mg ha-1 for H3, which was also the highest yield in China. Therefore, hybrids with H3-type source and sink characteristics should be selected in the future for high-yield cultivation under dense planting.

Experimental Evaluation of Nanofluid for Improved Cooling Efficiency in an AL Mini Channel Heat Sink

Abstract: Efficient heat transfer has become major need these days. In this thesis, both experimental and CFD investigations have to be carried out to evaluate the cooling performance of a mini-channel consisting of fins on upper surface of flat plate. Nano fluids contain a small fraction of solid nano particles in base fluids flowing through groves in bottom plate attached with heater at base. Nano fluids cools small channel heat sinks, have been anticipated to be an excellent heat dissipation method for the next generation electronic devices. Computational Fluid Dynamics (CFD) simulations is to be carried out to study the heat sinks heat transfer mechanism. The sectional geometry of channels affects the flow and heat transfer characteristics of mini channel heat sinks. The heat transfer principle states that maximum heat transfer is achieved in mini channels with minimum pressure drop across it. In this research work the experimental and numerical investigation for the improved heat transfer characteristics of mini channel heat sink using Al2O3/water nano with (1 and 2 % volume fraction) fluid is to be done. The fluid flow characteristics are also analysed for the serpentine shaped mini channel. Heating element of 130 W capacities is to be used to heat up the heating element of base plate. Keywords: Heat, Fluids, Heating, Nano, Fraction, Flow, Sink, Channel, Plate, Aluminum.

Diagnosis of the production cycle in the small shaft sinking

Shaft sinking is a classic activity in underground mines. In shafts with small cross-section or in mines with low mechanization indices it is common to use hand pneumatic drills and blasting by explosive gelatin in cartridges, employing natural draft or flexible ducts with axial fans for gases and fumes exhaustion, muck removal by hand shoveling into hoistable dumping buckets. System of this type has been studied here, consisting of a rectangular cross-section shaft (3.7 m x 2.0 m), with final depth of 94 m, excavated in order to obtain samples for a pilot-scale mineral processing testwork, before the open pit mine’s industrial startup. The shaft had a concrete collar and its walls were supported by wooden sets spaced 1.5 m and 25 mm thick wooden planks as liners. This shaft has been excavated in schist rocks belonging to the metamorphosed hydrothermal deposit of copper and gold located in Chapada (municipality of Mara Rosa, Brazil). Daily production worksheets covering one month campaign were statistically analyzed, encompassing the entire cycle of mining operations, namely drilling, charging and blasting, fumes exhaustion, mucking, wall and face trimming and scaling, and assemblage of support system. Operation downtimes were also quantified. Statistical analysis of productivity indices allowed the detection of critical points of the operation and the establishment reference for similar mining operations.

Effects of potassium foliage supplementation on Coix lacryma-jobi L. yield formation and source-sink relationship compared with those of soil supplementation

The medicinal value of Coix lacryma-jobi L. has been recognized worldwide, but yields are unstable. Potassium (K) is one of the three most required and widely used nutrients, but the global soil K storage and K utilization rates are low. Based on a strategy of K fertilizer separate application, 20% K fertilizer (i.e., 30 kg K2O ha−1) was applied in three ways (K soil application–SK30, K foliar spray–FK30, and no K application–K0) at the flowering stage, to compare the effects of K application methods on coix seed filling process, source–sink balance, and economic yield. Results showed that K application increased coix seed yield and lipid yield by 25.7% and 39.6%, respectively, and increased the 100-seed weight and seed setting rate by 10.7% and 7.4%, respectively. The increase in lipid yield caused by FK30 was due to the increase in seed yield, since there was no significant difference in oil content between SK30 and FK30. Coix has the characteristics of a large source and small sink, and FK30 has a strong promoting effect on sink organs. Potassium foliar spray significantly increased the rate of seed filling and accelerated seed maturity by 1.2–2.8 days compared to soil application. In summary, K foliar spray based on K fertilizer separate application is a feasible strategy for improving coix seed and lipid yields, promoting seed maturity, and reducing the leaf area per sink capacity. This strategy could effectively alleviate the adverse effects of K deficiency on coix economic yield during the seed filling stage.

Permafrost Active Layer Microbes From Ny Ålesund, Svalbard (79°N) Show Autotrophic and Heterotrophic Metabolisms With Diverse Carbon-Degrading Enzymes.

The active layer of permafrost in Ny Ålesund, Svalbard (79°N) around the Bayelva River in the Leirhaugen glacier moraine is measured as a small net carbon sink at the brink of becoming a carbon source. In many permafrost-dominating ecosystems, microbes in the active layers have been shown to drive organic matter degradation and greenhouse gas production, creating positive feedback on climate change. However, the microbial metabolisms linking the environmental geochemical processes and the populations that perform them have not been fully characterized. In this paper, we present geochemical, enzymatic, and isotopic data paired with 10 Pseudomonas sp. cultures and metagenomic libraries of two active layer soil cores (BPF1 and BPF2) from Ny Ålesund, Svalbard, (79°N). Relative to BPF1, BPF2 had statistically higher C/N ratios (15 ± 1 for BPF1 vs. 29 ± 10 for BPF2; n = 30, p < 10–5), statistically lower organic carbon (2% ± 0.6% for BPF1 vs. 1.6% ± 0.4% for BPF2, p < 0.02), statistically lower nitrogen (0.1% ± 0.03% for BPF1 vs. 0.07% ± 0.02% for BPF2, p < 10–6). The d13C values for inorganic carbon did not correlate with those of organic carbon in BPF2, suggesting lower heterotrophic respiration. An increase in the δ13C of inorganic carbon with depth either reflects an autotrophic signal or mixing between a heterotrophic source at the surface and a lithotrophic source at depth. Potential enzyme activity of xylosidase and N-acetyl-β-D-glucosaminidase increases twofold at 15°C, relative to 25°C, indicating cold adaptation in the cultures and bulk soil. Potential enzyme activity of leucine aminopeptidase across soils and cultures was two orders of magnitude higher than other tested enzymes, implying that organisms use leucine as a nitrogen and carbon source in this nutrient-limited environment. Besides demonstrating large variability in carbon compositions of permafrost active layer soils only ∼84 m apart, results suggest that the Svalbard active layer microbes are often limited by organic carbon or nitrogen availability and have adaptations to the current environment, and metabolic flexibility to adapt to the warming climate.

Hysterosalpingography

Hysterosalpingography Rosalie Moffett (bio) a radiologic procedure to investigate the shape of the uterine cavity and the patency of the fallopian tubes In ancient Rome, a haruspex didn’t see the futurein the viscera of the sacrifice, just the mood of the gods,their disposition. Even then, in the prediction,a little wiggle room. In the room, the machine, maneuverablefrom the ceiling, small sink. No place for my clothes. Sacrificetableau too boring for a painting. The liver we knowwas of particular interest, the liver they thought the maker of blood, the maker of life itself.I bled through the napkin put there to be bled on.The gynecologist showed up in her lead apron.How we know what we know we owe to the bronzelivers recovered with their diagrams intact. That recovermeans to find or get better rather than hide or upholster seems a kind of test. My uterus, a knocked-out toothof dark dye on the x-ray. My good fortuneto be born in this era of divination, all my insidesstill on my inside. I was taught in school the funduswas the roof of the womb, though in any house, any holloworgan, it’s just the part farthest from the opening.The eye has one. The stomach. The sky you might say is a blue ceiling and below,doors to this world open along with shiny black exits,unholstered. Flag ceaselessly half-mast, new massshooting, old mass shooting. What good is itto grope hopefully into the future? No one will recover [End Page 141] my x-rays from the earth. They’re behind my patientportal, password-protected entrance whose virtual cathedralstretches back and back, but cannot bestepped into. As with the airabove my home, there are limits to the ownershipof my prospects. The wide straight line of the freewaysparks an expansive mindset. Exquisite fruiton a package with the lesser thing enclosed.Marketing, a failed CIA plot to inoculateagainst letdown. I once thought a life was like an odd objectyou inched out of a lake, knowing little by little more what kind of thing you had, as I didfrom the cheap motorboat, fishing up twistedlumber mill rejects, propellers, or cattle skeletons.But once it was clear what it was, it was easyto let it slide back in. You can see whyI’m in need of a new thought. In need of somethinginsurance refuses to cover. The Statue of Libertyquivers in a foreground conjured by the Magic Eye bookin the clinic waiting room. Like any promisedeparting from a pattern, even a small softeningof focus breaks it. Twitch away to the coverage —or is it recoverage, or recovering—of anothershooting. Phone footage and shouting. Page regressingto its cryptic scheme of flag fragments. The original appealof Magic Eye was in the disbelief in anything thereto see. My organs packed between the crescent moonsof my hips on the screen. One-room house with a roof.The dye was to bloom out like smoke from two chimneys.The present kept falling all around like rain, like questionsin a lengthy poll on my user experienceof this world, whether it was worth it to cut free a door painted shut. Shouting and bloodin the footage, too much to let in. The mood of the godswas sought via birds and via entrails. Outcomes hiding therelike shapes in another dimension a special technique—half crossing of the eyes—calls into being.The good of this method, of any methodof divination, is how it spares one [End Page 142] the act of lookingat what has been hauled, dripping, into the light.The lake I’m remembering is a reservoirmade by the Army Corps of Engineerswho choked a river for its power. It holds its own moonand everything anyone throws in. American museumin the depths, unvisitable. It’s just as well. After a whileit must get easier to leave a door shut. To softenall attention. I never made a promiseto this...

Five‐Year Analysis of Evaposublimation Characteristics and Its Role on Surface Energy Balance SEB on a Midlatitude Continental Glacier

AbstractAs a principal pathway of moisture loss of cryosphere, the sublimation of snow or ice needs to absorb a high amount of energy to complete the phase transition, while related researches on how sublimation affects surface energy balance (SEB) are still insufficient, causing unclear conclusions. To characterize the seasonal variation of a mountain glacier's sublimation or evaporation and analysis its role on SEB, the meteorological and glaciological data over five‐year measurement period (2016–2020) were obtained on the top of August‐one glacier. In the non‐melt period of a year (January–May and October–December), sensible heat flux H was the dominant energy contributor to glacier surface (76%), followed by net radiation Rnet (22%). Sublimation removed average 85 mm (0.4 mm/day) of water vapor from surface for the dry and windy weather, and the latent heat flux of sublimation LEE accounted for 33% of energy sinks (67% of energy was stored in the glacier Qs). In the melt period (June–September), evaposublimation (mainly composed of evaporation) reached to 36 mm (0.3 mm/day), but LEE only played a small heat sink (14%) and the Qm (the energy for melting) had the largest proportion (70%). Rnet and H contributed 81% and 15% of surface energy, respectively. Obviously, under the global climate warming, the sublimation of non‐melt period seems to be effective in decrease the heating rate of glacier surface.

Does a Large Ear Type Wheat Variety Benefit More From Elevated CO2 Than That From Small Multiple Ear-Type in the Quantum Efficiency of PSII Photochemistry?

Recently, several reports have suggested that the growth and grain yield of wheat are significantly influenced by high atmospheric carbon dioxide concentration (CO2) because of it photosynthesis enhancing effects. Moreover, it has been proposed that plants with large carbon sink size will benefit more from CO2 enrichment than those with small carbon sink size. However, this hypothesis is yet to be test in winter wheat plant. Therefore, the aim of this study was to examine the effect of elevated CO2 (eCO2) conditions on the quantum efficiency of photosystem II (PSII) photochemistry in large ear-type (cv. Shanhan 8675; greater ear C sink strength) and small multiple ear-type (cv. Early premium; greater vegetative C source strength) winter wheat varieties. The experiment was conducted in a free air CO2 enrichment (FACE) facility, and three de-excitation pathways of the primary reaction of PSII of flag leaf at the anthesis stage were evaluated under two CO2 concentrations (ambient [CO2], ∼415 μmol⋅mol–1, elevated [CO2], ∼550 μmol⋅mol–1) using a non-destructive technique of modulated chlorophyll fluorescence. Additionally, the grain yield of the two varieties was determined at maturity. Although elevated CO2 increased the quantum efficiency of PSII photochemistry (ΦPSII) of Shanhan 8675 (SH8675) flag leaves at the anthesis stage, the grain number per ear and 1,000-kernel weight were not significantly affected. In contrast, the ΦPSII of early premium (ZYM) flag leaves was significantly lower than that of SH8675 flag leaves at the anthesis stage, which was caused by an increase in the regulatory non-photochemical energy dissipation quantum (ΦNPQ) of PSII, suggesting that light energy absorbed by PSII in ZYM flag leaf was largely dissipated as thermal energy. The findings of our study showed that although SH8675 flag leaves exhibited higher C sink strength and quantum efficiency of PSII photochemistry at the anthesis stage, these factors alone do not ensure improved grain yield under eCO2 conditions.

Growing our future: Assessing the outcome of afforestation programs in Ontario, Canada

The United Nations Framework Convention on Climate Change (UNFCCC) requires its signatories, including Canada, to estimate and report their annual greenhouse gas (GHG) emissions and removals. Forests are an important natural resource as they slow the accumulation of atmospheric carbon through the process of carbon sequestration. Due to the role of forests as carbon sinks, governments consider afforestation projects as feasible climate change mitigation strategies. This article outlines a spatially-explicit approach to validating afforestation data in Ontario, Canada. Validation is a user-supervised process that uses satellite imagery, remote sensing tools, and other auxiliary data to confirm the presence of seedlings planted through Forests Ontario’s 50 Million Tree program. Of the 12 466 hectares assessed, 83% is identified as afforested, 6% is not afforested and 10% is not determined. The area classified as successful afforestation is used as input for the Generic Carbon Budget Model (GCBM), to simulate afforestation effects on carbon stocks. Our findings show the afforestation activities will create a small carbon sink by 2060. From this project, it is evident that spatial validation of afforestation data is feasible, although the collection of additional standardized auxiliary data is recommended for future afforestation projects, if carbon benefits are to be reported.

Small sinking particles control anammox rates in the Peruvian oxygen minimum zone

Anaerobic oxidation of ammonium (anammox) in oxygen minimum zones (OMZs) is a major pathway of oceanic nitrogen loss. Ammonium released from sinking particles has been suggested to fuel this process. During cruises to the Peruvian OMZ in April–June 2017 we found that anammox rates are strongly correlated with the volume of small particles (128–512 µm), even though anammox bacteria were not directly associated with particles. This suggests that the relationship between anammox rates and particles is related to the ammonium released from particles by remineralization. To investigate this, ammonium release from particles was modelled and theoretical encounters of free-living anammox bacteria with ammonium in the particle boundary layer were calculated. These results indicated that small sinking particles could be responsible for ~75% of ammonium release in anoxic waters and that free-living anammox bacteria frequently encounter ammonium in the vicinity of smaller particles. This indicates a so far underestimated role of abundant, slow-sinking small particles in controlling oceanic nutrient budgets, and furthermore implies that observations of the volume of small particles could be used to estimate N-loss across large areas.

Comparison of the carbon, water, and energy balances of mature stand and clear-fell stages in a British Sitka spruce forest and the impact of the 2018 drought

Sitka spruce is the major conifer species in British upland forests and is predominantly managed as even-aged, single-species plantations with rotation lengths of less than 50 years using a “patch clear-felling” system. Evidence on the impact of clear-felling on the carbon, water and energy balances of plantation forestry is sparse and extreme weather events, such as the 2018 drought that occurred across Europe, are expected to have considerable impact. We used energy balance and gas flux data from a typical mature stand and a clear-felled site on peaty-gley soil at Harwood Forest in Northumberland, UK, over 4 years to quantify the impact of clear-felling and investigate how the drought of 2018 affected these fluxes. Felling resulted in an annual CO2 source (7.05 tCha−1yr−1) of similar magnitude in absolute terms to the mature stand sink (−7.09 tCha−1yr−1). The source was reduced with the growth of ground vegetation, and after tree replanting two years post-felling, the site was a weak source. Felling increased reflected radiation by 92%, reduced evapotranspiration by 28% and therefore increased site wetness by 8%, while replanting and the spread of ground vegetation increased evapotranspiration by 16% on average. The warm, dry spring and summer in 2018 increased evapotranspiration and reduced net carbon uptake of the mature stand by 30% compared to the mean of the previous three years, because of a small decrease in photosynthetic uptake and a small increase in ecosystem respiration. The drought conditions also increased ecosystem losses of CO2 at the clear-felled site by 28%. The clear-fell site would have turned into a small CO2 sink in the second year after replanting, if there had not been a drought.

Winter Air‐Sea CO2 Fluxes Constructed From Summer Observations of the Polar Southern Ocean Suggest Weak Outgassing

AbstractThe Southern Ocean plays an important role in the global oceanic uptake of CO2. Estimates of the air‐sea CO2 flux are made using the partial pressure of CO2 at the sea surface (), but winter observations of the region historically have been sparse, with almost no coverage in the Pacific or Indian ocean sectors south of the Polar front in the period 2004–2017. Here, we use summertime observations of relevant properties in this region to identify subsurface waters that were last in contact with the atmosphere in the preceding winter, and then reconstruct “pseudo observations” of the wintertime . These greatly improve wintertime coverage south of the Polar Front in all sectors, improving the robustness of flux estimates there. We add the pseudo observations to other available observations of and use a multiple linear regression to produce a gap‐filled time‐evolving estimate of from which we calculate the air‐sea flux. The inclusion of the pseudo observations increases outgassing at the beginning of the period, but the effect reduces with time. We estimate a 2004–2017 long‐term mean flux of −0.02 ± 0.02 Pg C yr−1 for the Southern Ocean south of the Polar Front, similar to comparable studies based on shipboard data. However, we diverge somewhat from an estimate which utilized autonomous float data for recent years: we find a small sink in 2017 of −0.08 ± 0.03 Pg C yr−1 where the float‐based estimate suggested a small source.