Atmospheric Carbon Sequestration Research Articles

Accounting of carbon sequestration and tradeoff under various climatic scenarios in alternative agricultural system: a comprehensive framework toward carbon neutrality

IntroductionThe increase in atmospheric CO2 concentration, which mainly is attributed to fossil-fuel combustion and deforestation, is often suggested as one of the prime causative factors toward accelerated global warming. This commends for sequestration of atmospheric carbon under terrestrial systems to partially offset fossil-fuel emissions. Concerning the same, agricultural sector presents an extensive opportunity, especially for countries such as India where over 55% of the population is engaged in the agriculture sector.MethodsSequestering atmospheric carbon in agriculture requires the adoption of climate-resilient alternative agriculture practices without compromising food security. The deliberated study highlights the options of alteration in current conventional farming practices and its economic evaluation for sequestrating carbon under two Climate Change (CC) scenarios, viz., RCP 4.5 and 8.5, over three temporal scales, i.e., 2020, 2030, and 2050. Considering the current land-use pattern and existing growth rate in land-use shifting, three land-use policies, namely, Business as Usual (BaU), Optimistic, and Pessimistic scenario, integrated with CC scenarios were contemplated. Six possible futuristic scenarios were generated for the assessment of carbon sequestration and its valuation following the Integrated Valuation of Ecosystem Services and Tradeoff (InVEST) model.ResultsThe results suggested that across the studied region adopting an optimistic policy over BaU and pessimistic scenario, carbon can sequestrate an additional 0.64 to 1.46 Mt. (2.35 to 5.36 million ton CO2e) having an economic value of 193.4 to 504.8 million USD.ResultsMoreover, the outcomes of the study are advocated for the policy of carbon credit in the agriculture sector, which shall contribute toward meeting various nationally determined contributions (NDCs) and sustainable development goals (SDGs) as well.

All tidal wetlands are blue carbon ecosystems.

Managing coastal wetlands is one of the most promising activities to reduce atmospheric greenhouse gases, and it also contributes to meeting the United Nations Sustainable Development Goals. One of the options is through blue carbon projects, in which mangroves, saltmarshes, and seagrass are managed to increase carbon sequestration and reduce greenhouse gas emissions. However, other tidal wetlands align with the characteristics of blue carbon. These wetlands are called tidal freshwater wetlands in the United States, supratidal wetlands in Australia, transitional forests in Southeast Asia, and estuarine forests in South Africa. They have similar or larger potential for atmospheric carbon sequestration and emission reductions than the currently considered blue carbon ecosystems and have been highly exploited. In the present article, we suggest that all wetlands directly or indirectly influenced by tides should be considered blue carbon. Their protection and restoration through carbon offsets could reduce emissions while providing multiple cobenefits, including biodiversity.

Influence of Irrigation on Biomass Partitioning in Above- and Belowground Organs of Trees Planted in Desert Sites of Mongolia

Planting trees is considered a crucial factor in mitigating the increase in carbon emissions in the atmosphere by generating plant biomass. In addition to advancing our understanding of how tree biomass is allocated in desert environments, we explore potential variations in biomass partitioning based on the irrigation regimes (4, 8, and 12 L h−1) supporting the growth of these trees. Specifically, this study compares the pattern of biomass distribution between above-ground and belowground organs of 11-year-old trees (U. pumila, E. moorcroftii, and T. ramosissima) planted in a desert site in Mongolia. An interesting result of this study is the demonstration that biomass partitioning among roots of different diameter classes differs between the tree species tested, suggesting that each tree species establishes its own type of root/soil interaction. The differences in biomass partitioning in roots could determine specificity in the strength of anchorage and efficiency of nutrition for the trees. We also demonstrate that the presence of plantations influences certain chemical properties of the desert soil, with differences depending on the tree species planted. In addition to presenting a method for planting trees in desert sites, this study underscores that a reliable evaluation of atmospheric carbon sequestration in trees must necessarily include root excavation to obtain an accurate measurement of biomass stored in belowground structures. Assessing the overall biomass produced by these trees allows us to determine the potential for carbon sequestration achievable through plantations established in desert sites.

Accumulation of soil microbial extracellular and cellular residues during forest rewilding: Implications for soil carbon stabilization in older plantations

Soil microbial residues are a critical component of stable soil organic carbon pools in terrestrial ecosystems. Plantations are anticipated to increase soil stable carbon stocks and contribute toward addressing global climate change. How rewilding, as a strategy to restore the multiple ecological functions of plantations, affects soil microbial residues remains to be elucidated. Here, we divided microbial residues into extracellular residues (using extracellular polymeric substances, i.e., EPS, as a proxy) and cellular residues (estimated by amino sugars) and investigated the changes in their accumulation over four decades (6–45 years) of Metasequoia glyptostroboides plantation development. It was found that forest rewilding resulted in a linear accumulation of soil microbial residues and enhanced their contributions to the soil organic carbon. Specifically, EPS-polysaccharide increased by 126.5%, while the total cellular residue carbon, fungal cellular residue carbon, and bacterial cellular residue carbon increased by 73.4%, 77.2%, and 54.3%, respectively. Correspondingly, the contributions of EPS-polysaccharide and total cellular residue carbon to the soil organic carbon increased by 66.1% and 32.1%, respectively. The main drivers behind extracellular and cellular residues differed, with fine root biomass being the main driver of extracellular residues, while soil nitrogen and organic carbon content were the main drivers of cellular residues. Our study demonstrated that through rewilding, microbial extracellular and cellular residues could continuously accumulate in soils and contribute significantly to the sequestration of atmospheric carbon, highlighting the need to incorporate both microbial residues into soil carbon models to address global climate change. The results suggested that plantations should be allowed to grow older rather than being prematurely harvested, as they promote soil carbon sequestration and stabilization, which has important implications for the establishment of stable soil carbon pools in plantations and can be an invaluable asset in the fight against climate change.

The fate of vegetation carbon stocks of India: Insights from a remote-sensed evaluation of carbon use efficiency

Vegetation carbon use efficiency (CUE), defined as the ratio of the net primary productivity (NPP) to gross primary productivity (GPP), is a critical metric for assessing the extent of sequestration of atmospheric carbon by vegetation into biomass. Evaluating CUE is essential for policymakers to devise carbon sequestration policies and also identify hotspots of carbon storage loss. Indian ecosystems face variable weather conditions across the year. However, the roles of weather variability, spatial patterns, and temporal dynamics are poorly understood, as much as the resilience to hydroclimatic perturbations that may influence CUE in Indian terrestrial ecosystems, particularly at sub-annual scales. The lack of sub-annual NPP datasets hinders remote sensing-based sub-annual CUE assessments. However, this study derived an 8-day scale NPP dataset through an empirical formulation on moderate-resolution imaging spectroradiometer (MODIS) products. This study assessed CUE dynamics for India across its six homogeneous meteorological regions (HMRs) including the major biomes of each HMR, encompassing croplands, forests, and grasslands, through a fine-scale remote sensing approach for 2000–2021. The results show pronounced variability of CUE across spatiotemporal scales governed by the water availability and temperature interplay, with hilly 0.59±0.01 and northwestern 0.33±0.02 regions exhibiting the highest and lowest CUE on an annual scale. Distinct patterns have been observed among the biomes, depending on the HMRs dictated by the land management practices of the regions. Similar pronounced CUE variability has been observed on seasonal scales. The study also derived sustainability maps of carbon stocks for India from the trend-persistence interplay of CUE, revealing alarming concerns across most HMRs, with peninsular India exhibiting a persistent decrease in CUE for 82% of its cropland area. A widespread loss of resilience of carbon stocks was observed, primarily caused by increased precipitation and warming under meteorological drivers, along with aridity induced by soil and atmospheric conditions. Overall, this study highlights the critical role of CUE in assessing the carbon sequestration potential of Indian ecosystems and the need for a better understanding of the factors that influence it to develop effective carbon sequestration policies.

Climate and breeding determined below-ground biomass allocation strategy in wheat

Farmland covers about 12% of the ice-free terrestrial surface, and crop below-ground biomass allocation plays a pivotal role in the sequestration of atmospheric carbon. Nevertheless, our understanding of the integrated response of crop belowground biomass allocation strategy to concomitant variation in key environmental factors related to water and nutrient availability remains limited. Furthermore, it is imperative to conduct further analysis to elucidate the influence of breeding efforts geared toward improving crop yield on the below-ground biomass allocation strategy. Here we compiled a global wheat root mass fraction (RMF) database with 221 observations from 39 studies to analyze the integrated response of RMF to climate, soil properties and filed managements, and the relationship of RMF and yield. We identified an aridity index (AI) threshold of 0.44 for wheat below-ground biomass allocation strategy, based on the effect of long-term climate on plow-layer soil organic carbon and field water capacity (FWC). The negative effect of nitrogen fertilizer rate on RMF along the AI gradient did not significantly change but the main mechanism shifted from indirect to direct effects. For AI < 0.44, the response of RMF to change of water availability was relatively conservative with the insignificant effects of FWC on RMF. However, RMF was highly sensitive to precipitation distribution during the growth stage because RMF decreased as the ratio of precipitation during the reproductive stage to the growth stage increased. We did not observe a significant correlation between RMF and yield within the main range of RMF so a large amount of intraspecific variation in belowground biomass allocation strategies had not been filtered out by breeding. For AI ≥ 0.44, RMF was highly sensitive to water resource availability as RMF significantly decreased with an increase in FWC. Yield decreased significantly with increasing RMF within the main range of RMF, resulting in highly consistent intraspecific belowground biomass allocation strategies under the pressure of breeding. The results suggested long-term climate condition and breeding played critical filters in wheat below-ground biomass allocation strategy and provided a more accurate prediction of RMF for global carbon cycle models and crop growth models.

Two-dimensional modeling of CO2 mineral trapping through the oxalate‑carbonate pathway: Influence of the root system model

Two-dimensional reactive transport models, one with a simplified root system and the other accounting for dynamically evolving root architecture, were constructed to examine the influence of model complexity on capturing the effect of soil-root dynamics relating to the Oxalate Carbonate Pathway (OCP) of the Iroko tree over 170 years. Oxidation of oxalate from fallen tree tissue by soil bacteria enables local soil pH increase, leading to the sequestration of atmospheric carbon in carbonate minerals (calcite) in the shallow soil surrounding the tree. Simulations of both root models corroborate previous one-dimensional models of the OCP focused on Ca and C mass balance, where high weathering rates of Ca-containing silicate minerals in bedrock, along with contributions from groundwater, provided sufficient Ca for precipitation of observed quantities of calcite. Both simulations demonstrate the development of a distinct high pH zone where oxalate is oxidized, Ca accumulates, and calcite precipitates (OCP zone); and a low pH zone where roots collect Ca, later returned to the top soil as calcium oxalate (Total Root Extent/TRE zone) via litterfall. While the extent of OCP zone development near the ground surface was very similar between simulations, differences in localized root water uptake between the two approaches resulted in variation in water and solute transport and influenced the geometry of the OCP zone at depth, with implications for calcite precipitation in the soil. Trends in CO2 and O2 partial pressures in the OCP zone were mirrored in the TRE zone, suggesting linkage between the two zones with regard to gas transport. Near the end of the tree's lifespan, results indicate that soil permeability decreases due to calcite precipitation may limit O2 ingress and availability in the shallow soil, while trapping CO2 released from the oxidation of organics in the shallow soil, with implications for the long-term sustainability of the OCP itself.

Tracing North Atlantic volcanism and seaway connectivity across the Paleocene–Eocene Thermal Maximum (PETM)

Abstract. There is a temporal correlation between the peak activity of the North Atlantic Igneous Province (NAIP) and the Paleocene–Eocene Thermal Maximum (PETM), suggesting that the NAIP may have initiated and/or prolonged this extreme warming event. However, corroborating a causal relationship is hampered by a scarcity of expanded sedimentary records that contain both climatic and volcanic proxies. One locality hosting such a record is the island of Fur in Denmark, where an expanded pre- to post-PETM succession containing hundreds of NAIP ash layers is exceptionally well preserved. We compiled a range of environmental proxies, including mercury (Hg) anomalies, paleotemperature proxies, and lithium (Li) and osmium (Os) isotopes, to trace NAIP activity, hydrological changes, weathering, and seawater connectivity across this interval. Volcanic proxies suggest that NAIP activity was elevated before the PETM and appears to have peaked during the body of the δ13C excursion but decreased considerably during the PETM recovery. This suggests that the acme in NAIP activity, dominated by flood basalt volcanism and thermogenic degassing from contact metamorphism, was likely confined to just ∼ 200 kyr (ca. 56.0–55.8 Ma). The hundreds of thick (&gt; 1 cm) basaltic ashes in the post-PETM strata likely represent a change from effusive to explosive activity, rather than an increase in NAIP activity. Detrital δ7Li values and clay abundances suggest that volcanic ash production increased the basaltic reactive surface area, likely enhancing silicate weathering and atmospheric carbon sequestration in the early Eocene. Signals in lipid biomarkers and Os isotopes, traditionally used to trace paleotemperature and weathering changes, are used here to track seaway connectivity. These proxies indicate that the North Sea was rapidly cut off from the North Atlantic in under 12 kyr during the PETM recovery due to NAIP thermal uplift. Our findings reinforce the hypothesis that the emplacement of the NAIP had a profound and complex impact on Paleocene–Eocene climate, both directly through volcanic and thermogenic degassing and indirectly by driving regional uplift and changing seaway connectivity.

A framework for a carbon-based urban vegetation typology - A thematic review

Generally, the carbon neutrality targets of cities underline the role of vegetation especially natural biotopes and ecosystems. City-wide carbon pool assessments have so far focussed on land cover and land use types, with the role of urban trees receiving particularly significant attention. However, the carbon sequestration and storage (CSS) capacity of various vegetation types in urban areas as well as their potential to enhance urban carbon sinks remains largely unexamined. Planning and managing urban green infrastructure (GI) requires a climate-wise strategy of CSS that provides a scalable link between habitats and individual plant species. Therefore, this study focusses on the CSS capacity of urban vegetation through a thematic review and identifies the key elements influencing CSS in cold-climate cities. The study further highlights that the basis for atmospheric carbon sequestration lies in the favourable growth and stomatal functioning of an individual plant. The CSS of individual plants forms the basis for urban GI and the ecosystem services they provide. Moreover, the growth of urban vegetation is affected by diverse urban growing conditions, which are under continuous change as vegetation is managed, used and modified by residents. Although soils are a major storage for carbon, the role of vegetation in transforming carbon from the atmosphere into soil organic carbon is fundamental. In this study, with; the understanding of the key drivers influencing CSS, we define a framework for a; carbon-based vegetation typology and discuss the links between growing conditions and maintenance practices with regard to the CSS capacity of diverse vegetation types. This framework provides a conceptual basis for further interdisciplinary research into the CSS of urban vegetation, for example, for CSS capacity modelling and life cycle assessment of urban vegetation. It also supports climate-wise planning, design and maintenance by formulating practical and science-based recommendations for multi-professional actors engaged in GI.

Reducing spatial resolution increased net primary productivity prediction of terrestrial ecosystems: A Random Forest approach

Net primary production (NPP) is a pivotal component of the terrestrial carbon dynamic, as it directly contributes to the sequestration of atmospheric carbon by vegetation. However, significant variations and uncertainties persist in both the total amount and spatiotemporal patterns of terrestrial NPP, primarily stemming from discrepancies among datasets, modeling approaches, and spatial resolutions. In order to assess the influence of different spatial resolutions on global NPP, we employed a random forest (RF) model using a global observational dataset to predict NPP at 0.05°, 0.25°, and 0.5° resolutions. Our results showed that (1) the RF model performed satisfactorily with modeling efficiencies of 0.53–0.55 for the three respective resolutions; (2) NPP exhibited similar spatial patterns and interannual variation trends at different resolutions; (3) intriguingly, total global NPP varied greatly across different spatial resolutions, amounting 57.3 ± 3.07 for 0.05°, 61.46 ± 3.27 for 0.25°, and 66.5 ± 3.42 Pg C yr−1 for 0.5°. Such differences may be associated with the resolution transformation of the input variables when resampling from finer to coarser resolution, which significantly increased the spatial and temporal variation characteristics, particularly in regions within the southern hemisphere such as Africa, South America, and Australia. Therefore, our study introduces a new concept emphasizing the importance of selecting an appropriate spatial resolution when modeling carbon fluxes, with potential applications in establishing benchmarks for global biogeochemical models.

Carbon storage capacity of Castanopsis hystrix plantations at different stand–ages in South China

The establishment of forest plantations is an excellent silvicultural alternative to improve atmospheric carbon (C) sequestration for climate change mitigation. In recent years, the importance of forest growth and C dynamics at different stand ages have drawn huge attention for investigation. To evaluate the impacts of different stand ages on the C storage capacity of Castanopsis hystrix plantations ecosystems, we measured biomass and C content in trees, understory, litter, and soil components from field measurements at different stand ages, i.e., 6–, 10–, 15–, 25–, and 34–year–old stands. Results showed that the C stocks in trees, understory vegetation, litter, soil and the whole ecosystem increased steadily with stand age. C. hystrix C storage capacity in the 6–, 10–, 15–, 25–, and 34–year–old stands were 29.17, 56.18, 85.60, 132.19 and 157.79 Mg ha−1, respectively, while the total ecosystem C storage capacity was 68.11, 106.11, 136.13, 187.34 and 226.14 Mg ha−1, respectively. Meanwhile, the C sequestration rate in the 6–10, 10–15, 15–25 and 25–35–year–old stands were 675.28, 588.35, 465.97 and 284.39 g m2 year−1, respectively. Similarly, total biomass of trees, understory, and litter increased with stand age. Our study indicated that C. hystrix plantations are still developing in the area, since live biomass and soil C continue to accumulate despite reduced C sequestration rates. The information provided here highlight the C stock and C sequestration rates of C. hystrix at different stand ages, providing baseline information on the C dynamics of young and older stand of C. hystrix in this region; Hence, such knowledge could be useful for designing more realistic policies to mitigate climate change, such as programs to maintain continuous forest growth.

The contribution of penguin guano to the Southern Ocean iron pool

Iron plays a crucial role in the high-nutrient, low-chlorophyll Southern Ocean regions, promoting phytoplankton growth and enhancing atmospheric carbon sequestration. In this area, iron-rich Antarctic krill (Euphausia superba) and baleen whale species, which are among their main predators, play a large role in the recycling of iron. However, penguins have received limited attention despite their representing the largest seabird biomass in the southern polar region. Here, we use breeding site guano volumes estimated from drone images, deep learning-powered penguin census, and guano chemical composition to assess the iron export to the Antarctic waters from one of the most abundant penguin species, the Chinstrap penguin (Pygoscelis antarcticus). Our results show that these seabirds are a relevant contributor to the iron remobilization pool in the Southern Ocean. With an average guano concentration of 3 mg iron g−1, we estimate that the Chinstrap penguin population is recycling 521 tonnes iron yr−1, representing the current iron contribution half of the amount these penguins were able to recycle four decades ago, as they have declined by more than 50% since then.

Multiple controls on carbon dioxide sequestration in the beagle channel (Southern Patagonia) in early fall

Subpolar coastal waters are key hotspots in the global carbon cycle. However, the small-scale distribution of partial pressure of carbon dioxide (pCO2) in these environments and the physical and biological controls underlying this variability are still poorly understood. Here, we examine simultaneous high-resolution spatial measurements of wind speed and pCO2, temperature, salinity, and in-vivo chlorophyll-a fluorescence (chl-a fluo, a proxy of phytoplankton biomass) in surface waters that were obtained during an oceanographic survey in the Argentinian Beagle Channel (subantarctic Atlantic Patagonian) in early fall 2017. The 240 km study transect (centered at 55°S - 67°W) was divided into two zones: (A1) The Beagle Channel innermost portion, semi-enclosed and subject to strong continental influence and (A2) its eastern outlet towards the open Southwest Atlantic. Discrete seawater samples were also collected for apparent oxygen utilization (AOU), nutrients and pH measurements. High-resolution spatial measurements revealed the persistence of pCO2 below atmospheric equilibrium, increasing in median (interquartile range 25–75%) from 314 μatm in the inner Beagle Channel (A1) to 348 μatm towards the adjacent open sea (A2). A decrease in atmospheric CO2 sequestration was associated with an increase in water temperature from 9.5 °C to 10.7 °C, salinity from 30.8 to 32.5, and chl-a fluo from 2.24 to 2.91 mg m−3 along the coastal-offshore gradient. Low AOU and nutrient levels were found in regions inside the channel. Indeed, the relationships between CO2 and temperature or salinity were significantly different from those expected from the theoretical solubility effect, indicating a dominance of metabolic over physicochemical controls on this gas. Moreover, physical factors such as vertical stratification contributed to the variable surface pCO2 values. These findings reveal the existence of short-scale spatial variability of CO2 in the Beagle Channel, improving our understanding of the multiple controls on atmospheric carbon sequestration in extensive subpolar continental shelves.

Sound Insulation Performance of Composites Developed using Waste Carbonaceous Materials

Mitigating vibration in a system has many advantages, from decreasing noise output to increasing component life. Therefore, it is necessary to eliminate the mechanical vibration and sound through appropriate measures. State-of-the-art techniques seeks the utilization of sustainable carbonaceous resources for the development of sound insulating materials to reduce the environmental externalities of the synthetic materials. It is noteworthy to mention that sustainable carbonaceous resources such as biochar, also assist in atmospheric carbon sequestration (capturing and storing CO2) and ultimately limit CO2 concentration in the environment. In the present work, carbonaceous material obtained from biomass waste was utilized as a filler with natural rubber as matrix to develop sound insulating materials. Furthermore, the physical, mechanical, and acoustical properties of developed composites were studied. The sound transmission loss of the composites was measured as per ASTM-E2611 using a four-microphone impedance tube. Noticeably, with the increase in biomass waste filler in the composite, significant improvement in the physical (density), mechanical (tensile strength) and acoustical (sound transmission loss) properties has been observed.

Responses of Grass Species to Elevated CO2 – A Review of Three Decades of Research and Future Direction

Rising atmospheric carbon dioxide accelerates growth and modifies physiological responses in plants. Over the last 40 years, the global scientific community had taken up initiatives to make out the role of plants in capturing and storing atmospheric carbon dioxide. This review consolidates the research of the past three decades on the responses of grass species to elevated levels of CO2. An enhancement in intercellular CO2 concentration, water use efficiency, photosynthesis, total non-structural carbohydrates, and total biomass was noticed in grass species under controlled growth systems supplied with varying levels of CO2. Each of these responses reflects the potency of grasses to survive and store ample carbon in CO2-enriched environments. Reduction in stomatal conductance, transpiration rate, and total nitrogen concentration was in effect positive responses, in connection with the acclimatization of plants at CO2-enriched environments. This review ascertains that in experimental microclimatic environments with varying CO2 regimes or varying treatment duration, grasses show positive growth responses. Thus it illustrates the efficient atmospheric carbon sequestration of grasses irrespective of their photosynthetic pathway (whether C3/C4).

How to not trade water for carbon with tree planting in water-limited temperate biomes?

The most widespread nature-based solution for mitigating climate change is tree planting. When realized as forest restoration in historically forested biomes, it can efficiently contribute to the sequestration of atmospheric carbon and can also entail significant biodiversity and ecosystem service benefits. Conversely, tree planting in naturally open biomes can have adverse effects, of which water shortage due to increased evapotranspiration is among the most alarming ones. Here we assessed how soil texture affects the strength of the trade-off between tree cover and water balance in the forest-steppe biome, where the global pressure for afforestation is threatening with increasing tree cover above historical levels. Here we monitored vertical soil moisture dynamics in four stands in each of the most common forest types of lowland Hungary on well-drained, sandy (natural poplar groves, and Robinia and pine plantations) and on poorly drained, silty-clayey soils (natural oak stands and Robinia plantations), and neighboring grasslands. We found that forests on sand retain moisture in the topsoil (approx. 20 cm) throughout the year, but a thick dry layer develops below that during the vegetation period, significantly impeding groundwater recharge. Neighboring sandy grasslands showed an opposite pattern, with often dry topsoil but intact moisture reserves below, allowing deep percolation. In contrast, forests on silty-clayey soils did not desiccate lower soil layers compared neighboring grasslands, which in turn showed moisture patterns similar to sandy grasslands. We conclude that, in water-limited temperate biomes where landscape-wide water regime depends on deep percolation, soil texture should drive the spatial allocation of tree-based climate mitigation efforts. On sand, the establishment of new forests should be kept to a minimum and grassland restoration should be preferred. The trade-off between water and carbon is less pronounced on silty-clayey soils, making forest patches and wooded rangelands viable targets for both climate mitigation and ecosystem restoration.

Experimental Study on the Carbon Sequestration Benefit in Urban Residential Green Space Based on Urban Ecological Carrying Capacity

The CO2 concentration of urban residential green space in Changsha was experimentally investigated. Based on the experimental results, the variation characteristics and influencing factors of CO2 concentration in residential areas were analyzed considering both the measuring time and ecological plant structure. Then, through the concept of urban ecological bearing capacity, the carbon sequestration index of the urban residential areas was proposed in this paper. Finally, the regulating effects of varieties of vegetation on CO2 concentration among four urban residential areas were deeply analyzed and discussed. Results showed that green space with an ecological plant structure of trees-shrubs-grass exhibited greater improvement in the environmental carbon balance than those of shrubs or grass, and the atmospheric carbon sequestration capacity was significantly affected by the total quantity of the green space.

Patterns of differentiation of the old arable horizon of fallow soils according to the content of mobile forms of manganese and copper

The differentiation of the old arable horizon (Ap old) by the content of mobile manganese (Mn) and copper (Cu) under fallow vegetation aged 15-20 years was studied. The accumulation of mobile Mn in the upper layer (0-10 cm), Cu in the 5-15 cm layer was observed. Linear modeling of the dependence of the content of Mn and Cu on alkali-soluble organic matter (OMP) and pH showed the influence of only one significant predictor on each element. The content of Mn has a significant strong (R2 adj.=0.72) influence of OMP. The pH has a statistically significant, but weak (R2 adj.= 0.19) effect on the Cu content. The difference in the patterns of differentiation is associated with the accumulation of mobile Mn by newly formed organic matter (OM) in fallows and the migration of mobile Cu with soluble fractions of OM in acidic soils. The study of changes in the mobility of heavy metals (HMs) in fallows is necessary to reduce environmental risks when changing land use, as well as to provide a realistic prediction of atmospheric carbon sequestration in fallow soils, taking into account changes in the level of toxicity of HMs. The relevance of these studies is associated with the fact that the removal of lands with heavy HM contamination from arable circulation in fallows is practiced more and more often.

The making of suberin.

Outer protective barriers of animals use a variety of bio-polymers, based on either proteins (e.g. collagens), or modified sugars (e.g. chitin). Plants, however, have come up with a particular solution, based on the polymerisation of lipid-like precursors, giving rise to cutin and suberin. Suberin is a structural lipophilic polyester of fatty acids, glycerol and some aromatics found in cell walls of phellem, endodermis, exodermis, wound tissues, abscission zones, bundle sheath and other tissues. It deposits as a hydrophobic layer between the (ligno)cellulosic primary cell wall and plasma membrane. Suberin is highly protective against biotic and abiotic stresses, shows great developmental plasticity and its chemically recalcitrant nature might assist the sequestration of atmospheric carbon by plants. The aim of this review is to integrate the rapidly accelerating genetic and cell biological discoveries of recent years with the important chemical and structural contributions obtained from very diverse organisms and tissue layers. We critically discuss the order and localisation of the enzymatic machinery synthesising the presumed substrates for export and apoplastic polymerisation. We attempt to explain observed suberin linkages by diverse enzyme activities and discuss the spatiotemporal relationship of suberin with lignin and ferulates, necessary to produce a functional suberised cell wall.

Tree diversity and carbon important species vary with traditional agroforestry managers in the Indian Eastern Himalayan region.

Traditional agroforestry systems, one of the time tested and dominant land use from tropical to sub-tropical regions, were recognized for their contributions to food production, biodiversity conservation, and atmospheric carbon sequestration. Their management often varies from region to region. However, these systems frequently mimic economically managed land uses due to increased pressure on the monetary requirement of their managers. The present study aims to evaluate (i) tree density, (ii) tree diversity indices, and (iii) identify the biomass carbon important tree species managed by different communities of the Indian Eastern Himalayan region. We found that the Mizo community harbored the highest number of tree species (35) in the traditional agroforestry system with the highest tree diversity index (3.47). Total biomass carbon of tropical agroforestry systems managed by different communities ranged between 4.72Mgha-1 (Meitei) and 29.26Mgha-1 (Bengali). Similarly, in the sub-tropical traditional agroforestry system, the highest and the lowest biomass carbon was observed in Mizo- (10.93Mgha-1) and Angami- (6.05Mgha-1) managed systems. Of the 31 biomass carbon, important species found across the traditional agroforestry systems,Artocarpus heterophyllus, had the highest occurrence (50%), followed byParkia timoriana(37.5) andAmoora rohituka,Delonix regia,Mangifera indica,andToona ciliata(25% for each species). Farmers' preference to cash return of a species, trees density, and basal area were the determinant factors in the carbon stock potential of these systems. The present study suggests that the farmers' preferred and dominant species in their agroecosystems have a limited scope of enhanced biomass carbon storage. Therefore, improvement of traditional agroforestry systems through selective incorporation of biomass carbon important tree species is recommended to enhance the carbon sink capacity of these systems.