Search Results (117)

Forests play a crucial role in carbon cycling, contributing significantly to global carbon cycling and climate change mitigation, but their capture strength is sensitive to the climatic zone in which they operate and its adjoining environmental stressors. This research investigated the carbon dynamics of a typical deciduous forest, the Daniel Boone National Forest (DBNF), in the Mixed-Humid climate of Kentucky, USA, employing the Eddy Covariance technique to quantify temporal CO₂ exchanges from 2016 to 2020 and to assess its controlling biometeorological factors. The study revealed that the DBNF functioned as a carbon sink, sequestering −1515 g C m⁻² in the study period, with a mean annual Net Ecosystem Exchange (NEE) of −303 g C m⁻²yr⁻¹. It exhibited distinct seasonal and daily patterns influenced by ambient sunlight and air temperature. Winter months had the lowest rate of CO₂ uptake (0.0699 g C m⁻² h⁻¹), while summer was the most productive (−0.214 g C m⁻² h⁻¹). Diurnally, carbon uptake peaked past midday and remained a sink overnight, albeit negligibly so. Light and temperature response curves revealed their controlling effect on the DBNF trees’ photosynthesis and respiration. Furthermore, clear seasonality patterns were observed in the control of environmental variables. The DBNF is a carbon sink consistent with other North American deciduous forests. Full article

Plant phenology is an important driver of inter-annual variability in peatland carbon uptake. However, the use of traditional phenology datasets (e.g., manual surveys, satellite remote sensing) to quantify this link is hampered by their limited spatial and temporal coverage. This study examined the use of phenology cameras (phenocams) and uncrewed aerial vehicles (UAVs) for monitoring phenology in a Scottish temperate peatland. Data were collected at the site over multiple growing seasons using a UAV platform fitted with a multispectral Parrot Sequoia camera. We found that greenness indices calculated using data from both platforms were in strong agreement with each other, and exhibited strong correlations with rates of gross primary production (GPP) at the site. Greenness maps generated with the UAV data were combined with fine-scale vegetation classifications, and highlighted the variable sensitivity of different plant species to dry spells over the study period. While a lack of suitable weather conditions for surveying limited the UAV data temporally, the phenocam provided a near-continuous record of phenology. The latter revealed substantial temporal variability in the relationship between canopy greenness and peatland GPP, which although strong over the growing season as a whole (r_s = 0.88, p < 0.01), was statistically insignificant during the peak growing season. Full article

Piper nigrum–Areca catechu intercropping mitigates soil problems related to continuous P. nigrum cropping, but the exact reason for this is not clear. In this study, the intercropping system increased P. nigrum’s single plant weight by 27.0–55.5% and unit yield per hectare by 5.1–33.5% in 2019–2022. Intercropping altered the metabolic profiles of root exudates from both species, with increases in flavonoids (epicatechin and 4′,5,6,7-Tetramethoxyflavone), alkaloids (litebamine), and amino acids (proline betaine, L-homocysteic acid and L-homocysteic acid). Intercropping further increased the abundance of dominant soil bacteria, including GAL15 (354.9%) and Bacteroidota (70.4%) in the P. nigrum rhizosphere, and Firmicutes (141.8%) and WPS2 (75.3%) in the A. catechu rhizosphere. In the intercropping system, the abundance of soil flavonoids, including tangeritin, trifolirhizin, and hexamethylquercetagetin, which participated in improving nutrient absorption and plant growth, increased by 106.4~356.0%, 28.9~45.5%, and 45.2~127.1%, respectively, during the whole growing period. Overall, intercropping with A. catechu promoted carbon input to the P. nigrum soil via root exudates. This increased the diversity of P. nigrum rhizosphere beneficial bacterial communities, as well as the amounts of nutrients and plant growth-promoting secondary metabolites. Together, these effects improved nutrient uptake and utilization, thereby driving the sustainable production of P. nigrum, and ultimately achieving higher yields. Full article

Previous research has investigated the effects of different grazing intensities on soil surface greenhouse gas (GHG) emissions, whereas the dynamics of GHG production and consumption within the soil profile and their responses to different grazing intensities remain unclear. In this study, a field experiment was conducted in 2017 and 2018 to evaluate the influences of three grazing intensities (none, light, heavy) on both soil surface and subsurface (0–60 cm) GHG fluxes estimated using chamber-based and concentration gradient-based methods, respectively. Results showed that soil at lower depths (30–60 cm) had higher carbon dioxide (CO₂) concentrations but lower methane (CH₄) concentrations. In contrast, soil profile nitrous oxide (N₂O) concentration did not vary with depth, possibly resulting from the relatively low soil moisture in the semiarid grassland, which increased air diffusivity across the soil profile. Grassland soil acted as a source of N₂O and CO₂ production but as a sink for CH₄ uptake, which mainly attributed to the topsoil (0–5 cm for N₂O, and 0–15 cm for CO₂ and CH₄). The estimated soil surface GHG flux rates based on the concentration gradient method did not align well with those directly measured using the chamber method. Furthermore, the cumulative N₂O flux over the study period was significantly higher for the concentration gradient method than the chamber method, whereas a contrary result was observed for CO₂ emission and CH₄ uptake. This study confirms that the grassland soil serves as an important source of CO₂ and N₂O emissions and a weak sink for CH₄ consumption, playing a crucial role in the annual carbon budget of livestock-grazed grassland ecosystems. Full article

The trans-translation system, mediated by transfer-messenger RNA (tmRNA, encoded by the ssrA gene) and its partner protein SmpB, helps to release ribosomes stalled on defective mRNA and targets incomplete protein products for hydrolysis. Knocking out the ssrA and smpB genes in various pathogens leads to different phenotypic changes, indicating that they have both cooperative and independent functionalities. This study aimed to clarify the functional relationships between tmRNA and SmpB in Aeromonas veronii, a pathogen that poses threats in aquaculture and human health. We characterized the expression dynamics of the ssrA and smpB genes at different growth stages of the pathogen, assessed the responses of deletion strains ΔssrA and ΔsmpB to various environmental stressors and carbon source supplementations, and identified the gene-regulatory networks involving both genes by integrating transcriptomic and phenotypic analyses. Our results showed that the gene ssrA maintained stable expression throughout the bacterial growth period, while smpB exhibited upregulated expression in response to nutrient deficiencies. Compared to the wild type, both the ΔssrA and ΔsmpB strains exhibited attenuated resistance to most stress conditions. However, ΔssrA independently responded to starvation, while ΔsmpB specifically showed reduced resistance to lower concentrations of Fe³⁺ and higher concentrations of Na⁺ ions, as well as increased utilization of the carbon source β-Methyl-D-glucoside. The transcriptomic analysis supported these phenotypic results, demonstrating that tmRNA and SmpB cooperate under nutrient-deficient conditions but operate independently in nutrient-rich environments. Phenotypic experiments confirmed that SsrA and SmpB collaboratively regulate genes involved in siderophore synthesis and iron uptake systems in response to extracellular iron deficiency. The findings of the present study provide crucial insights into the functions of the trans-translation system and highlight new roles for tmRNA and SmpB beyond trans-translation. Full article

The El Niño-Southern Oscillation (ENSO) alters ocean–atmosphere carbon exchange, but the mechanisms by which it affects the air–sea carbon flux (FCO₂) remain unclear. Here, we used gridded FCO₂ data from 2003 to 2021 to elucidate the control processes and regional differences in the influence of the ENSO on FCO₂ in the mid–low latitude Pacific Ocean. Overall, the mid–low latitude Pacific Ocean region was a net sink for CO₂, with an average uptake rate of −0.39 molC·m⁻²·year⁻¹. Specifically, during the La Niña period in 2010–2012, the absorption rate decreased by 15.38%, while during the El Niño period in 2015–2016, it increased by 30.77%. El Niño (La Niña) suppressed (promoted) biological primary production in the North Pacific, leading to reduced (enhanced) carbon uptake. El Niño (La Niña) also inhibited (promoted) physical vertical mixing in the Equatorial Pacific, leading to reduced (enhanced) carbon emissions. In the South Pacific, however, El Niño increased carbon uptake and La Niña decreased carbon uptake; although, not by these two processes. More frequent El Niño in the future will further reduce carbon absorption in the North Pacific and carbon emission in the Equatorial Pacific but increase carbon absorption in the South Pacific. Full article

Land use change and energy consumption caused by human activities is the primary source of carbon emissions and a driver of climate change. The study focused on the Yangtze River Delta (YRD), using the China Land Cover Dataset (CLCD) to calculate the region’s carbon emissions from 1990 to 2020. Based on the Natural Segment Method, the spatial distribution of carbon emissions in the YRD region were constructed by dividing them into three categories: heavy, medium, and light. The results indicate that: (1) Carbon emissions of the YRD region was 594.02 million tons at the end of 2020, an increase of 468.53 million tons compared with that of 1990. The impervious surface was the major source of carbon emissions, accounting for more than 98.51% of the total, and woodland was the most important carbon sink, accounting for more than 91.32% of the total carbon uptake. (2) The carbon emissions increase rate over the 30-year period has risen from rapid to gradual, with the fastest rate of increase occurring between 2000 and 2010. (3) Differences in economic development and land type lead to spatial variability in carbon emissions. Regions with substantial emissions were predominantly located in coastal areas, indicating a trend toward shifting inland. The assessment of carbon emissions is helpful for designing emissions mitigation policies. Full article

The carbon and nitrogen (N) metabolism of rice under different mid-stage N compensation timings is unclear. Two Japonica super rice cultivars were examined under four N compensation timings (N1-N3: N compensation at mid-tillering, panicle initiation, and spikelet differentiation. N0: no N compensation) and CK with no N application. Mid-stage N compensation increased the N concentrations of various tissues, and N2 showed the highest plant N uptake at both the heading stage, maturity, and the grain filling period. Among the treatments, N2 showed the highest N utilization efficiency. With delayed compensation timing, there was a gradual decrease in soluble sugar and starch concentrations in each tissue, accompanied by a decline in the non-structural carbohydrate (NSC) concentration. Specifically, N2 treatment exhibited the highest NSC accumulation and the remobilized NSC reserve, but NSCs per spikelet decreased with delayed compensation timing. The highest yield was also obtained with N2, exhibiting a 4.5% increase compared to the N0 treatment, primarily due to an improvement in spikelets per panicle. Conclusively, N compensation at the panicle initiation stage is a reasonable N management strategy that can coordinate the improvement of carbon and N metabolism, enhance N accumulation with efficient utilization and NSC accumulation, and ultimately increase the yield. Full article

The San Francisco Estuary (SFE) ecosystem receives anthropogenic ammonium (NH₄) from agricultural runoff and sewage treatment plants and has low chlorophyll levels. As observed in other aquatic systems, NH₄ at concentrations < 4 µmol/L inhibits nitrate (NO₃) uptake by phytoplankton and can reduce the frequency with which phytoplankton assimilate all available inorganic nitrogen (i.e., NO₃ and NH₄); paradoxically, elevated NH₄ can reduce the chances of phytoplankton blooms in some high NH₄ ecosystems. For blooms to occur, NH₄ must first be reduced to non-repressive levels, then NO₃ uptake can occur and is accompanied by more rapid carbon (C) uptake and chlorophyll accumulation. The consequence of this sequence is that when NO₃ uptake, C uptake, or chlorophyll concentrations are plotted against ambient NH₄, a rectangular hyperbola results. Here, these relationships are statistically described for a variety of SFE field data, and their management applications are discussed. These relationships enable ambient NH₄ to be used to predict both the likelihood of blooms and to investigate historical changes in productivity when no rate measurements were made. We apply the statistical relationship to a 40-year time series from the SFE during which there was an ecosystem-scale change in the estuarine foodweb with a drastic decline in pelagic fishes (the pelagic organism decline) and suggest that this period aligned with the lowest annual primary production and highest NH₄. The relationship may be generalizable to other high-nitrogen, low-growth systems and aid nutrient management decisions, assuming potential limitations are considered. Full article

Composite polyethersulfone (PES) membranes containing N-aminoethyl piperazine propane sulfonate (AEPPS)-modified graphene oxide (GO) were integrated with either of the two pretreatment processes (activated carbon (AC) adsorption or polyelectrolyte coagulation) to assess their effectiveness in mitigating membrane fouling during the treatment of abattoir wastewater. The AEPPS@GO-modified membranes, as compared to the pristine PES membranes, showed improved hydrophilicity, with water uptake increasing from 72 to 118%, surface porosity increasing from 2.34 to 27%, and pure water flux (PWF) increasing from 235 to 673 L.m⁻²h⁻¹. The modified membranes presented improved antifouling properties, with the flux recovery ratio (FRR) increasing from 59.5 to 93.3%. This study compared the effectiveness of the two pretreatment processes, AC, coagulation, and the integrated system (coagulation/AC-UF membrane), in the removal of natural organic matter (NOM) and improvement of abattoir wastewater’s pH, electrical conductivity, TDS, and turbidity. The integrated systems produced improved water quality in terms of pH, EC, TDS, turbidity, and organic content. The fluorescence excitation–emission matrix (FEEM) analysis exhibited almost no fluorescence peak post-treatment following organic loading removal. The quality of the water met the South African non-potable water reuse standards. The sole membrane treatment systems exhibited good fouling resistance without the pretreatment systems; however, integrating these systems can offer extended longer filtration periods, thereby assisting in cost aspects of the abattoir wastewater treatment system. Full article

Rising CO₂ levels, as predicted by global climate models, are altering environmental factors such as the water cycle, leading to soil waterlogging and reduced oxygen availability for plant roots. These conditions result in decreased energy production, increased fermentative metabolism, impaired nutrient uptake, reduced nitrogen fixation, and altered leaf gas exchanges, ultimately reducing crop productivity. Co-inoculation techniques involving multiple plant growth-promoting bacteria or arbuscular mycorrhizal fungi have shown promise in enhancing plant resilience to stress by improving nutrient uptake, biomass production, and nitrogen fixation. This study aimed to investigate carbon and nitrogen metabolism adaptations in soybean plants co-inoculated with Bradyrhizobium elkanii, Azospirillum brasilense, and Rhizophagus intraradices under waterlogged conditions in CO₂-enriched environments. Plants were grown in pots in open-top chambers at ambient CO₂ concentration (a[CO₂]) and elevated CO₂ concentration (e[CO₂]). After reaching the V5 growth stage, the plants were subjected to waterlogging for seven days, followed by a four-day reoxygenation period. The results showed that plants’ co-inoculation under e[CO₂] mitigated the adverse effects of waterlogging. Notably, plants inoculated solely with B. elkanii under e[CO₂] displayed results similar to co-inoculated plants under a[CO₂], suggesting that co-inoculation effectively mitigates the waterlogging stress, with plant physiological traits comparable to those observed under elevated CO₂ conditions. Full article

Fruit photosynthesis occurs in an internal microenvironment seldom encountered by a leaf (hypoxic and extremely CO₂-enriched) due to its metabolic and anatomical features. In this study, the anatomical and photosynthetic traits of fully exposed green fruits of Quercus coccifera L. were assessed during the period of fruit production (summer) and compared to their leaf counterparts. Our results indicate that leaf photosynthesis, transpiration and stomatal conductance drastically reduced during the summer drought, while they recovered significantly after the autumnal rainfalls. In acorns, gas exchange with the surrounding atmosphere is hindered by the complete absence of stomata; hence, credible CO₂ uptake measurements could not be applied in the field. The linear electron transport rates (ETRs) in ambient air were similar in intact leaves and pericarps (i.e., when the physiological internal atmosphere of each tissue is maintained), while the leaf NPQ was significantly higher, indicating enhanced needs for harmless energy dissipation. The ETR measurements performed on leaf and pericarp discs at different CO₂/O₂ partial pressures in the supplied air mixture revealed that pericarps displayed significantly lower values at ambient gas levels, yet they increased by ~45% under high CO₂/O₂ ratios (i.e., at gas concentrations simulating the fruit’s interior). Concomitantly, NPQ declined gradually in both tissues as the CO₂/O₂ ratio increased, yet the decrease was more pronounced in pericarps. Furthermore, net CO₂ assimilation rates for both leaf and pericarp segments were low in ambient air and increased almost equally at high CO₂, while pericarps exhibited significantly higher respiration. It is suggested that during summer, when leaves suffer from photoinhibition, acorns could contribute to the overall carbon balance, through the re-assimilation of respiratory CO₂, thereby reducing the reproductive cost. Full article

Low carbon management and policies should refer to local long-term inter-annual carbon uptake. However, most previous research has only focused on the quantity and spatial distribution of gross primary product (GPP) for the past 50 years because most satellite launches, the main GPP data source, were no earlier than 1980. We identified a close relationship between the tree-ring index (TRI) and vegetation carbon dioxide uptake (as measured by GPP) and then developed a nested TRI-GPP model to reconstruct spatially explicit GPP values since 1895 from seven tree-ring chronologies. The model performance in both phases was acceptable: We chose general regression neural network regression and random forest regression in Phase 1 (1895–1937) and Phase 2 (1938–1985). With the simulated and real GPP maps, we observed that the GPP for grassland and overall GPP were increasing. The GPP landscape patterns were stable, but in recent years, the GPP’s increasing rate surpassed any other period in the past 130 years. The main local climate driver was the Palmer Drought Severity Index (PDSI), and GPP had a significant positive correlation with PDSI in the growing season (June, July, and August). With the GPP maps derived from the nested TRI-GPP model, we can create fine-scale GPP maps to understand vegetation change and carbon uptake over the past century. Full article

The gross primary productivity (GPP) of vegetation stores atmospheric carbon dioxide as organic compounds through photosynthesis. Its spatial heterogeneity is primarily influenced by the carbon uptake period (CUP) and maximum photosynthetic productivity (GPP_max). Grassland, cropland, and forest are crucial components of China’s terrestrial ecosystems and are strongly influenced by the seasonal climate. However, it remains unclear whether the evolutionary characteristics of GPP are attributable to physiology or phenology. In this study, terrestrial ecosystem models and remote sensing observations of multi-source GPP data were utilized to quantitatively analyze the spatio-temporal dynamics from 1982 to 2018. We found that GPP exhibited a significant upward trend in most areas of China’s terrestrial ecosystems over the past four decades. Over 60% of Chinese grassland and over 50% of its cropland and forest exhibited a positive growth trend. The average annual GPP growth rates were 0.23 to 3.16 g C m⁻² year⁻¹ for grassland, 0.40 to 7.32 g C m⁻² year⁻¹ for cropland, and 0.67 to 7.81 g C m⁻² year⁻¹ for forest. GPP_max also indicated that the overall growth rate was above 1 g C m⁻² year⁻¹ in most regions of China. The spatial trend pattern of GPP_max closely mirrored that of GPP, although local vegetation dynamics remain uncertain. The partial correlation analysis results indicated that GPP_max controlled the interannual GPP changes in most of the terrestrial ecosystems in China. This is particularly evident in grassland, where more than 99% of the interannual variation in GPP is controlled by GPP_max. In the context of rapid global change, our study provides an accurate assessment of the long-term dynamics of GPP and the factors that regulate interannual variability across China’s terrestrial ecosystems. This is helpful for estimating and predicting the carbon budget of China’s terrestrial ecosystems. Full article

The karst area has become a high-risk area for Cadmium (Cd) exposure. Interestingly, the high levels of Cd in soils do not result in an excessive bioaccumulation of Cd in rice. Carbonate rock dissolution ions (CRIs) could limit the accumulation and translocation of Cd in rice. CRIs can become a major bottleneck in the remediation and management of farmlands in karst areas. However, there is limited research on the effects of CRIs in soils on Cd accumulation in rice. The karst area of lime soil (LS) and the non-karst areas of yellow soil (YS) were collected, and an external Cd was added to conduct rice cultivation experiments. Cd and CRIs (Ca²⁺, Mg²⁺, CO₃²⁻/HCO₃⁻, and OH⁻) in the rice–soil system were investigated from the grain-filling to maturity periods. The results showed that CRIs of LS were significantly higher than that of YS in different treatments. CRIs of LS were 2.05 mg·kg⁻¹ for Ca²⁺, 0.90 mg·kg⁻¹ for Mg²⁺, and 42.29 mg·kg⁻¹ for CO₃²⁻ in LS. CRIs could influence DTPA Cd, resulting in DTPA Cd of LS being lower than that of YS. DTPA Cd of YS was one to three times larger than that of YS. Cd content in different parts of rice in YS was higher than that of LS. Cd in rice grains of YS was one to six times larger than that of LS. The uptake of Cd from the soil during Filling III was critical in determining rice Cd accumulation. CRIs in the soil could affect Cd accumulation in rice. Ca²⁺ and Mg²⁺ had significant negative effects on Cd accumulation of rice at maturity and filling, respectively. CO₃²⁻/HCO₃⁻ and OH⁻ had significant negative effects on DTPA Cd in soil. Full article