Reduction In Precipitation Research Articles

Moderate precipitation reduction enhances nitrogen cycling and soil nitrous oxide emissions in a semi-arid grassland.

The ongoing climate change is predicted to induce more weather extremes such as frequent drought and high-intensity precipitation events, causing more severe drying-rewetting cycles in soil. However, it remains largely unknown how these changes will affect soil nitrogen (N)-cycling microbes and the emissions of potent greenhouse gas nitrous oxide (N2 O). Utilizing a field precipitation manipulation in a semi-arid grassland on the Loess Plateau, we examined how precipitation reduction (ca. -30%) influenced soil N2 O and carbon dioxide (CO2 ) emissions in field, and in a complementary lab-incubation with simulated drying-rewetting cycles. Results obtained showed that precipitation reduction stimulated plant root turnover and N-cycling processes, enhancing soil N2 O and CO2 emissions in field, particularly after each rainfall event. Also, high-resolution isotopic analyses revealed that field soil N2 O emissions primarily originated from nitrification process. The incubation experiment further showed that in field soils under precipitation reduction, drying-rewetting stimulated N mineralization and ammonia-oxidizing bacteria in favor of genera Nitrosospira and Nitrosovibrio, increasing nitrification and N2 O emissions. These findings suggest that moderate precipitation reduction, accompanied with changes in drying-rewetting cycles under future precipitation scenarios, may enhance N cycling processes and soil N2 O emissions in semi-arid ecosystems, feeding positively back to the ongoing climate change.

Enhanced ENSO-Unrelated Summer Variability in the Indo–Western Pacific under Global Warming

Abstract El Niño–Southern Oscillation (ENSO) is an important but not the only source of interannual variability over the Indo–western Pacific. Non-ENSO forced variability in the region has received recent attention because of the implications for rainy-season prediction. Using a 35-member CESM1 Large Ensemble (CESM-LE) and 30 CMIP6 models, this study shows that the ensemble means project intensified interannual variability for precipitation, low-level winds, and sea level pressure under global warming, associated with the enhanced large-scale anomalous anticyclone (AAC) over the tropical northwestern (NW) Pacific after the ENSO signal is removed. A decomposition based on the column water vapor budget reveals that enhanced precipitation variability is due to the increased background specific humidity. The resultant anomalous diabatic heating intensifies the AAC, which further strengthens the precipitation anomalies. Over the tropical NW Pacific, the wind-induced evaporative cooling on the southeastern flank of the AAC is countered by the increased shortwave radiation due to the strengthened precipitation reduction. Tropospheric temperature anomalies in the ensemble means show no significant change, suggesting no apparent change of the interbasin positive feedback between the AAC and northern Indian Ocean SST. Intermodel analysis based on CMIP6 reveals that models with a larger increase in ENSO-unrelated precipitation variability over the NW Pacific are associated with stronger background warming in the eastern equatorial Pacific, due to the modulated Walker and Hadley circulations.

Higher functional diversity improves modeling of Amazon forest carbon storage

The impacts of reduced precipitation on plant functional diversity and how its components (richness, evenness, divergence and composition) modulate the Amazon carbon balance remain elusive. We present a novel trait-based approach, the CArbon and Ecosystem functional-Trait Evaluation (CAETÊ) model to investigate the role of plant trait diversity in representing vegetation carbon (C) storage and net primary productivity (NPP) in current climatic conditions. We assess impacts of plant functional diversity on vegetation C storage under low precipitation in the Amazon basin, by employing two approaches (low and high plant trait diversity, respectively): (i) a plant functional type (PFT) approach comprising three PFTs, and (ii) a trait-based approach representing 3000 plant life strategies (PLSs). The PFTs/PLSs are defined by combinations of six traits: C allocation and residence time in leaves, wood, and fine roots. We found that including trait variability improved the model's performance in representing NPP and vegetation C storage in the Amazon. When considering the whole basin, simulated reductions in precipitation caused vegetation C storage loss by ∼60% for both model approaches, while the PFT approach simulated a more widespread C loss and abrupt changes in neighboring grid cells. We found that owing to high trait variability in the trait-based approach, the plant community was able to functionally reorganize itself via changes in the relative abundance of different plant life strategies, which therefore resulted in the emergence of previously rare trait combinations in the model simulation. The trait-based approach yielded strategies that invest more heavily in fine roots to deal with limited water availability, which allowed the occupation of grid cells where none of the PFTs were able to establish. The prioritization of root investment at the expense of other tissues in response to drought has been observed in other studies. However, the higher investment in roots also had consequences: it resulted, for the trait-based approach, in a higher root:shoot ratio (a mean increase of 74.74%) leading to a lower vegetation C storage in some grid cells. Our findings highlight that accounting for plant functional diversity is crucial when evaluating the sensitivity of the Amazon forest to climate change, and therefore allow for a more mechanistic understanding of the role of biodiversity for tropical forest ecosystem functioning.

Screening and Investigation on Inhibition of Sediment Formation in a Kuwait Light Crude Oil by Commercial Additives with Some Guidelines for Field Applications

The precipitation of asphaltene and waxes occurs when crude oil characteristics change as a consequence of pressure, temperature variations, and/or chemical modifications, etc. The costs associated with the cleaning of deposition on the production equipment and the loss of profit opportunities can go beyond hundreds of millions of USD. Thus, there is a strong incentive to search for ways to mitigate deposit formation during the crude production process. A light crude bottom hole fluid sample from a deep well with an asphaltene deposition problem was analyzed in the laboratory. Basic data on density, viscosity, bubble point, GOR, and asphaltene onset pressure were measured at a PVT laboratory. Asphaltene characterization, as a prescreening for appropriate inhibitors, has been conducted using asphaltene phase diagrams (APD). The APD generated from two developed software programs in both Matlab and Excel codes were favorably compared with the phase behavior of other oil samples available in the literature and has shown to be an excellent match. Various test methods were used to demonstrate the asphaltene instability of the oil samples. Eleven chemical inhibitors from five global companies were screened for testing to inhibit the precipitation. The optimum concentration and the amount of reduction in precipitation were determined for all of these chemicals to identify the most suitable chemicals. Finally, some recommendations are given for the field application of chemicals.

Trends in dental insurance claims in the United States in the context of the COVID-19 pandemic: A 3-year perspective (2019-2022).

We showed in a previous analysis the patterns of disruption for private dental insurance claims in the United States caused by the SARS-CoV-2 pandemic in 2020. The present report examines trends during 2020 and 2021, that is, contrasting perspectives during 2019 with the acute phase of the pandemic in 2020, and 2021. Private dental insurance paid claims from a data warehouse were obtained, encompassing a 5% random sample of records between January 2019 and December 2021 for child and adult insureds who filed a claim in 2019, 2020, and 2021. We classified claims into one of four categories based on the likelihood of being associated with urgent/emergency care. The precipitous reduction in dental care claims in March-June 2020 recovered to almost pre-pandemic levels by the fall of 2020. However, a downward decline in private dental insurance claims started in the late fall of 2020 and continued through 2021. Differential impacts in dental care categories-in terms of urgency of care-were evident 2021, closely resembling previous trends in 2020. Dental care claims from the first year of the 2020 SARS-CoV-2 pandemic were contrasted with perspectives in 2021. A downward trend in demand/availability changes in dental care insurance claims set in for 2021, perhaps linked to perceptions of the overall economic situation. Such downward trend has continued overall, even after considering seasonal changes and the acceleration of the pandemic during the Delta, Omicron, and other variants.

Tropical deforestation causes large reductions in observed precipitation

Tropical forests play a critical role in the hydrological cycle and can influence local and regional precipitation1. Previous work has assessed the impacts of tropical deforestation on precipitation, but these efforts have been largely limited to case studies2. A wider analysis of interactions between deforestation and precipitation—and especially how any such interactions might vary across spatial scales—is lacking. Here we show reduced precipitation over deforested regions across the tropics. Our results arise from a pan-tropical assessment of the impacts of 2003–2017 forest loss on precipitation using satellite, station-based and reanalysis datasets. The effect of deforestation on precipitation increased at larger scales, with satellite datasets showing that forest loss caused robust reductions in precipitation at scales greater than 50 km. The greatest declines in precipitation occurred at 200 km, the largest scale we explored, for which 1 percentage point of forest loss reduced precipitation by 0.25 ± 0.1 mm per month. Reanalysis and station-based products disagree on the direction of precipitation responses to forest loss, which we attribute to sparse in situ tropical measurements. We estimate that future deforestation in the Congo will reduce local precipitation by 8–10% in 2100. Our findings provide a compelling argument for tropical forest conservation to support regional climate resilience.

Influence of Chemical Treatment of Natural Fibres Using the SPSS Method

Chemical Treatments of Natural Fibre Chemical treatment of hazardous waste involves converting it into non-toxic gases by changing or altering its chemical characteristics. Various treatment methods are used, such as reducing solubility or acidity through neutralization or pH adjustment, precipitation or oxidation and reduction, hydrolysis and photosynthesis, chemical oxidation (such as ozonation, electrolytic oxidation, and hydrogen peroxide), and chemical removal (such as alkali metal dichlorine and alkali). Commonly used chemical treatment processes include metallization, activated chemical treatment processes, chemical precipitation, neutralization absorption, disinfection (using chlorine, ozone, UV light), and ion exchange. Natural fibers obtained from the plant kingdom include cotton, flax, jute, bamboo, sisal, and co-conut husks. Cotton and flax are examples of seed hairs, while jute is an example of stem (or bast) fibers. Sisal is an example of leaf fibers. Animal fibers include secretions such as wool, hair, and silk. Popular animal fibers include angora and mohair. This paper reviews various chemical properties of natural fiber-reinforced composites, including changes resulting from the use of natural fibers. Chemical treatments, such as alkali, silane, acetylation, benzoylation, acrylation, malate coupling agents, isocyanates, permanganate, and others are discussed in relation to their effect on the fiber surface. The aim of these treatments is to improve adhe-sion between the fiber and polymer matrix. As a result, water absorption of composites decreases and their mechanical properties are improved. The Statistical Package for Social Sciences, commonly known as SPSS, quickly gained popularity in the 80s and 90s, ex-tending beyond the commercial sector to the social sciences. The original name was dropped, and the name was shortened to "SPSS." Several attempts were made to introduce a word that fits the acronym "SPSS," but they often failed. In the early 2000s, "Statistical Packages and Software Services" was used for some years, but eventually dropped. "SPSS" became just a name and was no longer short for anything. There is, however, a detailed history of SPSS from 1968 to 2009, which is available to anyone interested. The industries included in this study are the non-metal mineral product industry, general equipment manu-facturing, mining and washing of coal, textile industry, food manufacturing industry, and special equipment manufacturing. The Cronbach's Alpha reliability test was conducted, and the overall Cronbach's Alpha value for the model is 0.744, indicating a 74% reli-ability rate. Based on the literature review, a model with a Cronbach's Alpha value of over 0.50 can be considered for analysis. The text appears to be correct as it is. The Cronbach's Alpha reliability test was conducted, and the overall Cronbach's Alpha value for the model is 0.744, indicating a 74% reliability rate. Based on the literature review, a model with a Cronbach's Alpha value of over 0.50 can be considered for analysis.

Impacts of Climate Change on Natural Runoff in the Yellow River Basin of China during 1961–2020

The change in natural runoff is highly relevant to total river flow dispatch and water resource utilization in the Yellow River Basin (YRB). Based on the annual mean temperature and total precipitation records from 70 meteorological stations from 1961–2020, the impact of climate change on the natural runoff of the YRB is investigated using the Mann-Kendall (M-K) test and Bivariate Wavelet analysis methods. Results show that the annual mean temperature over the YRB increased by 0.33 °C decade−1 during 1961–2020, with a warming rate of more than 0.40 °C decade−1 observed in its northern part. The annual total precipitation increases by 10–20 mm decade−1 in the northwest YRB, while it decreases by 20–30 mm decade−1 in the southeast YRB. The result of the M-K test shows abrupt variations in temperature and natural runoff, especially in the 1980s and 1990s. The decrease in natural runoff is closely tied to the increase (decrease) in temperature (precipitation), especially for the period 1993–2020. The bivariate wavelet coherence analysis further suggests that the decrease in the natural runoff, which has persisted over the past 60 years, is primarily driven by precipitation reduction rather than regional warming. In the stage of rapid warming, the inter-decadal influence of precipitation on natural runoff gradually changes to the influence of inter-annual fluctuation. The finding contributes to providing an important scientific basis for evaluating the optimal allocation of water resources in arid and semi-arid areas against the background of climate change.

Disruption of fungal hyphae suppressed litter-derived C retention in soil and N translocation to plants under drought-stressed temperate grassland

Litter decomposition often represents the largest carbon (C) and nitrogen (N) input into the soil and thereby supports soil nutrition cycling function. Common mycelial networks (CMNs) can promote soil C and N trades during the litter decomposition process. However, the degree to which this promotion depends on abiotic variables, such as drought, remains unresolved. Importantly, the influence of soil fungi mycelium on the turnover of litter-derived C and N could weaken under drought if disrupts fungal hyphae. Here, we used plant litter of stable isotope dual-labeling (13C and 15N), experimental drought (ambient, 30%, 50%, or 70% growing season precipitation reductions), and physical disruption to soil fungal hyphae (via soil core rotation) to investigate decomposition dynamics along the soil-plant-atmosphere continuum in a temperate grassland. On average, drought significantly slowed plant litter decomposition by up to 31.8%, but undisrupted fungal hyphae accelerated litter decomposition by up to 31.7% and promoted the release of C and N from plant litter. The intactness of fungal hyphae would have divergent effects on the allocation of litter-derived C and N during decomposition under drought conditions. Intact soil fungal hyphae contributed about 47% of litter-derived C transfer into soil microbial biomass after litter decomposition, but no significant effects in the soil, plant aboveground, or CO2 emissions, compared to hyphae disruption treatment. Undisrupted hyphae promoted approx. 82% of the turnover of litter-derived N from soil to plant and reduced content of litter-derived N in soil and N2O emission compared to hyphae disruption. We conclude that intact networks of soil fungal hyphae are essential to maintaining litter decomposition processes under drought conditions in temperate grassland ecosystems because the fungi promote releases of carbon and nitrogen from plant litter that facilitate carbon and nitrogen cycling.

Changes in Meteorological Elements and Its Impacts on Yunnan Plateau Lakes

In this study, we analyzed the main climatic factors influencing nine plateau lakes in Yunnan Province over the past 40 years (from 1980 to 2019) based on trend and mutation analyses. The results revealed that the air temperatures of these plateau lakes have increased, with an annual average air temperature increase of 0.18 °C per decade, during this 40-year period. From 2000 to 2005, there was an abrupt change in the air temperature increase, the rate of which was 0.20 °C per decade, and there were reductions in long-wave radiation, relative humidity, wind speed, precipitation, and snowfall. In addition, the rising trend in the air temperature of these lakes located in northwest Yunnan (temperate climate, higher elevation) was found to be significantly higher than that of the lakes in central Yunnan (subtropical climate, lower elevation), whereas in contrast, the declining trends in long-wave radiation, relative humidity, wind speed, and precipitation were more pronounced in central than in northwestern Yunnan.

Large weather and conflict effects on internal displacement in Somalia with little evidence of feedback onto conflict

Extreme weather and conflict may drive forced displacement. However, their individual contribution to displacement is not fully understood due to challenges around isolating individual channels of causality. Here, we use novel disaggregated data on internal displacement in all of Somalia’s subregions from 2016 to 2018 broken down by reported reason of displacement and combine it with weather and conflict data. This allows us to isolate the effects of extreme weather and conflict on forced displacement, as well as the effects of displacement on conflict itself. We find large non-linear effects of weather on displacement where an increase in temperature anomalies from 1 °C to 2 °C (to approx. 1.5 standard deviations, SD) leads to a tenfold increase in displaced people, and a reduction in precipitation from 50 mm to 0 mm (approx. 1.5SD) leads to around a fourfold increase in displacement. We find significant effects of conflict events on displacement (which are masked when the data is aggregated) with a 1.5 standard deviation increase in conflict events increasing displacement 50-fold. We further show that displacement itself has little detectable effect on the occurrence of conflict events.

Quercus insignis seedling response to climatic transfer distance in the face of climate change

Rising temperatures are causing increased tree mortality at lower elevations and upward migrations in montane tree communities. To reduce the risk of extinction from climate change, managed translocation or assisted migration could serve to support the management of endangered species, but is currently a controversial strategy with very limited information available from experimental field studies in the tropics. We examined the effect of climatic transfer distance (CTD; the climatic difference between the site of seed origin and the site of plantation) on the establishment of Quercus insignis, an endangered oak with a distribution restricted to cloud forests. If the natural population (seed origin) occurs at its optimum climate, a decline in seedling transplant performance is expected to occur with greater CTD. Enrichment plantings were established in three sites near the seed origin area (at 1400 m a.s.l.), and in five sites from an elevation similar to the seed source up to high elevations (1365 to 2531 m a.s.l.) in Mexico. We examined the effect of CTD on seedling survival and Relative Growth Rate (RGR) over a period of four years. In the provenance area, a 1.4 °C increase and a 25–30 % annual precipitation decrease were estimated to have occurred during the study period (2018–2021), relative to the reference climate (1960–1990) in which the population in the provenance area developed. We found no significant evidence to support lower seedling survival with greater CTD. High survival occurred in sites with a warmer temperature at present (up to 80 % survival), but also in colder sites at higher elevation (up to 90 %), revealing the high tolerance of Q. insignis to a wide range of climatic conditions. The RGR showed the expected decrease with greater CTD of the Aridity Index, reflecting the importance of the balance between temperature and water availability. These findings support the potential of Q. insignis enrichment plantings, both near the seed origin area and at higher elevation (currently 2–3 °C colder than in the provenance area) to compensate for the expected temperature increase. However, the projected reduction in precipitation and cloud immersion within the cloud forest belt associated with climate change, could act to limit growth and lead to lower establishment success.

Uncertainty in Future Projections of Precipitation Decline over Mesopotamia

Abstract For millennia, Mesopotamia was blessed by enough water supplied by the Tigris and Euphrates Rivers. However, the dwindling freshwater resource is no longer enough. In the future, climate change coupled with a growing population could considerably exacerbate the current water deficit. Based on simulations by carefully selected global and regional climate models, we conclude that these river basins may possibly face further water shortages (mainly due to a reduction in spring-season precipitation) in the next few decades (2021–50) under a scenario of high emissions of greenhouse gases. However, there is no consensus among models regarding these near-term (2021–50) projections of change in precipitation, and society is likely to face the challenge of how to prepare for this uncertain future. The story is different for the late decades of this century: we project, with significantly more confidence, a robust decrease in wet-season (winter to spring) precipitation over the headwaters of these river basins, worsening future water deficits and implying a century-long drying trend over Mesopotamia. Possible physical mechanisms are proposed and discussed. As global warming progresses, higher sea level pressure, centered on the Mediterranean Sea, will likely make upstream storms less frequent and weaker, leading to drying over Mesopotamia. Further, projections show a poleward migration of the fewer Mediterranean storm tracks, decreasing the frequency of storms that penetrate into Mesopotamia. Implementing a global net-zero carbon emissions policy by midcentury could mitigate the severity of the projected droughts in this region.

Effects of flux-cored arc welding technology on microstructure and wear resistance of Fe-Cr-C hardfacing alloy

This research presented the effects of flux-cored arc welding (FCAW) with and without preheating, gas-shielding and buffering conditions on the microstructure and wear resistance of Fe-Cr-C hardfacing alloy. The flux-cored wires based on austenitic nickel and Fe-Cr-C alloyed steel were used as buffer and hardfacing layers. The welding quality was inspected by visual test (VT) and penetrant test (PT). The structural characteristics were analyzed by optical microscope (OM), X-ray diffractometer (XRD), and scanning electron microscope with energy dispersive X-ray spectrometer (SEM-EDS). The results exhibited that the preheating, gas-shielding and buffering could improve the quality, dilution and weldability of the hardfacing weld. The structural phase of the hardfacing weld was found in the form of (Fe,Cr)7C3 mixed with martensite-austenite matrix (MA matrix). The buffering could combine the interphase of hardfacing to structural steel base resulting in the reduction of crack and carbide precipitation (Fe3C) at the fusion line from the effect of elemental dilution. The combination of buffer and hardfacing layers affected to crystallite size and fraction ratio of (Fe,Cr)7C3 to MA matrix increasing the elemental diffusions. According to the wear testing results (hardness, impact and abrasion), it was found that the preheating, gas-shielding and buffering FCAW provided an excellent wear resistance of Fe-Cr-C hardfacing alloy due to the present of (Fe,Cr)7C3 eutectic carbide in a high fraction of MA matrix resulting in good toughness-hardness balance properties. In addition, the suitable FCAW condition from the study could be applied for hardfacing of the tooth plate of crushing roller that was used in the biomass energy industry with better service life than traditional FCAW.

Virtual Clinical Trials Guided Design of an Age-Appropriate Formulation and Dosing Strategy of Nifedipine for Paediatric Use

The rapid onset of action of nifedipine causes a precipitous reduction in blood pressure leading to adverse effects associated with reflex sympathetic nervous system (SNS) activation, including tachycardia and worsening myocardial and cerebrovascular ischemia. As a result, short acting nifedipine preparations are not recommended. However, importantly, there are no modified release preparations of nifedipine authorised for paediatric use, and hence a paucity of clinical studies reporting pharmacokinetics data in paediatrics. Pharmacokinetic parameters may differ significantly between children and adults due to anatomical and physiological differences, often resulting in sub therapeutic and/or toxic plasma concentrations of medication. However, in the field of paediatric pharmacokinetics, the use of pharmacokinetic modelling, particularly physiological-based pharmacokinetics (PBPK), has revolutionised the ability to extrapolate drug pharmacokinetics across age groups, allowing for pragmatic determination of paediatric plasma concentrations to support drug licensing and clinical dosing. In order to pragmatically assess the translation of resultant dissolution profiles to the paediatric populations, virtual clinical trials simulations were conducted. In the context of formulation development, the use of PBPK modelling allowed the determination of optimised formulations that achieved plasma concentrations within the target therapeutic window throughout the dosing strategy. A 5 mg sustained release mini-tablet was successfully developed with the duration of release extending over 24 h and an informed optimised dosing strategy of 450 µg/kg twice daily. The resulting formulation provides flexible dosing opportunities, improves patient adherence by reducing frequent administration burden and enhances patient safety profiles by maintaining efficacious levels of consistent drug plasma levels over a sustained period of time.

Enhanced magnetostriction of rolled (Fe81Ga19)99.93Tb0.07 thin sheet by synergy strategy of secondary recrystallization and trace Tb-doping

Improving the magnetostriction of Fe-Ga thin sheets can significantly promote the magneto-mechanical conversion efficiency of Fe-Ga alloy devices at high-frequency magnetic fields. In this paper, the rolled (Fe81Ga19)99.93Tb0.07 thin sheet with excellent magnetostriction was developed by the synergy strategy of secondary recrystallization and trace Tb-doping. Centimeter-sized Goss grains were induced 0.27 mm-thick (Fe81Ga19)99.93Tb0.07 thin sheet by a composite inhibitor composed of nanometer-sized sulfides and Tb-rich precipitates. The remarkable reduction of the Tb-rich precipitates after quenching led to the dissolution of terbium in the matrix and result in the formation of the Tb-doping induced L60 nanoheterogeneities, which enhancing the lattice distortions in the matrix. The final saturation magnetostriction and the magnetostriction parallel to the rolling direction in (Fe81Ga19)99.93Tb0.07 thin sheets reached 378 ppm and 320 ppm, respectively, which is 30 % and 65 % greater than the undoped thin sheets. This Fe-Ga thin sheet with excellent magnetostriction, produced by a conventional rolling, annealing and quenching method, can greatly improve the conversion efficiency and apply to the next-generation magnetostrictive materials.

Vegetation Dynamics and Hydro-Climatic Changes during the Middle Holocene from the Central Himalaya, India

Understanding the spatiotemporal monsoonal variability during the Holocene helps in understanding the rise and fall of many civilizations. In this study, a 2.65 m high palaeo lake sedimentary profile from the Kumaun Lesser Himalaya, Uttarakhand State, India was pollen analysed to reconstruct the variability in the monsoonal precipitation during the Middle Holocene. The study revealed that between ~7522 and 7216 cal yr BP, conifers dominated mixed broad-leaved forests occurred around the landscape of the study area, indicating a less cold and dry climate with decreased monsoon precipitation. Broad-leaved taxa during this phase show increased values considerably, indicating amelioration in climatic condition, which could be, in global perspective, broadly falling within the time-interval of the Holocene Climate Optimum (HCO; 7000–4000 BP). Between ~7216 and 6526 cal yr BP, dense conifers-dominated mixed broad-leaved forests transformed the conifers-dominated broad-leaved forests around the study area under a cold and drier climate with further reduction in monsoon precipitation. Subsequently, between ~6526 and 5987 cal yr BP, conifers-dominated broad-leaved forests continued to grow, but with lesser frequencies, around the study area under a comparatively less cold and dry climate with reduced monsoon precipitation. Finally, between ~5987 and 5817 cal yr BP, the frequencies of conifers-dominated broad-leaved forests further decreased around the landscape of the study area under a comparatively lesser cold and dry climate, probably indicating decreased monsoonal precipitation. Hence, the present study mainly showed the dominance of conifers forests around the study area between ~7522 and 7216 cal yr BP, ~7216 and 6526 cal yr BP, ~6526 and 5987 cal yr BP and between ~5987 and 5817 cal yr BP; however, broad-leaved forests also demonstrated increasing tendency between ~7522 and 7216 cal yr BP in the milieu of cold and dry climates. Moreover, the study also revealed that a lake was formed around 7522 cal yr BP along the Kulur River, a tributary of Saryu River around the study area and existed until 5817 cal yr BP.

Tree growth periodicity in the ever‐wet tropical forest of the Americas

Abstract The occurrence of annual growth rings in tropical trees—the result of the seasonal activity of vascular cambium—has been explained by seasonal water deficit or flooding periods. However, little is known about the drivers of annual tree‐ring formation under tropical hyper‐humid conditions without clear seasonal dry periods or flooding (ever‐wet conditions). Shelford's law states that the deficit or the excess of environmental resources limits plant growth. Accordingly, we hypothesize that excess soil moisture, a slight seasonal reduction of precipitation and a reduction in light availability determine rhythmic growth in ever‐wet tropical forests. We first assessed the occurrence of rhythmic growth in 14 tree species from the Biogeographic Chocó Region (annual rainfall 7200 mm) using three methods: Radiocarbon (14C) dating (all studied species), tree‐ring synchronization (4 species that have replicates) and automatic dendrometers (two species). Then, we assessed the effect of environmental drivers (rainfall, short‐wave radiation, temperature and soil moisture) on tree growth based on tree ring and dendrometer observations. We present evidence of annual tree‐ring formation in all 14 studied tree species. Depending on the tree species, we observed positive and negative correlations between growth, water availability and light availability. These relationships suggest that both excess or deficit of environmental resources may explain the seasonal pattern of tree growth. Although we cannot differentiate between excess soil water and low light availability by high cloudiness, we suggest that cloudiness frequency could affect tree growth in these forests. Synthesis. We reveal the annual formation of growth rings in the unexplored wetter‐end tropical forests, where seasonal growth depends on either high soil moisture and hypoxia or light limitations by cloudiness and photosynthesis constraints.

Sulfuric acid weathering counteracts CO2 drawdown from silicate weathering in mountainous catchments from southwest China

Sulfide oxidation, coupled with carbonate weathering is thought to be a source of CO2 over geological timescales to offset CO2 drawdown from silicate weathering. Its impact on the carbon budget of weathering at the catchment scale is generally constrained by utilizing riverine water chemistry and the isotope value (δ34S) of sulfate. However, the multiple origins of riverine sulfate and the high variability of sulfide-derived δ34S certainly limit the determination of sulfate sources and thus our understanding of the role of sulfuric acid-induced weathering in the carbon budget. In this study, to quantify the carbon budget between weathering by carbonic and sulfuric acids in mountainous catchments (the Yinjiang River, the Shiqian River, and the Yuqing River) in southwest China, a Monte Carlo inversion model is employed for major element concentrations and sulfate δ34S (δ34SSO4). This inversion quantitatively partitions the cations and sulfate between different sources, and further identifies the pyrite-derived δ34S and the flux ratios of alkalinity to dissolved inorganic carbon (ΔALK/ΔDIC). Inversion results reveal that the majority of major cations (>90 %) is derived from carbonate (calcite and dolomite) dissolution, and that riverine sulfate budget is predominately contributed by pyrite oxidation and precipitation. In the Yinjiang River, the average δ34SSO4 is 8.4 ‰ in the upper and middle reaches, but declines significantly to 0.4 ‰ in the lower reaches. In the Shiqian River and Yuqing River, δ34SSO4 mainly cluster around 3.6–5.7 ‰ and 5.5–8.5 ‰, respectively. Inversion results suggest that the primary controls on δ34SSO4 are the variability of lithology and the variation in the proportional contribution of pyrite oxidation to riverine sulfate. In the Yinjiang River, the fraction of H2SO4-driven weathering is highly variable, and higher in the lower reaches than in the upper reaches, attributing to distinct underlying lithology in the catchment (a widespread distribution of coal-bearing strata). The weathering fluxes with 1 < ΔALK/ΔDIC < 2 evidenced that the negative alkalinity flux from carbonate weathering driven by sulfuric acid from both pyrite oxidation and acid deposition counteracts much of the alkalinity flux from silicate weathering. This is implicated on the timescale between marine carbonate precipitation and sulfate reduction (>5–10 kyr and <10 Myr), indicating that weathering in these catchments acts as short-term sinks of atmospheric CO2 but long-term sources of it. Moreover, reanalysis of prior datasets of karst-dominated catchments in China also highlight the important role of pyrite oxidation and acid precipitation in the carbon budget.

Hydrologic restoration of anthropoentically altered springs in the Sheldon National Wildlife Refuge in the Great Basin, USA

Springbox capped springs divert water for livestock and threaten spring conservation in the Great Basin. Springbox restoration is used to increase water availability at riparian zones and wet meadows. The purpose of our study was to compare six restoration methods used to increase soil moisture. We used a BACI design to compare percent soil moisture before and after restoration at 24 spring sites in Northwestern Nevada, U.S.A. Percent soil moisture was measured at 5-, 15-, 30-, and 45-cm depths during spring and summer months. Year 2017 was wetter than 2016 causing an increase in percent soil moisture in all restoration treatments. Empty springbox cases, cases filled with sand, and caseless gravel-filled springs produced the greatest increase in percent soil moisture at all depths. We recommend sand-filled casings because these funnel water to the surface while sand prevents casing collapse. We recommend sand over gravel because sand is easier to displace as water flows to the surface. The ratio of δ18O/d16O suggests that springs are fed by shallow groundwater derived from recent precipitation. Inter-annual reductions in precipitation driven by climate change may be the ultimate force determining the preservation of Great Basin spring ecosystems.