Climate Global Warming Research Articles

Reducing the source/sink ratio of grapevine to face global warming in a semi-arid climate: Effects on volatile composition of Cabernet Sauvignon grapes and wines.

The heterogeneity of the vineyard environment caused high variability in grape metabolites and flavor profiles, and the phenomenon was more prominent in recent years of climate change. Herein, distal leaf removal was applied in semi-arid Xinjiang to adjust the source to sink ratio of grapevines for three consecutive years (2018-2020). The grape-derived volatiles showed high correlations with specific climate factors such as temperature changes in the growth period. Results showed that distal leaf removal increased the solar radiation reaching the clusters in the first few days after applying LR treatments while not affecting the temperature. The improvement in fruity and floral aroma intensity by distal leaf removal was founded not only in grape metabolites but also in wines. Moderate cluster exposure brought by distal leaf removal was beneficial for the accumulation of isoprenoids, which therefore increased the fruity and floral intensity of wines. The carry-over effect did not show in consecutively defoliated vines among vintages regarding the wine aroma profile.

Trends and research features on greenhouse gas emissions from rice production: review based on bibliometric analysis

Greenhouse gas from rice production has become a great concern and the focus of a lot of research in recent years. The main aim of the study was to explore the research trend of GHG emissions from rice production by exploring the research hotspots and providing suggestions for future research directions over the period 1991 to 2020. A bibliometric analysis was conducted using the Scopus database, and the sample included 2535 articles. The methodology was based on descriptive analysis, co-occurrence analysis, factorial analysis, word dynamic over time, and the author's keyword analysis over time. The results indicate a remarkable increase in the number of articles published on this topic, mainly in the journals of "Agriculture," "Ecosystems," and "Environment." The main authors were Conrad R. and Wassmann R. Relating to the number of published articles, very few were contributed by African countries, whereas China, Japan, and India were the main contributors. The co-occurrence analysis showed that rice, methane, and nitrous oxide are the core keywords of the network. The multiple factorial analysis pointed out that greenhouse gas emissions from rice production depend on the farming practices, the environmental factors, and the plant growth as well. The evolutionary path showed that the current author's keywords are more related to global warming potential, climate change, and biochar. The findings of this review can help researchers and scholars by providing a better overview of development trends that have emerged over the past 30years and suggestions for the future direction in this field.

Sex difference in effects of intermittent heat exposure on hepatic lipid and glucose metabolisms

Global climate warming has drawn worldwide attention. However, the health impact of heat exposure is still controversial. This study aimed to explore the exact effects and sex differential vulnerability under intermittent heat exposure (IHE) patterns and tried to elucidate the potential mechanisms by which IHE modulated hepatic lipid and glucose homeostasis. Both female and male C57BL/6 N mice were randomly allocated to control group (22 ± 1 °C) or intermittent heat group (37 ± 1 °C for 6 h) for 9 consecutive days followed by 4-day recovery at 22 ± 1 °C in a whole-body exposure chamber. Male mice, but not female, being influenced by IHE with decreased body weight, improved insulin sensitivity and glucose tolerance. Next, the levels of hepatic triglyceride (TG) were decreased and free fatty acid (FFA) increased in male mice exposed to intermittent heat, accompanied with upregulated expression of anti-oxidative enzymes in the liver. In addition, IHE led to enhanced lipid catabolism in male mice by inducing fatty acid uptake, lipid lipolysis, mitochondrial/peroxisomal fatty acid oxidation and lipid export. And glycolysis and glucose utilization were induced by IHE in male mice as well. Mechanically, heat shock protein 70 (HSP70)/insulin receptor substrate 1 (IRS1)/AMPKα pathways were activated in response to IHE. These findings provide new evidence that IHE sex-dependently enhanced the metabolism of lipid and glucose in male mice through HSP70/IRS1/AMPKα signaling.

Heat is a Cause of the Global Climate Warming

Experimental-statistical equations are proposed for calculating the results of fossil fuel combustion. The calculation is illustrated by the example of fuel combustion by engines of a Boeing series aircraft. The main supplier of energy to the ecological system of Planet Earth is the Sun. The atmosphere of Planet Earth retains about 50% of the thermal (infrared) radiation of the Sun. This casts doubt on the role of CO2, whose concentration in the Earth's atmosphere is about 0.05%, in Global Climate Warming. Knowing how much fuel humanity produces per year, it is possible to calculate the amount of thermal energy produced per year. If in 2000 humanity produced 412*106 TJ of thermal energy, then the Sun supplied 38286*106 TJ of thermal energy to the Earth in 365 hours a year. It is expedient to reduce Global Warming by 1.5 - 2.0 degrees by installing a "Solar Umbrella" in the stratosphere - a filter for infrared (thermal) radiation from the Sun.

Significant increase in water vapour over India and Indian Ocean: Implications for tropospheric warming and regional climate forcing.

The increase in greenhouse gases (GHGs) due to anthropogenic activities enhances regional and global temperatures. The most abundant GHG, i.e., water vapour, has a vital positive feedback on the global warming and Earth's climate system. This study focuses on the spatial and temporal changes in water vapour in the troposphere over India and Indian Ocean as derived from the ground-based, satellite and reanalyses data, and assesses the impact on water vapour changes on the regional climate by analysing radiative effects. The analyses show that the annual mean column water vapour (CWV) is high over the northern Indian Ocean, Bay of Bengal and Peninsular India, ranging from 30 to 60 kg/m2. Most regions show significant positive trends in the annual mean CWV, about 0.1-0.2 kg/m2/yr. There is a significant positive trend in water vapour in the troposphere (except 200 hPa) over the India land regions, with the highest values at 1000 hPa (0.034 g/kg/yr). The corresponding water vapour radiative effect (WVRE) is about 20-80 W/m2, depending on seasons and regions. This study, therefore, indicates that the increase in tropospheric water vapour over India and Indian Ocean could affect the regional temperature and climate.

Volcanism driven Pliensbachian (Early Jurassic) terrestrial climate and environment perturbations

Initial breakup of Pangaea and opening of the Central Atlantic Ocean during the Early Jurassic resulted in widespread volcanism and was accompanied by significant changes in atmospheric composition, climate and environment of the Earth's surface system. Although profound changes in global geochemical cycles, palaeoclimate, and palaeoenvironments during the early part of the Toarcian Stage have been extensively studied and attributed to the emplacement of the Karro-Ferrar Large Igneous Province (LIP), similar changes in other parts of the Early Jurassic are less well known, especially in terrestrial settings. We studied Pliensbachian aged terrestrial strata from the Dameigou section in the Qaidam Basin of the Qinghai-Tibet Plateau to elucidate climate and environmental changes and their potential driving mechanisms. Three significant climate and environment perturbations were recognized by high-resolution mineralogical and geochemical analyses, with each characterized by peaks in kaolinite composition that indicate relatively warm and humid climates. Each kaolinite peak is accompanied by proxy evidence that indicates anoxic redox conditions, high paleoproductivity, and strong continental weathering prevailed, and coincides with negative carbon isotope excursions and peaks in Hg/TOC ratios that record three episodes of concurrent volcanism. The three episodes of volcanism are correlated with global events and suggest volcanism as the driving mechanism for major global climate and environment perturbations during the Pliensbachian. Each interval of volcanism released massive quantities of greenhouse gases and Hg into the atmosphere, leading to negative carbon isotope excursions and mercury anomalies in sedimentary strata. Global climatic warming induced by volcanism resulted in an enhanced hydrological cycle and can be correlated with more humid climatic conditions, intensified continental weathering and organic matter burial, lake expansion, and eutrophication. Such changes have important negative feedback on the global carbon cycle by increasing consumption of CO 2 in lacustrine settings, which in the late Pliensbachian led to the restoration of similar climates and environments that occurred pre-volcanism in the study area. • High-resolution Pliensbachian terrestrial climate and environmental change record. • Volcanism identified from negative carbon isotope excursions and Hg/TOC peaks. • Kaolinite, C-values, V/Cr ratios, and P/Al ratio peaks associated with volcanism. • Three Pliensbachian volcanic events coincide with climate and environment changes. • Volcanism driving environmental and climate change in terrestrial setting.

Behavioural thermoregulation by montane ungulates under climate warming

AbstractAimGlobal warming is threatening species survival worldwide. Cold‐adapted montane ungulates may be among the first species to be affected by global warming. Here, we investigate the behavioural thermoregulation hypothesis that montane ungulates buffer the effects of warming climate through behavioural adjustment.LocationFoping National Nature Reserve (FNNR) on the southern slopes of the Qinling Mountains, Shaanxi, China.MethodsWe used infrared camera traps over six consecutive years to monitor behavioural responses of montane ungulates to seasonal and diurnal changes in ambient temperature. We evaluated how seasonal altitudinal migration and changes to their daily activity budget may mitigate the effect of warming on montane ungulates.ResultsAll four montane ungulate species examined here preferred ambient temperatures <22°C in summer. On this basis, we estimate that 27.9% (+2°C) and 46.7% (+3°C) of suitable summer habitats will become unsuitable under climate change. Chinese muntjac and tufted deer displayed behavioural changes to daily activity budgets, which may help them overcome global climate warming to a certain extent. By contrast, golden takin and wild boar did not display similar behavioural changes, and it may be because they are not affected by current shifts in climate due to larger body size and thus lower thermal stress.Main ConclusionsThese analyses demonstrate different species responses to warming are likely and are determined by specific tolerances to ambient temperature thresholds. However, it remains to be seen whether species interactions caused by behavioural shifts may affect species ability to respond to climate.

Linkages between Typologies of Existing Urban Development Patterns and Human Vulnerability to Heat Stress in Lahore

The combined effects of global warming, urbanization, and demographic change influence climate risk for urban populations, particularly in metropolitan areas with developing economies. To inform climate change adaptation and spatial planning, it is important to study urban climatic hazards and populations at risk in relation to urban growth trends and development patterns. However, this relationship has not been adequately investigated in studies dedicated to climate vulnerability. This study identifies the typologies of development patterns within Lahore, Pakistan, investigates the heat vulnerability of residents at a neighborhood scale, and establishes a relationship between both of these factors. We identified urban clusters with diverse development patterns. Fourteen context- and site-specific indicators were selected to construct a human heat vulnerability index. Weighted sum, cluster analysis, and ANOVA test of variance were conducted to analyze the data. Our results demonstrate that development patterns significantly influence human vulnerability to heat stress, e.g., vulnerability is higher in older cities and undeveloped neighborhoods with less diverse land uses. These findings are essential for informing policy-makers, decision-makers and spatial planners about proactive adaptation planning in dynamic urban environments.

Soil properties resulting in superior maize yields upon climate warming

The impacts of global climate warming on maize yield vary regionally. However, less is known about how soil modulates regionally specific impacts and soil properties that are able to alleviate adverse impacts of climate warming on maize productivity. In this study, we investigated the impacts of multiple soil inherent properties on the sensitivity of maize yield (SY,T) to growing season temperature across China. Our results show that a 1°C warming resulted in the largest yield decline (11.2 ± 6.1%) in the mid-eastern region, but the moderate yield increase (1.5 ± 2.9%) in the north-eastern region. Spatial variability in soil properties explained around 72% of the variation in SY,T. Soil organic carbon (SOC) content positively contributed the greatest extent (28.9%) to spatial variation of SY,T, followed by field capacity (9.7%). Beneficial impacts of increasing SOC content were pronounced in the north-eastern region where SOC content (11.9 ± 4.3 g kg−1) was much higher than other regions. Other soil properties (e.g., plant wilting point, sand content, bulk density, and saturated water content) were generally negatively correlated with SY,T. This study is the first one to answer how soil inherent properties can modulate the negative impacts of climate warming on maize yield in China. Our findings highlight the importance of SOC in alleviating adverse global warming impacts on maize productivity. To ensure food security for a rapidly increasing population under a changing climate, appropriate farming management practices that improve SOC content could reduce risk of adverse effects of global climate warming through a gain in yield stability and more resilient production in China’s maize belt.

Joint control of alpine meadow productivity by plant phenology and photosynthetic capacity

Under global climate change, climate warming and changing precipitation patterns would greatly affect plant phenology and photosynthetic capacity and hence affect the gross primary productivity (GPP) of the sensitive alpine meadow. To deeply understand the variations in GPP, it is important to clarify the joint effects of plant phenology and photosynthetic capacity. In this study, 10-year continuous flux and microclimatic data and in situ phenology period observation data were used to explore the roles of growing season length (GSL) and the seasonal maximal capacity of carbon uptake (GPPmax) on annual cumulative gross primary productivity (GPPann). The results indicated that the temperature and water conditions, especially water conditions, dominated GSL and GPPmax and hence determined GPPann. Both GSL and GPPmax were dominated by annual precipitation, and the soil water content in August also showed a strong influence over them. GSL and GPPmax together could explain 87% of the variation in GPPann. Compared with GSL, GPPmax had stronger effects on the interannual variability (IAV) in GPPann. This study provides a new perspective on clarifying the proximate causes of IAV in GPPann. The IAV in GPPann of alpine ecosystems could be determined by these two key underlying processes, the length of the carbon uptake period and amplitude. These results are of critical importance for improving our ability to predict future changes in alpine meadow ecosystems.

Reconstruction of coastal flooding processes and human response at the end of the Liangzhu Culture, East China

Understanding coastal flooding processes in response to centennial-scale sea-level rise is essential in preparing for the challenge of present-day global warming. Mid-Holocene sea-level rise induced widespread coastal flooding along the East China coast and precipitated the collapse of the Neolithic Liangzhu Culture, the earliest known prehistoric state in East Asia. This paper presents multi-proxy analyses of sedimentology, grain size, total organic carbon (TOC), and alkaline-earth metals extracted by acetic acid (HAc) of a dated sediment core, ZK07, collected from Liangzhu City, with the aim of revealing the detailed progression of coastal flooding phases and the response of prehistoric people at the end of the associated Liangzhu Culture. A three-step succession of coastal flooding processes between ca. 4.6–4.3 cal kyr BP, brought about by relative sea-level rise, is evident in core ZK07. Initially, an increase in the local water level in response to the first phase of sea-level rise is indicated by a gradual increase in TOC at ca. 4630 cal yr BP. Subsequently, at ca. 4520 cal yr BP, a second phase of increased local water-level, consistent with further sea-level rise and salinity intrusion, is suggested by higher Sr concentrations accompanied by a sharp increase in TOC. Thirdly, at ca. 4480–4315 cal yr BP, low TOC content, high - but strongly fluctuating - Sr and Ba concentrations and coarser sediment grain size are all indicative of coastal inundation caused by both storm surges and river flooding associated with typhoon events that correspond with a concurrent phase of accelerated sea-level rise. Considering the evidence of cultural deposits preserved at Liangzhu City, it appears that the Liangzhu people were forced to respond rapidly to the inundation by abandoning the city at ca. 4480 cal yr BP. We suggest that relative sea-level rise and coastal flooding at the terminal stage of the Liangzhu Culture was the regional response to global climate warming and eustatic sea-level rise at that time. Given evidence that a contemporaneous cultural transition took place in the lower Yellow River basin, we further propose that global climate change around 4.5 cal kyr BP had a widespread impact on Neolithic cultural evolution in East China. Furthermore, the rise in local water levels and associated salinity intrusions may be considered as an early warning signal in monitoring future coastal flooding risk.

Field aging declines the regulatory effects of biochar on cadmium uptake by pepper in the soil

Biochar application is not only being widely promoted as an ideal strategy to mitigate global climate warming, but it also has the advantage of reducing heavy metal bioavailability and migration in the soil. However, studies on the effects of field aging on biochar to reduce heavy metals from the soil are still limited. The present study aimed to explore the effects and mechanisms of aged biochar added to the soil planted with pepper plants on cadmium (Cd) uptake. To achieve this, un-amended soil (control), soil amended with fresh biochar, and aged biochar (biochar recovered from a long-term field trial after 9 years) were used to investigate the effects of field aging on biochar adsorption efficiency. The results revealed that the amount of Cd in the plant planted in control soil, amended with fresh and aged biochar, accounted for 40 ± 6.10, 17.18 ± 1.19, and 18.68 ± 0.79, respectively. There was a significant difference (P < 0.05) in the amount of Cd that was uptaken by plants among all treatments. However, soil amended with fresh biochar significantly (P < 0.05) decreased the amount of Cd in plants compared with soil amended with aged biochar. This indicates that field aging declines the potential of biochar to lower heavy metal bioavailability and retention in the soil. This study demonstrates that long-term burial lessens the ability of biochar to interact with Cd and suggests that biochar amendment can lower Cd in the soil, depending on the freshness and aging of biochar.

Absolute globalization: The way to confront the global challenges

The world is currently confronted with multidimensional challenges which are cause of concern for the earth’s all living creations. The most remarkable challenges are global warming and global climate changes, tremendous poverty, environment pollution, warfare, antibiotic resistance, migration problems, and the spread of contagious and deadly diseases etc. The adverse effects of these are very devastating. They will affect hydrology and biology of earth, everything including economy, eco-system, and the substances. The challenging factors are interconnected, and acceleration and minimization are interlinked. The study is to analysis the challenges the world is currently confronting with and their potential impacts, the reasons behind the challenges and the potential way to overcome the challenges. The study is based on secondary sources of data and information including scientific and academic journals, articles, research papers, books, and other relevant sources to make a deep analysis, interpretation and re-interpretation and describe and explain the issue of this proposed study. The study recommends ‘Absolute Globalization,’ an integration of global economic, education, political, and social institutions where regionalism will be the cornerstone of the integration, as the way to confront the challenges.

Suppression of AMF accelerates N2O emission by altering soil bacterial community and genes abundance under varied precipitation conditions in a semiarid grassland.

Nitrous oxide (N2O) is one of the most important greenhouse gases contributing to global climate warming. Recently, studies have shown that arbuscular mycorrhizal fungi (AMF) could reduce N2O emissions in terrestrial ecosystems; however, the microbial mechanisms of how AMF reduces N2O emissions under climate change are still not well understood. We tested the influence of AMF on N2O emissions by setting up a gradient of precipitation intensity (+50%, +30%, ambient (0%), −30%, −50%, and −70%) and manipulating the presence or exclusion of AMF hyphae in a semiarid grassland located in northeast China. Our results showed that N2O fluxes dramatically declined with the decrease in precipitation gradient during the peak growing season (June–August) in both 2019 and 2020. There was a significantly positive correlation between soil water content and N2O fluxes. Interestingly, N2O fluxes significantly decreased when AMF were present compared to when they were absent under all precipitation conditions. The contribution of AMF to mitigate N2O emission increased gradually with decreasing precipitation magnitudes, but no contribution in the severe drought (−70%). AMF significantly reduced the soil’s available nitrogen concentration and altered the composition of the soil bacteria community including those associated with N2O production. Hyphal length density was negatively correlated with the copy numbers of key genes for N2O production (nirK and nirS) and positively correlated with the copy numbers of key genes for N2O consumption (nosZ). Our results highlight that AMF would reduce the soil N2O emission under precipitation variability in a temperate grassland except for extreme drought.

Rapid evolution of selfing syndrome traits in Viola arvensis revealed by resurrection ecology.

As part of global change, climate warming and pollinator decline are expected to affect plant phenology and plant-pollinator interactions. This paper aims at characterizing rapid evolution of life history traits and floral traits over two decades in the wild pansy (Viola arvensis), a common weed in agrosystems. We used a resurrection ecology approach with genotypes sampled in 1991 and 2012 from a population in Burgundy (France). The species has a mixed mating system (hereafter: mixed selfer) and presents a floral polymorphism. To correct for maternal effects, we measured plant traits in the second generation in a common garden (after a refreshing generation) to characterize plant evolution during the two decades. In addition, historical population selfing rates in 1991 and 2012 were inferred from microsatellites markers through heterozygote deficiency and identity disequilibrium. Phenotypic data revealed a significant advance in flowering date, reduced flower sizes and a higher propensity of plants to set seed by autonomous selfing. Moreover, we detected a change in color morph frequency with an increase of the pale morph frequency. In accordance with phenotypic data, the neutral genetic data revealed an increase in historical selfing rates from 0.68 in 1991 to 0.86 in 2012. Taken together, such data suggest that the wild pansy, a mixed selfer, is evolving a selfing syndrome that may be the consequence of reduced pollinator activity in agrosystems.

A comparative study on renewable energy policies between Japan and Malaysia

The world relies heavily on fossil fuels for energy generation, thereby leading to global warming and regional climate change. Renewable energy (RE) is one of the realisable solutions to tackle the drastically increasing energy demand. As the global push for RE culminates within the coming years, energy policies will be the key driver in promoting RE deployment. Japan as a developed country aims to achieve a 36–38% share of RE in the energy mix by 2030, whilst Malaysia being a developing country has set a goal of achieving 31% RE mix by 2025. This paper presents a comparative study of RE policies between Japan and Malaysia, with the RE policies of both countries being analysed and presented chronologically. Moreover, the factors that contributed to the effectiveness of the policy and the measures that can be taken to overcome the shortcomings of the policies are elaborated. It is observed that both countries have been actively implementing a series of RE policies since the 21st century, especially Japan after the Fukushima nuclear disaster in 2011. Japan has shown an outstanding achievement where it achieved 20.8% of RE mix in 2020 while Malaysia is still far behind its target at approximately 2% in the same year. Hence, the Malaysian government should follow Japan’s footsteps in adopting and enforcing RE policies, and at the same time increase civil awareness regarding RE and stimulate participation from various stakeholders.

Effective photoelectrocatalytic reduction of CO2 to formic acid using controllably annealed TiO2 nanoparticles derived from porous structured Ti foil

The rate of global warming and unfavorable climate changes caused by the drastic upsurge of carbon dioxide (CO2) emission has necessitated the development of approaches to limit the significantly high concentration of CO2 in the atmosphere. The photoelectrochemical reduction of CO2 results in a reduction of the energy required to transform this greenhouse gas into valuable end products. In this study, we fabricated cost-effective and novel 3D nanoporous structured (3DNS) TiO2 nanoparticles (T-NPs) on the surface of a thin titanium foil (T-foil) by chemical treatment with hydrogen peroxide (H2O2) followed by calcination at high temperatures in the range of 400–800 °C. The as-proposed samples were analyzed by several characterizations such as XRD, XPS, TEM, and Raman spectroscopy. At 600 °C, the anatase-dominated mixed phases of calcinated T-foil (TO600) were seen, and a maximum photocurrent density of 71.5 µA/cm2 was obtained, in comparison to the T-foils treated at other temperatures (TO400, TO500, TO700, and TO800). Because of the better photocurrent density, TO600 was selected as the photocathode material for photoelectrochemical CO2 reduction performed with or without the presence of solar light. The lowest CO2 reduction onset potential (−1.191 V) was observed on the TO600 sample in the presence of light with Ag/AgCl as the reference electrode. 1H NMR analysis of the product solution revealed the formation of formic acid as the major product of the CO2 reduction reaction after the chronoamperometric electrolysis was performed for more than 25 h. The maximum faradaic efficiency (64%) and formic acid yield (165 µmol cm−2 h−1) were obtained at an applied potential of − 1.3 V (vs. Ag/AgCl reference electrode) for TO600.

MODELING OF THE THERMAL REGIME OF DRAINED PEAT-BOGS SOILS IN BELARUSIAN POLESIE

The article presents the results of modeling predictive estimates of the distribution of heat resources in peat-bog soils at various rates of drainage, taking into account global climate warming for the period up to 2035. The proposed method makes it possible, using mathematical modeling, to obtain the temperature profile of soils, which is the basis for assessing changes in the temperature and thermal regimes of natural and drained soils of Belarusian Polissia due to changes in air temperature. The results obtained in the work can be used in the management of the water regime of reclaimed lands.

Contributions of three types of biocrusts to soil carbon stock and annual efflux in a small watershed of Northern Chinese Loess Plateau

Accurate estimation of soil carbon (C) stock and efflux in drylands is vital for understanding the C cycling processes and predicting global climate change. As a “living skin”, biocrusts strongly change soil C fixation and respiration, but till now it is still challenging to accurately estimate and assess biocrust's contributions to soil C stock and efflux, especially taking different types of biocrusts and annual scale into consideration. In a small representative watershed on the northern Chinese Loess Plateau, cyanobacterial crust (cyano crust), cyanobacteria and moss mixed crust (mixed crust), moss crust, and bare soil were sampled. The organic C content of the samples were determined in laboratory, and subsequently their C stocks were calculated. Moreover, the respiration rate (Rs) of biocrusts and bare soil were repetitively measured in field for a four-month period, respectively, and an optimal regression model was established based on the relationship between Rs and corresponding temperature and moisture of soil. Lastly, the daily Rs was extended to a whole year through model extrapolation, and the seasonal and annual C efflux was obtained through summing the daily respiration together. Our results showed that (i) the organic C content of three types of biocrusts were 69 %–159 % higher than that of bare soil, and the soil C stock at depth of 0–5 cm was 0.35, 0.51, 0.81, and 0.61 kg m−2 for bare soil, cyano crust, mixed crust, and moss crust, respectively. (ii) During the measurement period, the mean Rs of the four habitats were 1.13, 2.21, 2.86, and 2.56 μmol m−2 s−1, respectively, showing that the biocrusts increased Rs by 96 %–152 % in contrast to bare soil. (iii) The variations of Rs were best explained by soil temperature and moisture through the Gaussian model, which had the lowest AIC and RMSE. (iv) Based on model extrapolation, the estimated annual C efflux from bare soil, cyano crust, mixed crust, and moss crust were 228.0, 378.0, 894.0, and 679.0 g m−2, respectively, indicating that in annual scale biocrusts increased C efflux by 66 %–292 % compared with bare soil. The seasonal variations also implied that the C efflux of biocrusts in summer and autumn were significantly higher than that in winter and spring, but they all accounted for a considerable proportion and should not be neglected. In conclusion, different types of biocrusts are the dominant contributors of soil C fixation and respiration in drylands. More importantly, the increased soil C efflux from biocrusts is highly overwhelmed by their elevated photosynthetic capacity, which make biocrusts sequestrate a considerable amount of C. These effects on soil C are highly associated with biocrust's roles in restoring degraded soil and mitigating global climate warming.

Effects of altitude and slope on the climate–radial growth relationships of Larix olgensis A. Henry in the southern Lesser Khingan Mountains, Northeast China

BackgroundThe relationship between climate and radial growth of trees exhibits spatial variation due to environmental changes. Therefore, elucidation of how the growth–climate responses of trees vary in space is essential for understanding forest growth dynamics to facilitate scientific management with the ongoing global climate warming. To explore the altitudinal and slope variations of these interactions, tree-ring width chronologies of Larix olgensis A. Henry were analyzed in the southern Lesser Khingan Mountains, Northeast China.ResultsThe radial growth of L. olgensis exhibited significant 5- to 10-year periodic changes at three altitudes and two slopes, and the frequency change occurred mainly during the early growth stage and after 2000. The radial growth of L. olgensis was significantly negatively correlated with September precipitation only at low altitudes, but also with the mean temperature in July–August and the mean maximum temperature in June–August at high altitudes. The radial growth of L. olgensis at low and middle altitudes as well as on the sunny slope led to a higher demand for moisture, while temperature was the key limiting factor at high altitudes and on the shady slope.ConclusionsThe climate–radial growth relationship of L. olgensis exhibits altitudinal and slope variability. This study quantitatively describes the spatially varying growth–climate responses of L. olgensis in the southern Lesser Khingan Mountains, which provides basic data for the management of L. olgensis forests and the prediction of future climate impacts on forest ecosystems.