Topsoil Temperature Research Articles

Seasonal Dynamics of Culturable Yeasts in Ornithogenically Influenced Soils in a Temperate Forest and Evaluation of Extracellular Enzyme Secretion in Tausonia pullulans at Different Temperatures.

The culturable yeast communities in temperate forest soils under the ornithogenic influence were studied in a seasonal dynamic. To investigate the intense ornithogenic influence, conventional and "live" feeders were used, which were attached to trees in the forest and constantly replenished throughout the year. It was found that the yeast abundance in the soil under strong ornithogenic influence reached the highest values in winter compared to the other seasons and amounted to 4.8 lg (cfu/g). This was almost an order of magnitude higher than the minimum value of yeast abundance in ornithogenic soils determined for summer. A total of 44 yeast species, 21 ascomycetes and 23 basidiomycetes, were detected in ornithogenic soil samples during the year. These included soil-related species (Barnettozyma californica, Cyberlindnera misumaiensis, Cutaneotrichosporon moniliiforme, Goffeauzyma gastrica, Holtermanniella festucosa, Leucosporidium creatinivorum, L. yakuticum, Naganishia adeliensis, N. albidosimilis, N. globosa, Tausonia pullulans, and Vanrija albida), eurybionts (yeast-like fungus Aureobasidium pullulans, Debaryomyces hansenii, and Rhodotorula mucilaginosa), inhabitants of plant substrates and litter (Cystofilobasidium capitatum, Cys. infirmominiatum, Cys. macerans, Filobasidium magnum, Hanseniaspora uvarum, Metschnikowia pulcherrima, and Rh. babjevae) as well as a group of pathogenic and opportunistic yeast species (Arxiozyma bovina, Candida albicans, C. parapsilosis, C. tropicalis, Clavispora lusitaniae, and Nakaseomyces glabratus). Under an ornithogenic influence, the diversity of soil yeasts was higher compared to the control, confirming the uneven distribution of yeasts in temperate forest soils and their dependence on natural hosts and vectors. Interestingly, the absolute dominant species in ornithogenic soils in winter (when the topsoil temperature was below zero) was the basidiomycetous psychrotolerant yeast T. pullulans. It is regularly observed in various soils in different geographical regions. Screening of the hydrolytic activity of 50 strains of this species at different temperatures (2, 4, 10, 15 and 20 °C) showed that the activity of esterases, lipases and proteases was significantly higher at the cultivation temperature. Ornithogenic soils could be a source for the relatively easy isolation of a large number of strains of the psychrotolerant yeast T. pullulans to test, study and optimize their potential for the production of cold-adapted enzymes for industry.

Influence of snowpack on soil organic carbon decomposition in a northern peatland

Peatlands play a significant role in maintaining the carbon balance and regulating the climate. The turnover of soil organic carbon (SOC) in peatlands is mediated by snowpack, which affects microbial decomposition through its regulation of hydrothermal conditions. However, the impact of snowpack on carbon dynamics in peatlands is not fully understood, particularly in the context of decline in snowpack due to climate warming. To address this issue, an on-site experiment was conducted involving snowpack manipulation (undisturbed and snow removal) to investigate the effects of snowpack on SOC decomposition at depths of 0–30 cm (topsoil) and 30–60 cm (subsoil). Various techniques such as X-ray absorption near-edge structure, synchrotron radiation micro computed tomography technology and microbial metagenomics were utilized to measure SOC content and fractions, pore structure and bacterial community’s structure and function. Results showed that snow removal delayed the start of soil freezing date by 27 days and advanced the start of thawing date by 39 days, increased maximum freezing depth by 27.9 cm and frequency of freeze–thaw cycles, and decreased average temperature of topsoil and subsoil by 1.48 °C and 1.34 °C, respectively. Additionally, snow removal increased SOC content by 8.27 % and 3.19 % and its stability by 53 % and 13.92 % in the topsoil and subsoil, respectively, and decreased microbial decomposition potential functioning by 55.89 % and 5.75 % in both soil layers. The three-dimensional spatial distribution of SOC and soil pores at the micro-scale indicated that snow removal significantly influenced pore structure and microbe feedback loops, thereby affecting SOC decomposition. Notably, snow removal led to an increase in the proportion of micropores by 3.44 % and 4.41 % in the topsoil and subsoil, respectively, suggesting enhanced protection of pore structure and preservation of SOC during decomposition processes. Overall, the findings suggest that snow removal may intensify the response of carbon pools to climate change in peatlands.

Variation in Soil CO2 Fluxes across Land Cover Mosaic in Typical Tundra of the Taimyr Peninsula, Siberia

Increased warming in the Arctic is of great concern. This is particularly due to permafrost degradation, which is expected to accelerate microbial breakdown of soil organic carbon, with its further release into the atmosphere as carbon dioxide (CO2). The fine-scale variability of CO2 fluxes across highly mosaic Arctic tundra landscapes can provide us with insights into the diverse responses of individual plant communities to environmental change. In the paper, we contribute to filling existing gaps by investigating the variability of CO2 flux rates within different landscape units for dominant vegetation communities and plant species across typical tundra of the southern part of the Taimyr Peninsula, Siberia. In general, the variability of soil CO2 flux illustrates a four-fold increase from non-vascular vegetation, mainly lichens and mosses (1.05 ± 0.36 µmol m−2 s−1), towards vascular plants (3.59 ± 0.51 µmol m−2 s−1). Barren ground (“frost boils”) shows the lowest value of 0.79 ± 0.21 µmol m−2 s−1, while considering the Arctic “browning” phenomenon, a further substantial increase of CO2 flux can be expected with shrub expansion. Given the high correlation with top soil temperature, well-drained and relatively dry habitats such as barren ground and non-vascular vegetation are expected to be the most sensitive to the observed and projected temperature growth in the Arctic. For mixed vegetation and vascular species that favor wetter conditions, soil moisture appears to play a greater role. Based on the modeled seasonal pattern of soil CO2 flux and precipitation records, and applying the rainfall simulations in situ we outlined the role of precipitation across enhanced CO2 emissions (i.e., the “Birch” effect). We found that a pulse-like growth of soil CO2 fluxes, observed within the first few minutes after rainfall on vegetated plots, reaches 0.99 ± 0.48 µmol m−2 s−1 per each 1 mm of precipitation, while barren ground shows 55–70% inhibition of CO2 emission during the first several hours. An average additive effect of precipitation on soil CO2 flux may achieve 7–12% over the entire growing season, while the projected increased precipitation regime in the Arctic may strengthen the total CO2 release from the soil surface to the atmosphere during the growing season.

Drought effects on soil greenhouse gas fluxes in a boreal and a temperate forest

AbstractChanging water regimes (e.g. drought) have unknown long-term consequences on the stability and resilience of soil microorganisms who determine much of the carbon and nitrogen exchange between the biosphere and atmosphere. Shifts in their activity could feedback into ongoing climate change. In this study, we explored soil drought effects on soil greenhouse gas (GHG; CO2, CH4, N2O) fluxes over time in two sites: a boreal, coniferous forest in Finland (Hyytiälä) and a temperate, broadleaf forest in Austria (Rosalia). Topsoil moisture and topsoil temperature data were used to identify soil drought events, defined as when soil moisture is below the soil moisture at the permanent wilting point. Data over multiple years from automated GHG flux chambers installed on the forest floor were then analyzed using generalized additive models (GAM) to study whether GHG fluxes differed before and after drought events and whether there was an overall, multiyear temporal trend. Results showed CO2 and N2O emissions to be more affected by drought and long-term trends at Hyytiälä with increased CO2 emission and decreased N2O emissions both following drought and over the entire measurement period. CH4 uptake increased at both sites both during non-drought periods and as an overall, multiyear trend and was predominantly affected by soil moisture dynamics. Multiyear trends also suggest an increase in soil temperature in the boreal forest and a decrease in soil moisture in the temperate forest. These findings underline forests as an important sink for CH4, possibly with an increasing rate in a future climate.

Sunlight can have a stronger influence than air temperature on soil solarisation: observational evidence from Australia

Soil solarisation is a method for pest and weed control pioneered in agriculture, and it is increasingly being adopted by restoration practitioners. Solarisation works by covering moist soil during hot periods with a sheet of clear plastic. The success of soil solarisation depends in large part on increasing the temperature of the topsoil. Topsoil temperature depends on several physical variables, including soil moisture content, ambient temperature, and sunlight intensity. In restoration scenarios, solarisation can be used to reduce weed and pathogen loads prior to planting target plants. It is rarely possible to have tight control over all the variables that are important for solarisation; however, practitioners can time interventions to maximise seasonal temperature and sunlight intensity. In this study, we investigated how these two key physical variables – temperature and sunlight – contributed to the success of soil solarisation. We found that while both ambient temperature and sunlight contributed to soil temperature, the data suggests that sunlight was the more influential driver of soil temperature. These results show that, when planning for soil solarisation during ecological restoration, land managers can benefit by considering sunlight as well as air temperature. The result that sunlight may be the more influential driver of soil temperature empowers land managers to better plan solarisation using sunlight projections, even when temperature is not optimal or is unpredictable.

Microclimate mapping using novel radiative transfer modelling

Abstract. Climate data matching the scales at which organisms experience climatic conditions are often missing. Yet, such data on microclimatic conditions are required to better understand climate change impacts on biodiversity and ecosystem functioning. Here we combine a network of microclimate temperature measurements across different habitats and vertical heights with a novel radiative transfer model to map daily temperatures during the vegetation period at 10 m spatial resolution across Switzerland. Our results reveal strong horizontal and vertical variability in microclimate temperature, particularly for maximum temperatures at 5 cm above the ground and within the topsoil. Compared to macroclimate conditions as measured by weather stations outside forests, diurnal air and topsoil temperature ranges inside forests were reduced by up to 3.0 and 7.8 ∘C, respectively, while below trees outside forests, e.g. in hedges and below solitary trees, this buffering effect was 1.8 and 7.2 ∘C, respectively. We also found that, in open grasslands, maximum temperatures at 5 cm above ground are, on average, 3.4 ∘C warmer than those of the macroclimate, suggesting that, in such habitats, heat exposure close to the ground is often underestimated when using macroclimatic data. Spatial interpolation was achieved by using a hybrid approach based on linear mixed-effect models with input from detailed radiation estimates from radiative transfer models that account for topographic and vegetation shading, as well as other predictor variables related to the macroclimate, topography, and vegetation height. After accounting for macroclimate effects, microclimate patterns were primarily driven by radiation, with particularly strong effects on maximum temperatures. Results from spatial block cross-validation revealed predictive accuracies as measured by root mean squared errors ranging from 1.18 to 3.43 ∘C, with minimum temperatures being predicted more accurately overall than maximum temperatures. The microclimate-mapping methodology presented here enables a biologically relevant perspective when analysing climate–species interactions, which is expected to lead to a better understanding of biotic and ecosystem responses to climate and land use change.

Total Soil CO2 Efflux from Drained Terric Histosols.

Histosols cover about 8-10% of Lithuania's territory and most of this area is covered with nutrient-rich organic soils (Terric Histosols). Greenhouse gas (GHG) emissions from drained Histosols contribute more than 25% of emissions from the Land Use, Land Use Change and Forestry (LULUCF) sector. In this study, as the first step of examining the carbon dioxide (CO2) fluxes in these soils, total soil CO2 efflux and several environmental parameters (temperature of air and topsoil, soil chemical composition, soil moisture, and water table level) were measured in drained Terric Histosols under three native forest stands and perennial grasslands in the growing seasons of 2020 and 2021. The drained nutrient-rich organic soils differed in terms of concentrations of soil organic carbon and total nitrogen, as well as soil organic carbon and total nitrogen ratio. The highest rate of total soil CO2 efflux was found in the summer months. Overall, the rate was statistically significant and strongly correlated only with soil and air temperature. A trend emerged that total soil CO2 efflux was 30% higher in perennial grassland than in forested land. Additional work is still needed to estimate the net CO2 balance of these soils.

Widespread cooling of topsoil under nitrogen enrichment and implication for soil carbon flux

Increasing reactive nitrogen (N) to terrestrial ecosystems is considered to enhance ecosystem carbon sink, which plays a critical role in ameliorating global warming. Besides this indirect buffering of temperature rise, the N-induced enhancement of vegetation growth may exert a biophysical cooling effect on soils. However, the magnitude and drivers of this cooling effect have rarely been evaluated. Here, using a global meta-analysis with 321 paired measurements, we demonstrated a widespread topsoil cooling (−0.30 °C in average) under anthropogenic N enrichment, which was primarily associated with the increase in aboveground biomass. This biophysical cooling could also buffer topsoil temperature rise by an average of 0.39 °C under experimental warming. Further, the reduced soil temperature was found to contribute to a reduction of soil respiration rate as temperature declines gradually. Overall, our results underpin a previously overlooked function of global N enrichment—the lowering of topsoil temperature, which suggests that the warming of topsoil may not be as fast as previously predicted under future global change scenarios. This biophysical cooling effect will also slow down soil carbon emissions and further mitigate climate warming.

Warming positively promoted community appearance restoration of the degraded alpine meadow although accompanied by topsoil drying.

On-going climate warming is threatening the ecological function of grassland ecosystems. However, whether warming has positive effects on community microhabitats and appearance, especially in degraded grasslands, remains elusive. To address this issue, we conducted a 2-year field experiment on the severely degraded alpine meadow and undegraded alpine meadow with nowarming and warming treatments. Community coverage and height in degraded meadow significantly increased under warming, while these changes were not significant in undegraded meadow. Two-year warming increased the community height of degraded meadow and undegraded meadow by 56.55% and 10.99%, respectively. Warming also increased community coverage by 41.88% in degraded meadow and decreased community coverage by 3.01% in undegraded meadow. Moreover, the response of topsoil temperature to warming was stronger in degraded meadow (6.89%) than in undegraded meadow (-0.26%), while the negative response of topsoil moisture to warming was weaker in degraded meadow (-13.95%) than in undegraded meadow (-20.00%). The SEMs further demonstrated that warming had positive effects on topsoil temperature and community height, while had negative effects on topsoil moisture both in degraded and undegraded meadows. Our results confirm that warming-induced soil drying is an important pathway affecting the community appearance in alpine meadows. These findings highlight that warming has positive effects on community height and coverage and is particularly effective in improving community coverage appearance in severely degraded alpine meadow with topsoil drying.

Optimized Farmland Mulching Improves Rainfed Maize Productivity by Regulating Soil Temperature and Phenology on the Loess Plateau in China

Owing to global warming, continuously increasing the grain yield of rainfed maize is challenging on the Loess Plateau in China. Plastic film mulching has been extensively utilized in dryland agriculture on the Loess Plateau. However, higher topsoil temperatures under film mulch caused rainfed-maize premature senescence and yield loss. Here, we aimed to explore the influence of topsoil temperature driven by novel double mulching patterns on rainfed maize productivity based on the excellent moisture conservation function of plastic film. A maize field experiment was conducted in two different areas, namely Changwu, a typical semi-arid area, and Yangling, a dry semi-humid area. The experiment followed a randomized block design with three replications. Five flat-planting practices were examined in 2021 and 2022: (1) bare land (CK), (2) transparent film mulching (PFM), (3) black film mulching (BFM), (4) double mulching of PFM with a black polyethylene net (PFM + BN), and (5) double mulching of PFM with whole maize stalks (PFM + ST). Soil hydrothermal conditions, maize growth dynamics, grain yield, water use efficiency (WUE), and economic returns were quantified under different mulching practices. Under double mulching treatments, topsoil temperatures were lower than PFM by 1.7–2.0 °C at the two sites (p < 0.05), whereas BFM was slightly lower than that of PFM by 0.6–0.7 °C at Yangling (p > 0.05). The average growth period for maize under double mulching was longer than that under PFM by 8–11 days at the two sites. Double mulching treatments significantly improved the leaf area index (LAI), chlorophyll relative content (SPAD), and aboveground biomass compared to CK and PFM during the late growth stage. Compared with PFM, average grain yield increased by 14.93%, 18.46%, and 16.45% in Changwu (p < 0.05) under BFM, PFM + BN, and PFM + ST, respectively, and by 2.71%, 24.55%, and 20.38% in Yangling. The corresponding WUEs also increased. Additionally, net income under BFM was higher than that under other treatments, and there were no significant (p > 0.05) differences between PFM + ST and BFM in Changwu. However, PFM + ST in net income averaged 10.72–52.22% higher than other treatments, and its output value was 19.51% higher in Yangling. In summary, smallholder farmers can adopt PFM + ST to improve rainfed-maize productivity in the Loess Plateau in China.

Short-term effect of different returning methods of maize straw on the temperature of black soil plough layer

Clarifying the effect of different maize straw returning methods on soil temperature is crucial for optimizing the management of farmland straw and the efficient utilization of heat resources in the black soil region of Northeast China. To investigate the impacts of straw returning methods on soil temperature, we conducted a field experiment with four treatments during 2018 and 2020, including plough tillage with straw returning (PTSR), rotary tillage with straw returning (RTSR), no-tillage with straw returning (NTSR), and a control treatment of conventional ridge tillage without straw returning (CT). We measured soil temperature and water content at the 5 cm, 15 cm and 30 cm soil layer, and the straw coverage rate during the 3-year maize growth period. We further analyzed the differences of soil temperature in different soil layer under different treatments, accumulated soil temperature and growing degree-days (GDD) above 10 ℃, daily dynamics of soil temperature, the production efficiency of air accumulated temperature among different treatments, and explored factors causing the difference of soil temperature and the production efficiency of air accumulated temperature. Our results showed that different treatments mainly affected soil temperature from the sowing to emergence stage (S-VE) of maize. The daily average soil temperature showed a trend of CT>PTSR>RTSR>NTSR. The differences of soil temperature under different treatments showed a decreasing trend as growth process advanced and soil depth increased. Compared with the CT treatment, soil temperature at 5 cm depth was decreased by 0.86, 1.84 and 3.50 ℃ for PTSR, RTSR, and NTSR treatments, respectively. NTSR significantly reduced the accumulated temperature of ≥10 ℃ in different soil layers and GDD. The accumulated temperature ≥ 10 ℃ at the 5, 15, and 30 cm soil layers decreased by 216.2, 222.7, and 165.1 ℃·d, and the GDD decreased by 201.9, 138.7 and 123.9 ℃·d, respectively. In addition, production efficiency of air accumulated temperature decreased by 9.7% to 15.6% for NTSR. Conclusively, PTSR and RTSR had significant impacts on topsoil temperature during the maize growing period from sowing to emergence, but did not affect the accumulated soil temperature and the production efficiency of air accumulated temperature. However, NTSR significantly reduced topsoil temperature and production efficiency of air accumulated temperature.

Shallow-incorporated straw returning further improves rainfed maize productivity, profitability and soil carbon turnover on the basis of plastic film mulching

Ridge and furrow plastic film mulching (RFM) has improved net primary productivity (NPP) to a high level in semi-arid rainfed agricultural regions. Yet, it is unclear whether there is still a room for further improvement on NPP while stabilizing soil organic carbon through returning previous maize stover pieces. To address this issue, maize stubbles were smashed into pieces and in situ ploughed into 30 cm topsoil at a semi-arid site in northwest China from 2016 to 2017. This was done using the Pioneer 335 maize variety with three treatments (CK, ridge and furrow without mulching; RFM, ridge and furrow with plastic mulching; RFML, 3.49 t ha−1 of maize stover returning in RFM; RFMH, 5.24 t ha−1 of returning in RFM). The results indicated that maize stover returning exhibited similar trend as RFM at early cool seedling stage, raising the topsoil temperature. However, in warm and dry silking stage (2017), both stover returning rates reduced soil temperatures by 1.33 and 0.8 ◦C relative to RFM and CK (P < 0.05), respectively. The soil water storage increased significantly in RFMH by 17.3% and RFML by 28.5% relative to that of RFM, in a warm and dry growing season (2017). Critically, stover returning increased (P < 0.05) soil organic carbon and light fraction organic carbon turnover across the two growing seasons. By improving hydrothermal conditions, stover returning in RFM increased biomass accumulation and grain yield (P < 0.05), leading to higher (P < 0.05) net economic benefit, with greater above-ground biomass NPP (74.5–93.2%) and below-ground biomass NPP (88.5–89.4%), compared with CK. In conclusion, maize stover returning of stover pieces into topsoil might be a promising solution to enhance carbon turnover for higher net primary productivity on the basis of plastic film mulching in semiarid rainfed region.

Spatial pattern consistency and repeatability of proximal soil sensor data for digital soil mapping

AbstractData from proximal soil sensors can facilitate digital soil mapping at high spatial resolutions. However, their use for predicting static soil properties, such as texture, is affected by spatio‐temporal changes in environmental and measurement conditions. In this research study, seasonal changes in spatial patterns and repeatability of data provided by a platform that simultaneously measures the red (Red) and near infrared (NIR) reflectance, apparent soil electrical conductivity (ECa), temperature, and volumetric moisture content of topsoil (at 3–6 cm depth) were assessed. Test fields are located in Southern Finland with textures dominated by clay and fine sandy till. During single scans, mean relative differences between the data from duplicated measurement points ranged from ~4% to 6% and were the highest for temperature and Red values. The consistency of spatial patterns across seasons (spring and autumn 2021 and 2022) was the highest for ECa values, and the lowest for NIR. ECa and moisture were significant for predicting the clay contents at a cereal grain crop site, whereas temperature was significant at grass ley sites. Errors were generally lower when using spring data compared with autumn data (RMSE ranging from 4.8% to 11.1% for the data from different fields and measurement dates). For the fields, where static soil properties change at small spatial scales, spatially detailed moisture and temperature data support the understanding of seasonal changes in the spatial patterns derived from multi‐sensor data, and the corresponding changes in the performance of calibration models.

Differential responses of CO2 and latent heat fluxes to climatic anomalies on two alpine grasslands on the northeastern Qinghai–Tibetan Plateau

Discrete extreme heat events, deluges, and droughts will become more frequent and disproportionately affect the processes and functions of grassland ecosystems. Here, we compared the responses of CO2 and heat fluxes to natural extreme events in 2016 in a lower alpine meadow and neighboring upper shrubland on the northeastern Qinghai–Tibetan Plateau. Unlike insensitive sensible heat flux, latent heat flux (LE) increased by 21.8 % in the meadow and by 56.4 % in the shrubland during a dry period and subsequent compound hot-dry period in August. Changes (Δ, data for 2016 minus the corresponding means from other years) in the heat flux at both sites were determined by changes in solar radiation (ΔSwin), as sufficient soil moisture was available. ΔLE was more sensitive to ΔSwin in the open-canopy shrubland, reflecting its greater capacity for evaporative cooling to buffer climate anomalies. CO2 fluxes responded weakly to extreme wet or dry events but strongly when those events were accompanied by exceptional heat. During single or compound hot events, the mean changes in total ecosystem respiration (ΔTER) increased by about 30 % in both grasslands, although ΔTER was more sensitive to changes in the topsoil temperature in the more productive meadow than in the shrubland. The mean changes in gross primary productivity (ΔGPP) fluctuated by <10 % in the warmer meadow but increased by 29.3 % in the cooler shrubland relative to the respective baseline, probably because of the differences in canopy structure and root depth and the consequent high-temperature stress on vegetation photosynthesis. The changes in net ecosystem CO2 exchange (ΔNEE) were significantly related to ΔTER in the meadow and increased by 55.8 %, whereas ΔNEE was controlled mainly by ΔGPP in the shrubland and decreased by 22.4 %. Overall, both alpine grasslands were resistant to rainfall anomalies but susceptible to exceptional warmth, with the differential responses being ascribed to canopy structure and root depth. Our results provide helpful insights based on which the carbon sequestration and water-holding functions of alpine grasslands during future climate change can be predicted.

Effects of land use-land cover on soil water and salinity contents

Soil salinization due to inadequate land management is considered one of the main threats to the sustainable development of agroecosystems in arid and semiarid regions. Approximately 20% of irrigated areas in the word are threatened by secondary soil salinization. To explore the influence of land use-land cover (LULC) on soil water and salinity in those regions, farmland areas planted with spring-sown wheat (Triticum aestivum L.) or alfalfa (Medicago sativa L.), and bare land (CK) in the Qinwangchuan irrigated region of Gansu Province in China were selected as the research objects. The characteristics of surface vegetation (coverage, height, biomass), surface micro-environmental factors (light intensity, soil temperature) and soil physicochemical properties (moisture and salinity) were measured successively for four years, and their changes and quantitative relationships were analyzed. The results showed that the coverage, height, and biomass of surface vegetation (or stubble) under different LULCs in spring and autumn were significantly different (p < 0.05) and ranked as follows: alfalfa field > wheat field > bare land. With the increasing surface vegetation, the surface light intensity and topsoil temperature at a depth of 5 cm indicated decreasing trends; the water content in the 0–5-cm soil layer showed an increasing trend, while that in the 0–40-cm layers displayed the opposite trend; the salinity at depths of 0–5 and 0–40 cm indicated a decreasing trend. Correlation analysis showed that there was a significant negative correlation between the vegetation characteristics and the salinity in the 0–5- and 0–40-cm soil layers (p < 0.01), while opposite correlations were observed between the vegetation characteristics and the water content in the 0–5- and 0–40-cm soil layers. Regression analysis showed that a 1% increase in vegetation coverage would decrease the salinity at depths of 0–5 and 0–40 cm by 2.5 and 1.0 uS.cm−1, respectively. In summary, farmland planted with spring-sown crops with short growth periods or abandoned in semiarid and arid irrigated regions would gradually experience an increase in soil salinity, whereas the planting of perennial alfalfa could inhibit and lessen soil salt accumulation at depths of 0–5 and 0–40 cm, which is beneficial to improve the soil quality. In addition, this study also revealed the change rule of soil salts under different LULCs in semiarid regions, the fastest increasing stage of topsoil salts, and the importance of surface vegetation and stubble cover in controlling soil salinization.

Permafrost Effect on the Spatial Distribution of CO2 Emission in the North of Western Siberia (Russia)

The landscapes in the discontinuous permafrost area of Western Siberia are unique objects for assessing the direct and indirect impact of permafrost on greenhouse gas fluxes. The aim of this study was to identify the influence of permafrost on the CO2 emission at the landscape and local levels. The CO2 emission from the soil surface with the removed vegetation cover was measured by the closed chamber method, with simultaneous measurements of topsoil temperature and moisture and thawing depth in forest, palsa, and bog ecosystems in August 2022. The CO2 emissions from the soils of the forest ecosystems averaged 485 mg CO2 m−2 h−1 and was 3–3.5 times higher than those from the peat soils of the palsa mound and adjacent bog (on average, 150 mg CO2 m−2 h−1). The high CO2 emission in the forest was due to the mild soil temperature regime, high root biomass, and good water–air permeability of soils in the absence of permafrost. A considerable warming of bog soils, and the redistribution of CO2 between the elevated palsa and the bog depression with water flows above the permafrost table, equalized the values of CO2 emissions from the palsa and bog soils. Soil moisture was a significant factor of the spatial variability in the CO2 emission at all levels. The temperature affected the CO2 emission only at the sites with a shallow thawing depth.

The detection of clandestine graves in an arid environment using thermal imaging deployed from an unmanned aerial vehicle.

The Middle East is one of the world regions that has frequently suffered from armed conflicts that resulted in mass burials. However, the detection of clandestine graves in such an arid environment by deploying remote sensing payload on unmanned aerial vehicles (UAVs) has received little attention. The present study used a UAV equipped with a thermal sensor aimed at narrowing down the search area of possible gravesites in the arid climate of Kuwait. The enclosed research area, which includes both control and experimental mass graves, was imaged for 18 months. The variation in topsoil temperature and soil moisture between the graves and their surroundings was evaluated. The results of the analysis demonstrated the effectiveness of thermal imaging techniques in detecting heat produced from buried sheep carcasses and detecting the change in grave soil moisture for our research environment for 7 and 10 months, respectively. The buried animals significantly influenced the topsoil temperature (p = 0.044), while the height from which the images were captured had an insignificant effect on the measured temperature within the range tested (p = 0.985). Furthermore, there was a negative correlation (-0.359) between grave temperature and the calculated soil moisture. The results from these cost- and time-effective search methods presented in this study confirm their potential for the detection of burial sites in an arid environment.

Soil cooling can improve maize root-shoot growth and grain yield in warm climate

Global warming causes topsoil temperatures to increase, which potentially leads to maize yield loss. We explored the effects of soil warming/cooling on root-shoot growth and maize grain yields by performing pot experiments with a heat-sensitive maize hybrid (HS208) and a normal maize hybrid (SD609) in warm temperate climate in 2019 and 2020. Our results reveal, for the first time, differences in root characteristics, leaf photosynthetic physiology, and yield responses to soil warming and cooling between normal and heat-sensitive maize varieties under a warm temperate climate. Soil warming (+2 and 4 °C) inhibited whole root growth by decreasing root length, volume, and dry mass weight, which indirectly reduced leaf photosynthetic capacity and decreased grain yield/plant by 15.10–24.10% versus control plants exposed to ambient temperature. Soil cooling (−2 °C) promoted root growth and leaf photosynthesis, and significantly increased grain yield of HS208 by 12.61%, although no significant change was found with SD609. It can be seen that under unfavorable conditions of global warming, selection of excellent stress-resistant hybrids plays an important role in alleviating the soil heat stress of maize in warm temperate climate regions.

A multiphase model developed for mesoscopic heat and mass transfer in thawing frozen soil based on lattice Boltzmann method

Subgrade engineering in cold region collapsed and settled under the influence of global warming, this was mainly due to the thawing frozen soil. The heat and mass transfers in thawing frozen soils are generally described with continuity equations on the macroscopic scale. However, the processes of ice melting and water migration in soil were rarely described on the mesoscopic scale. In this study, a multiphase pseudo-potential model with enthalpy-based module was developed based on lattice Boltzmann method to predict the distributions of temperature and water content in the thawing process of frozen soil. The force source terms in pseudo-potential model were given as adhesive force, cohesive force, temperature drive force and bulk force to describe the interaction between multiple components in thawing process, and the enthalpy-based module was employed to realize the process of phase transition in soil. The complex initial conditions of thawing process were measured and then set in simulation for the first time. The results showed that as compared with the measured soil temperatures and water contents at different top soil temperature (5 °C and 10 °C) and times (0, 12, and 36 h), the relative errors of model were 0.01 % ∼ 0.72 % and 0.10 % ∼ 19.31 % for the soil temperatures and water contents, respectively. Further, the developed pseudo-potential model can also be used to detail the mesoscopic heat and mass transfers in thawing soils.

Global spatiotemporal trend of satellite-based soil moisture and its influencing factors in the early 21st century

Soil moisture (SM) plays a significant role in water, energy, and carbon cycles, and is a key variable related to multiple sustainable development goals. The frequent occurrence of extreme events in the 21st century complicates the understanding of terrestrial SM change and its drivers under diverse environmental conditions, particularly in the global scope. Here we globally explored the spatial-temporal trend of satellite-based SM (ESA CCI SM) and its possible drivers under a variety of environmental factors (land cover, soil texture, terrain, and vegetation coverage) during 2000–2021. Results indicate that global SM has generally declined with a rate of −0.10 × 10−3 m3m−3 yr−1 which is mainly dominated by the drying trend of the southern hemisphere. The moisture replenishment role of precipitation dominates in areas with relatively high SM values, and the positive influence of vegetation and precipitation on SM is prominent in regions where SM values are relatively low. But vegetation has a pronounced negative impact on SM north of 60°N and in southeastern China. Compared with precipitation and vegetation, topsoil temperature has less impact on SM globally. Land cover types, soil properties, elevation, and vegetation cover influence SM variability and its response to climate and vegetation to varying degrees. For example, the overall wetting trend of SM is unique under loam soils and high elevations (> 1000 m) in terms of different soil texture and elevations. The increase in vegetation cover within a certain amount is accompanied by the wetting of SM, but in densely vegetated regions such as forests, the water retention effect of vegetation on SM is weakened. An evaluation of ‘Dry gets drier, wet gets wetter’ (DDWW) paradigm from the SM viewpoint shows the paradigm summarizes 41.06% of areas with significant SM changes. Precipitation replenishment and vegetation water retention profoundly impact the ‘wet gets wetter’ and ‘dry gets wetter’ patterns. Temperature is a strong influencing factor of the ‘wet gets drier’ pattern, while the reduction of vegetation and precipitation jointly affect the ‘dry gets drier’ pattern. These findings can deepen the understanding of SM changes in relation to climate, ecology, and land surface features, particularly in the 21st century with profound changes of the environment.