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• Soil temperature was monitored before and during a fire in a tropical rainforest. • Clear cutting the forest increases the amplitude of the daily soil temperature. • Fire only affected soil temperature in the first centimeter of the soil. • Soil moisture depended on hillside position and affected soil temperature behavior. • Nutrient contents were affected in the litter layer, but not in the mineral soil. Fire is an important component of shifting cultivation systems. Although its effects on soil properties depend on its severity and duration, few studies have measured soil temperature during burns at different depths and in relation to topography in tropical forests. Frequent rain keeps the soil moist in these ecosystems, but soil moisture does not only depend on precipitation but also on relief position. Here we monitor soil temperature at 1 and 10 cm depth before the burn along elevation gradients of three logged hillsides to establish the daily temperature variation, and to compare it with the soil temperature under forested sites and during the burn. Additionally, moisture content and physicochemical properties of the soil were measured before and after the burn. Results before the burn indicate a larger daily temperature amplitude in logged versus forested areas, and specially at crests and shoulder positions in comparison to backslopes and toeslopes. The fire increased soil temperature only in 1 cm depth, and for less than 40 degrees at most of the sites. Soil moisture content was negatively correlated with maximum temperature during the burn, however, also fuel loads and litter thickness determined fire intensity, with the spatial distribution of these variables being unrelated to topography. Nutrient contents changed only in the litter layer, in which C and N diminished by 35 % and 24 %, respectively, while total Ca, Mg, K and P increased by 210, 202, 318, 235 % respectively. We conclude that soil moisture contents contributed to maintain fire intensity low at the studied site. [ABSTRACT FROM AUTHOR]

• Shrubs significantly changed the water vapor transport pattern. • The maximum water vapor flux of shrubland (SL) lags bare land (BL) for 6 h. • Shrubs constantly drive the liquid water (q l) and water vapor (q v) flux migrate to the root zone during dry period. • BL was dominated by cumulated upward q l and downward q v , while SL was downward q l and q v. Understanding the dynamic changes of soil water flux is essential for sustaining fragile ecosystems in desert regions worldwide. Here, we calibrated the Hydrus-1D model in a data-rich monitoring area of Mu Us Sandy Land to explore the differences in liquid and water vapor transport processes between bare land (BL) and shrubland (SL), then elucidate the regulatory mechanisms of sparse shrubs on soil water flux during the dry period. The result showed that shrubs regulated and remolded the soil hydrological processes, significantly changing the soil water transport pattern, prompting the liquid and water vapor flux to be continuously transported to the vicinity of the root zone (30–120 cm). Specifically, during the dry period, SL has multiple divergent zero-flux planes, mainly located at 0–30 cm depth of the ground. However, due to transpiration demand and soil temperature lag caused by the canopy, the liquid and water vapor flux below the zero-flux plane of SL constantly moved to the root zone, resulting in its soil water flux exhibiting the consistent downward cumulative flux in liquid and water vapor, accounting for 63% and 36% of the total water flux. In contrast, the BL's zero-flux plane was 60–75 cm inside the soil. The liquid water flux constantly migrated from the zero-flux plane up to the ground during the day and night. While the water vapor flux transferred to the zero-flux plane during the day and inverse at night. Therefore, the cumulated upward liquid and downward water vapor flux were dominated in the BL, accounting for 62% and 21% of the total water flux, respectively. This study supported the regulation of dryland shrubs on soil hydrological processes well through the perspective of water vapor transport, which was important for clarifying the mechanism of water vapor transport in the vadose zone and its ecological function. [ABSTRACT FROM AUTHOR]

• With increasing water temperature, the stability of aggregates decreases. • Parent material affects the sensitivity of aggregate stability to water temperature. • The soil erosion resistance decreases with the increasing water temperature. Water temperature has an important effect on soil aggregate stability. In this study, six soils derived from different parent materials in the hilly region of southern China were selected, and the mean weight diameter (MWD), geometric mean diameter (GMD), and soil erodibility (K value) were measured under different water temperature conditions. The aim of this study was to investigate the influence of water temperature on soil aggregate stability and erodibility. As the water temperature increased from 5 °C to 40 °C, the average content of >5 mm water-stable aggregates decreased by 57.13 %, while the average content of <0.25 mm water-stable aggregates increased by 214.41 %. The MWD and GMD of the six different parent soil types exhibited a decreasing trend with increasing water temperature. The trend of the K value was opposite to that of these values. The influence of water temperature on soil aggregate stability is mainly attributed to the thermal effect on the viscosity of soil water and the expansion of clay minerals. As the water temperature increases, the water viscosity coefficient, water density and water surface tension gradually decrease. Moreover, the response of soil aggregate stability and erosion resistance to water temperature varies with soil depth and parent material type. The topsoil exhibits greater sensitivity to water temperature than does the subsoil. Shale (SH) soils and quartz sandstone (QS) soils exhibited higher sensitivities, and Quaternary red clay (QRC) soils exhibited the lowest sensitivity to water temperature among the six soils. This difference is mainly attributed to differences in the contents of expansive clay minerals and organic matter. These results indicate that soil aggregate stability and erosion resistance decrease with increasing water temperature, which may be one reason for severe soil erosion under extremely high temperature and rainfall conditions in the southern red soil hilly region during summer. [ABSTRACT FROM AUTHOR]

• The effects of moisture, type, porosity of soil on thermal property were studied. • Soil and water temperature increases after sun exposure were important factors. • The ANN model was proposed to provide accurate soil moisture estimation. • A rapid, repeatable, and low-price method was proposed to estimate soil moisture. Data of soil water content measured at regular time intervals could be used to set an irrigation schedule for farmland. Changes in soil water content could also provide an early warning of potential slope slippage. An artificial neural network is proposed for detecting soil water content from five variables: soil and water temperature changes after sunlight exposure, plant coverage rates, fine-grained soil content, and effective soil particle size. Temperature changes were detected using thermal images taken using an unmanned aerial vehicle equipped with a thermal camera in the morning and at noon. Plant coverage was estimated using visible light photograph, and the fine-grained soil content, effective particle size, and soil water content were determined from laboratory tests of soil samples. An optimized neural network was established by analyzing the performance of various neural network parameters. The mean square error of the optimized neural network reached a minimum value of 0.10061 in the validation data set at the 12th epoch, the training was stopped to avoid overfitting. The correlation coefficients for the training, validation, testing, and overall data sets were 0.880, 0.772, 0.810, and 0.847 respectively. The target values and the predicted values of the neural network are highly correlated. Thus, the proposed neural network is effective for predicting soil water content. A relative importance analysis revealed that soil and water temperature changes after sunlight exposure had the greatest influence on the neural network's results. [ABSTRACT FROM AUTHOR]

• The relationship between gross N turnover and temperature and moisture varies on annual and seasonal scales. • The gross N turnover under the influence of temperature and water is different between field and laboratory conditions. • Soil temperature has more influence on soil gross nitrogen turnover than moisture. Understanding how soil nitrogen (N) turnover responds to temperature and soil moisture alterations is important for accurately predicting responses of soil N availability and plant productivity to global climate change. However, few studies had explored such questions under natural conditions. We investigated effects of temperature and moisture on soil gross N turnover with an annual scale field experiment in an Inner Mongolian grassland and a laboratory incubation experiment. In the field experiment, on the annual scale both gross ammonification and nitrification rates showed a hump-shaped response to temperature, with maximum rates occurring around 10 °C and 5 °C, respectively. Gross ammonification rates did not respond to soil moisture, and gross nitrification rates decreased first and then increasing with soil moisture, which the threshold was 35% water holding capacity (WHC). Totally, soil temperature explained more variation than moisture in gross ammonification (0.30 VS 0.04) and nitrification (0.24 VS 0.14) rates. On the seasonal scale, both soil temperature and moisture showed generally significant effects on gross N turnover. Grazing had no effects on soil temperature and moisture sensitivity of gross N turnover on the annual scale, but increased the sensitivity of gross ammonification to soil moisture during the spring freeze–thaw period. In the laboratory incubation experiment, gross ammonification and nitrification rates increased with the increase of temperature, although there was no difference between 20 °C and 30 °C. Gross ammonification rates reached a maximum at 50% WHC, while gross nitrification rates did not respond to soil moisture until 100% WHC. Soil temperature explained more variation than moisture in gross ammonification (0.71 VS 0.01) and nitrification (0.37 VS 0.25) rates. Our results imply that climate warming may have greater impact on gross nitrogen turnover compared to changes in rainfall, however it remains great uncertainty due to the low explanation of soil temperature and moisture. [ABSTRACT FROM AUTHOR]

• Freezing (25 d) took longer than thawing (19 d) from 0 to 100 cm profile. • High moisture prewinter raised the saturated water layer throughout thawing. • High moisture prewinter prolonged the freeze–thaw period and reduced the freeze–thaw cycles. • The depth of zero temperature amplitude was deeper under low moisture prewinter. • Initial water affects freeze–thaw by governing profile water vertical migration. The freeze–thaw characteristics are of great hydrological significance in seasonally frozen agricultural soil and may vary for different initial moisture conditions because of variability in land use, topography, tillage and climate change. However, the initial soil moisture regimes before winter freezing that control the dynamics of profile freeze–thaw cycles remain unclear. This study explored the soil profile freeze–thaw dynamics under different prewinter moisture regimes located in a seasonally frozen Mollisol in China. The high, medium and low soil moisture regimes were simulated by infiltrating different water into the soil profiles before winter freezing. We investigated the soil temperature and water content at five depths from October 2017 to May 2018. Our results revealed that the variation in soil water storage occurred after infiltration before winter freezing and lasted throughout the thawing period. The highest soil water occurred above a depth of 20 cm in the early days of the thawing period under all treatments. During the thawing period, the soil water content was highest above depths of 0–20 cm, 20–40 cm and 40–60 cm under high, medium and low infiltration, respectively. Freezing took longer than thawing from 0 cm to 100 cm soil depths. Freezing started later and thawing ended later under higher soil moisture conditions prewinter. The top 10 cm of soil experienced intense soil temperature rise and fall cycles with an average of 20 cycles during the thawing, and higher moisture conditions reduced the freeze–thaw cycles. The depth of zero amplitude in soil temperature under high, medium and low soil water was estimated as approximately 140, 134 and 160 cm, respectively. Our findings suggest that more attention should be given to the top layers and sidewall layers under the lower prewinter soil moisture conditions. This study provides a very detailed understanding of soil temperature and moisture dynamics over a full winter freeze–thaw cycle and would makes a worthy contribution in seasonally frozen areas where few such comprehensive datasets exist. [ABSTRACT FROM AUTHOR]

• Warming and precipitation reduction significantly affect Rs in sandy grasslands. • ST plays a dominant role in Rs during the early and whole growing seasons. • SM plays a dominant role in Rs during the middle and late growing seasons. • Rs is co-regulated by hydrothermal factors, soil properties and vegetation characteristics. • ST and SM remain the main factors determining Rs in sandy grassland. Soil respiration (Rs) is one of the largest carbon fluxes from terrestrial ecosystems to the atmosphere, and there are still a great deal of uncertainties in the estimation of soil carbon emissions from terrestrial ecosystems. Grassland ecosystems are fragile and sensitive to climate change, so it is crucial to reveal the effects of temperature and precipitation changes on Rs in sandy grasslands. Here, we examined the effects of experimental warming and precipitation reduction on Rs in the sandy grassland of Horqin and the relationships between different environmental factors and Rs. It was found that: (1) Soil temperature (ST) and soil moisture (SM) showed consistent seasonal variations with Rs during the growing season; (2) Warming increased Rs significantly in the middle of the growing season and throughout the growing season, and had no significant effect on Rs at the beginning and late of the growing season. Precipitation reduction reduced Rs significantly in the early and middle of the growing season and throughout the growing season, but had no significant effect on Rs at the late of the growing season. The interaction of warming and precipitation reduction only significantly reduced Rs in the middle and late of the growing season; (3) ST played a dominant role in Rs in the early growing season and throughout the growing season, and SM played a dominant role in Rs in the middle and late of the growing season; (4) Rs was significantly and positively correlated with ST and SM in the growing season; (5) Rs was regulated by the combination of hydrothermal factors, soil properties, and vegetation characteristics, of which hydrothermal factors are the main influencing factors in the growing season. Our results provide direct evidence to elucidate the effects of climate change on Rs in sandy grasslands. [ABSTRACT FROM AUTHOR]

Abstract The degradation of soil and vegetation substantially damages ecosystem functions. Litter crusts play an active role in the vegetation restoration and management in desert ecosystems. In this study, the effects of litter crusts on surface microhabitats and species formation on sandy land were studied in the wind-water erosion crisscross region in the Mu Us Desert, northwest China. Soil microhabitat features including moisture, temperature, and organic matter content were measured in different positions of litter crusts and bare sand, seedling species richness, and total seedling number of all species were recorded in litter crusts on the sand's surface. The results showed that there were significant differences between litter crusts and bare sand in terms of soil moisture, temperature, organic matter content, and light intensity. Compared with that of bare sand, soil moisture below litter crusts was increased by an average of 17.0% overall, soil organic matter content was increased by 77.5% at the 0–5 cm depth and by 80.8% at the 5–10 cm depth. Litter crusts decreased soil temperature and light intensity by an average of 16.6% and 31.6%, respectively. Seedling species richness and total seedling number of all species were significantly higher in litter crusts than those in bare sand. Our findings revealed that litter crusts modify the surface microhabitats of sand by maintaining soil moisture, regulating soil temperature, increasing soil nutrients, and reducing light intensity, thus promoting species establishment in the wind-water erosion crisscross region. Highlights • Litter crusts are important for vegetation restoration in desert ecosystems. • Litter crusts significantly increased top soil moisture and organic matter content. • Litter crusts significantly decreased soil temperature and light intensity. • Litter crusts significantly advanced seedling richness and numbers than bare sand. • Litter crusts modify the sand surface microhabitats and promote species establishment. [ABSTRACT FROM AUTHOR]

• Couples time-lapse ERT and GPR with probing sensors to monitor a lab scale soil infiltration test. • Calibrated petrophysical relationships enable a more precise characterization of water content dynamics. • Reveals impacts of short-term transient hydrological process on joint surface geophysical survey. • Observed changes in soil electrical resistivity/ dielectric constant are converted to changes in infiltration rate. • Constructs an unsaturated flow model to describe the subsurface infiltration process. This paper presents an integrated geophysical method to characterize the vadose zone by conducting lab-scale infiltration experiments, during which time-lapse electrical resistivity tomography (ERT) sections and ground penetrating radar (GPR) profiles were simultaneously and continuously captured together with soil moisture and temperature probing devices installed at various depths. Time series water content data obtained from the moisture sensors, coupled with discreetly calibrated petrophysical relationships and time-lapse datasets from ERT and GPR, were combined to monitor the spatial–temporal evolution of soil water content during wetting and drying and to track the downward progression of wetting front. Reduction in electrical resistivity as well as increment in dielectric constant were converted to rising soil moisture, and then further scaled into cumulative infiltration through integration with corresponding wetting depth as observed through the experiment. Robust estimates regarding controlling vadose zone parameters such as infiltration rate and hydraulic conductivity were subsequently achieved by fitting the results from complementary investigations with an unsaturated infiltration model. With calibrated saturated hydraulic conductivity fitted well with reported and experimentally derived ranges, it's suggested that the model is capable of reflecting average changes in infiltration rate at the lab scale. However, the model intrinsically lacks the ability to provide spatial variations of hydraulic parameters, thereby further investigation is essential to establish a suitable model for characterizing the more complex vadose zone at field scale. [ABSTRACT FROM AUTHOR]

Soil erosion and sediment transport measurement is a time-consuming and difficult step yet important part of hydrological studies. Hence, use of models has become commonplace in estimating soil erosion and sediment transport. In this study, we used an artificial neural network (ANN) to simulate soil erosion rates. A geographic information system (GIS) was used as a pre-processor and post-processor tool to present the spatial variation of the soil erosion rate. The ANN was trained, optimized and verified using data from the Kasilian watershed located in the northern part of Iran. Field plots were used to estimate soil erosion values on the hillslopes. A Multi Layer Perceptron (MLP) network was adopted, where the soil erosion rate was the output variable and the rainfall intensity and amount, air and soil temperature, soil moisture, vegetation cover and slope were the inputs. After the training process, the network was tested. According to the test results, the ANN can estimate soil erosion with an acceptable level (coefficient of determination = 0.94, mean squared error = 0.04). The verified network and its inputs were used to estimate soil erosion rates on the hillslopes. Finally, a soil erosion rate map was generated based on the results of the verified network and GIS capabilities. The results confirm the high potential when coupling an ANN and a GIS in soil erosion estimation and mapping on the hillslopes. [ABSTRACT FROM AUTHOR]

Soil respiration ( R s ), conventionally considered as net soil CO 2 flux, is an important link in the terrestrial carbon cycle. However, existing estimates of R s in drylands may be erroneous, because of the abiotic soil CO 2 flux. This may seriously hamper our understanding of the carbon cycle of desert ecosystems. In this study, we monitored CO 2 flux of natural and sterilized soils, and obtained the net and abiotic soil CO 2 flux in a desert ecosystem in Ningxia, China, and then computed R s by using these data. Daily R s was much larger than the net soil CO 2 flux both in the growing and non-growing season. Further analysis indicated that R s was controlled by soil temperature ( T s ) over the annual cycle, and an exponential model could provide a good prediction of R s . During the growing season, R s increased significantly with rising soil water content ( VWC ) ( P < 0.05). A bivariate ( T s and VWC ) exponential–power model had a better performance for predicting R s in the growing season than a T s -only model. However, during the non-growing season, this model failed to simulate R s . Our results suggest that R s is greatly underestimated, and the exponential model is more applicable for annual R s prediction. [ABSTRACT FROM AUTHOR]

In natural ecosystems, soil respiration is one of the important components of carbon emission into the atmosphere – CO 2 efflux. Soil CO 2 efflux has both temporal (due to temperature and moisture changes) and spatial variability, which can be explained by different types of soil, soil use and management, as well as the influence of vegetation on CO 2 efflux. The aim of this study was to measure the spatial variability of soil CO 2 efflux, soil temperature and soil moisture in areas of archaeological dark earth cultivated with the guandu bean (GB) and pasture (PT), compared to soil use in natural forests (NF) in Amazonas state, Brazil. To that end, regular meshes were marked out in areas of forest (6 × 6 m spacing), guandu bean (4 × 5 m spacing) and pasture (8 × 8 m spacing) measuring 2500 m 2 , 1700 m 2 and 4800 m 2 , respectively, with 88 sample points georeferenced in each area. Soil CO 2 efflux (FCO 2 ) and soil temperature (ST) were measured at the intersection points of the meshes, and soil samples were collected at a depth of 0.00–0.10 m to determine soil moisture (SM) in the laboratory. FCO 2 measurements were taken using LI-6400 systems. Soil temperature (ST) was measured at 0.00–0.10 m, using a portable thermistor thermometer, and soil moisture (SM) using soil samples collected at 0.00–0.10 m. FCO 2 and ST were lower in the forest area, with higher SM content, no difference between FCO 2 and ST in GB and PT, but with lower SM content in PT. The models of the experimental semivariogram were predominantly spherical, except for FCO 2 in the NF and GB areas, and SM in the PT area, which were fit to the exponential model. The maps of spatial distribution patterns indicate a trend in concentration, with a positive correlation between FCO 2 and SM and negative correlation between FCO 2 and ST in natural forest. Positive correlations were observed between FCO 2 and ST and SM in GB, but in PT, FCO 2 correlations were restricted to SM. [ABSTRACT FROM AUTHOR]

The influence of soil water content and temperature on the three thermal properties, namely volumetric heat capacity (C), thermal conductivity (K t ) and diffusivity (D) were analysed in laboratory using the KD 2 Pro Thermal Analyser. Five water content and temperature levels were investigated in a two-factor factorial experiment. The results showed an interaction effect between water and temperature on all the thermal properties. From the analysis, three important water content and temperature combinations were identified, i.e. wetting of a dry soil with a rising temperature (up to 60 °C), the effect of freezing (0 °C) and thawing (10 °C) with increasing water content, and the excessive wetting of soils beyond 0.16 mm 3 mm − 3 with increasing temperature. Wetting of dry soils with little water improved all thermal properties of these aeolian soils. Hence, a 94, 703 and 346% increase in C, K t and D has been observed between dry and slightly wetted soils. On the other hand, an average 55% decrease in C, 137 and 367% increase in K t and D, respectively, were observed due to an increase in temperature from 0 to 60 °C in the two water contents. Freezing (0 °C) and thawing (10 °C) temperatures also had a significant influence in the volumetric heat capacity of the soils. As a result, there was an average 8% increase in C as the temperature changed from 0 to 10 °C while a 42% decrease was recorded due to a change in water content from 0 to 0.39 mm 3 mm − 3 . Though the influence of freezing and thawing temperatures was negligible, K t decreased by 11% and D increased by 10% due to an increase in water content from 0 to 0.39 mm 3 mm − 3 . The effect of the excess addition of water with a rising temperature differs for the three thermal properties. Hence, C and K t increased at a decreasing rate with addition of water up to DUL whereas D increased dramatically with increasing water content up to 0.16 mm 3 mm − 3 . Throughout all water contents, C increased with temperature. Thermal conductivity and diffusivity also increased with temperature up to DUL and 0.16 mm 3 mm − 3 , respectively, followed by a decrease with increasing temperature. [ABSTRACT FROM AUTHOR]

Climate change has different manifestations in various regions all over the world. Such changes strongly affect ecosystem services, environmental and agricultural stability. Soils play a crucial role in the complex system that generates climate change. However, the nature and structure of response of different soils to climate change is still distant to be interpreted. Bearing in mind that climate simulations can help us to comprehend soil balance in the future, we defined the purpose of this study: to project temporal and spatial changes of temperature and moisture in four different soils under A1B scenario for the periods 2021–2050 and 2071–2100 with respect to the period 1961–1990. For this analysis climate data obtained by the ECHAM5 model simulations, dynamically downscaled by the coupled regional climate model EBU-POM (Eta Belgrade University-Princeton Ocean Model), were used. The 43 sites in Vojvodina region (Serbia) were analyzed for pedological parameters and climate elements. The projected changes at the end of 21st century (2071–2100) can be summarized as follows: (i) increase in the mean annual soil temperature up to 3.5 °C in the surface layer 0–10 cm and up to 1.8 °C in average for 0–200 cm depth and decrease in the mean soil moisture up to 0.039 kg kg − 1 in the subsurface layer 40–100 cm and up to 0.019 kg kg − 1 in average for 0–200 cm depth, which corresponds to decrease of 16% and 7%, respectively; (ii) Chernozerms proved to be more sensitive to temperature increase in contrast to water affected soils (Fluvisols, Gleysols and Vertisols) that showed the lowest susceptibility; (iii) Chernozems also showed higher sensitivity to moisture loss than Cambisols, Arenosols and Umbrisols that showed the lowest susceptibility; and (iv) it was assumed that predicted changes in soil temperature and moisture will cause significant changes in soil respiration, release of CO 2 , soil processes, agriculture, biodiversity and ecosystem functioning. [ABSTRACT FROM AUTHOR]

[Display omitted] • Significant differences in freeze–thaw processes between farmland and shelterbelt. • The migration and increment of soil water content in farmland were greater than in shelterbelt. • Land use patterns and initial soil water content had a greater impact on the occurrence of freeze–thaw processes than soil texture. • Soil texture was closely related to the amount of water migration during freeze–thaw. Seasonal freeze-thawing can affect the movement and distribution of soil moisture and thus impact the management of agroforestry. In this study, we analyzed the differences in the freeze-thawing of farmland and its shelterbelt by monitoring the dynamics of soil temperature (ST) and soil water content (All soil water content involved in this study is volumetric water content, SWC) at a depth of 0–100 cm in arid and semi-arid regions of northern China. The results showed significant differences in the freeze–thaw process between farmland and shelterbelt. Freeze-thawing in the upper soil layer (0–60 cm) of farmland and shelterbelt was significantly affected by air temperature (AT). Still, the shelterbelt was more resistant to freezing than farmland and maintained a higher soil temperature at all depths. The fluctuations of soil temperature and soil water content were also lower in shelterbelt than in farmland. In addition, farmland was frozen first but thawed later than the shelterbelt, with more freeze–thaw cycles. The migration and increment of soil water content were more significant in farmland than in shelterbelt at each soil depth during freeze–thaw. Land use patterns and initial soil water content had a greater impact on the timing of freeze–thaw onset than soil texture, but the latter was associated with soil water content migration. Our results improved the understanding of seasonal freeze–thaw processes and their effects on agroforestry. They can be used to develop appropriate management strategies for agriculture and forestry. [ABSTRACT FROM AUTHOR]

In this work, we investigated how the reindeer grazing in subarctic boreal Scots pine forests and climate (air temperature and the amount of precipitation) affects soil temperature, soil water content, and ultimately the CO 2 efflux from forest soils. The study was carried out in years 2013 and 2014, where 2013 was an extremely dry year (especially the summer), while 2014 was a “normal” year. Our work showed that in subarctic mature pine forests, soil temperatures were higher, and soil water content was fluctuating more on grazed areas compared to non-grazed areas in both years. On both years, the soil water content on the grazed area was higher in June and the situation changed in the second half of July when the moisture content in the non-grazed area remained higher. There was a negative correlation between soil water content and soil temperature. The soil CO 2 effluxes were mostly affected by the year of measurement, time of measurement (different months through growing season), soil temperature and also by the management (grazed or non-grazed) resulting in higher CO 2 emissions on the grazed areas. Soil moisture content was not affecting the soil CO 2 efflux. The average soil CO 2 efflux values were significantly higher in the year 2014 compared to the year 2013 mainly due to differences in soil temperature at the beginning of season. [ABSTRACT FROM AUTHOR]

Monitoring permafrost and active layer is essential for prognostic research of future climate scenarios. Although biotic factors have a prominent role in active layer behavior, apart from vegetation effects, their influence remains little investigated. It is generally assumed that frozen ground exerts influence on nesting fauna, whereas, on the other hand, land colonization by birds, such as penguins can also interfere with the soil thermal regime. However, to our knowledge, no studies report on permafrost and active layer regime changes under penguin activity. We present a comparative study of two adjacent sites located in Hope Bay, one representing an active penguin rookery-S1, and another, an adjacent abandoned site currently vegetated-S2. Soil temperature and water content, and air temperature were monitored hourly from 2009 to 2011. Current penguin activity and the resulting deposition of guano during spring and summer in S1 is an important factor for explaining the higher number of thaw degree days due to direct physical impact and chemical reactions caused by rapid guano decomposition. In the vegetated S2 site, the snow pack lasted longer, showing the highest mean minimum temperature and larger thermal insulation, as well as larger FDD than those found in the bare soil of the active rookery (S1), and lower n-F, due to greater thermal insulation. Penguins played a significant role in changing the active layer depth and thermal regime, and represent a neglected actor on the ground thermal regime in Antarctic terrestrial environments. [ABSTRACT FROM AUTHOR]

Objective of this study was to compare the effects of forest and herbaceous vegetation covers on soil temperatures (average daily maximum, minimum, and mean daily temperatures), soil moisture, and chemical content of the soil water. Soil moisture and soil temperature were monitored at three different soil depths (40, 80 and 120 cm) and rain water samples and soil water samples from 40 cm and 80 cm soil depths were collected for 20 weeks on a weekly basis depending on precipitation events. Soil water samples were analyzed for total alkalinity, total nitrogen, calcium hardness, chloride, electrical conductivity, organic matter, pH, potassium, sodium, sulfate, and total hardness. Experiment was as a 3-way factorial in a split plot design with whole plots in blocks and repeated measures with two replications. Data were analyzed by using ANOVA and means were separated with Tukey test. Soils under the forest and herbaceous vegetation covers showed significant difference in terms of overall mean daily maximum, minimum, and average daily temperatures. Overall average daily maximum and minimum temperatures were 9.94 °C and 9.75 °C, respectively for the soils in the forest plot while they were 11.08 °C and 10.87 °C for those in the herbaceous plot. Woody vegetation removal significantly increased overall mean daily temperature from 9.84 °C to 10.98 °C and overall mean daily volumetric soil moisture content of the soils from 32% to 48%. Chemical content of the soil water from both study sites were similar except for chloride and sulfate content. Soil water from forestland had a lower chloride but higher sulfate content than the soils from herbaceous vegetation covered area. On the other hand, chemical content of the soil water from forestland did not show significant changes with soil depth while total alkalinity, calcium hardness, electrical conductivity, pH, sodium, sulfate, and total hardness increased significantly with soil depth in the soils under herbaceous vegetation cover. [ABSTRACT FROM AUTHOR]

• There was no significant correlation between soil fungal and bacterial a-diversity and elevation. • Soil temperature (ST), soil water content (SWC), and total phosphorus (TP) were the driving factors affecting the elevation distribution pattern of soil fungal communities. • Soil fungi were more sensitive than bacteria in response to elevation changes. • The network complexity of soil bacteria is higher than that of fungi. The Qinghai-Tibet Plateau is one of the most sensitive regions in response to global climate change. Because soil bacteria have a considerable influence on ecosystem function, it is essential to understand their responses to different climates. We investigated the effects of elevation change on soil microbial diversity and community structure in the Abies georgei var. smithii forest of the Sygera Mountains in southeastern Tibet. We sampled soils from 0 to 10 cm depth at 3500 m, 3900 m and 4300 m asl, and examined changes in fungal and bacterial communities using Illumina MiSeq sequencing. The results showed that 1) fungal and bacterial diversity (Shannon index) did not change significantly (P > 0.05) with increasing elevation, and 2) elevation had no effect on the community structure of bacteria but had a significant effect on the community structure of fungi. Redundancy analysis showed that elevation, soil temperature (ST), soil water content (SWC), and total phosphorus (TP) were drivers of changes in fungal community structure. 3) Elevation had no significant effect (P > 0.05) on the relative abundance of the dominant bacterial phylum in the soil but had a significant effect (P < 0.05) on the relative abundance of the dominant fungal phylum. The dominant bacterial phyla were Proteobacteria, Actinobacteria, Acidobacteria, and Choroflexi, whereas the dominant fungal phyla were Basidiomycota, Ascomycota and Mortierllomycota. The relative abundance of Basidiomycota at 3900 m was significantly higher (P < 0.05) than that of Ascomycota at 3500 m and 4300 m, while the relative abundance of Ascomycota at 4300 m was significantly lower (P < 0.05) than that of Basidiomycota at 3500 m and 4300 m. and 4) the complexity of the bacterial network was the lowest at 3900 m elevation, while the most complex at 3500 m elevation. The fungal network complexity was lower than that of the bacteria. In conclusion, soil fungal communities are more sensitive to changes in elevation than are bacterial communities. [ABSTRACT FROM AUTHOR]

• The freeze–thaw cycle affected the soil hydrological process in active layer; • There were significant differences in soil hydrothermal processes at the slope scales and profile scales; • The redistribution of soil water during the freezing and thawing periods is affected by vegetation." The Qinghai-Tibet Plateau (QTP) is a region with an extensive area of permafrost that is very sensitive to climate change. In this study, soil water and thermal dynamic processes in the active layer of the QTP permafrost area at the profile and slope scales were investigated. The results showed that the hydrothermal process in the active layer soil was strongly affected by freezing and thawing processes and external weather conditions. The temperature of the active layer fluctuated in tandem with air temperature. The soil water content was more stable during the freezing period and showed a "double-hump" trend during the thawing period. The correlation coefficient between soil and air temperature decreased with depth, from 0.896 in the surface soil layer to 0.082 in the deep soil layer; and the correlation coefficient between unfrozen water content and soil temperature during the freezing period showed an overall increasing trend with depth. The soil layers at different depths at the top and bottom of slope profiles differed in their hydrothermal processes due to the physicochemical properties and texture of the soil and vegetation types. The water-heat exchange of the surface soil is more frequent than that of the deep soil, and the frequency is more at the bottom than at the top of the slope. The soil water content at a depth of 0.25 m was the highest in the profile in association with a higher organic matter content and the blocking effect of dense roots. The changes of soil hydrothermal process in the active layer accelerated the hydrological cycle and the spatial–temporal variability in water resources in the frozen soil area. These effects might lead to a series of ecological and environmental problems, such as permafrost degradation and desertification in the QTP alpine meadow ecosystem. [ABSTRACT FROM AUTHOR]

• Soil carbon release was evaluated in a Caragana korshinskii plantation after extreme rainfall events. • Extreme rainfall changes significantly affected the soil carbon release. • Soil carbon release increases with soil depth over the period of extreme rainfall events. • Temperature sensitivity only increased at 10 cm soil depth after extreme rainfall due to the pulsed soil carbon release. • Unstable soil carbon release after extreme rainfall events can affect the soil carbon cycle. Projected increases in the frequency and magnitude of extreme rainfall events can profoundly impact terrestrial ecosystems. However, the response of soil carbon release (RS) at various depths to these events and associated regulatory processes has not been well-documented in small watersheds. We measured the mean CO 2 concentration, soil moisture (SM), and soil temperature (ST) at depths of 10, 50, and 100 cm in situ before and after extreme rainfall events between June and September 2019, in a typical small watershed of the Loess Hilly Region, China. RS, calculated using Fick's first law in one dimension, revealed the relationships between RS and extreme rainfall events. During the study period, we screened four extreme rainfall events, of which three were used. The mean RS at 10, 50, and 100 cm soil depths after extreme rainfall (post-RS) were significantly higher than those before (pro-RS) (P < 0.05). Simultaneously, decreased ST at a depth of 10 cm and increased SM at a depth of 10 cm during periods of extreme rainfall contributed to decreased RS at a depth of 10 cm. By contrast, the RS at depths of 50 and 100 cm were enhanced during periods of extreme rainfall and peaked between days two and four after the extreme rainfall events due to the significant stimulating increase in SM (P < 0.05); the relative change in RS at 50 cm soil depth was the largest. Moreover, the RS values at three soil depths were changed by extreme rainfall events (with higher SM to RS), yet the R 2 of the ST was lower after extreme rainfall. In addition, after extreme rainfall, the temperature sensitivity (Q 10) increased at a depth of 10 cm, while it decreased at depths of 50 and 100 cm. These findings imply that more CO 2 is released from deep soil in semi-arid shrubs under extreme rainfall events with sustained increase for 2–4 days. The results will help predict the impact of future climate change on regional carbon emissions and improve the accuracy of predictive model. [ABSTRACT FROM AUTHOR]

• Thermal effects on soil hydraulic and mechanical properties were investigated. • An increasing temperature decreased the soil Ψ in the middle stage of SWRC. • The soil cohesion increased as the power function with increasing soil Ψ. • The soil friction angle increased as the linear function with increasing soil Ψ. • The increase in soil temperature decreased soil matric suction and shear strength. The soil hydrologic and mechanical properties play an important role in the slope stability in the red soil hilly region of southern China. In this study, the red soil layers in a collapsing gully wall were used to investigate the effects of temperature on the soil water retention curve (SWRC) and shear strength. The results showed that the SWRCs of the red soil under different temperatures could be accurately described by the van Genuchten (VG) model (R 2 > 0.95, root mean square error (RMSE) < 0.024). An increasing temperature significantly decreased the soil water holding capacity (WHC), especially in the intermediate range of the SWRCs of the red soil. The soil saturated hydraulic conductivity (Ks) increased linearly with temperature. The soil cohesion and soil friction angle decreased by approximately 44.13% and 30.40% respectively when the soil water content increased from 0.24 cm3 cm−3 to 0.42 cm3 cm−3. The mean soil cohesion and soil friction angle decreased approximately 8.56 kPa and 1.34° respectively when the soil temperature increased from 25 °C to 40 °C. Regression analysis showed that the soil cohesion increased as the power function with increasing matric suction (0–2000 kPa), and friction angle increased as the linear function with increasing matric suction. These results illustrated that an increase in temperature will decrease soil matric suction and shear strength but enhance the soil infiltration rate under certain soil moisture levels. Therefore, the stability of a collapsing gully wall will sharply decrease under the conditions of high temperature and heavy rain in summer. [ABSTRACT FROM AUTHOR]

[Display omitted] • Thinning promoted the increase of soil recalcitrant C and stability of SOC pool. • Increase of ligninase activity was associated with soil moisture and temperature. • Thinning induced SOC pool stability was mainly related to soil C-degrading enzyme. Forest thinning greatly affects the soil organic carbon (SOC) pool by changing the soil microenvironment, organic matter input, and microbial metabolism. However, the heterogeneity of thinning intensity, recovery stage, and microclimatic conditions increases uncertainty about the effect of thinning on SOC. The activities of C-degrading enzymes (ligninases and cellulases) secreted by soil microorganisms can be used to explore the effects of thinning on soil C storage. Our meta-analysis showed that forest thinning significantly increased soil temperature (ST), soil moisture (SM), and pH, but significantly decreased litter and fine root biomass. Moderate thinning and recovery time extension increased soil C storage, SOC, and recalcitrant organic C (ROC). An increase in the thinning intensity significantly improved ligninase activity, while decreasing cellulase activity and extending recovery time after thinning. Increased SOC, soil labile organic C (LOC), and ROC with thinning were associated with increased ligninase activity that was significantly positively correlated with soil pH, SM, and ST after thinning. The variation in soil ligninase: cellulase ratio induced by thinning was significantly positively correlated with the increases of soil ROC: LOC ratio and SOC after thinning. Therefore, forest thinning enhanced SOC pool stability through the effect of ligninases and cellulases on SOC sequestration. The global pattern of soil C-degrading enzymes in response to thinning has deepened our understanding of the mechanism by which thinning affects the SOC cycle. [ABSTRACT FROM AUTHOR]

Moso bamboo forests represent an important forest type commonly found throughout subtropical China and are characterized by fast growing forests, and involves intensive management, such as reclamation, fertilization, and understory removal. However, effects of intensive management on soil respiration ( R S ) and net ecosystem production (NEP) remain unclear. In this study, R S was partitioned into root respiration ( R R ), litter respiration ( R L ), and soil organic matter derived respiration ( R M ) by litter removal and trenching approaches. One-year measurements of respiration rates, soil temperature, and soil moisture were conducted in an unmanaged and an intensively managed stand. Regardless of stand management, R S and source components increased exponentially with soil temperature and linearly with soil moisture. Temperature sensitivity ( Q 10 ) ranged from 1.6 to 2.5, with the highest value for R M , highlighting the importance of R M in regulating the response of R S to soil temperature change. Annual R S , R R , R L , and R M were 32.6, 10.7, 6.9, and 15.0 t CO 2 ha − 1 a − 1 for unmanaged stand, compared to 38.6, 12.5, 7.1, and 18.9 t CO 2 ha − 1 a − 1 for intensive managed stand, respectively, indicating that intensive management increased R S by R R and R M . Intensive management also increased NEP with 17.2 t CO 2 ha − 1 a − 1 for unmanaged stand and 20.4 t CO 2 ha − 1 a − 1 for intensive managed stand. This increase was mainly attributed to the increase in net primary production of bamboo forests under intensive management. However, the sustainability of intensive management needs further investigation due to the reduction of soil organic carbon content after intensive management. Forest management associated with the reduction in soil CO 2 flux and increase in stand production should be developed for Moso bamboo forests. [ABSTRACT FROM AUTHOR]

Identified from the USDA Natural Resources Conservation Service databases, soils with an abrupt textural change (ATC)occur in four orders (Alfisols > Mollisols, Ultisols > Aridisols), 14 suborders and 31 great groups and represent nearly 1000 series in the USA. More than three-quarters (79%) of the soils have an argillic horizon and 21% have a natric horizon. An albic horizon is present in 40% of the soils. More than half (58%) of the soils with an ATC occur in Pale- great groups, suggesting older materials. Soil series with an ATC occur primarily in fine (56%) and clayey (14%) particle-size classes; smectitic (49%) and mixed (40%) mineral classes; mesic (39%) and thermic (33%) soil-temperature classes; and ustic (31%), xeric (27%), and aridic (21%) soil-moisture classes. On average, the texture of the eluvial and illuvial horizons varies by two classes on the soil-textural triangle. Of the several theories accounting for the origin of soils with an ATC, clay illuviation from the eluvial to the illuvial horizon must be considered a major process. More than halfof the soils are derived from alluvium and other stratified materials; residual soils may also contain sedimentary layering, which is important in the development of an ATC. Elevenpercent of the soils have a lithologic discontinuity at the eluvial-illuvial junction, which may influence the development of an ATC. The ATC in soils with an aquic soil-moisture regime (13%), such as the Argialbolls, may reflect plugging of the argillic horizon with fine clays which causes lateral subsurface flow that removes clay from the albic horizon.Climate may be important in the development of ATC in the USA, in that many of the soils are subject to extended dry periods, followed by intense thunderstorms. A third (34%) of the soils with an ATC occur in Texas. There are about 271,000 km 2 of soils with an ATC in the USA, which accounts for 3.2% of the total land area. [ABSTRACT FROM AUTHOR]

• Modified biochar decreased pH of salt-affected soils in an intercropping system. • Oversupply of biochar had negative impact on soil water and crop yield. • A 10 t ha−1 biochar application rate was recommended to improve soil and yields. Biochar application in agricultural salt-affected soils has shown strong potential to amend soil and promote production. The effect of biochar on soil properties and crop yield varies with crop, soil, biochar properties and climate. Thus, it is critical to select suitable biochar and their application amounts for ameliorating salt-affected soils while improving its conditions and crop yields. The objectives of this study were to investigate the effect of biochar application rates on soil properties, water and temperature conditions and crop yields in saline-alkali soils under cotton-sugarbeet intercropping. We used a three-year (2018–2020) field experiment with biochar application rates of 0, 10, 50 and 100 t ha−1 in 2018, 0, 10, 25, 50 and100 t ha−1 in 2019 and 0, 10, 25 and 30 t ha−1 in 2020. Soil bulk density decreased and thus porosity increased with application of biochar. Soil pH decreased with increasing biochar application amount and the rate of change ranged from −0.003 to −0.004 per ton of biochar. Biochar application at 10 t ha−1 increased soil water content (SWC) and weighted planar soil water storage (WPSWS) in all three experimental years, while oversupply of biochar decreased SWC. Application of biochar moderated soil temperature fluctuations. The yield of cotton and sugarbeet first increased and then decreased with increasing amount of biochar. Considering the effects of biochar on soil water, temperature, and crop yields, 10 t ha−1 biochar amount was proposed as an appropriate application rate for saline-alkali soils. The results provided valuable information on appropriate biochar rates to amend salt-affected soils and their properties while increase crop yields. [ABSTRACT FROM AUTHOR]

• The meadow-rice mixed ecosystem acted as CO 2 sink and CH 4 source. • CH 4 emissions were regulated by soil moisture during the dry period. • The seasonal dynamics of GPP, R eco , and CH 4 throughout the growing season were mainly regulated by T s and T a. Although previous studies have illustrated the variations in carbon dioxide (CO 2) and methane (CH 4) fluxes for different types of wetlands, there have been few reports on those of meadow-rice mixed ecosystems in semi-arid regions. In this study, eddy covariance (EC) technique was utilized to measure CO 2 and CH 4 fluxes for a meadow-rice mixed ecosystem during the growing season in 2020 in the Horqin Sandy Land, North China. The results indicated obvious diurnal and seasonal variations in gross primary productivity (GPP), ecosystem respiration (R eco), net CO 2 exchange (NEE), and CH 4 flux, with high levels during the vigorous growing stage and low levels during the early and late growing stages. The mean daily GPP, R eco , NEE, and CH 4 were 11.33 g CO 2 m−2 d−1, 6.37 g CO 2 m−2 d−1, −4.96 g CO 2 m−2 d−1, and 81.97 mg CH 4 m−2 d−1, respectively. The accumulated values of GPP, R eco , NEE, and CH 4 during the growing season were 1,756.54 g CO 2 m−2 (478.62 g C m−2), 987.30 g CO 2 m−2 (269.02 g C m−2), −769.24 g CO 2 m−2 (−209.60 g C m−2), and 12.7 g CH 4 m−2 (9.55 g C m−2), respectively, showing that the meadow-rice mixed ecosystem acted as CO 2 sink and CH 4 source. Low intensity CH 4 emissions were maintained during the dry period and were controlled by soil moisture (SM). The seasonal dynamics of GPP, R eco , and CH 4 throughout the growing season were mainly controlled by soil temperature (T s) and air temperature (T a). [ABSTRACT FROM AUTHOR]

The effective depth of transfer (EDT) between surface soil and runoff was determined by varying the physical properties of the soil, rain intensities (RIs), slope gradients, initial water contents, and soil amendment. The effects of these factors on the EDT were quantified with simulated rain. The EDT increased (0.12–1.09 cm) with an increase of RI and slope gradient (0–30°), and the effect of RI was attributed to increases in raindrop impact and runoff energy, which enhanced mixing in the surface soil. Slope gradient accelerated the velocity of water flow and decreased the stabilities of soil particles. The EDT increased from 0.192 cm to 0.709 cm with an increase in the initial water content, because variation in initial water content influenced soil infiltrability and detachability. The EDT exponentially decreased from 0.99 to 0.44 cm and from 0.86 to 0.36 cm for increasing amounts of dry granular and dissolved polyacrylamide (PAM), respectively, applied to the soil, likely because PAM improved the soil structure and prevented the formation of a crust. With soil-particle constitution ranging from silty clay to sandy loam, soil infiltration rate increased, and the EDT exponentially decreased with parameters K d and K p . We obtained an equation describing the combined effects of the various factors on the EDT by regression analysis. Analyses of root mean square errors and the coefficients of multiple determination indicated that calculated values fit the experimental data very well. This relationship provided a method of estimating the EDT and improved the prediction of the transport of adsorbed chemicals in solution, because current models of chemical transport use fixed values. [ABSTRACT FROM AUTHOR]

Soil moisture is important for plant growth in semi-arid ecosystems. In this study, spatial variations in soil moisture at depths of 0–6 m on seven hillslopes of China's Loess Plateau planted with korshinsk peashrub were analyzed based on soil moisture observations. The objective of this study was to compare the spatial patterns in soil moisture in shallow and deep soil layers at the hillslope scale under the influence of large-scale vegetation restoration. The results showed that: (1) the topographic wetness index was positively correlated with soil moisture near the surface (0–1 m), but negatively correlated with soil moisture at depths below 2 m; and (2) the negative relationship was found between biomass and soil moisture content in deep layers. Soil moisture in shallow layers was more likely to be affected by topographic factors. However, comparisons of soil moisture at different slope positions indicated that the effect of topographic factors on the variability of deep soil moisture was altered, mainly because plants with different biomasses may differ in their consumption of soil water and thus cause greater spatial variations in deep soil moisture. The introduced vegetation may alter the spatial pattern of deep soil moisture influenced by topographic factors at the hillslope scale, and the biomass may have a determining role in the spatial variation of deep-layer soil moisture content. [ABSTRACT FROM AUTHOR]

• Provide thermal regime of uppermost soil layer on the central Tibetan Plateau. • The thermal regime of soil experienced warming during the past 20 years. • Latitude and altitude controlled the soil thermal regime at the macroscale. • Partial correlation quantified the influences of local factors on soil temperature. Permafrost degradation related to global warming has been widespread in the Tibetan Plateau (TP), manifesting prominently as variations in the soil thermal regime, an essential characteristic of permafrost. Altered soil thermal conditions can influence the energy and water balance between the atmosphere and land, leading to the release of stored carbon dioxide and methane. In this study, reanalysis and observed soil temperature data were combined to analyse the long-term changes in the thermal regime of the uppermost soil layer at six sites in the central TP. MERRA2 and ERA5-Land had the highest quality in matching the observed data at each site. The mean annual soil temperature ranged from −0.11 °C to 4.75 °C (averaging 1.73 °C) and warms at 0.059° C a - 1 . The mean annual first dates of freezing and thawing and the mean duration of freezing were 123.23 ± 10.85 d , 285.67 ± 10.34 d , and 161.44 ± 20.54 d , respectively, indicating lagged, advanced, and shortened trends with 0.54 ± 0.49 d a - 1 , 0.50 ± 1.06 d a - 1 , and 1.05 ± 1.16 d a - 1 , respectively. The mean annual freezing and thawing N-factors were 0.53 ± 0.13 and 2.43 ± 2.09, respectively. The maximum and minimum monthly average soil temperatures were 11.81 ± 2.17 °C in July and −9.54 ± 3.24 °C in January, respectively. Partial correlation analysis was used to quantify the influences of factors (including surface air temperature, snow depth, rainfall, normalised difference vegetation index [NDVI], shortwave radiation, and soil moisture) on soil temperature implicated surface air temperature as the most significant influencing factor in the increased soil temperature. Rainfall and NDVI were implicated as being likely to suppress the soil temperature warming. This study provides detailed information about the thermal regime of the uppermost soil in the central TP and facilitates validation of the land surface model. [ABSTRACT FROM AUTHOR]

• ERT correlates well with FDR and helps reveal spatial subsurface heterogeneities. • Soil freezing depth in an undulating terrain varies with slope aspects. • Local terrain heterogeneities affect soil erosion initiating processes. The occurrence of freeze–thaw cycles modifies water infiltration processes and surface runoff generation. Related processes are complex and are not yet fully investigated at field scale. While local weather conditions and soil management practices are the most important factors in both runoff generation and surface erosion processes, local terrain heterogeneities may significantly influence soil erosion processes in catchments with undulating terrain. This paper presents a field-based investigation of spatial and temporal heterogeneities in subsurface soil moisture and soil temperature associated with freezing, thawing, and snowmelt infiltration. The field setup consists of a combination of traditional point measurements performed with frequency domain reflectometry (FDR) and electrical resistivity tomography (ERT). The transect was approximately 70 m long and spanned an entire depression with a north-facing slope (average slope of 11.5%) and a south-facing slope (average slope of 9.7%). The whole depression was entirely covered with stubble. Observed resistivity patterns correspond well to the measured soil moisture patterns. During the observation period, the north facing slope froze earlier and deeper compared with the south facing slope. Freeze–thaw cycles were less pronounced in the north-facing slope than in the south-facing slope. There were also differences in soil temperature and soil moisture patterns between lower and upper parts of the monitored depression. These indicate that initiation and development of runoff related processes, and consequently soil erosion, in regions with freeze–thaw cycles may differ significantly depending on local terrain characteristics. Consequently, it indicates that spatial terrain heterogeneities, especially slope aspects, may be important when studying soil erosion processes, water flow and nutrient leaching in lowlands where patchy snowpacks and dynamic freeze–thaw cycles are predominating. [ABSTRACT FROM AUTHOR]

[Display omitted] • Biocrusts increase evaporation rate by 10% on average in laboratory experiments. • All types of biocrusts increase evaporation rate by >42% in field experiments. • Biocrusts increase soil moisture (θ) by 9–44% compared with bare soil at 0–10 cm. • Biocrusts decrease soil temperature by 4.7–4.9 °C at 0–10 cm depth after rainfalls. • Reshaped soil properties and increased θ of biocrusts are key factors of increasing E. Soil evaporation is a three-stage process and plays a vital role in soil physical, chemical, and biological processes, as well as global climate change. As an important living skin, biocrusts strongly influence most soil properties and support fundamental ecosystem functions. Although there are many studies concerning biocrust effects on surface soil hydrological processes, it still remains unclear how biocrusts impact soil evaporation and their potential effects on the water budget in drylands. In this study, we selected aeolian sandy soil (bare soil) and three types of biocrusts, specifically cyanobacteria (cyano), cyanobacteria and moss mixed crusts (cyano-moss), and moss crusts (moss), on the northern Chinese Loess Plateau. By utilizing weighing micro-lysimeters in simulated and ∼4 months in-situ field evaporation experiments, we investigated all evaporation stages containing stages I–II and III, as well as the soil evaporation rate (E) of all treatments. The soil moisture (θ) and temperature (T) at 2 cm and 10 cm depths were also measured in field. Our results showed that biocrust types strongly influenced E in the ranked order of moss > cyano-moss > cyano > bare soil. The cumulative evaporation amount (E c) of all types of biocrusts was significantly higher than that of bare soil in simulated experiments. Particularly, moss increased E c by 15.7% compared with bare soil. The results of in-situ field measurements illustrated that the E of cyano, cyano-moss, and moss was increased by 42.4%, 55.5%, and 46.9%, respectively, compared with the bare soil, and these increasing effects became more pronounced after rainfall events. Additionally, all types of biocrusts markedly increased θ and decreased T at 0–10 cm depth of soil, but cyano and cyano-moss increased T (by up to 5.7 °C) at 2 cm depth during the non-rainfall periods. The increasing effects of biocrusts on E were reasonably attributed to their higher contents of fine particles and organic matter, as well as their higher field capacity in contrast to bare soil. All these regulations of biocrusts on soil properties further reshaped soil water and temperature regimes and finally changed soil evaporation. In conclusion, biocrusts may greatly intensify surface soil water loss due to their higher E. However, their greater θ and lower T in comparison to bare soil may partially offset these negative effects in return, and they may have feedback impacts on surface soil water and heat balances in drylands. [ABSTRACT FROM AUTHOR]

The main objective of this paper is to discuss the range of temperature and moisture differences and variability in tundra vegetation and Arctic soils in the context of weather changes during the growing season. Research was carried out in Wedel Jarlsberg Land (SW Spitsbergen) in a small non-glaciated catchment in the vicinity of the Polish Polar Station in Hornsund. Measurements of air and soil temperature and changes in volumetric soil water content were carried out between June 24 and September 9 of 2008. The studied sites represented: (1) Turbic Cryosol, poorly covered by vegetation and exhibiting evidences of strong cryogenic processes; (2) Hyperskeletic Cryosol covered by a community of wet moss tundra vegetation with variable moisture which evolves under the influence of water flowing from the adjacent mountain slopes occupied by Little Auk colonies; and (3) Haplic Cryosol covered by lichen–herb–heath tundra vegetation, located on a raised marine terrace. Hyperskeletic Cryosol is the wettest of all the soil profiles studied. This profile shows the largest fluctuations in water content, related to the rate of snow melting on mountain slopes and the outflow of ablation water. The volumetric soil water content in Hyperskeletic Cryosol varies from 29% to 71%, with an average value of 49%. The mean volumetric soil water content in the driest Haplic Cryosol is 6% and ranges from 3% to 10% throughout the growing season. This is related to its sandy texture and a large number of stones, which leads to fast infiltration of snowmelt water and rainfall. Turbic Cryosol shows an intermediate volumetric water content ranging from 21% to 38%, with a mean value of 30%. The thermal regimes of the soils studied are also variable. The warmest soil was the driest Haplic Cryosol, as no influence of cold thawing water was observed. During the measurement period, the mean soil temperature at a depth of 10cm in Haplic Cryosol was 6.3°C. Turbic Cryosol was ca. 1.2°C–1.5°C colder than Haplic Cryosol. Hyperskeletic Cryosol was the coldest in comparison with the other soils studied because of the moss cover having insulating capacity. The temperatures recorded in this profile at a depth of 10cm reached a mean value of 3.2°C. The results indicate that cold water inflow from melting snow cover greatly affects soil temperature in the first part of summer (ablation season). This is related to an increase in solar radiation and air temperature leading to more intensive snow melting. This relationship is particularly evident in the first ten days of July. The highest soil surface temperatures (>20°C) were recorded in the beginning of July under intense solar radiation (25–27MJ/m2 d−1). In the second part of August, thermal gradients were weaker and soil temperatures in all the pedons studied were almost the same, ranging between +3°C and +6°C. This was due to limited solar energy inflow and heat migration into the soil transported with rainfall. [ABSTRACT FROM AUTHOR]

Abstract: The emission of CO2 from soil to the atmosphere is a major challenge throughout the world in both developed and developing countries, due to its critical role in the intensification of global warming. An incubation experiment was conducted to investigate CO2 emission potentials of Ultisol soils under residues of peanut (green manure) and rice (rice straw) and moisture regimes 60% (W1) and 120% (W2) of water holding capacity at different temperature ranges i.e. low to medium 5–20°C (T1 to T4), medium to high 25–30°C (T5 to T6) and very high 35–45°C (T7 to T9). Comparing two contrasting plant residues, we found that the incorporation of GM (green manure) residue significantly (P<0.05) increased the CO2 emission potential of Ultisol soils at both moisture regimes and all temperature ranges, and this increase tended to improve with the increase of temperature ranges. Conversely, RS residue mixed treatments showed significantly low production and emission of CO2, at all temperature ranges and both water regimes. This indicated that type and quality of plant residues have significant impact on the CO2 production and emission capacity of soils and plant residues with low decomposition, high stability and high lignin, cellulose and hemicelluloses compounds can be successfully used as an organic amendment to control the emission and production of CO2 from soil to atmosphere, by converting soils from CO2–C sources to sinks. We revealed that moisture and temperature also had a significant (P<0.05) effect on the CO2 production and emission potential of Ultisol soils, but this effect was indirect through influencing the rate of decomposition of the organic inputs. Our results suggested that applied amendments e.g. addition or incorporation of plant residues are in fact major factors which control the CO2 emission potential of soils by converting soils from CO2–C sources to sinks. On the other hand, other abiotic factors like temperature and moisture are indirect regulator of CO2 production and emission by influencing decomposition of these incorporated organic inputs. [Copyright &y& Elsevier]

Abstract: A soil respiration dataset was examined to determine the importance of environmental factors relating to seasonal variation in soil surface CO2 flux on the eastern slope of the Cofre de Perote Volcano (Mexico). The results are reported as follows: (1) on the upper section (2500masl), average soil respiration varied from 10.3 to 21.5mgCm−2 h−1 in coniferous forest, 14.8 to 30.3mgCm−2 h−1 in corn field, and 13.4 to 29.9mgCm−2 h−1 in abandoned corn field. Soil respiration decreased in spring, when the soil temperature was higher and soil water was lower, while it increased in summer, with non-limiting conditions of soil water. (2) On the lower section (1650masl), the average soil respiration varied from 22.5 to 89.6mgCm−2 h−1 in tropical montane cloud forest, 17.9 to 128.1mgCm−2 h−1 in corn–potato–corn rotation, and 63.0 to 203.2mgCm−2 h−1 in grassland. Soil respiration began to rise in late spring, corresponding to the transition from the dry to wet season and reaching its highest value in summer. (3) Soil respiration rates showed a positive exponential correlation with soil temperature (R2 =0.52; P <0.0001). The model related soil respiration to soil temperature and soil water, explaining 58% of variation. These results suggest that soil temperature and soil water co-regulate soil respiration. Thus, the dataset suggests that global warming could have a negative effect on soil water availability, resulting in decreasing soil respiration. [Copyright &y& Elsevier]

• Higher latitudes regions will witness a high soil NO 3 – production. • Frequent freeze–thaw process may accelerate the soil NO 3 – production. • Soil NO 3 – may reach 18 mg/l concentration during winter only in future. Winter season is characterized by lowering of air temperature and soil temperature, and deceleration of soil nitrogen cycle. Despite low soil temperature, soil NO 3 – is found on the soil surface and in the streams of temperate and higher latitude regions towards the end of winter season. With the rise in global air temperature, the soil temperature is expected to warm up accordingly. Plausible effects of future soil temperature changes in affecting the production and movement of soil NO 3 – within a vertical profile were studied in the present paper. Four Representative Concentration Pathways (RCP) scenarios were considered to estimate the effects of change in air temperature on soil temperature at different depths within a vertical profile and on the soil nitrate status. Since winter season is known to have low to no soil nitrate utilization (due to microbial inactivity and low utilization by biomass), plausible effects of winter warming in the future decades were studied. The occurrence and movement of soil NO 3 – during winter, raises a concern regarding the future warming climate's response. Long-term records from Hubbard Brook Experimental Forest, New Hampshire, USA, were used for observation, calibration, and validation purposes. Non-linear relationship between air temperature, soil moisture, soil temperature, and soil NO 3 – status at different soil depths, were assessed using support vector regression (SVR) models. Soil temperature and soil NO 3 – status at different soil depths were predicted using SVR models, under the four different RCP scenarios. The projections under different RCP scenarios suggested - significant production of soil NO 3 – during winter (approx. 18 mg/l by the year 2095 under a "business as usual" scenario), and movement of soil NO 3 – towards soil surface before the beginning of plant-growing season. [ABSTRACT FROM AUTHOR]

• Alpine gravelization by glacier melting seriously eroded downstream grassland. • Alpine gravelization decreased alpine grassland coverage, biomass density, and diversity. • Alpine gravelization initiated extreme soil aridity of hillside alpine grassland. • Alpine gravelization initiated disappearance of some species and plant functional groups. Alpine gravelization by glacier melting may subsequently cause degradation of downstream vegetation. The thinning rates of glaciers outside ice sheet peripheries in some regions has doubled over the past 20 years. However, no study is available about the effects of alpine gravelization on alpine meadow ecosystem. Here, by investigating and measuring the community characteristics, soil moisture, and soil temperature of alpine meadows under three different gravel coverage levels (No gravel covered meadow, half gravel covered meadow, and fully gravel covered meadow), we examine the response of surface microhabitats and community to gravel cover on a typical hillside alpine meadow. Results showed that gravel cover significantly decreased soil/gravel ratio and topsoil moisture. Topsoil water content of the half-covered and the fully-covered gravel meadow was outstandingly low and reached<8% and 5%, respectively. Meanwhile, the larger decrease rates for coverage (−72.53%), above- and below-ground biomass (−76.61% and −94.09%), community density (−81.76%), species richness (−77.75%) and diversity (−55.98%) were found after gravel cover. Gravel cover induced the changes of the dominant species composition from Kobresia pygmaea to Setaria viridis , and ultimately to Trigonotis peduncularis and Ranunculus pedatifidus. Cyperaceae functional group species almost disappeared with increasing gravel coverage. In general, the increase in gravel coverage caused a decrease in soil water content, coverage, above-ground and under-ground biomass, community density, species richness, and the disappearance of Cyperaceae functional group species. Our results provide a new insight into the effect of alpine gravelization on soil water environment and alpine meadow degradation. [ABSTRACT FROM AUTHOR]

Abstract: Profile samples from 0 to 70cm depth were collected in five plant zones along a hydrological gradient in a typical land/inland water ecotone, Northeast China. Total phosphorous (TP), organic phosphorous (OP), inorganic phosphorous (IP) and available phosphorous (AP) were measured to study their horizontal and vertical distribution patterns in the land/inland water ecotone, as well as their important influencing factors such as soil organic carbon (SOC) and water level. Our results demonstrated that the levels of TP, OP, IP and AP were generally higher in the flooding zone (zone A), the over-wetted zone (zone B) and the drying and wetting zone (zone C), but the drying zones (zones D and E) contained lower P concentrations. Soil P was mainly concentrated in upper soils (0–30cm) and the P levels decreased with depth, except for small accumulative peaks in the 50 to 70cm soil increment for TP and OP in zone C and for IP and AP in zone A. Surface soils in zones D and E had a lower mean SOC:OP ratio than zones A, B and C, reflecting the higher probability of OP mineralization in the drying zones. However, higher mean values of the IP:OP and AP:TP ratios were found in zone A (P <0.05), indicating that increasing soil moisture may be the most important agent determining IP release rate and biological availability. The significantly positive correlations with soil organic matter (SOM) and clay content would contribute to P retention in zones A, B and C (P <0.01) where the soils contained relatively high organic matter and clay content. The results obtained in this study suggest that the distributions and dynamics of P forms in soil, especially in the land/inland water ecotone, can be significantly impacted by various biogeochemical and environmental factors (i.e., soil moisture, SOM, and clay content). [Copyright &y& Elsevier]

Abstract: In terrestrial ecosystems, soil respiration is a key pathway of carbon to the atmosphere. It is highly variable in time and space. Its temporal variability at a single point can be reasonably described by changes in soil temperature and moisture. However, it is much more difficult to determine the drivers of its spatial variability. The aim of this study was to elucidate the interrelationship between the spatial variability of soil respiration and the spatial variability of soil redistribution as well as other soil and crop properties. The study was carried out in a small agricultural watershed (4.2ha) subjected to water and tillage erosion processes. During three crop cycles (one of sugar beet, two of winter wheat) soil respiration, soil temperature, and soil moisture were measured in situ at least bi-weekly at 20–22 locations. The first stage was to analyse the interrelation of soil temperature as an important control of soil respiration and soil redistribution. In the second stage, measured CO2 effluxes were standardised to 15°C and mean fluxes at each location were calculated for the sugar beet year, as well as two growing phases under winter wheat. The mean CO2 effluxes for the five resulting phases at each measuring location were correlated to soil and crop properties and modelled soil redistribution. Moreover, the intercorrelation of all explanatory variables was analysed using principal component analyses, and these principal components were correlated to standardised CO2 effluxes. Except for the second phase in 2009 with combined autotrophic and heterotrophic respiration, which was dominated by root respiration, in all phases there was a tendency that CO2 effluxes at erosional sites were smaller than at depositional sites. The combined analysis of CO2 effluxes, erosion, and other explanatory variables indicates that for heterotrophic respiration (between rows in the case of sugar beet and before significant plant growth in the case of winter wheat) the spatial variability of median grain size and bulk density had the most consistent effect on the spatial variability of soil respiration. In contrast, soil moisture was less important and topsoil SOC had more or less no effect on CO2 effluxes. Only in two measuring phases (Phase 2 2008 and Phase 1 2009) did the combined analysis show that total erosion was one of the dominant variables for the spatial variability in CO2 effluxes. In general, the relatively inconsistent effect of soil erosion status on spatial variability of CO2 effluxes is somewhat surprising, as there are a number of different reasons which support the assumption that CO2 effluxes at erosional sites should be smaller than at depositional sites. A major reason for the observed behaviour might be the compensating effect of tillage and water erosion and the counteracting effects of both processes on soil respiration. This underlines the importance of field-scale studies to gain further insight into the interrelation of soil redistribution and CO2 effluxes. [Copyright &y& Elsevier]

Abstract: Soils are the third biggest sink of carbon on the earth. Hence, suitable land uses for a climatic condition are expected to sequester optimum atmospheric carbon in soils. But, information on how climatic conditions and land uses influence carbon accumulation in the soils on the Himalayan Mountains is not known. This study reports the impact of four climatic conditions (sub-tropical, altitude: 500–1200m; temperate 1200–2000m; lower alpine 2000–3000m; upper alpine, 3000–3500m) and four land uses (forest, grassland, horticulture, agriculture) on the concentrations and stocks of soil organic carbon (SOC) in upper (0–30cm) and deeper (30–100cm) soil depths on the western Himalayan Mountains of India. The study also explored the drivers which influenced the SOC stock build up on the mountains. Rainfall and soil moisture showed quadratic relations, whereas temperature declined linearly with the altitude. SOC stock as well as concentration was the highest (101.8Mgha−1 in 0–30cm, 227.97Mgha−1 in 0–100cm) in temperate and the lowest in sub-tropical climate (37Mgha−1 in 0–30cm, 107.04Mgha−1 in 0–100cm). Pattern of SOC stock build up across the altitude was: temperate>lower alpine>upper alpine>sub-tropical. SOC stocks in all land uses across the climatic conditions, except agriculture in lower alpine, was higher (0.7 to 41.6%) in the deeper than upper soil depth. SOC stocks in both the depths showed quadratic relations with soil temperature and soil moisture. Other factors like fine soil particles, land-use factor and altitude influenced positively whereas slope and pH, negatively to the SOC stocks. In all climatic conditions, other than temperate, SOC stocks were greater in natural ecosystems like forests and pastures (112.5 to 247.5Mgha−1) than agriculture (63 to 120.4Mgha−1). In temperate climate, SOC stock in agriculture (253.6Mgha−1) on well formed terraces was a little higher than forest (231.3Mgha−1) on natural slope. These observations, suggest that land uses on temperate climate may be treated as potential sinks for sequestration of the atmospheric carbon. However, agriculture in subtropical climate need to be pursued with due SOC protection measures like the temperate climate for greater sequestration of the atmospheric carbon. [Copyright &y& Elsevier]

• The insulated effect of peat on permafrost is obtained by field data. • Peat can prevent heat from air in warm season. • Peat can protect soil from heat loss in cold season. Rising temperatures result in permafrost degradation in cold regions, but with considerable spatial heterogeneity due to local factors including peat. Peat plays an important role in the permafrost carbon cycle by impacting the soil thermal and hydrologic characteristics. Here we use field observations to describe the role of peat on permafrost thaw based on comparisons at two sites: EBoTA characterized by primarily peat, and PT5 with more mineral soils. Compared to PT5, soil temperature at the EBoTA site was lower in the warm season, but higher in the cold season. Freezing onset was generally 0–19 days later at the PT5 site compared to EBoTA throughout the soil column, except at the 0.1 m depth where it occurred 11 days earlier. The average thawing onset at PT5 was 18–96 days earlier. There were 20–119 more freezing days and 19–118 fewer thawing days at EBoTA than at PT5, and the zero annual amplitude and active layer thickness were lower at EBoTA. Finally, the mean annual ground temperature was greater at PT5, and was even above 0 °C in three recent years. These results illustrate peat's thermal insulation effect on permafrost due to its low thermal conductivity and high moisture content. Snow depth increases also amplify the insulation effect. These field observations therefore not only verify, but also quantify the protective role of peatlands on permafrost. [ABSTRACT FROM AUTHOR]

• Annual mean R s and Q 10 values in HD were significantly higher than those in LD. • R s was mainly controlled by θ in the summer and T s in the other seasons. • Double variable equation was better than single to predict R s at the annual scale. • Annual R s in HD was positively related with θ , NDVI and SOM, negatively with T s. • Annual θ was the main factor controlling annual Q 10 at both sites. Although correlations between soil respiration (R s) and environmental factors in different ecosystems have been extensively investigated, results based on long-term experiments are limited. In this study, we analyzed the correlations between R s and soil temperature (T s), moisture (θ), the normalized difference vegetation index (NDVI), and soil organic matter (SOM) based on an 11-year field campaign in abandoned farmland (HD) and bare land (LD) areas with a Cambisol soil type in the eastern Loess Plateau of China. The results showed that the mean annual R s and annual temperature sensitivity (Q 10) values in HD were significantly larger than those in LD during the measurement period. R s and the annual contribution ratio (R ratio) of root respiration (R r) to R s in HD increased significantly with vegetation recovery years. On the annual scale, R s was controlled primarily by T s at both sites. However, in the summer months, R s was controlled by θ rather than T s. A two-variable model, including T s and θ , could more accurately predict the temporal variations in R s at the annual and seasonal time scales than a single-variable model, and the explanatory power of the equations in HD was significantly larger than that in LD. On the interannual scale, variations in the annual R s and R r showed significant positive correlations with the annual θ and NDVI and SOM, and negative correlations with T s in HD. Moreover, the annual Q 10 was significantly positively related to θ in HD. In LD, the only significant relationship was between the annual Q 10 and the annual θ. All differences between HD and LD in R s , T s , and θ and their correlations were attributed to differences in vegetation. Our findings highlight the importance of long-term observations for the accurate estimation of CO 2 efflux in semiarid regions and the impact of vegetation changes on soil respiration. [ABSTRACT FROM AUTHOR]

• Warming significantly increased CH 4 emission by 52%. • N addition reduced the positive effect of warming on CH 4 flux. • Warming and N addition together did not significantly change CH 4 flux. • CH 4 flux positively correlated with GPP. • Soil T, soil moisture, DOC and TN were the main controls for CH 4 flux. Methane (CH 4) fluxes in boreal peatlands could be impacted by global warming and N deposition. However, the interaction of these factors remains poorly understood and has not been considered in coupled climate-carbon models. In this study, manipulated warming and N deposition (ammonium nitrate) were conducted for five years in a coastal bog in western Newfoundland, Canada. Consistent with previous studies, warming significantly increased CH 4 emission by 52%, which might be due to the increase of microbial activity and vegetation growth. Although N addition alone did not alter CH 4 emissions, it significantly reduced the positive effect of warming on CH 4 fluxes. We attributed this finding to three possible reasons: (1) N addition caused a shift in root allocation from deep to shallow roots, which decreased labile substrates for CH 4 production under warming; (2) warming promoted vegetation uptake of ammonium (NH 4 +), which alleviated the inhibition of NH 4 + to methanotrophs and subsequently increased CH 4 oxidation under N addition; and (3) the combination of warming and N addition increased maintenance respiration of vascular plants compared with warming alone, thus reducing net primary production and root exudates for CH 4 production. In addition, we found that soil temperature, soil moisture, DOC and TN were the main controls on CH 4 fluxes. Our results indicate that the combined effect of N deposition and warming should not be ignored. Otherwise, the emission of CH 4 in bogs will be overestimated under future scenarios of climate warming and N deposition increase. Our study can be further applied as empirical evidence for the parameterization of temperature-dependence and nutrient-dependence of CH 4 fluxes in biogeochemical models of boreal peatlands. [ABSTRACT FROM AUTHOR]

• Lakes in the endorheic basin exhibited a rapid expansion since 2000. • The significant lake expansion was observed in the Hoh Xil region. • Lake expansion was closely related to precipitation and permafrost degradation. • Meltwater from permafrost thawing contributes to 21% of lake volume change. • Glacier retreat contributed to expansion of several large lakes. The QTP (Qinghai-Tibet Plateau) holds the greatest concentration of high-elevation inland lakes in the world, and most of these lakes are located in the QTP endorheic basin. Accelerated lake expansion in the endorheic basin since 2000 has been confirmed by many studies, but there is disagreement as to which components of the water balance explain most of the lake expansion. In this paper, based on Landsat images, meteorological data, glacier data and permafrost monitoring data, we analyzed the spatial–temporal changes in lake area and further explored the driving factors behind rapid lake expansion in different zones in the endorheic basin. The results suggested that the spatial pattern of trends in lake area in the endorheic basin from 2000 to 2017 showed a southwest-northeast transition from contracting to slightly expanding to rapidly expanding. More importantly, the dramatic lake expansion observed in most regions was statistically significant (0.01 ~ 26.29 km2/yr). Although retreating glaciers may have contributed to lake growth, this can not fully explain the recent lake expansion. We find that increasing precipitation was the primary driver behind lake expansion, and that permafrost degradation accelerated lake expansion. Lakes on the northern slope of the Gangdise Mountains, fed by the most rapidly retreating glaciers, were relatively stable or even contracted. In contrast, most of the non-glacier-fed lakes in the Hoh Xil region and the central endorheic basin nevertheless experienced significant expansion and slight expansion, respectively, which were mainly attributed to the greatest increase in AP (annual precipitation). Remarkable lake expansion was found in the continuous permafrost zone. The increasing ALT (active layer thickness) and soil temperature of permafrost resulted in an increase in meltwater from ground ice, the partial release of soil moisture and an amount of unfrozen water content, which has contributed to supply lakes and accelerated lake expansion. [ABSTRACT FROM AUTHOR]

• Vegetation degradation could decrease CH 4 emissions and increase Re fluxes. • Soil temperatures at 5 and 10 cm were the main controls on Re variability. • Soil temperature and water content were the main controls on CH4 emission. • Less CH 4 flux in vegetation degradation peatland was due to low soil water content. Vegetation plays a critical role in regulating ecosystem carbon (C) processes in peatlands, but vegetation faces serious degradation on the Tibetan Plateau, China. However, how vegetation degradation affects on carbon processes of peatlands remains unclear. Using the static chamber technique, we compared ecosystem respiration (Re) and methane (CH 4) fluxes for healthy vegetation (HV) and degraded vegetation (DV) during two growing seasons (2013 and 2014) on peatlands of the Tibetan Plateau. We also determined the dominant factors controlling Re and CH 4 fluxes. The average Re flux for DV (218.04 ± 95.08 mg C m-2h−1 in 2013 and 219.03 ± 140.96 mg C m-2h−1 in 2014) was considerably larger than that at the HV(163.78 ± 87.51 mg C m-2h−1 in 2013 and143.91 ± 84.44 mg C m-2h−1 in 2014), whereas the average CH 4 fluxes for DV (0.06 ± 0.20 mg C m-2h−1 in 2013 and 0.04 ± 0.07 mg C m-2h−1 in 2014) were significantly lower than the corresponding fluxes for HV (2.19 ± 2.05 mg C m-2h−1 in 2013 and 0.85 ± 0.95 mg C m-2h−1 in 2014). The Re fluxes for the two vegetative treatments had the same temporal trends, with the peaking flux observed in July 2014. The temporal patterns of CH 4 fluxes were similar to Re for two vegetation treatments where fluxes peaked in July 2014. Soil temperatures were found to be the primary factors influencing temporal Re fluxes. Soil temperatures and soil water content (SWC) were found to be the dominant factors influencing temporal CH 4 flux for HV, while the main control for CH 4 emission was the SWC for DV. Therefore, vegetative condition must be considered when estimating Re and CH 4 flux from peatlands, particularly under the current situation of climate warming. [ABSTRACT FROM AUTHOR]

• Elevation and slope aspect affected leaf stoichiometry of Oxytropis ochrocephala. • Variation of leaf stoichiometry with elevation was mainly affected by MAT, SOC and SOC:STP. • Variation of leaf stoichiometry with slope aspect was mainly affected by ST and SWC. Slope aspect and elevation gradient, important topographic factors, affect plant growth and leaf carbon:nitrogen:phosphorus (C:N:P) stoichiometry by regulating local water and energy balances. The response of leaf stoichiometry to topographic factors reflects plant adaptation strategies to different habitats. Common in various grasslands across China, Oxytropis ochrocephala Bunge. is well known in pastoral areas for its toxicity. The effects of partial or full slope sunniness (south-facing) or shadiness (north-facing) and elevation (2400 m, 2600 m, 2800 m, 3000 m, or 3200 m) on the leaf C:N:P stoichiometry of O. ochrocephala was investigated in northwest China's Qilian Mountains. While leaf C:N:P stoichiometry of O. ochrocephala changed with elevation, there was no uniform pattern of change: the greatest leaf C and P concentrations ([C] leaf , and [P] leaf) were measured at an elevation of 2800 m (417.81 g kg−1 and 1.17 g kg−1, respectively); the lowest [C] leaf was 360.43 g kg−1 at 2400 m, and the lowest [P] leaf was 0.81 g kg−1 at 2600 m. The greatest leaf N concentration ([N] leaf) was 38.29 g kg−1 at 3200 m, and the lowest was 31.94 g kg−1 at 2600 m. Leaf C:N, C:P and N:P ratios were all relatively greater at 2600 m. Across the elevation gradient, O. ochrocephala leaf nutrient concentrations and their stoichiometries were mainly determined by mean annual temperature, soil organic carbon, and soil organic carbon to soil total phosphorus ratio. The [C] leaf , [N] leaf , and [P] leaf were significantly greater on north-facing slope aspects (393.86 g kg−1, 38.04 g kg−1, and 1.16 g kg−1, respectively) than on south-facing slope aspects (365.39 g kg−1, 32.98 g kg−1, and 0.92 g kg−1, respectively). Leaf C:N, C:P, and N:P ratios were significantly lower on north-facing slope aspects (10.43, 416.49, and 39.73, respectively) than on south-facing slope aspects (11.14, 512.57, and 45.98, respectively). Differences in leaf nutrient concentrations and their stoichiometries in O. ochrocephala leaves between slope aspects were mainly determined by soil temperature and soil moisture content. In terms of leaf N:P ratios across the elevation gradient and the two slope aspects, results indicated that the growth of O. ochrocephala in the study region was mainly restricted by P. [ABSTRACT FROM AUTHOR]

• Moderation of soil temperature under conservation agriculture. • HYDRUS-2D model could successfully simulate couple of soil water and temperature. • Optimization was done through inverse modelling. • Simulated maximum soil temperature was lower in zero tillage with residue retention. Although conservation agriculture (CA) practices are being promoted, there is insufficient information on how these activities affect soil thermal regimes. An experiment was conducted in the long-term CA condition to compare soil hydrothermal environment with conventional agriculture under wheat crop. Two different tillage practices viz. zero tillage with residue retention (ZT + R) and conventional tillage with residue incorporation (CT + R), were followed. Soil temperature was observed at 2, 10 and 20 cm soil depths at 2 h interval using platinum resistance digital soil thermometer during three simulation periods, 33–52, 77–93, 106–125 days after sowing (DAS). Simultaneously, soil moisture content at 0–5, 5–15 and 15–25 cm were measured by gravimetric method to compute heat parameters. It was observed that maximum soil temperature (ST) was under CT + R than ZT + R. Maximum ST was 17.3, 13.9 and 13.6 °C at 2, 10 and 20 cm, respectively under ZT + R, on 85 DAS while it was 18.1, 14.6 and 14.1 °C, respectively under CT + R treatment. The amplitude of ST was high at depth of 2 cm than at 10 and 20 cm and it was also higher under CT + R than ZT + R. In this study modelling using HYDRUS-2D was carried out to simulate the ST. Soil thermal parameters were optimized using inverse solution approach and used for model. Accuracy of the simulation using HYDRUS-2D, was assessed by comparing the predicted values against observed. Results indicated a better performance of the model in predicting the ST for 2 and 10 cm depth with R2 between 0.66 and 0.87 and 0.71–0.85 for ZT + R and CT + R, respectively during all the three simulation periods. The performance was less satisfactorily for 20 cm depth with R2 between 0.47 and 0.55 and 0.53–0.69 for ZT + R and CT + R, respectively during all simulations. [ABSTRACT FROM AUTHOR]

• Effects of straw addition to soil under aerobic/anaerobic incubation were studied. • 13C-labeled rice straw was used as the experimental material. • Straw promoted CO 2 and CH 4 emissions during the whole and anaerobic periods. • Straw addition elicited a positive priming effect on SOC mineralization. • Soil temperature affected the studied emissions more than soil moisture. Paddy soil from a site in northeast China was incubated with 13C-labeled rice straw in a laboratory study, and the effects of soil temperature and moisture on CO 2 and CH 4 emissions were measured using stable isotope ratio mass spectrometry. Aerobic incubation experiments were conducted at three soil temperatures (−10 °C, 0 °C, and 10 °C) and two soil moistures (60% and 100% water-filled pore space (WFPS)) in a laboratory for 24 weeks to simulate the rice-fallow season. An anaerobic incubation experiment was carried out for 16 weeks under a soil temperature of 25 °C and a 1 cm submerged layer to simulate the rice-growing season. Our results showed that increases in both soil temperature and soil moisture significantly promoted the cumulative CO 2 emissions from rice straw during aerobic incubation. Furthermore, during anaerobic incubation, the cumulative emissions of CO 2 and CH 4 from rice straw decreased with increasing aerobic incubation soil temperature and soil moisture. The CO 2 and CH 4 emission ratios from rice straw throughout the incubation duration ranged from 6.6–15.7% and 0.0–3.0%, respectively. The addition of rice straw promoted a priming effect on native soil organic carbon (SOC) mineralization and produced CO 2 emissions, which positively impacted priming during the aerobic (rice-fallow season) and anaerobic incubation (rice-growing season). The positive priming effect of rice straw on the CO 2 emission duration ranged from 75.0% to 274.3% by the end of the 40-week incubation period. Furthermore, the aforementioned effect first increased and then decreased as the aerobic incubation soil temperature increased, with the greatest effect at 0 °C and lowest at 10 °C. These results suggest that high temperature during the rice-fallow season promotes the decomposition of rice straw C and leads to a decreased positive priming effect on native SOC during the rice-fallow and rice-growing seasons under the seasonal conditions of northeast China, and that it also leads to decreased CH 4 production during the rice-growing season. These results have scientific significance for rational utilization of rice straw and mitigation of greenhouse effect in northeast China. [ABSTRACT FROM AUTHOR]

• Q 10 generated by simple regression was larger than temperature-only based Q 10. • θ significantly confound responses of R s to temperature over short periods. • The presence of biocrusts may make R s being more sensitive to variation in θ. • The temperature-only based Q 10 of R s was similar to that at ecosystem level. A precise prediction of the response in soil respiration (R s) to climate warming requires the temperature-driven portion of the response to be characterized separately from the global, undecomposed response. Eliminating non-temperature-driven effects, which tend to confound the response in R s , is possible with Singular Spectrum Analysis (SSA), a non-parametric approach to timeseries analysis. R s and ancillary data were collected at three microsites in a desert-shrubland ecosystem in northwest China over a three-year period (i.e., 2013–2015). The microsites include desert-sites with non-biocrusted, lichen-crusted, and moss-crusted soil surfaces, or NC, LC, and MC, respectively. Results revealed that temperature sensitivity in R s (i.e., Q 10) based on the original, unprocessed R s -data and a seasonal equation relating R s to temperature were similar among microsites, with similar amplitudes in R s. High-frequency bins of R s , with sub-signals with a period < 90 days, obtained by subtracting the low-frequency bins from timeseries of R s , were positively correlated with soil moisture (θ) at all microsites. Whereas, the same high-frequency bins were individually decoupled from soil temperature at LC and MC. This suggests that the influence of θ on the response in R s to temperature dominated the R s -measurements over the shorter term. After eliminating the non-temperature effects on R s with SSA, Q 10 tended to produce lower values, i.e., 1.40, 1.28, and 1.34 for NC, LC and MC, respectively, when compared to cases where non-temperature effects were not removed, yielding a mean of 2.28. Q 10 -values estimated with SSA-processed R s -data were consistent with those published at the ecosystem level (i.e., R e ~ 1.40). The research suggests that SSA-adjusted Q 10 -values tend to be similar with those at the ecosystem scale. Future theoretical work is anticipated using a convergent temperature-only-based value of Q 10 between R s and R e across ecosystems. [ABSTRACT FROM AUTHOR]

• Soil Water Repellency is high under eucalypts regardless wildfire or slope aspect. • Comparing to the unburnt site, wildfire reduced SWR in the first post-fire years. • SWR is higher and less spatially variable under unburnt eucalypts in dry periods. • Comparing to the unburnt site, slope aspect had minimum impact on SWR after burning. • Wildfire causes greater, or quicker, temporal changes in soil moisture content. Wildfire can induce, enhance, or destroy natural soil water repellency (SWR) depending mostly on soil burnt severity, soil and vegetation types, soil organic matter (SOM) content and type, soil texture, peak soil temperature and remaining time and, antecedent soil moisture content (SMC). In Portugal, SWR in eucalypt stands has been shown to increase surface runoff under dry antecedent SMCs in both burnt and unburnt sites, thereby enhancing soil erosion. Despite the many hydrological implications of SWR, intensive field monitoring under a wide range of SMCs is still limited. This study aimed to improve our understanding of the role of slope aspect and wildfire on the temporal evolution of SWR in Mediterranean environments, which will be helpful for hydrological modelling and post-fire soil erosion risk assessment. In this sense, two burnt eucalypt plantations (wildfire of July 2010) were selected along a neighbouring, long-unburnt eucalypt stand, in north-central Portugal, in order to assess SWR and SMC's in a high temporal resolution. During the first two post-fire years, at 1–2 week intervals, surface (2.5 cm depth) SWR and SMC were monitored using the "molarity of an ethanol droplet" (MED) test and a soil probe, respectively. The results showed that the observed annual SWR was very high to extreme (80% of measurements ≥ 6 ethanol class) for all three sites. Wildfire reduced the annual median SWR by one class (extreme to very high) for both post-fire years. During prolonged dry periods the unburnt site was significantly more repellent (P < 0.01) and less spatially variable (P < 0.01) than the recently burnt site, while in the wet periods there was no significant difference. After burning, slope aspect did not have a strong impact on the annual median SWR class. However, the north-west aspect site recorded significantly (p < 0.01) greater annual frequencies of extreme repellency than the south-east aspect site (70–73% vs. 51–55%). [ABSTRACT FROM AUTHOR]