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• 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]

• 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]

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]

[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]

• 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]

• 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]

[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]

• 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]

• 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]

• 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]

• For soil nitrogen losses, tea garden had above 3.28 times than bamboo forest. • Soil N 2 O fluxes were the greatest in spring but the lowest in winter. • Leachate NO 3 –-N concentrations were maximum in winter but minimum in summer. • Threshold of soil temperature controlled soil N 2 O fluxes. • Threshold of precipitation during the previous seven days controlled NO 3 –-N leaching. Due to the economic benefits, land use change (e.g. deforest to tea or fruit plantation) has been widely occurred in the south-eastern hilly area of China. This may stimulate serious soil nitrogen (N) losses due to large fertilizer inputs (about 1–2 times of that in regular rice-wheat rotation). Therefore, we investigated the soil N 2 O fluxes and leachate NO 3 –-N concentrations and their responses to multiple factors on a tea garden (TG) hillslope and an adjacent bamboo forest (BF) hillslope. Soil N 2 O fluxes and leachate NO 3 –-N concentrations on the TG hillslope were 3.28 and 4.24 times of those on the BF hillslope, respectively. Soil N 2 O fluxes measured in spring were the greatest while those measured in winter were the lowest. However, the measured leachate NO 3 –-N concentrations were the greatest in winter but the lowest in summer. On both hillslopes, soil temperature (ST) and precipitation during the previous seven days (API7) were positively related to soil N 2 O fluxes but negatively related to leachate NO 3 –-N concentrations, while the ground water table depth was opposite. Soil water content (SWC) and the ratio of SWC/field capacity (SWC/FC) negatively influenced leachate NO 3 –-N concentrations on both hillslopes. Positive influences of SWC and SWC/FC on soil N 2 O fluxes were observed on the TG hillslope, while quadratic relationships were observed on the BF hillslope. Thresholds of ST and API7 were existed in the controlling the spatial variations of soil N 2 O fluxes and leachate NO 3 –-N concentrations on both hillslopes. When ST was > 9.5 °C, spatial variations in soil N 2 O fluxes were controlled by topography, soil properties and soil hydrological parameters on both hillslopes. Similarly, when API7 were < 58.0 mm, the spatial variations in leachate NO 3 –-N concentrations were also influenced by these factors on both hillslopes. Finding of this study will supplement the knowledge of soil N 2 O emissions and NO 3 –-N leaching from the tea planation and bamboo forest. [ABSTRACT FROM AUTHOR]

Biocrusts are widely distributed throughout the world in dryland ecosystems, but their respiration rate (R s) and responses to soil temperature and mositure have not yet been fully investigated. In a semiarid region of the Loess Plateau in China, the R s of moss-dominated biocrusts was continuously (104 days) measured in summer through an automated soil respiration system, and their relationships with soil temperature and moisture at 2, 5, and 10 cm depths were intensively analyzed. The results showed the biocrusts had 115% higher (t = −3.82, P < 0.001) R s during day and 44% higher (t = −10.22, P < 0.001) R s during night as compared with the underlying soil; they averagely increased R s by 81% (2.52 vs. 1.39 μmol m−2 s−1) across day and night. More specifically, the R s of biocrusts ranged from 0.33 to 6.33 μmol m−2 s−1 in wet conditions (soil moisture ≥ 0.15 cm3 cm−3) and 0.27 to 2.83 μmol m−2 s−1 in dry conditions (soil moisture = 0.05 cm3 cm−3), with a daily mean of 2.11 μmol m−2 s−1. Particularly, in wet conditions the R s of biocrusts had positive responses to increasing temperature, and their relationship was well fitted with an exponential function (R 2 ≥ 0.44; P < 0.001), with a Q 10 value ranging between 1.73 and 2.08. Similarly, the R s of biocrusts was positively correlated with soil moisture, but their relationship was not well fitted with the quadratic function (R 2 ≤ 0.22). A model based on the soil moisture and temperature at 2 cm depth performed much better (R 2 = 0.53; P < 0.001) with R s than that based on the soil moisture and temperature at 5 or 10 cm depth or even air temperature. In conclusion, moss biocrusts made a significant contribution to soil respiration in semiarid ecosystem, firstly (and directly) due to the rich and diversified microbial communities in biocrust layer and secondly (and indirectly) due to the biocrust effects on soil temperature and moisture regimes. The temperature and moisture at 2 cm depth (biocrust layer) should be employed with a higher priority in simulating R s of biocrusted surfaces, rather than the commonly used soil depth (5 cm) in estimating R s of the ordinary soil without biocrusts. Unlabelled Image • Biocrusts increased respiration rate (R s) by 81% as compared with underlying soil. • R s of biocrusts ranged from 0.05 to 9.50 μmol m−2 s−1 with a mean of 2.11 in summer. • R s of biocrusts was highly dependent on moisture and temperature (Q 10 = 1.73–2.08). • Soil temperature and moisture at 2 cm depth are capable of estimating R s of biocrusts. [ABSTRACT FROM AUTHOR]