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The middle and upper reaches of the Han river are involved in the South-to-North Water Diversion Project, and the change of runoff affects the amount of adjustable water. In order to investigate the change of runoff in the middle and upper reaches of the Han river basin under climate change, based on the SWAT (Soil & Water Assessment Tool, SWAT) model, we have developed a new model, which is based on the Soil & Water Assessment Tool (SWAT), five global climate models and four Shared Socioeconomic Pathways (SSPs) scenarios are simulated under future climate scenarios (2021-2021) in the upper and middle reaches of the Han river Basin. Based on the SWAT (Soil & Water Assessment Tool) model, we applied five global climate models and four Shared Socioeconomic Pathways (SSPs) scenarios from the latest 6th Coupled Model Intercomparison Project Phase 6 (CMIP6), and simulated the temporal and spatial changes of runoff in the middle and upper reaches of the Han river basin in the near term (2021-2040), middle term (2041-2060), and long term (2061-2080) under the future changes of climate scenarios. The results showed that: (1) compared with the baseline period (2000-2014), rainfall and temperature increased significantly under all model scenarios, and under the "two-carbon" scenario, the increase in temperature and precipitation was smaller than that of the high-carbon scenario, and the watershed was developing towards wetting and warming. (2) The future runoff in the study area showed a significant increasing trend under the SSP2-4.5 and SSP5-8.5 pathways, relative to the historical period, and the runoff decreased in some years in the upstream near, middle and far periods. 8.5 pathways show a significant increasing trend, relative to the historical period, and runoff decreases in some years in the upstream near-, mid-, and far-periods. (3) Intra-annual distribution was more even, and runoff increased during the dry period from November to June of the following year, which improved the drought-resistant capacity of the basin. (4) Spatially, the increase in runoff was dominated by the central and eastern parts of the country, and runoff decreased under the high-carbon scenario in the near future, but showed an increasing trend in the long term, with an increasing trend in future runoff at the source area of the South-to-North Water Diversion Project. [ABSTRACT FROM AUTHOR]

Methane is a powerful greenhouse gas with a global warming potential 34 times greater than carbon dioxide. The emitter flow rate, as a fundamental parameter of drip irrigation systems, controls the horizontal and vertical distribution of soil water, resulting in distinct soil wetting patterns. At the same time, the soil wetting pattern influences soil temperature, aeration, and the movement and transformation of nitrogen, all of which affect soil microbial activity and consequently methane uptake. Understanding the role of the emitter flow rate of drip irrigation in regulating the diffusion, oxidation and surface uptake of methane in the soil is crucial to increasing the potential of methane uptake in drip-irrigated croplands to mitigate global climate change. In this study, a two-year field experiment combining static chamber gas chromatography with the concentration gradient method was conducted in 2021 and 2022 in Wuwei, Gansu of China. Three drip irrigation flow rates (F1: 1.3 L/h, F2: 2.0 L/h, F3: 3.0 L/h) were set to investigate the characteristics of methane diffusion, absorption, and surface net uptake in different soil layers and their responses to soil environmental factors. The results showed that soil methane concentrations decreased with increasing soil depth. There was no significant difference in the average surface methane concentration between treatments, and the average methane concentration in the 0-60 cm soil layer showed F3 > F2 > F1. The value in the F3 treatment was significantly higher than F1 by 11.9% in the 0-20 cm soil layer. The average methane concentration of F3 treatment was significantly higher than that of F2 and F1 treatments by 8.5%, 26.8% (>20-40 cm soil layer) and 10.2%, 19.1% (>40-60 cm soil layer), respectively. Average surface methane uptake fluxes were 85.4, 80.2 and 78.5 μg g/(m−2 h) for F1, F2 and F3 treatments, respectively, and were significantly increased by 6.4% and 8.9% for F1 treatment compared to F2 and F3 treatments (P < 0.05). The average methane diffusion flux in the 0-20 cm and >20-40 cm soil layers was significantly higher in the F1 treatment than in the F2 and F3 treatments, while the average methane diffusion flux in the 40-60 cm soil layer was significantly lower in the F1 treatment than in the F2 and F3 treatments. The cumulative methane uptake in the F1 treatment increased by 5.9%-13.8% compared to the F2 and F3 treatments, respectively. Methane uptake primarily occurred in the 0-20 cm soil layer, accounting for 72.1%-82.5% of the total uptake. Emitter flow rate had significant effects on soil water-filled pore space, soil oxygen concentration and nitrogen content (P < 0.05). Among various soil environmental factors, soil water-filled pore space had the most significant influence on soil methane concentration. Cumulative surface methane uptake fluxes were significantly and positively correlated with cumulative methane diffusion fluxes (downward) in the 0-20 and >20-40 cm soil layers, and cumulative methane diffusion fluxes in the >20-40 cm soil layer were significantly positively correlated with the values in the 0-20 cm soil layer. Cumulative methane transformation fluxes in the 0-20 cm soil layer were significantly and positively correlated with cumulative methane diffusion fluxes in the 0-20 cm soil layer, and cumulative transformation fluxes in the >20-40 cm soil layer were significantly and positively correlated with cumulative diffusion fluxes in the 0-20 and >20- 40 cm soil layers. The lower values of soil water-filled pore space in the surface soil of the F1 treatment facilitated the entry of methane from the atmosphere into the soil and its diffusion into deeper layers, thereby increasing methane uptake. In addition, the potato yield and irrigation water use efficiency under F1 treatment were relatively highest. Soil methane uptake, diffusion, and transformation were influenced by soil water distribution. Therefore, it should be considered to regulate the soil wetting area through an appropriate emitter flow rate to enhance the soil methane sink capacity and potato yield in the drip irrigation management. The results can provide a valuable information for soil carbon sinks and potato yield improvement in drip irrigated soils. [ABSTRACT FROM AUTHOR]

Copyright of Arid Zone Research / Ganhanqu Yanjiu is the property of Arid Zone Research Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Arid Land Geography is the property of Chinese Academy of Sciences, Xinjiang Institute of Ecology & Geography and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

[Objective] The aims of this study are to analyze the spatiotemporal differentiation and variation of soil moisture in the Mongolian Plateau, and to quantify the influence of key driving factors, so as to provide a theoretical basis for regional ecological restoration and sustainable ecosystem development. [Methods] Based on the ERA5 soil moisture data, the spatial differentiation and changes of soil moisture at the depth of 0—289 cm in the Mongolian Plateau from 2000 to 2020 were revealed, and the impacts of different environmental factors such as meteorology, normalized difference vegetation index (NDVI), terrestrial water storage anomaly (TWSA), soil texture, and topography were further quantified. [Results] (1) From 2000 to 2020, soil moisture in the Mongolian Plateau displayed a distribution characteristic of high level in the northeast and low level in the southwest. From shallow to deep layers, the soil moisture presented a change trend of no significant increase (0—28 cm), no significant decrease (28—100 cm) and significant decrease (100—289 cm) . (2) There were 58.5%, 76.7%, 91.3%, and 98.8% of the regions with Hurst index greater than 0.5. The change trend of soil moisture in most regions in the future will be the same as in the past. The drying of soil moisture in the northwestern Mongolian Plateau and central Inner Mongolia may further aggravate. (3) Temperature, TWSA, precipitation, and NDVI were the dominant environmental factors affecting the spatial distribution of soil moisture. Most of the factor interactions showed a bi-factor enhancement effect, and the spatial differentiation of soil moisture in the Mongolian Plateau was the result of the joint action of multiple factors. (4) The changes in surface and subsurface soil moisture were mainly positively affected by precipitation, and the dominant control areas accounted for 98.7% and 94.8% of the total vegetated area of the plateau, respectively. The main control areas of precipitation and TWSA on soil moisture at the layer of 28—100 cm concentrated in areas covered by forestland and grassland, with the dominant area accounting for 38.7% and 38.8%, respectively. The decrease in TWSA was the main driving force leading to the drying of soil moisture in the layer of 100—289 cm, with the main dominant area accounting for 58.6%. The increase in water consumption by vegetation and the increase in temperature dominantly controlled the changes in soil moisture in layer of 100—289 cm in 16.2% and 14.8% of the plateau, respectively. [Conclusion] The spatial and temporal differentiation and change patterns of soil moisture are obvious, and the main driving forces of soil moisture at each depth are different. This is of great significance to the ecological restoration of the Mongolian Plateau and the sustainable development of the ecosystem. In the future, the impact of human activities on it should be analyzed in depth. [ABSTRACT FROM AUTHOR]

Under the background of climate change, vegetation restoration in arid area ecosystem is faced with great challenges, which has important research value and is also an important research direction of ecology. In this paper, CiteSpace software was used to carry out data mining and econometric analysis on the research progress of vegetation restoration in arid area ecosystem. Besides, the number of papers published under this topic, the trend of change, the main research strength and the development path of the research topic were presented. The study found that (1) the overall volume of papers showed a significant growing tendency on the whole, and generally experienced three growth stages of slow, steady and rapid growth. The research hotspots were different at different stages. At present, the research mainly focuses on clustering topics such as “soil moisture”, “abandoned farmland”, “biological soil skinning” and “layered soil”, and the cross-study of engineering, hydrology, geosciology and other related disciplines is increasing day by day. (2) China, the United States and Spain were the countries with the largest number of publications, and the Chinese Academy of Sciences was the research institution with the largest number of publications. Li Xinrong and others constituted the core group of authors under the research topic. (3) The strategies of vegetation restoration in response to drought stress and the changing rules of the structure and function of different restored ecosystems under the background of climate change may be the research hotspots of vegetation restoration in arid areas in the near future. [ABSTRACT FROM AUTHOR]

Plant species in alpine swamp meadow which is a successional stage of dried alpine wetland, is sensitive to changes in soil water content, and thus it is important to understand the responses of common species of alpine swamp meadow to changed soil water condition. In order to determine the effects of different soil water content on plants of alpine swamp meadow, we transplanted 17 common species from an alpine swamp meadow to a manipulated environment located in Maqu county of Gansu Province, eastern Qinghai-Tibetan Plateau. These plants were then subjected to three soil moisture regimes: flooding (FD), control treatment (CK), and slightly drought (SD). The net photosynthesis （A）, stomatal conductance (g) and leaf dry mass per unit area (LMA) were measured for leaves from 6 plants each species per treatment. We calculated the difference of A, g and LMA between FD or SD and CK for each species, and the relationships between A and g or LMA was analyzed. Results are as follows. (1) The LMA of alpine swamp meadow common species was significantly affected by soil water condition, and there were different responses among different species. (2) Significant habitat-specific responses of gas exchange to water condition were found among the species. (3) There were significant correlations between A and g under both treatments, but it was not for A and LMA. As a conclusion, the common species of alpine swamp meadow was strongly influenced by soil water content, in additional; there was significant habitat-specific responses of the morphological traits or physiological taints to different soil water condition. Our findings suggested that the species composition of alpine swamp meadow was very sensitive to change in soil water condition. In the context of global climate change, which is predicted to alter the precipitation regime of alpine area, will be significantly influence the composition and structure of alpine swamp meadow community in the future. This should be considered carefully for protection and restoration of alpine grassland. [ABSTRACT FROM AUTHOR]

Copyright of Arid Zone Research / Ganhanqu Yanjiu is the property of Arid Zone Research Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Arid Zone Research / Ganhanqu Yanjiu is the property of Arid Zone Research Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Remote Sensing is the property of Editorial Office of Journal of Remote Sensing & Science Publishing Co. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Arid Zone Research / Ganhanqu Yanjiu is the property of Arid Zone Research Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Arid Zone Research / Ganhanqu Yanjiu is the property of Arid Zone Research Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Irrigation & Drainage is the property of Journal of Irrigation & Drainage Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Evapotranspiration (ET) is a key link in the hydrological and energy cycle in agricultural irrigation and water resource management. An accurate and quantitative estimation of regional ET is crucial to clarify the land-air interaction and global climate change. MOD16 model has been one of the most commonly-used remote sensing models to obtain the regional ET using the Penman-Monteith (P-M) equation. However, the MOD16 model cannot directly consider the soil moisture using the Relative Humidity (RH), Vapor Pressure Deficit (VPD), and Leaf Area Index (LAI), leading to some uncertainties in the ET estimation. In this study, an attempt was made to improve the MOD16 model using the normalized water index (NDWI) as an additional item of soil moisture. As such, the modified surface impedance of the MOD16 model (the improved model named MOD16-sm) was achieved to verify and apply in the arid oasis located in northwest China. Model validation included the comparative (between ET estimates and measurements) and error analyses. The comparative analyses between ET estimates and measurements showed that the scatter distribution of ET observations and estimates by the MOD16-sm model was very close to the 1:1 straight line. The accuracy of ET estimates acquired by the MOD16-sm model increased, with a higher Coefficient of Determination (R² ) of 0.77, a lower Root Mean Square Error (RMSE) of 0.8 mm/d, and a lower Mean Absolute Deviation (MAE) of 0.46 mm/d, while the accuracy of ET estimates obtained by the MOD16 model was low, with a lower R² of 0.64, a higher RMSE of 0.93 mm/d, and a higher MAE of 0.7 mm/d, indicating the convincible MOD16-sm model. Error analyses showed that the percentage error ranges of ET estimates by the two models were significantly different, and the maximum percentage error of ET estimates by the MOD16 model was higher than that by the MOD16-sm model, indicating the better performance of the MOD16-sm model on the ET estimates. The comparative analyses between ET estimates and measurements indicated that the MOD16-sm model corrected some overestimations of the MOD16 model, particularly with the better performance for the influence of soil moisture on ET estimations. The model application was conducted to analyze the spatial distribution of ET estimates, and the frequency distribution histograms on ET estimates. Correspondingly, the spatial distribution of ET estimates was closely related to the land use types, with the high vegetation cover regions (such as farmland, and woodland) in the high ET values, while the sparse vegetation cover areas (such as villages) showing the low ET values, which was in line with the objective facts. The ET frequency distribution demonstrated that the MOD16-sm model can be expected to serve as the heterogeneity of ET flux in the different vegetation cover areas. Therefore, it is feasible and reasonable for the improved MOD16 model by the Normalized Difference Water Index (NDWI) as an additional item of soil moisture. The finding can also provide a strong reference for the higher accuracy of regional ET estimations. [ABSTRACT FROM AUTHOR]

The Qinghai-Tibet Plateau (QTP), known as the “Asian Water Tower”, is extremely sensitive to climate change. Studying the impacts of permafrost degradation on evapotranspiration is conducive to improving the understanding of the response of hydrological processes and water balance to climate change in the QTP. Based on the Budyko-Fu hypothesis, a coupled hydrothermal model was constructed to account for the active layer deepening of the permafrost regions with a model parameterization scheme suitable for the QTP. The results show that the annual average evapotranspiration in the permafrost regions on the QTP is 275. 6 mm during 1982—2018 and shows a descending gradient from southeast to northwest. The overall evapotranspiration in the permafrost areas on the QTP increased significantly at a rate of 3. 57 mm / a (p < 0. 05). Deepening of the active layer causes increased evapotranspiration while ignoring the permafrost degradation would result in an underestimation of evapotranspiration by about 2. 2% . The effects of permafrost degradation on evapotranspiration exhibit a significant spatial heterogeneity. The lower the soil available water capacity and vegetation coverage are, the more sensitive the responses of evapotranspiration to permafrost degradation become. [ABSTRACT FROM AUTHOR]

Soil moisture has been one of the most important factors for crop and pasture growth, depending mainly on global climate change and the water cycle. It is very necessary to accurately monitor the soil moisture for the sustainable management of agriculture and livestock. In this study, a combined inversion of Multivariable Linear Regression (MLR) and Random Forest (RF) Soil moisture model was established to compare with the Inverse Distance Weighting (IDW) spatial interpolation of soil moisture using the Landsat 8 OLI multispectral imagery, surface biophysical properties, and topographic parameters. Field measurement of soil water content was also used to construct an empirical model before that. Two indicators were selected to evaluate the models using the Granger-Ramanathan (GR), including the coefficient of determination (R 2 ) and Root Mean Square Error (RMSE). The inversion of the spatial distribution of soil moisture was then determined using single and combined models. There was a significant correlation between the different biophysical/topographic parameters and the surface soil moisture. In the surface biophysical characteristics, the correlation between the surface temperature, vegetation index, building index, water body index, albedo, brightness, greenness and surface soil moisture were significant. The correlation between the elevation/slope of topographic parameters and the soil surface moisture were extremely significant. There were different sensitivities of biophysical/topographic parameters to the surface soil moisture. Among them, there was the most significant correlation between the surface temperature and surface soil moisture. The interpolation model presented a higher accuracy in April and lower in August. The MLR and RF models presented higher accuracy in August and lower in April. The reason was that the vegetation growth was received a significant effect on the surface temperature in the sand area in August, where the model as the main variable was more sensitive to the prediction of surface soil moisture. The R ² of the RF model was above 0.8 in August and April, which was better than the MLR and IDW model, respectively, whereas the RMSE was the smallest. The RMSE of the RF model was roughly comparable to that of the MLR model, and differed significantly from that of the IDW model, which was lower than those of the IDW model, respectively. The highest inversion accuracy was achieved by the combined model, in which the R ² was above 0.85 in August and April, with the small increase compared with the optimal single RF model. The surface temperature and elevation were the dominant factors to determine the soil moisture content in different months. The overall soil moisture content was low, containing less than 20% (more than 95% of the total area) in most areas. The spatial distribution of soil moisture was closely related to the topographic landscape type, with the higher soil moisture content on the high and steep slopes in the north and southeast areas, whereas, the lower soil moisture content in the flat areas in the north-central region [ABSTRACT FROM AUTHOR]

Copyright of Remote Sensing for Natural Resources is the property of Remote Sensing for Natural Resources Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The Qinghai-Tibet Plateau has been greatly sensitive to global climate change in recent years, particularly the change in water storage. However, the differences in multi-source data and calculation have caused great uncertainty in the accurate estimation of terrestrial water storage. Taking the Yarlung Zangbo River Basin located in the southeast of the Qinghai-Tibet Plateau as the study area, this study aims to investigate the spatio-temporal variation characteristics of terrestrial water storage change (TWSC). The performance evaluation of TWSC was conducted using the GRACE (Gravity Recovery and Climate Experiment) data from 2003 to 2017, combining with ERA5 (the fifth-generation reanalysis product of the European Centre for Medium-Range Weather Forecasts) data and GLDAS (Global Land Data Assimilation System) data. Four sets of TWSC were obtained using ERA5 data and GLDAS data from 2003 to 2017, where the terrestrial water balance (PER) and the summation (SS) were used to estimate TWSC, compared with TWSC derived from GRACE. It was found that TWSC estimated by the SS was more consistent than the PER in both temporal and spatial patterns with TWSC derived from GRACE, whereas, TWSC estimated by the SS using GLDAS was most consistent with the results from GRACE over the Yarlung Zangbo River Basin. A sensitivity analysis was carried out using GLDAS and the SS, in order to further investigate the influence of different components on the estimation of TWSC. It was found that SS (GLDAS) performed best for TWSC estimation over the Yarlung Zangbo River Basin, when only soil moisture and snow water equivalent were taken into consideration, with the basin average TWSC correlation coefficient of 0.53. Therefore, the SS calculated from the soil moisture and snow water equivalent was utilized to further explore the long-term temporal and spatial evolution of TWSC from 1948 to 2017 over the Yarlung Zangbo River Basin. TWSC showed a significantly increasing trend from 1948 to 2017. The wavelet analysis indicated that there was an abrupt change in TWSC around 2002 during 1948—2017. There was a significant increase before 2002 (slope=0.024 mm/month, P<0.01), and a significant decrease (slope=−0.397 mm/month, P<0.01) after 2002. The change trend of soil water content and snow water equivalent before and after 2002 is consistent with TWSC. Additional attribution analysis was performed on the abrupt change in TWSC before and after 2002. The contributions of changes in soil moisture and snow water equivalent to TWSC were 61% and 39% during 1948—2002, respectively, whereas, a much more significant domination of soil moisture was identified during 2003—2017. The contributions of changes in soil moisture and snow water equivalent to TWSC were 99% and 1%, respectively. Compared with the change in snow water equivalent, the change in soil moisture dominated the long-term variation of TWSC during 1948—2017. In terms of spatial distribution, TWSC showed a large spatial heterogeneity, mainly in the middle reaches with a high intensity of human activities and the Yarlung Zangbo River Basin with intensive glaciers. The finding can provide reliable data support to explore the spatio-temporal evolution of terrestrial water storage in data-scarce alpine regions. [ABSTRACT FROM AUTHOR]

Liming is the most widely used for the soil acidity, further to maintain soil pH that is optimal for crop growth. The variation in the soil pH is closely related to the soil organic carbon (SOC) mineralization, thereby to the global climate change. In addition, the moisture is also one of the most crucial environmental factors influencing the SOC mineralization via changing the SOC bioavailability and oxygen transport. In response to exogenous additives, the physicochemical and biochemical properties of soils are normally different with distinct parent materials. It is necessary to clarify the effects of liming and moisture on organic carbon mineralization of acidic soils. In the present study, the acidic paddy soils with two parent materials were used to evaluate the effects of dolomite addition and moisture on the SOC mineralization. Two types of soils were treated with and without dolomite addition under different soil moisture conditions, including 50%, 90%, and 130% of water holding capacity (WHC), and further incubated for 45 days. The results showed that the SOC mineralization rates of two soils were significantly affected by the dolomite addition. Nevertheless, there was no remarkable interaction effect between dolomite addition and moisture. The organic carbon mineralization of two soils was inhibited under a low soil moisture of 50% WHC, whereas, the combined effects of dolomite addition and moisture on the SOC mineralization varied with soil texture under a high soil moisture of 90% to 130% WHC. The amount of organic carbon mineralization from the soil with granite gneiss as parent material (brown red soil) under flooding condition (130% WHC) was higher than that under the moisture of 90% WHC, while the scenario was the opposite from the soil with the Quaternary red earth as parent material (red soil). Furthermore, only the former soil demonstrated a significant interaction effect of dolomite addition and moisture on the amount of SOC mineralization. The effects of dolomite addition, moisture, and their interaction were significant on the pH of two soils. After dolomite addition, the pH value of two soils increased with the increase in moisture content, where a target value (pH 6.5) was achieved under a low soil moisture condition (50% WHC). The effects of dolomite addition and moisture were significant on the DOC content of brown red soil, but their interaction was not significant. Moreover, only the effect of moisture on the DOC content of red soil was significant. The MBC contents of two soils increased significantly with the increase of moisture content, but the effects of dolomite addition and its interaction with moisture were not significant. In the path analysis, the DOC rather than MBC content of two soils was directly affected by the soil pH value. In addition, the fluxes of CO2 emission in the two soils were directly affected by the DOC rather than MBC content. The soil pH had no direct effect on the fluxes of CO2 emission in the two soils, indicating that the microbes played a major role in CO2 emissions. Therefore, both soil moisture and natural properties can be considered to evaluate the effect of dolomite application on SOC mineralization. The finding can provide a potential promising guidance and proposals for the rational application of dolomite additives in the agricultural production. [ABSTRACT FROM AUTHOR]

Soil respiration is the primary pathway for the global carbon cycle, but the response mechanism of soil respiration to global change and anthropogenic perturbation in semiarid grassland in the context of global change is still unclear. In this study, a field experiment was conducted to explore the effects of nitrogen (N) addition, anthropogenic perturbation, and their interactions on soil respiration throughout the growing season from May to September in 2017, in Horqin sandy land, northern China. In the field research, the nitrogen deposition included no nitrogen and nitrogen addition (10 g/(m²·a)), whereas, anthropogenic perturbation consisted of control, burning, and clipping activities. In soil respiration, the components and environmental factors, including soil temperature, soil moisture and soil microbial biomass carbon, were monitored in the whole plant growing season. The monitoring data was used to identify the effects of single factor, such as nitrogen deposition, burning and clipping, and their interaction on soil respiration, as well as the contributions of microbial and root respiration to soil respiration. The results showed that the soil respiration presented obvious seasonal dynamics, with the highest in July. Both soil temperature and soil moisture can regulate the seasonal variability pattern of soil respiration in the semiarid grassland, while nitrogen deposition, burning or clipping cannot alter that. The contribution ratios of microbial respiration to soil respiration were 64.68%, 54.99%, 69.20%, 57.88%, 50.50% and 57.66% under no nitrogen (N0)+control, N0+burning, N0+clipping, nitrogen addition (N10)+control, N10+burning and N10+clipping, respectively, indicating that the microbial respiration was main contributor to soil respiration in this semiarid grassland. The increased nitrogen deposition can remarkably enhance the root respiration by 42% (P<0.001), resulting in a significant increase in soil respiration by 17% (P<0.001). In the nitrogen addition, there was no significant effect on microbial respiration in this semiarid grassland, due to the nitrogen deposition cannot efficiently change soil microbial biomass. It infers that the decrease of soil carbon sequestration induced by nitrogen addition can mainly stem from the increase in the root respiration under the future global nitrogen deposition addition. The burning significantly increased the soil temperature, and thereby enhanced the root respiration by 25% (P<0.01), but it cannot efficiently increased the soil respiration, due to the reduction of microbial respiration that induced by the decrease of soil microbial biomass. Furthermore, the single nitrogen deposition enhanced the positive effect of single burning on soil respiration, indicating that both the nitrogen deposition and burning can be used to synergistically promote the soil respiration in this semiarid grassland. The clipping process significantly reduced the soil temperature by 7% (P<0.001), inducing the root respiration decreased by 20% (P<0.05). Moreover, the clipping significantly decreased the soil microbial biomass, and thus reduced the microbial respiration by 13% (P<0.001), thereby to effectively inhibit the soil respiration (16%, P<0.001). However, the nitrogen deposition and clipping had no significant interaction on the soil respiration. Different influences of nitrogen deposition, burning and clipping on soil respiration can provide the sound basis for the prediction of the soil carbon cycle, and for the scientific management of natural grassland in sandy grassland under the global climate change. [ABSTRACT FROM AUTHOR]

Understanding the mechanisms underlying drying-wetting cycles and their consequence for vegetation dynamic is important for sustainable eco-environmental development in alpine regions. We investigated these in this paper by taking the Yarlung Zangbo River (YZR) basin in southeast Qinghai-Tibet Plateau as an example. The standardized precipitation evapotranspiration index (SPEI) in the region was calculated using the global land data assimilation system (GLDAS) from 1982 to 2015 to represent the drying-wetting cycles. The spatiotemporal variation of the dry-wet cycles and the responsive vegetation dynamic was investigated using the remotely sensed NDVI (normal difference vegetation index) from GIMMS (global inventory modeling and mapping studies). The results showed that: 1) Spatiotemporal variation of both precipitation and surface air temperature calculated from GLDAS agreed well with the ground-truth data. 2) The spatiotemporal changes in the dry-wet cycles calculated from the SPEI from 1982 to 2015 showed that the YZR basin became increasingly wet from 1982-1999 but changed course in 2000 and has been become increasingly drier since. In particular, the arid areas showed a tendency of wetting whereas the humid areas tended to become drying. 3) The overall vegetation calculated from the NDVI had been in increase from 1982 to 2000 but changed course in 2000 and has been in decline since. In terms of spatial distribution, areas with higher NDVI value represented vegetation degradation, while areas with lower NDVI represented an improvement in vegetation. 4) Approximately 71.83% of the areas saw a positive correlation between the SPEI and NDVI, mainly in the middle and low reaches of the basin which have a high vegetation coverage. Areas showing negative correlation between SPEI and NDVI were small and not statistically significant. The high consistency between spatiotemporal variation of the NDVI and SPEI indicated that the drying-wetting cycles played an important role in vegetation dynamics. 5) The driving forces of the dry-wet cycles were precipitation, surface air temperature, potential evapotranspiration and soil water content, which were consistent with that estimated from SPEI. In addition, the SPEI showed that soil water content was the dominant factor impacting the drying-wetting in 92.17% of the areas in the region. Results of this study have important implications for evaluating water cycles and the associated vegetation dynamics in alpine regions. [ABSTRACT FROM AUTHOR]

Drought has become a problem that is universally faced by global terrestrial ecosystems. Northeast China is dominated by a temperate monsoon climate and located in an area sensitive to global climate changes, and one of the main impacts of climate changes in Northeast China is manifested as drought in growing seasons. The drought area has a gradual increase trend, and drought has become the main agro-meteorological disaster in this region which is also the main maize planting area in China. Drought normalization seriously restricts the stable development of maize production in Northeast China. So in this paper, we took spring maize in Liaoning Province as an example and made clear the drought variation characteristics in different growth stages by using the data of MODIS, FY-3A, relative soil moisture and growth stages and the methods of RS, GIS and statistical analysis. Then we analyzed the correlation between multi-time scale remote sensing indexes and relative soil moisture in different soil depth, and established the remote sensing monitoring index set and models of relative soil moisture for each growth stage and soil depth. The accuracy of the monitoring models was verified and the application research of monitoring the drought of spring maize in Liaoning Province was studied. The results showed that: From 1993 to 2012, drought occurred in each growth stage of spring maize in Liaoning Province and the highly frequent drought occurred in the period from 1999 to 2002. The drought grade in each year was mainly light drought, and the drought was the most serious at milk stage, followed by heading stage. There was no significant correlation between the monitoring indexes and relative soil moisture at sowing and emergence stage, but there was a significant or extremely significant correlation between them at three-leaf and maturity stage. The monitoring index LSWI (land surface water index) had a strong ability to monitor relative soil moisture, followed by WI (water index). Multi-index coordination could improve the monitoring ability of relative soil moisture by remote sensing means, and the monitoring ability at 10-day scale was generally higher than that at 5-day scale and 20-day scale. Based on the monitoring models of soil relative humidity, the drought condition of partial growth stages and soil depth from 2001 to 2004 was monitored. The overall monitoring accuracy was 73.32%, in which the monitoring accuracy of jointing and three-leaf stage was more than 85%. The dynamic monitoring of drought grades in different growth stages in 2000 was realized. The monitoring results were consistent with the agro-meteorological observation records in terms of the growth stages and space. This study would be very significant to improve the capacity of disaster prevention and mitigation by monitoring spring maize accurately and synchronously on a large range. [ABSTRACT FROM AUTHOR]

The Loess Plateau is the main rain-fed agricultural area in western China, and water shortage is a critical factor restricting vegetation establishment and growth in this region. Under the influence of global climate change in recent years, significant changes have taken place in climate characteristics of the Loess Plateau, which will have a far-reaching impact on evaporation and transpiration under different vegetation conditions. Therefore, there is needed to make a in-depth research on the response of evaporation and transpiration to climate change for typical afforestation tree species, which has remarkable theoretical and practical significance in providing useful indications for tree species selection, water use efficiency improvement and ecosystem restoration. In order to evaluate the effects and mechanism of climate change on evaporation and transpiration of typical artificial afforestation tree species, a field experiment was carried out in the growing season of 2015－ 2016 (April 15th-October15th) at Nanxiaohegou basin (35°41′-35°44′N,107°30′-107°37′E), a typical small basin in gully region of the Loess Plateau selected by the Yellow River Water Conservancy Commission of China. In three sample plots of Robinia pseudoacacia, Platycladus orientalis and Pinus tabulaeformis, soil physical parameters of three soil depth (0-40 cm, >40-100 and >100-200 cm) and the distribution of root density were measured, and soil moisture content, leaf area index, evaporation, precipitation and meteorology data were observed during the study period, from which simulation models of transpiration and evaporation in three experimental plots were established using Hydrus-1D software. The uncertainty of models parameters were analyzed through the Morris method, and the results showed that parameters of pore size distribution (40–100 cm) (n2), saturated water content (40-100cm) (θs2), field water capacity (θf), optimum threshold for root water absorption (h1), lower threshold for root water absorption (h2), soil water potential for permanent wilting (h3), extinction coefficient (μ), and parameter of vegetation interception model (a) had a great influence on transpiration, and the parameters related to the physiological characteristics of vegetation (h1, h2, h3, μ, and a) were the important reasons for the differences in transpiration of three tree species. The measured soil moisture content and evaporation data from 2015 were used to calibrate the model, and the data from 2016 were used to validate the model. Nash-suttcliffe efficiency coefficients were all above 0.700. The calibrated models were used to simulate evaporation and transpiration process under different presupposition scenarios derived from related research on climate characteristics of the study area, and the results showed that: 1) The effects of climate change in the future and different hydrological years on Robinia pseudopodia transpiration were greater than that in evaporation, while the opposite was true for Platycladus orientalis and Pinus tabuliformis. 2) Under all climate scenarios, the amount of transpiration for above tree species were distributed in 128.8-282.6, 99.3-200.3 and 140.5-220.5 mm, respectively, while the amount of evaporation were distributed in 94.6-135.4, 116.5-187.3 and 123.8-212.5 mm, respectively, and the transpiration and evaporation were both shown in the following aspect: the wet year > the normal year > the dry year. 3) As for transpiration, the response degree of three tree species to the climate characteristics of the future and different hydrological years was: Robinia pseudoacacia > Platycladus orientalis > Pinus tabuliformis, when it came to the evaporation, it was just the opposite. 4) In the same period of the future climate scenarios, the amount of transpiration in Robinia pseudoacacia plot was the largest among all tree species in wet and normal year, while in the dry year, the tree species with largest amount of transpiration was Pinus tabulaeformis. 5) The influence of precipitation on the transpiration and evaporation in growing season was stronger than that of temperature, and regression analysis indicated that the precipitation in growing season had a very significant linear function (P<0.01) with transpiration and evaporation for all 3 tree species. This study may provide valuable information for rational management of artificial afforestation tree species and restoration of the local ecological environment. [ABSTRACT FROM AUTHOR]

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