Root zone soil moisture(RZSM)is a critical parameter for drought monitoring,agriculture,and vegetation growth.In situ measurements of RZSM are scarce,and therefore,RZSM products are derived mainly through modeling app...Root zone soil moisture(RZSM)is a critical parameter for drought monitoring,agriculture,and vegetation growth.In situ measurements of RZSM are scarce,and therefore,RZSM products are derived mainly through modeling approaches.This study evaluated seven RZSM products,including ERA5,MERRA2,CFSR,SMAP level 4,GLDASNOAH2.1,GLDAS-Catchment2.2,and SMOS CATDS Level 4,using 1153 ground sites across China.The evaluations aimed to address which products perform better,how well they capture the seasonal variations,and how they perform under different land surface and climate conditions.Results showed that MERRA2 and NOAH had the best performance,with MERRA2 having a better ability to capture surplus and deficit soil moisture conditions.The study also revealed that precipitation forcing plays a vital role in improving RZSM simulations.Conversely,ERA5 overestimates RZSM,and SMOS exhibits a dry bias.From the time series variability,all datasets except SMOS can capture the temporal dynamics of RZSM well.Moreover,the accuracy of the RZSM products varies significantly in tropical climate zones.This study provides crucial insights for improving land surface and hydrological models in estimating RZSM,which will help in drought management and agriculture production.展开更多
Soil erosion and bank degradation is a major post-dam concern regarding the riparian zone of the Three Gorges Reservoir. The development and succession of vegetation is a main countermeasure,especially to enhance bank...Soil erosion and bank degradation is a major post-dam concern regarding the riparian zone of the Three Gorges Reservoir. The development and succession of vegetation is a main countermeasure,especially to enhance bank stability and mitigate soil erosion by the root system. In this study, the roots of four prevailing grass species, namely, Cynodon dactylon, Hemarthria altissima, Hemarthria compressa, and Paspalum paspaloides, in the riparian zone were investigated in relation to additional soil cohesion. Roots were sampled using a single root auger. Root length density（RLD） and root area ratio（RAR） were measured by using the Win RHIZO image analysis system. Root tensile strength（TR） was performed using a manualdynamometer, and the soil reinforcement caused by the roots was estimated using the simple Wu＇s perpendicular model. Results showed that RLD values of the studied species ranged from 0.24 cm/cm3 to20.89 cm/cm3 at different soil layers, and RLD were significantly greater at 0–10 cm depth in comparison to the deeper soil layers（＆gt;10 cm）. RAR measurements revealed that on average 0.21% of the reference soil area was occupied by grass roots for all the investigated species. The measured root tensile strength was the highest for P. paspaloides（62.26MPa） followed by C. dactylon（51.49 MPa）, H.compressa（50.66 MPa）, and H. altissima（48.81MPa）. Nevertheless, the estimated maximum root reinforcement in this investigation was 22.5 k Pa for H.altissima followed by H. compressa（21.1 k Pa）, P.paspaloides（19.5 k Pa）, and C. dactylon（15.4 k Pa） at0–5 cm depth soil layer. The root cohesion values estimated for all species were generally distributed at the 0–10 cm depth and decreased with the increment of soil depth. The higher root cohesion associated with H. altissima and H. compressa implies their suitability for revegetation purposes to strengthen the shallow soil in the riparian zone of the Three Gorges Reservoir. Although the soil reinforcement induced by roots is only assessed from indirect indicators, the present results still useful for species selection in the framework of implementing and future vegetation recovery actions in the riparian zone of the Three Gorges Reservoir and similar areas in the Yangtze River Basin.展开更多
Soil moisture is critical for vegetation growth in deserts.However,detailed data regarding the soil moisture distribution in space and time in the Gurbantunggut Desert of China have not yet been reported.In this study...Soil moisture is critical for vegetation growth in deserts.However,detailed data regarding the soil moisture distribution in space and time in the Gurbantunggut Desert of China have not yet been reported.In this study,we conducted a series of in situ observation experiments in a fixed sand dune at the southern edge of the Gurbantunggut Desert from February 2014 to October 2016,to explore the spatio-temporal variation of soil moisture content,investigate the impact of Haloxylon ammodendron(C.A.Mey.)Bungeon soil moisture content in its root zone,and examine the factors influencing the soil moisture spatial pattern.One-way analysis of variance,least significant difference tests and correlation analysis were used to analyze the data.The results revealed that the soil moisture content exhibited annual periodicity and the temporal variation of soil moisture content throughout a year could be divided into three periods,namely,a moisturegaining period,a moisture-losing period and a moisture-stable period.According to the temporal and spatial variability,the 0–400 cm soil profile could be divided into two layers:an active layer with moderate variability and a stable layer with weak variability.The temporal variability was larger than the spatial variability in the active layer,and the mean profile soil moisture content at different slope positions displayed the trend of decreasing with increasing relative height and mainly followed the order of interdune area>west and east slopes>slope top.The mean profile soil moisture content in the root zone of dead H.ammodendron individuals was significantly higher than that in the root zones of adult and young individuals,while the soil moisture content in the root zone of adult individuals was slightly higher than that in the root zone of young individuals with no significant difference.The spatial pattern of soil moisture was attributable to the combined effects of snowfall,vegetation and soil texture,whereas the effects of rainfall and evaporation were not significant.The findings may offer a foundation for the management of sandy soil moisture and vegetation restoration in arid areas.展开更多
Water scarcity is often a major limiting factor in cotton (Gossypium hirsutum L.) production, and sustaining productivity and profitability with limited water is a major challenge for the cotton industry. A good under...Water scarcity is often a major limiting factor in cotton (Gossypium hirsutum L.) production, and sustaining productivity and profitability with limited water is a major challenge for the cotton industry. A good understanding of the magnitude, timing and spatial distribution of cotton soil water extraction is important for proper irrigation management, and for development of accurate crop models and decision support systems. The overall objective of this study was to evaluate the water extraction distribution of cotton under different irrigation regimes. Specific objectives were to quantify: 1) the depth of soil water extraction as a function of time, 2) the percent of seasonal water extraction from each soil depth, and 3) the relationship between depth of soil water extraction and canopy height. To meet these specific objectives, daily and seasonal cotton soil water extraction were determined from continuous records of water content in the soil profile measured from four irrigation treatments during a field experiment. We found that cotton extracted soil water from as deep as 150 cm, but the percent of seasonal extraction sharply decreased with soil depth. The top 50 cm soil layer accounted for 75% of the seasonal extraction and the top 80 cm, for 90%. We also found that from 32 days after sowing (DAS) to 100 DAS, the depth of soil water extraction increased linearly at a rate of 1.89 cm·day-1 or 2.36 times the increase in crop canopy height. These findings suggest that cotton producers should manage irrigations to maintain adequate moisture in the top 80 cm of the soil profile rather than relying on moisture stored deeper in the profile.展开更多
基金financially supported by the National Key R&D Program of China(grant number 2022YFC3002804)the National Natural Science Foundation of China(Grant Nos.42071327 and 41971032)the western Ordos drought monitoring project.
文摘Root zone soil moisture(RZSM)is a critical parameter for drought monitoring,agriculture,and vegetation growth.In situ measurements of RZSM are scarce,and therefore,RZSM products are derived mainly through modeling approaches.This study evaluated seven RZSM products,including ERA5,MERRA2,CFSR,SMAP level 4,GLDASNOAH2.1,GLDAS-Catchment2.2,and SMOS CATDS Level 4,using 1153 ground sites across China.The evaluations aimed to address which products perform better,how well they capture the seasonal variations,and how they perform under different land surface and climate conditions.Results showed that MERRA2 and NOAH had the best performance,with MERRA2 having a better ability to capture surplus and deficit soil moisture conditions.The study also revealed that precipitation forcing plays a vital role in improving RZSM simulations.Conversely,ERA5 overestimates RZSM,and SMOS exhibits a dry bias.From the time series variability,all datasets except SMOS can capture the temporal dynamics of RZSM well.Moreover,the accuracy of the RZSM products varies significantly in tropical climate zones.This study provides crucial insights for improving land surface and hydrological models in estimating RZSM,which will help in drought management and agriculture production.
基金Financial support for this study was jointly provided by the National Natural Science Foundation of China (Grant No. 41201272)the Chinese Academy of Sciences Action-plan for West Development (Grant No. KZCX2-XB3-09)the Chinese Academy of Science (Light of West China Program)
文摘Soil erosion and bank degradation is a major post-dam concern regarding the riparian zone of the Three Gorges Reservoir. The development and succession of vegetation is a main countermeasure,especially to enhance bank stability and mitigate soil erosion by the root system. In this study, the roots of four prevailing grass species, namely, Cynodon dactylon, Hemarthria altissima, Hemarthria compressa, and Paspalum paspaloides, in the riparian zone were investigated in relation to additional soil cohesion. Roots were sampled using a single root auger. Root length density（RLD） and root area ratio（RAR） were measured by using the Win RHIZO image analysis system. Root tensile strength（TR） was performed using a manualdynamometer, and the soil reinforcement caused by the roots was estimated using the simple Wu＇s perpendicular model. Results showed that RLD values of the studied species ranged from 0.24 cm/cm3 to20.89 cm/cm3 at different soil layers, and RLD were significantly greater at 0–10 cm depth in comparison to the deeper soil layers（＆gt;10 cm）. RAR measurements revealed that on average 0.21% of the reference soil area was occupied by grass roots for all the investigated species. The measured root tensile strength was the highest for P. paspaloides（62.26MPa） followed by C. dactylon（51.49 MPa）, H.compressa（50.66 MPa）, and H. altissima（48.81MPa）. Nevertheless, the estimated maximum root reinforcement in this investigation was 22.5 k Pa for H.altissima followed by H. compressa（21.1 k Pa）, P.paspaloides（19.5 k Pa）, and C. dactylon（15.4 k Pa） at0–5 cm depth soil layer. The root cohesion values estimated for all species were generally distributed at the 0–10 cm depth and decreased with the increment of soil depth. The higher root cohesion associated with H. altissima and H. compressa implies their suitability for revegetation purposes to strengthen the shallow soil in the riparian zone of the Three Gorges Reservoir. Although the soil reinforcement induced by roots is only assessed from indirect indicators, the present results still useful for species selection in the framework of implementing and future vegetation recovery actions in the riparian zone of the Three Gorges Reservoir and similar areas in the Yangtze River Basin.
基金supported by the National Natural Science Foundation of China (41671032, U1303181, U1806215)the National Key Research and Development Programs of China (2016YFC0501401, 2016YFD0200303, 2016YFC0501309, 2016YFC0501201)+1 种基金the National Basic Research Program of China (2013CB429902)the Key Deployment Project of the Chinese Academy of Sciences (KFZD-SW-112-03-02)
文摘Soil moisture is critical for vegetation growth in deserts.However,detailed data regarding the soil moisture distribution in space and time in the Gurbantunggut Desert of China have not yet been reported.In this study,we conducted a series of in situ observation experiments in a fixed sand dune at the southern edge of the Gurbantunggut Desert from February 2014 to October 2016,to explore the spatio-temporal variation of soil moisture content,investigate the impact of Haloxylon ammodendron(C.A.Mey.)Bungeon soil moisture content in its root zone,and examine the factors influencing the soil moisture spatial pattern.One-way analysis of variance,least significant difference tests and correlation analysis were used to analyze the data.The results revealed that the soil moisture content exhibited annual periodicity and the temporal variation of soil moisture content throughout a year could be divided into three periods,namely,a moisturegaining period,a moisture-losing period and a moisture-stable period.According to the temporal and spatial variability,the 0–400 cm soil profile could be divided into two layers:an active layer with moderate variability and a stable layer with weak variability.The temporal variability was larger than the spatial variability in the active layer,and the mean profile soil moisture content at different slope positions displayed the trend of decreasing with increasing relative height and mainly followed the order of interdune area>west and east slopes>slope top.The mean profile soil moisture content in the root zone of dead H.ammodendron individuals was significantly higher than that in the root zones of adult and young individuals,while the soil moisture content in the root zone of adult individuals was slightly higher than that in the root zone of young individuals with no significant difference.The spatial pattern of soil moisture was attributable to the combined effects of snowfall,vegetation and soil texture,whereas the effects of rainfall and evaporation were not significant.The findings may offer a foundation for the management of sandy soil moisture and vegetation restoration in arid areas.
文摘Water scarcity is often a major limiting factor in cotton (Gossypium hirsutum L.) production, and sustaining productivity and profitability with limited water is a major challenge for the cotton industry. A good understanding of the magnitude, timing and spatial distribution of cotton soil water extraction is important for proper irrigation management, and for development of accurate crop models and decision support systems. The overall objective of this study was to evaluate the water extraction distribution of cotton under different irrigation regimes. Specific objectives were to quantify: 1) the depth of soil water extraction as a function of time, 2) the percent of seasonal water extraction from each soil depth, and 3) the relationship between depth of soil water extraction and canopy height. To meet these specific objectives, daily and seasonal cotton soil water extraction were determined from continuous records of water content in the soil profile measured from four irrigation treatments during a field experiment. We found that cotton extracted soil water from as deep as 150 cm, but the percent of seasonal extraction sharply decreased with soil depth. The top 50 cm soil layer accounted for 75% of the seasonal extraction and the top 80 cm, for 90%. We also found that from 32 days after sowing (DAS) to 100 DAS, the depth of soil water extraction increased linearly at a rate of 1.89 cm·day-1 or 2.36 times the increase in crop canopy height. These findings suggest that cotton producers should manage irrigations to maintain adequate moisture in the top 80 cm of the soil profile rather than relying on moisture stored deeper in the profile.
