| 1. |
- Zhang, Wenxin, et al.
(författare)
-
Convergence and divergence emerging in climatic controls of polynomial trends for northern ecosystem productivity over 2000–2018
- 2023
-
Ingår i: Science of the Total Environment. - : Elsevier BV. - 1879-1026 .- 0048-9697.
-
Tidskriftsartikel (refereegranskat)abstract
- Southwest China has been the largest terrestrial carbon sink in China over the past 30 years, but has recently experienced a succession of droughts caused by high precipitation variability, potentially threatening vegetation productivity in the region. Yet, the impact of precipitation anomalies on the vegetation primary productivity is poorly known. We used an asymmetry index (AI) to explore possible asymmetric productivity responses to precipitation anomalies in Southwest China from 2003 to 2018, using a precipitation dataset, combined with gross primary productivity (GPP), net primary productivity (NPP), and vegetation optical depth (VOD) products. Our results indicate that the vegetation primary productivity of Southwest China shows a negative asymmetry, suggesting that the increase of vegetation primary productivity during wet years exceeds the decrease during dry years. However, this negative asymmetry of vegetation primary productivity was shifted towards a positive asymmetry during the period of analysis, suggesting that the resistance of vegetation to drought, has increased with the rise in the occurrence of drought events. Among the different biomes, grassland vegetation primary productivity had the highest sensitivity to precipitation anomalies, indicating that grasslands are more flexible than other biomes and able to adjust primary productivity in response to precipitation anomalies. Furthermore, our results showed that the asymmetry of vegetation primary productivity was influenced by the effects of temperature, precipitation, solar radiation, and anthropogenic and topographic factors. These findings improve our understanding of the response of vegetation primary productivity to climate change over Southwest China.
|
|
| 2. |
- Tan, Xiao, et al.
(författare)
-
Design of a new TDR probe to measure water content and electrical conductivity in highly saline soils
- 2018
-
Ingår i: Journal of Soils and Sediments. - : Springer Science and Business Media LLC. - 1439-0108 .- 1614-7480. ; 18:3, s. 1087-1099
-
Tidskriftsartikel (refereegranskat)abstract
- Purpose: The inappropriate irrigation is accelerating the soil salinization in western irrigation districts of China. The amelioration of salinized land must be based on large amount of water content and salinity data. Plastic coated TDR has been designed to measure water content accurately in highly saline soil, but the soil bulk electrical conductivity cannot be measured due to the coated materials. In order to measure the volumetric water content and bulk electrical conductivity in highly saline soils at the same time, a parallel three-wire TDR probe with central rod coated which was used to measure water content and a triangle three-wire TDR probe which was used to measure electrical conductivity were integrated in one probe with four rods and one slide switch. Materials and methods: The influence of angle in triangle three-wire TDR probe and the non-working rod on water content or electrical conductivity measurement were fully discussed through HFSS simulation and NaCl solution test. In the soil column experiment, four levels of salinity, 0.2, 0.4, 0.6, and 1.0% were set, the soil water content decreased from 30% in mass through the evaporation and measured by TDR and electronic balance. Then the probe was calibrated by model of Topp and Evett with these data. Results and discussion: The results show that probe has the largest EPA (polarization degree index) in angle from 97° to 138°; the non-working rod will enhance the EPA during this angle range and the four-wire probe with angle of 120° is optimal; the PVC is a better insulated material which can improve the effective salinity scope; the Evett model could improve the water content measurement greatly especially in soil with higher salinity. Conclusions: This new four-wire insulated probe can be applied as a beneficial use to monitor the moisture and electrical conductivity in highly saline soils.
|
|
| 3. |
- Wu, Mousong, et al.
(författare)
-
Coupled water transport and heat flux in seasonally frozen soils : uncertainties identification in multi-site calibration
- 2020
-
Ingår i: Environmental Earth Sciences. - : Springer Nature. - 1866-6280 .- 1866-6299. ; 79:23
-
Tidskriftsartikel (refereegranskat)abstract
- The modeling of seasonally frozen soils is significant for understanding the hydrological process in cold regions. The water and heat transports of two seasonally frozen sites in northern China were simulated with the process-oriented CoupModel, and a more efficient Monte Carlo based method was employed to identify the uncertainties in multi-site calibration. Results showed that water and heat measured at different sites could be explained by 15 merged parameters includingFreezepoint FWi (d(1)), EquilAdjustPsi (psi(eg)), AlbedoKExp (ka), RoughLBareSoilMom (z0M) etc. with common ranges to some extent and three parameters MinimumCondValue (k(min,uc)), WindLessExchangeSoil (r(a,max)(-1)), and SThermalCondCoef (s(k)) related to soil hydraulic conductivity, surface aerodynamic resistance and snow thermal conductivity respectively were identified to be site-dependent with site-specific ranges. The promotion in performance indices of interest variables indicated that the proposed systematic method had the potential to improve the multi-site simulation of heat and water in frozen soils based on CoupModel. However, the range ratios and posterior distributions of the merged parameters indicated the model structural uncertainty in CoupModel. And the comparison of the simulated variables between two sites demonstrated that the model structure uncertainty originated from the lack of consideration for the detailed processes related to ice cover and freezing point depression induced by soil solute. More detailed information on study sites as well as consideration of more detailed processes in frozen soil water-energy balance will expand the scope of model application in cold regions.
|
|
| 4. |
- Wu, Mousong, et al.
(författare)
-
Improved soil hydrological modeling with the implementation of salt-induced freezing point depression in CoupModel : Model calibration and validation
- 2020
-
Ingår i: Journal of Hydrology. - : Elsevier B.V.. - 0022-1694 .- 1879-2707.
-
Tidskriftsartikel (refereegranskat)abstract
- Soil freezing/thawing is an important mechanism to control soil water and heat redistribution in mid-to-high latitudes. Salt in the agricultural soil from mid-to-high latitudes can alter characteristics of soil freezing/thawing cycle and then affect soil thermal and hydrological processes in winter and finally cause salinization in spring. To quantify the impacts of soil salinization on soil water and heat transport in saline soils, we conducted field experiments on soil water and heat dynamics in two typical agricultural regions of northern China with different climate and soil conditions. The coupled soil heat and water model—CoupModel has been extended to account for the dynamic impacts of salt on freezing point depression. The newly-added module improved the representation of soil freezing point depression by significantly improving model performance between simulated and measured soil temperatures, especially around freezing point, with mean error (ME) for the soil temperature at various depths reduced by 16% to 77% for the entire winter period. With a systematic model calibration approach, processes related to energy balance and soil freezing/thawing have been well constrained for both study sites with different characteristics for soil hydrology and energy balance. The model generally showed good performance with respect to soil moisture and temperature for both the calibration and validation periods. Our study has demonstrated a new modeling approach to successfully account for the impacts of salt on soil freezing/thawing and the new module can be a useful tool to address the salinization problems in mid-to-high latitudes with respect to climate change and water management.
|
|
| 5. |
- Wu, Mousong, et al.
(författare)
-
Simulation of dynamical interactions between soil freezing/thawing and salinization for improving water management in cold/arid agricultural region
- 2019
-
Ingår i: Geoderma. - : ELSEVIER SCIENCE BV. - 0016-7061 .- 1872-6259. ; 338, s. 325-342
-
Tidskriftsartikel (refereegranskat)abstract
- In cold/arid agricultural regions seasonal freezing/thawing of soils can result in soil salinization in winter; therefore, it is crucial to understand the mechanisms behind soil salinization during winter for better water management in agriculture. In Hetao Irrigation District of Inner Mongolia, northern China, we used the CoupModel (version 5) considering dynamical impacts of salt on soil freezing point to simulate soil salt dynamics and soil freezing/thawing in three winters during 2012-2015. The simulated soil temperature at different depths was improved by 10% with respect to the Nash-Sutcliffe coefficient NSE R-2 when dynamical salt impact on freezing point was taken into accounted. Simulations revealed that ice coverage on soil surface as well as water stored in drainage ditches during winter cause more severe salinization in spring due to improper Al (Autumn Irrigation) practices combining poor drainage systems. A new Al practice with earlier irrigation date (i.e. 10 d earlier than 2012/2013 winter regulation), longer irrigation period (i.e. 7 d instead of 3 d), but with less irrigation water (reduced by 20% from 2012/2013 winter regulation) was then proposed. The new AI practice can control groundwater level and salt accumulation better during winters, Our results highlight the importance of combining detailed field irrigation tests with a process-based model accounting for interactions between soil freezing/thawing and salinization to improve water management efficiency in cold/arid agricultural regions.
|
|
| 6. |
|
|
| 7. |
- Wu, Mousong, et al.
(författare)
-
Solute and water effects on soil freezing characteristics based on laboratory experiments
- 2015
-
Ingår i: Cold Regions Science and Technology. - : Elsevier BV. - 0165-232X .- 1872-7441. ; 115, s. 22-29
-
Tidskriftsartikel (refereegranskat)abstract
- Laboratory experiments were conducted to study effects of water and solute on soil freezing using TDR and temperature sensor combination methods. ANOVA methods were applied for analyzing significance for solute influences on soil freezing characteristic curve (SFCC). Results showed that higher initial water content influenced the SFCC by increasing liquid water content at the same temperature due to more water connection with soil pores, and adsorbed by soil particles. ANOVA results showed solute content and solute type all had significant effects (P < 0.001 to P < 0.5) on soil freezing processes. And solute in soil resulted in a lower freezing point of soil, which made more liquid water co-exist with ice at negative temperatures. And solute concentration condensing due to liquid water decline would also impede soil freezing processes by decreasing osmotic potential. Due to the physical and chemical process of soil solution, different ions also presented some differences in SFCC parameter estimation. Based on a trial and error method, a prediction model was also built, and it behaved well in predicting SFCC under different water and solute conditions.
|
|
| 8. |
- Wu, Mousong, et al.
(författare)
-
Water, Salt and Heat Influences on Carbon and Nitrogen Dynamics in Seasonally Frozen Soils in Hetao Irrigation District, Inner Mongolia, China
- 2019
-
Ingår i: Pedosphere. - : SCIENCE PRESS. - 1002-0160 .- 2210-5107. ; 29:5, s. 632-641
-
Tidskriftsartikel (refereegranskat)abstract
- To investigate carbon soils under saline and shallow groundwater supply conditions, in-situ lysimeter experiments with different groundwater table depths (WTD = 1.8 and 2.2 m) were conducted in Inner Mongolia, China during the wintertime of 2012-2013. Changes in soil organic C and total N in multiple layers during various periods, as well as their relationships with soil water, salt, and heat dynamics were analyzed. Accumulation of soil organic C and total N during freezing periods was strongly related to water and salt accumulation under temperature and water potential gradients. Water and salt showed direct influences on soil C and N dynamics by transporting them to upper layer and changing soil microbial activity. Salt accumulation in the upper layer during freezing and thawing of soil affected microbial activity by lowering osmotic potential, resulting in lower C/N ratio. Nitrogen in soil tended to be more mobile with water during freezing and thawing than organic C, and the groundwater table also served as a water source for consecutive upward transport of dissolved N and C. The changes in C and N in the upper 10 cm soil layer served as a good sign for identification of water and salt influences on soil microbial activity during freezing/thawing.
|
|
| 9. |
- Chen, Haorui, et al.
(författare)
-
Forecasting the human and climate impacts on groundwater resources in the irrigated agricultural region of North China Plain
- 2023
-
Ingår i: Hydrological Processes. - : Wiley. - 0885-6087 .- 1099-1085. ; 37:3
-
Tidskriftsartikel (refereegranskat)abstract
- Climate change has caused significant impacts on water resource redistribution around the world and posed a great threat in the last several decades due to intensive human activities. The impacts of human water use and management on regional water resources remain unclear as they are intertwined with the impacts of climate change. In this study, we disentangled the impact of climate-induced human activities on groundwater resources in a typical region of the semi-arid North China Plain based on a process-oriented groundwater modelling approach accounting for climate-human-groundwater interactions. We found that the climate-induced human effect is amplified in water resources management ('amplifying effect') for our study region under future climate scenarios. We specifically derived a tipping point for annual precipitation of 350 mm, below which the climate-induced human activities on groundwater withdrawal will cause significant 'amplifying effect' on groundwater depletion. Furthermore, we explored the different pumping scenarios under various climate conditions and investigated the pumping thresholds, which the pumping amount should not exceed (4 x 10(7) m(3)) in order to control future groundwater level depletion. Our results highlight that it is critical to implement adaptive water use practices, such as water-saving irrigation technologies in the semi-arid regions, in order to mitigate the negative impacts of groundwater overexploitation, particularly when annual precipitation is anomalously low.
|
|
| 10. |
- Chen, Peng, et al.
(författare)
-
Use of Be-10 isotope to predict landscape development in the source area of the Yellow River (SAYR), northeastern Qinghai-Tibet Plateau
- 2019
-
Ingår i: Journal of Environmental Radioactivity. - : ELSEVIER SCI LTD. - 0265-931X .- 1879-1700. ; 203, s. 187-199
-
Tidskriftsartikel (refereegranskat)abstract
- The magnitude of soil and sediment erosion and accumulation processes can profoundly affect landscape development and hamper efficient management of natural resources. Consequently, estimating the rates and causes of these processes is essential, particularly in remote regions, for prediction of changes in landform and river evolution and protection of local ecosystem. We here present the results of a soil and sediment erosion investigation in the Source Area of the Yellow River (SAYR), northeast Qinghai-Tibet Plateau based on a combined analysis of Be-10 cosmogenic isotope and Soil and Water Assessment Tool (SWAT) simulation modelling. The data reveal variable soil erosion trends that range between 103 and 830 t km(-2) a(-1). The low values occur in the western part of the basin that are associated with low sediment yield, while the high values appear in the dominant sediment export part of the basin along the main stream of the Yellow River in the east. Generally, soil and sediment accumulation is characterized by high Be-10 concentration in the western part and the northwest of Ngoring Lake. The style of landform development by the erosion/accumulation processes is closely linked to the distribution and degradation extent of the permafrost in the study region. Soil surface erosion increases with more permafrost degradation from the western to the eastern part of the basin, and surface soil particles are dominantly removed from the surface rather than deeper layers.
|
|
