Zokor activity promotes soil water infiltration in the Mu Us sandy land of northern Shaanxi,China

Zokors are common subterranean rodents that inhabit agricultural fields, shrublands, and grasslands in the arid and semi-arid regions of China. Zokor burrowing activities can alter soil structure and affect soil hydrological processes;however, there are few studies regarding their effects on soil preferential flow in the Mu Us sandy land. An evaluation of the effects of zokor disturbance on their habitat and soil water is important for understanding the ecological role of zokors in the soil ecosystem of the Mu Us sandy land. A field dye-tracing experiment was conducted in the Gechougou watershed on the southeastern edge of the Mu Us sandy land to investigate the effect of zokor burrowing activity on soil preferential flow characteristics. Our results showed that the density of zokor tunnels was the highest(0.40–0.46 m m^(-2)) under 30%–50% vegetation coverage and that the tunnels were approximately 3 cm from the surface.Both stained area ratio and stained path number were higher at sites with zokors than without zokors. Stained path widths were 10–80 and > 80 mm at zokor-harboring sites exhibiting homogeneous flow and heterogeneous finger flow, respectively. In the absence of zokors, homogeneous flow and highly interacted macropore flow were predominant. Soil water content below the zokor tunnels was higher than that above the tunnels. Moderate disturbance of soil structure by zokor activity facilitated soil water infiltration. These results enabled a better understanding of the effect of soil fauna on soil structure and hydrological processes and provided recommendations for ecological construction and renovation in arid and semi-arid regions.

Global patterns of soil phosphatase responses to nitrogen and phosphorus fertilization

Hydrolysis of organic phosphorus(P) by soil phosphatases is an important process of P cycling in terrestrial ecosystems, significantly affected by nitrogen(N) and/or P fertilization. However, how soil acid phosphatase(ACP) and alkaline phosphatase(ALP) activities respond to N and/or P fertilization and how these responses vary with climatic regions, ecosystem types, and fertilization management remain unclear. This knowledge gap hinders our ability to assess P cycling and availability from a global perspective. We performed a meta-analysis to evaluate the global patterns of soil ACP and ALP activities in response to N and/or P addition. We also examined how climatic regions(arctic to tropical), ecosystem types(cropland, grassland, and forest), and fertilization management(experiment duration and fertilizer type and application rate) affected changes in soil phosphatases after fertilization. It was shown that N fertilizer resulted in 10.1% ± 2.9% increase in soil ACP activity but a minimal effect on soil ALP activity. In contrast, P fertilizer resulted in 7.7% ± 2.6% decrease in soil ACP activity but a small increase in soil ALP activity. The responses of soil ACP and ALP activities to N and/or P fertilization were largely consistent across climatic regions but varied with ecosystem types and fertilization management, and the effects of ecosystem types and fertilization management were enzyme-dependent. Random forest analysis identified climate(mean annual precipitation and temperature) and change in soil pH as the key factors explaining variations in soil ACP and ALP activities. Therefore, N input and ecosystem types should be explicitly disentangled when assessing terrestrial P cycling.

An empirical approach to predict regional organic carbon in deep soils

Deep soil organic carbon(SOC)plays an important role in carbon cycling.Precisely predicting deep SOC at the regional scale is crucial for the accurate assessment of carbon sequestration potential in soils but has been challenging for a century.Herein,we developed a depth distribution function-based empirical approach to predict SOC in deep soils at the regional scale.We validated this approach with a dataset from four regions of the world and examined the application of this approach in China’s Loess Plateau.We found that among the reported depth distribution functions describing vertical patterns of SOC,the negative exponential function performed best in fitting SOC along the soil profile in various regions.Moreover,the parameters(i.e.,Ceand k)of the negative exponential function were linearly correlated to surface SOC(0–20 cm)and the changing rates of SOC within the topsoil(0–40 cm).Based on the above relationships,the empirical equations for predicting the negative exponential parameters are established.The validation results from site-specific and regional dataset showed that combining the negative exponential function and such empirical equations can precisely predict SOC concentration in soils down to 500 cm depth.Our study provides a simple,rapid and accurate method for predicting deep soil SOC at the regional scale,which could simplify the assessment of deep soil SOC in various regions.

Humic acid transport in saturated porous media:Influence of flow velocity and influent concentration

Understanding the transport of humic acids（HAs） in porous media can provide important and practical evidence needed for accurate prediction of organic/inorganic contaminant transport in different environmental media and interfaces. A series of column transport experiments was conducted to evaluate the transport of HA in different porous media at different flow velocities and influent HA concentrations. Low flow velocity and influent concentration were found to favor the adsorption and deposition of HA onto sand grains packed into columns and to give higher equilibrium distribution coefficients and deposition rate coefficients, which resulted in an increased fraction of HA being retained in columns.Consequently, retardation factors were increased and the transport of HA through the columns was delayed. These results suggest that the transport of HA in porous media is primarily controlled by the attachment of HA to the solid matrix. Accordingly, this attachment should be considered in studies of HA behavior in porous media.

Human and climatic drivers of land and water use from 1997 to 2019 in Tarim River basin,China

Climate and human activities change spatial and temporal distribution of water and land use.The Tarim River,the largest inland river in China,faced a long-term exploitation of land and water over a rapid economic development.We analyzed land and water use from 1997 to 2019 in Tarim River Basin by Landsat images,and data on hydrology,climate,population,economy and PM_(2.5)(air particulate matter≤2.5μm).Agricultural land expanded the fastest(4-11%),followed by natural vegetation(15-16%)and water area(4-5%)with population and economic increase.Air quality(PM_(2.5)μg m^(−3))improved in upper(62-27)and middle(48-17)reaches.The water area in lower increase 5%because of ecological water delivery since 2000.Land use in the lower reach was dominated by agriculture,where the downstream runoff consumption increased by 6.8 times.The average annual air temperature and precipitation gradually increased by 0.5℃and 51 mm in source and 0.9℃and 30 mm in main reaches.The average annual water consumption in upper and middle reaches was 4×10^(9)m^(3),accounting for 87%of input runoff in the main reach.Water consumption in middle reach increased by 33 times in 2009-2017.The industry structure was changing from primary to secondary and tertiary industry.To sum up,implementation of water saving strategies and ecological water delivery restored local ecology.Sustainable strategies should be applied facing industrialization.Furthermore,changing the industry structure and restoring the degraded farmlands to grasslands or forests would keep sustainability of Tarim River Basin.

A review on transport of coal seam gas and its impact on coalbed methane recovery

This paper presents a summary review on mass transport of coal seam gas(CSG)in coal associated with the coalbed methane(CBM)and CO_(2) geo-sequestration enhanced CBM(CO_(2)-ECBM)recovery and current research advances in order to provide general knowledge and fundamental understanding of the CBM/ECBM processes for improved CBM recovery.It will discuss the major aspects of theory and technology for evaluation and development of CBM resources,including the gas storage andflow mechanism in CBM reservoirs in terms of their differences with conventional natural gas reservoirs,and their impact on CBM production behavior.The paper summarizes the evaluation procedure and methodologies used for CBM exploration and exploitation with some recommendations.

黄土高原土壤水可持续利用的思考与建议

As the birthplace of the Chinese civilization, China’s Loess Plateau(CLP) has an area of ~640,000 km2 and supports a population of more than 100 million people. It has a history of intensive agriculture more than 1000 years. The loess deposit of CLP is the largest and deepest in the world. The abundance of silt grains in the loess deposit makes it relatively homogeneous, porous and prone to soil erosion.

Response of soil CO_2 efflux to precipitation manipulation in a semiarid grassland

Soil CO_2efflux（SCE） is an important component of ecosystem CO_2 exchange and is largely temperature and moisture dependent, providing feedback between C cycling and the climate system. We used a precipitation manipulation experiment to examine the effects of precipitation treatment on SCE and its dependences on soil temperature and moisture in a semiarid grassland. Precipitation manipulation included ambient precipitation, decreased precipitation（- 43%）, or increased precipitation（＋ 17%）. The SCE was measured from July2013 to December 2014, and CO_2 emission during the experimental period was assessed.The response curves of SCE to soil temperature and moisture were analyzed to determine whether the dependence of SCE on soil temperature or moisture varied with precipitation manipulation. The SCE significantly varied seasonally but was not affected by precipitation treatments regardless of season. Increasing precipitation resulted in an upward shift of SCE–temperature response curves and rightward shift of SCE–moisture response curves,while decreasing precipitation resulted in opposite shifts of such response curves. These shifts in the SCE response curves suggested that increasing precipitation strengthened the dependence of SCE on temperature or moisture, and decreasing precipitation weakened such dependences. Such shifts affected the predictions in soil CO_2 emissions for different precipitation treatments. When considering such shifts, decreasing or increasing precipitation resulted in 43 or 75% less change, respectively, in CO_2 emission compared with changes in emissions predicted without considering such shifts. Furthermore, the effects of shifts in SCE response curves on CO_2 emission prediction were greater during the growing than the non-growing season.

Soil type-dependent effects of drying-wetting sequences on aggregates and their associated OC and N

Evaluating the impacts of drying-wetting(DW)cycles on soil aggregates and their associated organic carbon(OC)and nitrogen(N)is crucial to understand the OC and N cycles.Soils are likely subjected to DW cycles with different sequences depending on seasons or in agroecosystems.However,studies on how DW sequences influence OC and N dynamics within aggregates,and whether this effect is dependent on soil type,are relatively limited.Herein,two DW sequences,i.e.,drying-wetting-dryingwetting(2DW)and wetting-drying-wetting-drying(2WD)treatments were designed,and a consistent wetting(CW)was set as a control to assess the effects of DW sequences.Four soils(Entisol,Ultisol,Anthrosol and Mollisol)varying in texture and OC content were used.The aggregate size distribution,the OC,total N(TN),readily oxidizable OC(ROOC)and mineral N(Min-N)content in aggregates were determined.Results showed that 2DW treatment increased but 2WD treatment decreased the large aggregates of Entisol and Ultisol,while 2DW and 2WD treatments synchronously increased the large aggregates of Anthrosol but decreased them of Mollisol.Two DW treatments increased the OC in each aggregate of Entisol,Anthrosol and Mollisol but decreased them of Ultisol.The 2DW didn't affect but 2WD treatment decreased ROOC in 1e2 mm aggregates of Entisol and<0.25 mm aggregates of Ultisol and Mollisol.The 2DW and 2WD treatments minimally affected TN but potentially influenced Min-N in aggregates.The 2DW and 2WD treatments both decreased the Min-N in each aggregate size class of Entisol and Mollisol,while 2DW increased but 2WD treatment decreased Min-N in each aggregate of Ultisol and Anthrosol.These results indicated that the varied effects of DW sequences and the interactive effects of soil type with DW sequences on aggregate turnover and OC and N cycling should be reconsidered to provide more precisive evidences for global C and N cycles under the scenario of future climate changes.