Contribution of soil macropores to water infiltration across different land use types in a desert–oasis ecoregion

Abstract

Surface soil hydraulic properties play critical roles in controlling water infiltration, evaporation, and soil water storage, in‐turn affecting the evolution of soil pore structure in cultivated desert soils of arid areas. The variability in soil pores and hydraulic properties caused by conversion of native semidesert soils to agroforestry use alters soil water storage and water budget in the desert–oasis ecotone. The objective of this study was to investigate that land use conversion alters surface soil hydraulic properties and enhances the contribution of soil macropores to water flow in the Linze desert–oasis ecoregion. Water infiltration and soil pores characteristics with nine replicates were measured using a disc tension infiltrometer across four habitat types (Haloxylon ammodendron shrublands, Populus gansuensis forests, Medicago sativa Linn grasslands, and Zea mays croplands) during the growing season. Soil properties and hydraulic conductivity characteristics clearly varied across the four habitat types. Saturated hydraulic conductivity was 0.177, 0.126, 0.118, and 0.031cm min−1 in the forest, grassland, shrubland, and cropland, respectively, with the corresponding average soil moisture being 7.6, 6.7, 0.9, and 19.2%. Clay content, bulk density, and initial soil moisture were the key soil physicochemical properties affecting saturated hydraulic conductivity (Ks). The macropores (> 0.5 mm in radius) accounted for 15–60% of total water flow, while 0.25–0.5 mm pores contributed to 12–24% across the four habitat types. The contribution of >0.5 mm pores to water flow in the forest was 3.3–4.0‐times greater than in shrubland and cropland, due to greater soil macroporosity (58 cm−3 cm3 ) and undisturbed soil pore structure. Land use conversion has a positive impact on soil properties, structure features, and soil hydraulic properties, and as a consequence, enhance the complexity of water exchange in the arid areas.

Soil macroporosity and water flow in the root zone of oases in hyper‐arid regions

“…The annual average sunshine duration is 3051 h. Annual average wind speed is 3.2 m/s. The main landscape types in the study area are farmlands in oasis region and shrublands in desert region (Zhang et al, 2021). The irrigated farmlands are distributed along the middle reaches of Heihe River.…”

“…The procedure is called "loss on ignition" since the organic matter is burned off during the process (Davies, 1974), which removed most of the soil organic matter from the soil samples (Heiri et al, 2001). The values of soil organic matter were validated based on the measurements using the dichromate oxidation method in the study areas (Zhang et al, 2017(Zhang et al, , 2021.…”

“…Decayed roots provide preferential downward pathways for water to infiltrate the soil, influencing solute migration and contaminant transport (Backnäs et al, 2012;Nimmo, 2021), improving soil permeability, and influencing soil water distribution in different land use types (Hendrickx & Flury, 2001;Jarvis, 2020). As indirectly inferred by the related studies, root-mediated water flow might have a profound impact on the exchange of surface water and groundwater in arid regions (Li et al, 2013;Liu et al, 2020;Zhang et al, 2021).…”

“…In a semi‐arid watershed (Extremadura, Spain), infiltration rate was significantly correlated with root channels (van Schaik, 2009). However, the biomass of roots is relatively low, and the turnover of roots is slow in hyper‐arid regions (Lai et al, 2016; Li et al, 2013; Zhang et al, 2021). In fact, the mechanisms of soil macropores and water flow regulated by the root zone environment have not been investigated in oasis farmlands.…”

Temporal variation of saturated and near‐saturated soil hydraulic conductivity and water‐conducting macroporosity in a maize‐wheat rotation under conventional and conservation tillage practices

“…SHPs at and near‐saturated conditions are very important for water and solute transportation processes (Tian et al, 2019) and is often used to indirectly characterize macropore structure under various management practices (Çerçioğlu et al, 2019; Patra et al, 2022; Schlüter et al, 2020; Zhang et al, 2021). Although the tension or disc infiltrometer is the most common in‐situ method to assess structural related SHPs, it causes inconsistencies in the results due to soil surface disturbance.…”