The contributions of root morphological characteristics and soil property to soil infiltration in a reseeded desert steppe

Infiltration of precipitation is the main source of water for soil water replenishment in arid and semiarid regions and plays a critical role in influencing the restoration of degraded grassland. However, the effects of reseeded vegetation on soil infiltration in grasslands remains unclear. Here, we measured soil infiltration rate (IR), root characteristics, and soil properties for four plant treatments (Agropyron mongolicum, Lespedeza potaninii, A. mongolicum x L. potaninii (1:1), and A. mongolicum x Astragalus melilotoides (1:1)) five years after reseeding and enclosure in degraded desert steppe, and continuously grazed steppe used as a control. Results showed that the IR among treatments presented as A. mongolicum > L. potaninii > A. mongolicum x A. melilotoides > A. mongolicum x L. potaninii > the grazed steppe. Correlation analysis indicated that root length density, root surface area, root volume, soil organic matter, non-capillary porosity, capillary porosity, and total porosity were positively correlated with initial, steady, and average IR (p < 0.05, or 0.01), yet root biomass and soil bulk density did not significantly influence IR (p > 0.05). The study also indicated that the higher IR of A. mongolicum was associated with higher soil organic matter and soil porosities at soil depths of 0-40 cm than in L. potaninii plots. Whereas, the higher IR of monocultures was associated with higher values of root length density, root surface area, and root volume at soil depths of 0-30 cm than mixtures. However, both root morphological characteristics and soil properties were significantly determined by the volumes of fine roots (diameter <= 2 mm). Therefore, in this study, the fine root volume played a crucial role in regulating soil infiltration via determining root morphological characteristics and forming soil pores and pathways.