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Abstract Deep soils represent a dynamic interface between surface soils and saprolite or bedrock, influencing water flow, solute and gas exchange, and mineral and organic matter transformations from local to global scales. Root architecture reflects land cover and soil heterogeneity, enabling vegetation access to resources that vary temporally and spatially while shaping soil structure and formation. However, how land use can influence roots and soil structure relatively deep in the subsurface (>30 cm) remains poorly understood. We investigate how cropland‐related land use and subsequent vegetation recovery alter rooting dynamics and soil structure in deeper horizons. Using a large‐scale data set representing multiple land uses as a means of varying root abundance across four soil orders, we demonstrate that B horizon root loss and regeneration are linked to changes in multiple soil structural attributes deep within soil profiles. Our findings further suggest that the degree of soil development modulates the extent of structural transformations, with less‐developed soils showing greater susceptibility to root‐associated structural shifts. The greatest change in structural development and distinctness was observed in Inceptisols, while Ultisols exhibited the least change. Such soil structural changes affect water flowpaths, carbon retention, and nutrient transport throughout the subsurface. This work thus underscores the need for Earth system models to capture dynamic soil structural attributes that respond to land‐use change. We suggest that changes in deep‐rooting abundance, such as those accelerating in the Anthropocene, may be an important agent of subsurface structural change with meaningful implications for contemporary and future ecosystem feedbacks to climate.
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Surficial soil changes and precipitation patterns interact to govern propagation of deep soil solutes produced by weathering.
Climate models project changing patterns of precipitation and increases in temperature that modify soil moisture dynamics. Land use and changing frequency and intensity of precipitation can induce changes in soil structure and rooting abundances at timescales shorter than commonly considered. Soil structure is a critical ecosystem that governs water flow through soil profiles and across landscapes, and can influence weathering rates and thus solute release and soil development. We hypothesize that the altered soil structure and modification of rooting depth distributions linked to land use change can influence soil solute concentrations, and that those shifts in solute release are dependent on patterns of precipitation. We installed suction lysimeters to collect soil water for ~3 y in two grassland regions with distinct mean annual precipitation (800 mm y-1, 1100 mm y-1) in native prairie, agriculture, and post-agriculture land uses at depths of 10, 40, and 120 cm. We linked solute concentrations to soil moisture, aggregate-size distribution, pore geometry, and rooting depth distributions to assess how land use change and the altered rooting abundance it imposes can modify soil structure and hydrologic fluxes, and to infer how soil weathering can shift deep in the subsurface. We reveal how soil moisture residence time and the soil pore network can govern solute production, and the importance of precipitation and thus of soil moisture accumulation over growing seasons for mineral weathering and solute production. Specifically, we find that the solubility potential of multiple weathering products and organic carbon increases with precipitation, dominance of relatively small aggregates at the surface, and fewer coarse roots. Enhanced solute concentrations at depth may also reflect transport down-profile. Our findings reveal unintended consequences of land use change that influence important hydrologic dynamics and nutrient cycling in the vadose zone and how deeply and how persistently unexpected consequences of changes in land cover can propagate.
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- Award ID(s):
- 2121639
- PAR ID:
- 10505018
- Publisher / Repository:
- AGU 2023 abstracts
- Date Published:
- Journal Name:
- AGU abstract
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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