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From Soils to Streams: Connecting Terrestrial Carbon Transformation, Chemical Weathering, and Solute Export Across Hydrological Regimes
Author(s) -
Wen Hang,
Sullivan Pamela L.,
Billings Sharon A.,
Ajami Hoori,
Cueva Alejandro,
Flores Alejandro,
Hirmas Daniel R.,
Koop Aaron N.,
Murenbeeld Katie,
Zhang Xi,
Li Li
Publication year - 2022
Publication title -
water resources research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.863
H-Index - 217
eISSN - 1944-7973
pISSN - 0043-1397
DOI - 10.1029/2022wr032314
Subject(s) - weathering , dissolved organic carbon , carbonate , soil water , carbon cycle , mineralization (soil science) , total organic carbon , subsurface flow , environmental science , hydrology (agriculture) , streams , temperate climate , biota , geology , environmental chemistry , soil science , ecosystem , groundwater , geomorphology , chemistry , oceanography , ecology , computer network , geotechnical engineering , computer science , biology , organic chemistry
Soil biota generates carbon that exports vertically to the atmosphere (CO 2 ) and transports laterally to streams and rivers (dissolved organic and inorganic carbon, DOC and DIC). These processes, together with chemical weathering, vary with flow paths across hydrological regimes; yet an integrated understanding of these interactive processes is still lacking. Here we ask: How and to what extent do subsurface carbon transformation, chemical weathering, and solute export differ across hydrological and subsurface structure regimes? We address this question using a hillslope reactive transport model calibrated using soil CO 2 and water chemistry data from Fitch, a temperate forest at the ecotone boundary of the Eastern temperate forest and mid‐continent grasslands in Kansas, USA. Model results show that droughts (discharge at 0.08 mm/day) promoted deeper flow paths, longer water transit time, carbonate precipitation, and mineralization of organic carbon (OC) into inorganic carbon (IC) (∼98% of OC). Of the IC produced, ∼86% was emitted upward as CO 2 gas and ∼14% was exported laterally as DIC into the stream. Storms (8.0 mm/day) led to carbonate dissolution but reduced OC mineralization (∼88% of OC) and promoted DOC production (∼12% of OC) and lateral fluxes of IC (∼53% of produced IC). Differences in shallow‐versus‐deep permeability contrasts led to smaller difference (<10%) than discharge‐induced differences and were most pronounced under wet conditions. High permeability contrasts (low vertical connectivity) enhanced lateral fluxes. Model results generally delineate hillslopes as active CO 2 producers and vertical carbon transporters under dry conditions, and as active DOC producers and lateral carbon transporter under wet conditions.