Partitioning soil respiration refines carbon intensity estimates by isolating soil carbon mineralization from root respiration
Heesu Jeon, Nictor Namoi, Chunhwa Jang, Soonho Hwang, Cheng‐Hsien Lin, Colleen R. Zumpf, Emily Heaton, DoKyoung LeeAbstract
Perennial energy crops are promoted for soil carbon (C) sequestration, greenhouse gas (GHG) mitigation, and high biomass yields on marginal lands. Accurate field‐level GHG quantification is central to carbon intensity (CI) estimation. We quantified soil CO 2 and N 2 O fluxes over two growing seasons (2024–2025) in switchgrass ( Panicum virgatum L.) and corn ( Zea mays L.) on marginal land, partitioning total soil respiration (RT) into heterotrophic respiration (RH) and autotrophic respiration (RA) components by chamber‐based root exclusion. Cumulative RT was 47% greater in switchgrass than corn; RH did not differ between crops, indicating greater RA in switchgrass, and N 2 O emissions were 3.17‐fold lower. Biometric CI estimated from RH revealed switchgrass as a net soil C sink (−1.95 Mg CO 2 ‐eq Mg − 1 harvested biomass) and corn as a net source (+0.68 Mg CO 2 ‐eq Mg − 1 ). Without partitioning, RT‐based CI for switchgrass was near neutral (−0.02 Mg CO 2 ‐eq Mg − 1 ), confirming RH partitioning is necessary for accurate CI estimation in perennial energy cropping systems.