Plant competition regulates carbon accumulation and partitioning in C3 and C4 cereals under contrasting water regimes

Abstract

Carbon sequestration in agroecosystems plays a pivotal role in regulating the global carbon cycle and mitigating climate change. Cereal-based cropping systems occupy a substantial proportion of global agricultural land; however, the influence of plant competition on carbon accumulation and partitioning within these systems remains insufficiently quantified. This study investigated how intra- and inter-specific competition affects total carbon content (TCC) and its allocation to above-ground carbon (ACC) and below-ground carbon (BCC) in cool-season (C3) and warm-season (C4) cereals under contrasting water regimes. Two controlled pot experiments were conducted using four C3 cereals (wheat, barley, rye, and oats) and three C4 cereals (corn, sorghum, and foxtail millet) grown in pure and mixed stands. Carbon accumulation was estimated using biomass-derived carbon coefficients. Results revealed significant species-specific and competition-driven differences in carbon partitioning. Barley, rye, and oats accumulated higher TCC in pure stands, whereas wheat exhibited improved carbon accumulation under specific mixed stands. In warm-season cereals, corn consistently showed the highest ACC, BCC, and TCC, particularly when grown with millets. Under the specific conditions of this study, C4 cereals exhibited greater carbon accumulation than C3 cereals, reflecting inherent photosynthetic advantages; however, because the two experiments differed in species, plant density, and treatment structure, direct comparisons between C3 and C4 cereals require further validation under more uniform experimental conditions. Importantly, increasing crop diversity from two-species to three- or four-species mixtures generally reduced per-plant carbon accumulation due to intensified interspecific competition. Carbon allocation was predominantly above-ground; however, below-ground carbon varied significantly with competition intensity and water regime. These findings demonstrate that plant competition is a critical but underexplored driver of agroecosystem carbon balance. Understanding competition-mediated carbon partitioning can guide the design of climate-smart cropping systems that enhance plant carbon content while sustaining productivity.

The authors' abstract, as published at the source. Carbon Balance and Management, 2026 · DOI ↗