Moore Caitlin E, Blakely Bethany, Pederson Taylor L, Gomez-Casanovas Nuria, Gibson Christy D, Knecht Anya M, Aslan-Sungur Guler, DeLucia Evan H, Heaton Emily A, VanLoocke Andy, Meyers Tilden, Bernacchi Carl J
School of Agriculture and Environment, The University of Western Australia, Crawley, Western Australia, Australia.
Centre for Water and Spatial Science, The University of Western Australia, Crawley, Western Australia, Australia.
Glob Chang Biol. 2025 Jun;31(6):e70291. doi: 10.1111/gcb.70291.
As global atmospheric CO rapidly approaches a key tipping point, there is an urgent need to implement strategies to reverse this pattern. A generally accepted understanding of carbon (C) in agricultural fields includes: (H1) substantial C loss occurs when natural vegetation is converted to crops, (H2) soils typically reach a steady-state C concentration under contemporary practices, and (H3) improved management or crop selection can enhance soil C stocks over time. Significant variability exists, but studies consistently show large C losses from agricultural ecosystems, supporting H1. Although steady-state C levels (H2) are commonly assumed, measuring C gains or losses in mature agroecosystems is challenging. Efforts to increase soil C storage (H3) have limited data due to the diversity of potential practices, compounded by substantial variability in soil C measurements. Here, long-term (7-17 year) ecosystem C flux data from diverse cropping systems revealed that conventionally tilled annual row crops (maize and soybean) act as significant long-term atmospheric C sources, challenging H2. Furthermore, conservation tillage practices reduced C losses compared with conventional tillage but showed minimal evidence for long-term ecosystem C storage, even after 20+ years. This indicates that no-till practices reduce C losses but imply that no soil C is added, challenging H3. By contrast, perennial Miscanthus × giganteus, Panicum virgatum, and restored tallgrass prairie systems store C at the ecosystem scale more effectively than minimally tilled annual row crops. Analysis over multiple years demonstrates significant ecosystem C storage with perennial crops, varying by species, starting in the first year of transition. These findings, although focused on one region, suggest that the assumptions of steady-state C levels and increased storage from conservation practices do not universally apply and that significant changes to agroecosystems are required to increase C storage.
随着全球大气中的二氧化碳迅速逼近一个关键的临界点，迫切需要实施扭转这一趋势的策略。对农业领域碳（C）的普遍认识包括：（H1）当自然植被转变为农作物时，会发生大量碳损失；（H2）在当代农业实践下，土壤通常会达到碳浓度的稳态；（H3）随着时间的推移，改进管理或作物选择可以增加土壤碳储量。尽管存在显著差异，但研究一致表明农业生态系统存在大量碳损失，这支持了假设H1。虽然通常假定存在碳稳态水平（H2），但测量成熟农业生态系统中的碳增益或损失具有挑战性。由于潜在实践的多样性，以及土壤碳测量的巨大差异，增加土壤碳储存（H3）的努力所依据的数据有限。在这里，来自不同种植系统的长期（7至17年）生态系统碳通量数据显示，传统翻耕的一年生行播作物（玉米和大豆）长期以来是大气碳的重要来源，这对假设H2提出了挑战。此外，与传统耕作相比，保护性耕作减少了碳损失，但即使经过20多年，也几乎没有长期生态系统碳储存的证据。这表明免耕实践减少了碳损失，但意味着没有增加土壤碳，对假设H3提出了挑战。相比之下，多年生的巨芒草、柳枝稷以及恢复的高草草原系统在生态系统尺度上比最少翻耕的一年生行播作物更有效地储存碳。多年的分析表明，多年生作物从转型的第一年起就开始在生态系统中大量储存碳，因物种而异。这些发现虽然聚焦于一个地区，但表明碳稳态水平的假设以及保护性实践增加碳储存的假设并不普遍适用，需要对农业生态系统进行重大变革才能增加碳储存。
