Interannual variation in soil respiration and its components across cropland, grassland, and pasture in the agro-pastoral ecotone of Northern China

Authors: WANG, DEPING - China Agricultural University; ZHOA, KUN - China Agricultural University; Monaco, Thomas; JIN, SANGLING - China Agricultural University; RONG, YUPING - China Agricultural University

Submitted to: Agriculture, Ecosystems & Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/27/2025
Publication Date: 4/9/2025
Citation: Wang, D., Zhoa, K., Monaco, T.A., Jin, S., Rong, Y. 2025. Interannual variation in soil respiration and its components across cropland, grassland, and pasture in the agro-pastoral ecotone of Northern China. Agriculture, Ecosystems & Environment. https://doi.org/10.1016/j.agee.2025.109672.
DOI: https://doi.org/10.1016/j.agee.2025.109672

Interpretive Summary: Soil respiration arises from autotrophic and heterotrophic sources and understanding controlling factors is essential to estimate grassland carbon sequestration under various land-use practices. We conducted a three-year experiment between 2021 and 2023 in the agro-pastoral ecotone of Northern China across three land-use types, including two perennial pastures composed of either Medicago sativa or Bromus inermis, two annual croplands planted with either Avena sativa or Solanum tuberosum, and two natural grasslands that had been either fenced or clipped annually. Average respiration for pastures exceeded both croplands and grasslands in 2022 and 2023. In addition, the ratio of heterotrophic/overall respiration were lowest in the Bromus inermis pasture. We also found that heterotrophic respiration is carbon flux source controlling the magnitude of soil respiration of all land-use types. Structural equation models of these systems revealed that heterotrophic respiration was primarily controlled by soil temperature in croplands and pastures, while soil water content had this role in grasslands. These results suggest that grasslands will likely decrease soil CO2 emissions in the agro-pastoral ecotone of Northern China under global climate change projections. When land use changes are permitted, our results indicate that planting Solanum tuberosum cropland or Bromus inermis pasture will maintain lower soil heterotrophic respiration and Q10 values during the growing season compared to the other land-use types.

Technical Abstract: Quantitative understanding of the temporal patterns of soil respiration (Rs), its components (i.e., autotrophic respiration (Ra) and heterotrophic respiration (Rh)), and their controlling factors is essential to estimate grassland carbon sequestration under various land use practices. However, the sensitivity and magnitude of Rs seasonal patterns to land-use change remain poorly understood. We conducted a three-year experiment in the agro-pastoral ecotone of Northern China across three land-use types, including two perennial pastures composed of either Medicago sativa or Bromus inermis, two annual croplands planted with either Avena sativa or Solanum tuberosum, and two natural grasslands that had been either fenced or clipped annually. We measured Rs and its components along with a suite of biotic and abiotic factors over three growing seasons (2021 – 2023). Mean Rs over the growing seasons for pastures was 224 – 270 mg CO2 m-2 h-1, which was significantly (P < 0.001) higher than croplands (188 – 190 mg CO2 m-2 h-1) and natural grasslands (192 – 197 mg CO2 m-2 h-1) in 2022 and 2023. The Rh/Rs ratios across the different land use types ranged from 0.5 – 0.8, with the lowest values found in the Bromus inermis pasture. Results also indicate that Rh is the primary factor regulating the magnitude of Rs across all land use types. Based on structural equation models, soil temperature was the key predictor of Rh in croplands and pastures (effect size = 0.67 and 0.54, respectively), while soil water content was the primary predictor of Rh in grasslands. In croplands, the temperature sensitivity (Q10) of Rh for Avena cropland was significantly (P < 0.001) higher than that for Solanum cropland, whereas no significant differences were found between pasture types. Our results suggest that grasslands will likely decrease soil CO2 emissions in the agro-pastoral ecotone of Northern China under global climate change projections. When land use changes are permitted, our results indicate that planting Solanum tuberosum cropland or Bromus inermis pasture will maintain lower soil heterotrophic respiration and Q10 values during the growing season compared to the other land-use types.