Relatively few studies have documented the impacts of afforestation, particularly production forestry, on belowground carbon dioxide (CO₂) effluxes to the atmosphere. We evaluated the changes in the soil CO₂ efflux—a proxy for soil respiration (Rs)—for three years following a native grassland conversion to eucalypt plantations in southern Brazil where minimum tillage during site preparation created two distinct soil zones, within planting row (W) and between-row (B). We used root-exclusion and carbon (C)- isotopic approaches to distinguish Rs components (heterotrophic-Rh and autotrophic-Ra respirations), and a CO₂ profile tube (1-m deep) to determine the concentration ([CO₂]) and isotopic C signature of soil CO₂ (δ¹³[CO₂]). The soil CO₂ efflux in the afforested site averaged 0.37 g CO₂ m⁻² h⁻¹, which was 56% lower than the soil CO₂ efflux in the grassland. The δ¹³CO₂ in the afforested site ranged from − 14.1‰ to − 29.4‰, indicating a greater contribution of eucalypt-derived respiration (both Rh and Ra) over time. Higher soil CO₂ efflux and lower [CO₂] were observed in W than B, indicating that soil preparation creates two distinct soil functional zones with respect to C cycling. The [CO₂] and δ¹³[CO₂] decreased in both zonal positions with eucalypt stand development. Although the equilibrium in C fluxes and pools across multiple rotations is needed to fully account for the feedback of eucalypt planted forests to climate change, we provide quantitative information on soil CO₂ dynamics after afforestation and show how soil preparation can leverage the feedback of planted forests to climate change.

相对较少的研究记录了造林，特别是生产林业对地下二氧化碳（CO ₂）排放到大气中的影响。我们评估了巴西南部的原生草地转换为桉树人工林后三年内土壤CO ₂流出量（土壤呼吸（Rs）的替代物）的变化，在该场地种植期间，最小的耕作在种植行内产生了两个不同的土壤带（ W）和行间（B）。我们使用了根排阻法和碳（C）-同位素方法来区分Rs组分（异养Rh和自养Ra呼吸），并使用CO ₂剖面管（深1米）来确定浓度（[CO ₂ ]） CO _2的同位素和同位素C特征（δ ¹³ [CO ₂ ]）。绿化场的土壤CO ₂排放平均为0.37 g CO ₂ m ^-2 h ^-1，比草原土壤CO ₂排放低56％。的δ ¹³ CO ₂在绿化站点范围从- 14.1‰至- 29.4‰，表明桉树导出的呼吸（包括Rh和Ra）为随时间的更大的贡献。与B相比，W的土壤CO ₂流出量更高，[CO ₂ ]较低，这表明土壤准备相对于C循环产生了两个不同的土壤功能区。的[CO ₂ ]和δ ¹³ [CO₂ ]随着桉木林分的发育，两个纬向位置均下降。尽管需要多次旋转过程中碳通量和碳池的平衡来充分说明桉树人工林对气候变化的反馈，但我们提供了造林后土壤CO ₂动态的定量信息，并显示了土壤准备如何利用人工林的反馈应对气候变化。