Upland soils are the main methane (CH₄) biological sink, and may be affected by land-use change. Changes in land uses and soil management affect soil properties that control diffusion of gases, which in combination with microbial activity, determine CH₄ flux (fCH₄) through the soil. Net CH₄ fluxes and diffusivity -estimated by the CH₄ diffusion coefficient- were measured in three common land uses typical from Pampean plains, South America (natural grassland NG; Eucalyptus globulus Labill. afforestation E; and agricultural land AL: oat, soybean and red clover in successive cultivation) during two years (March 2017–March 2019). Methane fluxes in the soil-atmosphere interface were measured using the static chamber technique, and a diffusion model was applied to estimate soil CH₄ diffusivity from soil porosity. We aimed to quantify the effect of land use change (both E and AL vs. NG, the reference system) on fCH₄ and gas diffusivity due to changes in the soil parameters. Soils were net sinks in the three land uses, with mean CH₄ flux higher in the afforestation, intermediate in the natural grassland and lower in the agricultural land (− 10.99 ± 5.85, − 8.9 ± 5.32 and − 4.58 ± 4.19 ng CH₄ m⁻² s⁻¹, respectively). CH₄ fluxes varied significantly through seasons and space coinciding with variations in water-filled pore space and air-filled pore space variables (ρ > 0.7 and <−0.7 respectively; p < 0.05). Land-use change metric for methane flux ΔfCH₄ was − 2.1 ± 3.7 and 4.4 ± 2.5 for NG-E and NG-AL, respectively, indicating a significant increment in net CH₄ uptake when the natural grassland is afforested and a decrease when it was converted to agricultural use. This change was mainly explained by changes in soil physical properties (bulk density, soil water content, WFPS and air filled porosity). In relation to this, soil CH₄ diffusion coefficient followed the same pattern as fCH₄ (0.024 ± 0.011; 0.015 ± 0.007 and 0.008 ± 0.007 cm² s⁻¹ for E, NG and AL respectively); and allowed us to recalculate mean CH₄ fluxes. Theoretical and in situ measured CH₄ fluxes were similar and followed the same patterns across land uses, suggesting the possibility to determine CH₄ fluxes by means of simple measures of soil properties (bulk density and soil water content) and soil CH₄ gradient concentration.

高地土壤是主要的甲烷（CH ₄）生物汇，可能会受到土地利用变化的影响。土地利用和土壤管理的变化影响控制气体扩散的土壤特性，这些特性与微生物活动相结合，决定了通过土壤的CH ₄通量 (fCH _{4 )。}净 CH ₄通量和扩散率（由 CH ₄扩散系数估算）在南美洲潘佩恩平原的三种常见土地用途（天然草地 NG；Eucalyptus globulus Labill.植树造林 E；和农业用地 AL：在两年（2017 年 3 月至 2019 年 3 月）期间连续种植的燕麦、大豆和红三叶草。使用静态室技术测量土壤-大气界面中的甲烷通量，并应用扩散模型从土壤孔隙度估计土壤 CH _{4扩散率。}我们旨在量化土地利用变化（E 和 AL 与 NG，参考系统）对 fCH ₄和土壤参数变化引起的气体扩散率的影响。土壤是三种土地利用的净汇，平均 CH ₄通量在造林中较高，在天然草地中居中，在农业用地中较低（- 10.99 ± 5.85，- 8.9 ± 5.32 和 - 4.58 ± 4.19 ng CH ₄ m ^-2秒^-1，分别）。CH ₄通量随季节和空间的变化而显着变化，这与充水孔隙空间和充气孔隙空间变量的变化相一致（ρ > 0.7 和 <-0.7；p < 0.05）。NG-E 和 NG-AL的甲烷通量 ΔfCH ₄的土地利用变化指标分别为− 2.1 ± 3.7 和 4.4 ± 2.5，表明天然草地造林后 CH ₄净吸收显着增加，而当其已转为农业用途。这种变化主要是由土壤物理性质（堆积密度、土壤含水量、WFPS 和充气孔隙度）的变化来解释的。与此相关，土壤 CH _{4扩散系数遵循与 fCH 4}相同的模式（E、NG 和 AL 分别为 0.024 ± 0.011；0.015 ± 0.007 和 0.008 ± 0.007 cm ² s ^-1）；并允许我们重新计算平均 CH ₄通量。理论和原位测量的 CH ₄通量相似，并且在土地利用中遵循相同的模式，这表明通过简单测量土壤特性（体积密度和土壤含水量）和土壤 CH ₄梯度浓度来确定 CH _{4通量的可能性。}