覆盖作物轮作改善砂姜黑土生物孔隙结构的多尺度研究OA

[Objective]Biopores constitute a critical component of the soil pore network,exhibiting significantly greater efficiency in facilitating the transport of water,solutes,and gases compared to nonbiopores.However,quantitative analysis of biopores at a single scale exhibits significant limitations in resolving morphological characteristics,elucidating developmental dynamics,and evaluating functional attributes.[Method]To comprehensively characterize soil biopores distribution patterns,this study integrated a 5-year rotational field experiment on lime concretion black soil with high-resolution X-ray computed tomography(CT)scanning.The investigation was conducted at three distinct scales:(1)large column scale(10 cm diameter×20 cm height soil columns),(2)small column scale(5 cm diameter×5 cm height soil cores),and(3)aggregate-scale(3-5 mm aggregates).We systematically examined the effects of different cropping systems-conventional wheat-maize rotation(WM)versus cover crop rotations(wheat-Cassia occidentalis:WY,and wheat-Cassia tora Linn.:WJ)-on biopore characteristics within the 0-20 cm soil layer.Furthermore,we critically evaluated the applicability of each scale for biopore network analysis.[Results]This study developed an improved biopores segmentation protocol comprising three key steps:(1)initial classification of pores into connected and isolated networks,(2)application of 3D distance transform watershed algorithms to separate biopores and nonbiopores,and(3)implementation of a Random Forest classifier leveraging morphological feature parameters(blobness,sphericity,compactness,and plateness)for scale-specific biopores segmentation across all three observational scales.Compared to the WM treatment,the WY treatment significantly increased bioporosity by 237％,243％,and 119％at the large column,small column,and aggregate scales(P<0.05),respectively.Similarly,the WJ treatment resulted in an increase of bioporosity by 111％,217％,and 114％at the large column,small column,and aggregate scales(P<0.05),respectively.At the large column scale,biopores exhibited significantly larger diameters than those at small column and aggregate scales,with mean diameters ranging from 1 444-3 374 μm and maximum diameters reaching from 4 792-8 854 μm(P<0.05).This scale effectively captured the biopores network architecture and directly revealed vertical continuity patterns throughout the 0-20 cm plow layer.However,large column scale analysis showed limited detection capability for fine biopores(<60 μm in diameter),reflecting inherent resolution constraints of the methodology.The small column effectively identified medium-to-fine biopores(30-60 μm)and primarily correlates with soil physical properties governing hydraulic conductivity and gas transport.Microscale aggregate analysis can resolve ultra-fine biopores(60-30 μm in diameter),with quantitative characterization revealing these biopores occupy 21.6％-34.4％of total aggregate porosity.Aggregate scale analysis provides critical insights into root-soil architecture interactions and reveals fundamental mechanisms of soil organic carbon physical protection within microhabitats.[Conclusion]This study demonstrated that cover cropping significantly enhanced soil biopore networks across multiple scales.We propose that future research adopt integrated multiscale approaches to fully unravel the spatial distribution and temporal evolution of these biopore systems.