Quantitative analysis of soil pores under natural vegetation successions on the Loess Plateau

Soil pore is a key attribute of the soil structure that affects soil reservoir under natural vegetation recovery on the Loess Plateau. This study is to quantitatively analyze soil pore parameters, measured with Computed Tomography (CT) at 15-57 mm depths under five different vegetation succession stages using a concept of substituting space for time in the Ziwuling Forest Region of the Loess Plateau. The results showed that the soil pore parameters, such as pore number, porosity, circularity, and fractal dimension, increased significantly under the natural vegetation successions and varied with the pattern climax community stage > pioneering arbor community stage > scrub community stage > herbaceous community stage > abandoned farmland stage, indicating that natural vegetation recovery could remarkably improve soil pore characteristics. With the vegetation succession, this positive effect will be strengthened gradually, which means that the soil pore parameters may appear to be best at the climax community stage. Soil organic matter content increased linearly with the soil pore parameters (P < 0.001). Increased organic matter accumulation was one of the major reasons for the changes in soil pore characteristics in natural vegetation succession.