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The complexity and uncertainty of pore structures, hinder the understanding of the water infiltration process along a soil profile. In this study, soil pore structures quantified by X-ray computed tomography (CT) scanning and infiltration processes traced using stable hydrogen and oxygen isotopes were lin k ed under three land uses (forestland, citrus land, and rainfed cropland) in the red soil region of southern China. Our results showed that 95% of the soil pore diameters in the surface layer (0–20 cm) in forestland, citrus land, and rainfed cropland were concentrated in the ranges of 0.05–2.46, 0.05–2.24 and 0.05–1.04 mm, respectively. Rainfed cropland had the most soil micropores, along with a high porosity and poor connectivity, while there were more large, well-connected tubular pore channels in the forestland and citrus land. Hydrogen and oxygen stable isotopes were effective in tracing soil water infiltration processes under saturated and near-saturated conditions. The soil infiltration depths of citrus land, forestland, and rainfed cropland were 45, 40, and 25 cm, with "new water" volumes of 37.2, 26.4, and 22.3 mm, respectively. CT-based porosity and the soil texture were considered crucial indicators in the evaluation of the exchange between "old water" and "new water" during infiltration processes. More specifically, the soil structure of the limiting layer not only controlled the infiltration rate but also played an extremely important role in the infiltration mechanism, reflected by the different ratios of "new water". The soil pore characteristics mainly affected soil water transport, while other soil properties played more important roles in soil water retention. • Land use affected the profile distribution of soil pore characteristics. • More information came from the stable isotope abundance of soil water than its contents. • The exchange ratio of "new water" and "old water" was obtained by stable isotopes. • Soils with well-connected structures had a higher proportion of "new water". • The pore structure of the limiting layer controlled the infiltration rate and mechanism. [ABSTRACT FROM AUTHOR]

• Soil microbial community profiles were significantly altered in the degraded patches. • Soil microbial abundance remained unaffected by the degraded path formation. • Degraded path formation increased soil nitrifier and plant pathogen proportions. • Degraded path formation altered the soil microbial co-occurrence pattern. • Degraded path formation impeded the recovery of degraded alpine meadows. Approximately half of global grasslands are degraded. Although soil microbes play a key role in ecosystem functioning, their response to grassland degradation has not been fully investigated. In particular, degraded patch formation is the main feature of alpine meadow degradation, but little is known about its effect on soil microbes. In this study, soils were collected from three patch-degraded Tibetan alpine meadows to examine the effects of degraded patch formation on soil microbial communities. The alpine meadows at the three sites were in the third to fifth stages of degradation, respectively. Soil microbial abundance and community structure were determined through real-time PCR and MiSeq sequencing, respectively. The results showed that the degraded patch formation significantly decreased microbial respiration rates, changed the interaction patterns among microbial taxa, and increased fungal diversity, but did not significantly affect microbial abundance. Additionally, both prokaryotic and fungal community composition was significantly altered by the degraded patch formation. The functional predictions based on FAPROTAX and FUNGuild suggested that degraded patch formation significantly increased the proportion of nitrifiers, plant pathogenic fungi, and saprotrophic fungi, especially when mattic epipedons were eroded. The increased relative abundance of nitrifiers and pathogenic fungi can aggravate the risk of nitrogen leaching and plant diseases, respectively. Therefore, degraded patch formation can impede the recovery of degraded alpine meadows by changing soil microbial community composition. [ABSTRACT FROM AUTHOR]