Land use patterns can change the structure of soil bacterial communities. However, there are few studies on the effects of land use patterns coupled with soil depth on soil bacterial communities in the karst graben basin of Yunnan province, China. Consequently, to reveal the structure of the soil bacterial community at different soil depths across land use changes in the graben basins of the Yunnan plateau, the relationship between soil bacterial communities and soil physicochemical properties was investigated for a given area containing woodland, shrubland, and grassland in Yunnan province by using next-generation sequencing technologies coupled with soil physicochemical analysis. Our results indicated that the total phosphorus (TP), available potassium (AK), exchangeable magnesium (E-Mg), and electrical conductivity (EC) in the grassland were significantly higher than those in the woodland and shrubland, yet the total nitrogen (TN) and soil organic carbon (SOC) in the woodland were higher than those in the shrubland and grassland. Proteobacteria, Verrucomicrobia, and Acidobacteria were the dominant bacteria, and their relative abundances were different in the three land use types. SOC, TN, and AK were the most important factors affecting soil bacterial communities. Land use exerts strong effects on the soil bacterial community structure in the soil’s surface layer, and the effects of land use attenuation decrease with soil depth. The nutrient content of the soil surface layer was higher than that of the deep layer, which was more suitable for the survival and reproduction of bacteria in the surface layer.

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Accurately interpreting the stable oxygen isotopic composition (δ18O) of cave drip water is critical to the retrieval of palaeoclimatic information based on the δ18O records preserved in speleothem calcite. Substantial cave monitoring data sites of interest can make essential contributions. In this study, six speleothem drip water sites and one pool water site were selected for a five‐year (2013–2017) monitoring of O and H stable isotope ratios in Maomaotou Big Cave, Guilin, South China. The results reveal that the drip water δ18O generally inherits the signals in the precipitation but may lag behind by times ranging from 1 to 6 months. Variations in drip water δ18O are determined by climatic variables operating over several time scales. At the individual storm‐event scale, drip water δ18O is a function of rainfall amount, moisture source δ18O and hydrological processes within the vadose zone. Moisture from nearby Beibu Bay in the northwest of the South China Sea often causes the rainfall and thus drip water to be enriched in 18O at Maomaotou Cave, for example. Seasonally or annually, the higher amounts of precipitation associated with the occurrence of El Niño events (e.g. in 2015/2016) result in more depleted drip water δ18O. On the interannual scale, variations of drip water δ18O are linked to changes in the intensity of the East Asian summer monsoon (EASM), the Southern Oscillation Index (SOI) and the West Pacific Subtropical High (WPSH). An enhanced EASM coupled with La Niña‐like conditions likely results in depleted precipitation δ18O, as does a stronger WPSH that leads to more rainfall. This study illustrates the importance of understanding these complex and varying external environmental conditions that contribute to δ18O changes in drip water, when interpreting the palaeoclimatic information contained in speleothems.

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