Soil water dynamics and deep soil recharge in a record wet year in the southern Loess Plateau of China

Terrestrial water cycles are influenced by hydrologic and textural properties of the deep loess layer in the Loess Plateau. Analyses of soil water profile distributions are needed to understand the regional water cycle processes and to guide agricultural production and sustainability. The objective of this study was to quantify the extent of deep soil water recharge and soil water profile dynamics during 1987-2003, especially in a record wet year of 2003, in common cropping systems in a semiarid-subhumid region of the southern Loess Plateau. The Chinese Ecological Research Network (CERN) site and a long-term rotation experiment site in a flat tableland were selected for this study. Soil moisture profiles were measured by a neutron probe to a depth of 6 m in 2003. The precipitation of 954 mm at the Changwu County Meteorological Station in 2003 was 63.4% higher than the long-term average (584 mm), and was a record high since 1957. Although cropping systems affected deep soil water recharge, the persistent dry soil layer formed between 2- and 3-m depths in croplands, resulting from many years of intensive cropping, was fully replenished in all cropping systems in 2003. Further frequency analysis indicated that the desiccated layer between 2- and 3-m depths would be fully recharged at least once in about 10 years for all existing cropping systems excluding continuous alfalfa. This finding should alleviate concerns about the formation of a permanent deep-soil desiccation layer as well as its potential impact on the long-term sustainability of the existing intensive cropping systems in the region.     

Minimally invasive evaluation of the anaesthetic efficacy of MS‐222 for ornamental discus fish using skin mucus biomarkers

Skin mucus has been demonstrated to provide stress biomarkers for evaluating the physiological status, providing new convenient and non‐invasive methods to detect stress response in fish. Here, we investigated the anaesthetic efficacy of tricaine methanesulphonate (MS‐222; 75–115 mg/L) for discus Symphysodon aequifasciata (34.27 ± 4.46 g; 8.10 ± 0.59 cm) using skin mucus stress biomarkers. The induction time, recovery time and respiratory frequency were also determined. According to the criteria for anaesthesia and recovery, discus fish to reach stage A3 (deep anaesthesia) within 3 min and to reach stage R4 (full recovery of normal behaviour) within 5 min were observed at 95–105 mg/L MS‐222. Respiratory frequency increased first and then decreased during MS‐222 exposure and increased after recovery. At 10 min after deep anaesthesia, a lower mucus glucose was only observed at 115 mg/L MS‐222. No change in mucus cortisol and increased lactate were observed in all treatments. Increased mucus protein was observed at 75, 85 and 95 mg/L MS‐222. At 10 min after recovery, increased mucus glucose and decreased mucus protein were observed at 85, 95 and 115 mg/L MS‐222, but increased mucus cortisol only at 115 mg/L and lactate only at 75 and 105 mg/L MS‐222. At 24 hr after recovery, mucus glucose returned to the initial level only at 75, 95 and 105 mg/L MS‐222, while cortisol at 75 and 85 mg/L and protein and lactate at 75 mg/L respectively. Overall, the effective dose of MS‐222 for discus fish has been suggested to be 95–105 mg/L.     

Microsatellite analysis of genetic diversity and genetic structure of the Chinese freshwater mussel Solenaia carinata (Bivalvia: Unionidae)

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