Soil stability characteristics of mulberry lands at hydro-fluctuation belt in the Three Gorges Reservoir area, China

Abstract

The hydro-fluctuation belt in the Three Gorges Reservoir area is a typical seasonal and artificial wetland system and ecologically fragile zone. Using the widely existing mulberry forest lands in the hydro-fluctuation belt as an example and the 180-m water-level forest land as a control, this paper analyzes the soil stability of mulberry forestlands at different water levels in the hydro-fluctuation belt by analyzing and comparing the changes between soil physical and mechanical properties. The results indicated that (1) water-level changes, such as rising, flooding, draining, and exposure, affect the soil structure in mulberry forestlands. The soil agglomeration statuses for the soil layers decreased from 180 > 175 > 170 > 165 m, and the soil agglomeration statuses at a depth of 0∼20 cm decreased by 43.79, 44.95, and 57.45% compared with the control. (2) The soil water stability index decreased as follows: 180 > 170 > 175 > 165 m, which only accounted for 50.00, 47.73, and 40.91% of the control. In addition, the soil water stability indexes for the topsoils at various water levels were 1.87 (180 m), 1.67 (175 m), 2.92 (170 m), and 1.86 (165 m) times greater than those of the subsoils; thus, the resistance to hydraulic dispersion and disintegration were greater in the topsoil than in the subsoil. (3) The soil aggregate stability index decreased from 180 > 165 > 170 > 175 m and by 22.75, 23.53, and 35.29% compared with the control. (4) The soil shear strengths (composed of the cohesive force C and the internal friction angle φ) of the topsoils at water levels of 175, 170, and 165 m were significantly lower than in the control, and the internal friction angles decreased by 10.52, 19.08, and 43.25% and the cohesive force decreased by 9.88, 16.36, and 27.51%, respectively. The stability of the soil structure was greatly influenced by the soil clay content, soil organic matter content, and waterlogging duration. The study results could provide scientific support for soil and water conservation in the hydro-fluctuation belt and for biological filter construction in the Three Gorges Reservoir area to control the transport of sediment and non-point source pollutants.

The impact of the endophytic bacterial community on mulberry tree growth in the Three Gorges Reservoir ecosystem, China

“…Hydro‐fluctuation belts, also known as riparian zones, are a unique ecotone that connects terrestrial and aquatic habitats (Briar et al ., 2012; Huang et al ., 2013a). The hydro‐fluctuation belt of the Three Gorges Reservoir Region, in the upper section of the Yangtze River, China, is an artificially created seasonal wetland system (Jiang et al ., 2015). It covers about 349 km 2 areas and was created when the annual flow of the Yangtze river was regulated by the construction of the Three Gorges Dam (Liu and Willison, 2013).…”

“…Mulberry trees have also been reported to exhibit a higher survival rate than other woody species exposed to the winter flood period in the hydro‐fluctuation belt of the reservoir (Wang et al ., 2012). Mulberry has thus been planted for several years in the hydro‐fluctuation belt of the reservoir for ecological restoration (Wang et al ., 2012; Jiang et al ., 2015). The stress of prolonged waterlogging, however, has negatively affected the health and survival of trees; while some survive others are subject to die back (Huang et al ., 2013b).…”

“…Little information is available, however, on whether the composition of the microbiota differs in different mulberry compartments (rhizosphere, root, stem, leaves, etc.). Several studies have also described the ecological and environmental problems that exist in the hydro‐fluctuation belt of the Three Gorges Reservoir zone (Huang et al ., 2013a; Jiang et al ., 2015; Liu et al ., 2016), but have not addressed the potential role of the endophytic microbiome in plant response within this stressful environment.…”

Vertical niche differentiation of comammox Nitrospira in water-level fluctuation zone of the Three Gorges Reservoir, China

“…Soil in the WLF zone is flooded at high water levels, which gives it some similarity to wetland soil. However, different from other wetland soils, due to the influence of periodic inundation, the nutrient composition in the Three Gorges WLF zone showed a general downwards trend during the inundation period [36,37]. Some studies showed that CMX are more adaptable to low-nutrient environments [2,38].…”

Combined analysis of transcriptomics and metabolomics on the cumulative effect of nano-titanium dioxide on mulberry seedlings

“…They can withstand harsh environmental conditions such as drought, flooding and high salt, and have a strong ability to preserve soil and play a role in ecological restoration ( Guha et al., 2010 ; Yang et al., 2014 ; Li et al., 2018 ). And also can be used for reservoir shelterbelt forest construction ( Wang et al., 2012a ; Jiang et al., 2015 ). It is worth noting that TiO 2 NPs have shown great potential in agriculture ( Li et al., 2016 ; Wu et al., 2017 ), but no studies reporting the effect of TiO 2 NPs accumulation on mulberry have been performed.…”