Abstract
Aggregate is the basic unit of soil structure, which is crucial to the sustainability of soil system functions such as structural stability and Fertility Maintenance. Three Gorges Dam (TGD) has extensively led to a dramatic hydrological regime alteration, which may consequently affect various soil physical properties. The aim of this study was to investigate the long-run temporal variation of soil aggregate stability as induced by water-level fluctuations in the riparian zone of the Three Gorges Reservoir (TGR). Sampling plots were established along different elevations considering the interval of 5 m, starting from 150 m to 175 m. A Laser Diffraction based analysis that allows the measurement of soil aggregate stability after the removal of soil organic matter helped to particularly study the effect of external factors on soil aggregate stability of the study area. In addition, wet-sieving method considering the effect of chemical binding agents was used to quantify aggregate stability. The present results indicated a significant increase of Mean Volume Diameter, MVD (p < 0.05) within the study period. Continuous drying-wetting cycles mended soil aggregate stability with a 14.25% increase of the MVD from 2012 to 2016. In the Water-Level Fluctuation Zone (WLFZ), the lower land has predominantly contributed to the increase of soil aggregate stability compared to upper land, with an increase of 62.19% and 37.81% for MVD, 60.88% and 39.12% for D10, 95.34% and 4.66% for D90 at lower and upper elevations, respectively. Sediment deposition below 165 m has precluded a direct effect of water stress on soil aggregates, which certainly declined soil disaggregation. The removal of SOM while analyzing aggregate stability by LD may explain the contradiction between the resulted MVD, and the MWD and GMD. The increase of MWD and GMD was mainly attributed to the increase of SOM with r2 = 0.89 (p < 0.01) and r2 = 0.90 (p < 0.01), while the increase of MVD was highly predicted by the decrease of SOM with r2 = 0.88 (p < 0.01). Since this study presents a remarkable change of soil in the riparian area due to dry-wet cycles, our results may help to deeply understand the soil ecology and environmental changes in the WLFZ.
Highlights
And edaphologically, soil structure is referred to as the size, shape, strength, and pore capacity of soil aggregates to sustain and transfer soil fluid materials and the ability to support roots growth and enlargement [1]
The present study investigated the temporal variation of soil aggregate stability being affected by wetting and drying cycles occurring in the Water-Level Fluctuation Zone (WLFZ) of the Three Gorges Reservoir (TGR)
This study evaluated the long-run temporal dynamic changes of soil aggregate stability and particle size distribution in the riparian zone of the TGR using an Laser Diffraction (LD)
Summary
And edaphologically, soil structure is referred to as the size, shape, strength, and pore capacity of soil aggregates to sustain and transfer soil fluid materials and the ability to support roots growth and enlargement [1]. Aggregate stability is primarily considered as the indicator of soil quality. It plays an important role in indicating the susceptibility of soil to degradation [4]. Aggregated soil is the result of the interaction of various factors such as soil organic carbon, soil texture, wet-dry cycles, etc. In this regard, SOC plays a key role in stabilizing soil aggregates [7]. There are two main groups of factors influencing soil aggregate stability namely primary soil characteristics such as clay composition and organic matter and external factors such as dry-wet cycles [10]. Few studies investigated the impacts of external factors regardless of the effect of soil organic matter
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