Abstract
BackgroundDrying and rewetting process, frequently occurred during climatic changes, is an important process in soil aggregate slacking and dissolution. The severer interference of human activities on global climate makes the extreme climate scenarios like drought and rainstorm occur frequently. Therefore, there is necessity to further our understanding on the impact of the drying–wetting cycles and initial water content on the breakdown of soil aggregates. The typical yellow–brown earth composed of water–stable and water–unstable aggregates is selected. Variations of water-stable aggregate size distributions after drying-wetting cycles are measured by wet sieving, under variable initial water content and cycles respectively.ResultsDrying-wetting cycles cause a significant aggregate slaking, especially within the first two cycles. After that, most aggregates show more slacking resistant. The variation curves of the proportion of water-stable aggregates with the size 1–5 mm shows a coexistence of slaking process and supplement. The critical initial water content (about 24%) and turning point (with the aggregate size of 0.3 mm) are proposed to describe the effects of initial water content on size distribution of water-stable aggregates. Overall, the increase of initial water content strengths the water stability. In addition, the mathematical model for the relative leakage ratio based on the drying–wetting cycle, initial water content and size distribution are established.ConclusionsThe findings reported in this paper may be capable of supporting the intensive study for the breakdown mechanism and assessing the leakage potential under the influence of climate change. However, there exists a certain mismatch between the drying-wetting cycles in the tests and in practice, mainly in the frequency and intensity, which should be paid more attention.
Highlights
Drying and rewetting process, frequently occurred during climatic changes, is an important process in soil aggregate slacking and dissolution
Water stability of soil aggregate Based on the previous researches on the water stability of aggregates, the following characteristic parameters are applied to describe the water stability of the soil aggregates in this study
The mass percent contents of soil aggregates with the size greater than 0.25 mm or 5 mm after wet sieving are used as the evaluation index for the water stability, which can be symbolled as WSA0.25 and WSA5
Summary
Frequently occurred during climatic changes, is an important process in soil aggregate slacking and dissolution. Variations of water-stable aggregate size distributions after drying-wetting cycles are measured by wet sieving, under variable initial water content and cycles respectively. The karstification can induce land degradation, vegetation coverage loss, excess soil erosion, and the karst rocky desertification eventually (Wang et al, 2004). All these conditions lead to severe pressure on geo–disaster reduction and social resilience to disasters. Lal (2003) described the soil erosion process as a four-stage process involving detachment of particles, breakdown of aggregates, transport and redistribution of sediments over the landscape and deposition in depressional sites or aquatic ecosystems. As the most predominant process during the formation of karst rocky desertification, large amounts of studies have documented the aspects of soil erosion. Lal (2003) described the soil erosion process as a four-stage process involving detachment of particles, breakdown of aggregates, transport and redistribution of sediments over the landscape and deposition in depressional sites or aquatic ecosystems. Foster (1982), Hogarth et al (2004), Rouhipour et
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