Abstract
Foliar decomposition has significant effects on nutrient cycling and the productivity of riparian ecosystems, but studies on the impact of related hydrological dynamics have been lacking. Here, the litterbag method was carried out to compare decomposition and nutrient release characteristics in situ, including three foliage types [two single-species treatments using Taxodium distichum (L.) Rich., Salix matsudana Koidz., or a mixture with equal proportions of leaf mass], three flooding depths (unflooded, shallow flooding, and deep flooding), two hydrodynamic processes (continuous flooding and flooded-to-unflooded hydrological processes), and one hydrological cycle (1 year) in the riparian zone of the Three Gorges Reservoir. The results showed that both hydrological processes significantly promoted foliage decomposition, and all foliage types decomposed the fastest in a shallow flooding environment (P < 0.05). The mixed-species samples decomposed most quickly in the flooded hydrological process in the first half of the year and the unflooded hydrological process in the second half of the year. Flooding also significantly promoted the release of nutrients (P < 0.05). Mixed-species samples had the fastest release rates of carbon and nutrients in the flooded hydrological process in the first half of the year and the unflooded hydrological process in the second half of the year. Foliage decomposition was also closely related to environmental factors, such as water depth, temperature, and hydrological processes. Our research clarified the material cycling and energy flow process of the riparian ecosystem in the Three Gorges Reservoir area. It also provided a new reference for further understanding of foliage decomposition and nutrient release under different hydrological environments.
Highlights
As the largest hydroelectric power project in human history, the Three Gorges Reservoir (TGR) has always received widespread attention (Chen et al, 2020a,b; Arif et al, 2021; He et al, 2021; Zheng et al, 2021)
Hydrological Regime, Decomposition, Nutrient Release fluctuation range (145–175 m a.s.l., up to 30 m) and a prolonged flooding duration each year (Ye et al, 2011; Li et al, 2013; Xu et al, 2013; Yuan et al, 2013; Holbach et al, 2014). This dramatically alters the conditions of riparian ecosystems and results in the formation of a reservoir water-level fluctuation zone (Zhang and Lou, 2011; Yang et al, 2012; Zhang, 2018; Arif et al, 2020)
It is worth noting that when the water level rises, the leaves of the trees are inevitably submerged and decompose; when the water level drops half a year later, the leaves that have not been completely decomposed may flow downstream with the water and continue to be decomposed in the waterbody, or they may stay on the riparian land and undergo dry condition decomposition
Summary
As the largest hydroelectric power project in human history, the Three Gorges Reservoir (TGR) has always received widespread attention (Chen et al, 2020a,b; Arif et al, 2021; He et al, 2021; Zheng et al, 2021). Hydrological Regime, Decomposition, Nutrient Release fluctuation range (145–175 m a.s.l., up to 30 m) and a prolonged flooding duration each year (Ye et al, 2011; Li et al, 2013; Xu et al, 2013; Yuan et al, 2013; Holbach et al, 2014) This dramatically alters the conditions of riparian ecosystems and results in the formation of a reservoir water-level fluctuation zone (i.e., seasonal fluctuations causing the land to be periodically flooded and dried, and the formation of an alternating dry and wet land–water transition zone, which is defined as the area between the normal water level) (Zhang and Lou, 2011; Yang et al, 2012; Zhang, 2018; Arif et al, 2020). This is not conducive to our understanding of the material cycle and energy flow process of the riparian ecosystem
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