Evaluating the Effects of Pressure Indicators on Riparian Zone Health Conditions in the Three Gorges Dam Reservoir, China

Abstract

The possible negative impacts of flow regulation on riparian zone conditions can be observed due to the disruption of the natural flow regime in reservoirs. In spite of considerable literature on the qualitative effects of external disturbances on riparian health indicators (RHIs), quantitative evaluations of such changes induced by pressure are rare in the literature. Our study evaluated the effects of pressure indicators on the RHIs, and the responses of RHIs relevant to the riparian zones of the Three Gorges Dam Reservoir (TGDR), China, by using the field-based approach. This paper is a component of a large project—rapid appraisal of riparian condition for the TGDR, China. The analysis has compared pressures (13 indicators) and RHIs (27 indicators) determined from the transects (259) identified throughout the TGDR (within 15 counties) by categorizing into upstream, midstream, and downstream. By using basic statistical techniques (Kruskal-Wallis tests and Pearson’s correlation), pressure indicators were found to significantly differently influence RHIs for the categorized three sections of the riparian zones of the TGDR. The correlation analysis confirmed that the pressure indicators correlated (range of r = −0.496–0.971) with the RHIs (enlisted as habitat, plant cover, regeneration, erosion, and exotic parameters). Moreover, pressure indicators were found to have a highly significant influence on erosion and habitat parameters, but moderate effects on plant cover, exotic and regeneration parameters. In addition, the highest relative effect of the pressure indicators was detected in the upstream transects, whereas the lowest was in the downstream transects. Agglomerative Hierarchical Cluster analysis also confirmed the substantial dissimilarity in the upstream transects, whereas significant similarities were identified between midstream and downstream transects. These results may be particularly important in the planning stages, to help administrators and planners form better priorities and treatments for reach-scale conservation and restoration of wide-ranging riparian zones.

Effects of Hydrological Regime on Foliar Decomposition and Nutrient Release in the Riparian Zone of the Three Gorges Reservoir, China

“…When compared with other reservoirs, the new hydrologic regime of the TGR reverses the variation of the natural dry/flood pattern (rising in winter and falling in summer), with a large 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 ). Therefore, the riparian ecosystem in the TGR has both abundant resources in the terrestrial ecosystem and periodic hydrological fluctuations in the aquatic ecosystem, creating a huge area with a unique biogeochemical function.…”

Responses of Swamp Cypress (Taxodium distichum) and Chinese Willow (Salix matsudana) Roots to Periodic Submergence in Mega-Reservoir: Changes in Organic Acid Concentration

“…The mean annual precipitation is 1200 mm, and most rainfalls are in May and June. Plants suffer drought due to high air temperature and relatively fewer rainfalls in July and August [43,44].…”

Diagnostic Evaluation and Preparation of the Reference Information for River Restoration in South Korea

“…Qualitat del Bosc de Ribera (QBR) Index considers key aspects of vegetation, such as coverage and structure, as well as morphological aspects and anthropogenic interference in the landscape [53]. The Riparian Strip Quality Index (RSQI) evaluates the ecological condition of riparian habitats based on the percentage of riparian vegetation [42,52]. The Riparian Condition Index (RCI) considers five components such as riparian vegetation cover, biodiversity condition, hydrologic stress, morphological condition, and catchment disturbance.…”

“…Various indices developed by incorporating such environmental factors have been proposed to evaluate the riparian conditions of rivers. Riparian health indicators and pressure indicators, vegetation state, and morphological condition have been usually adopted [ 15 , 51 , 52 ]. Qualitat del Bosc de Ribera (QBR) Index considers key aspects of vegetation, such as coverage and structure, as well as morphological aspects and anthropogenic interference in the landscape [ 53 ].…”