Patterns of development and succession of vegetated hummocks in slacks of the Alexandria coastal dune field, South Africa

Elliott, Bridget L.; Kerley, Graham I. H.; McLachlan, Anton

doi:10.1007/bf02730471

Cited by 5 publications

(1 citation statement)

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“…Vegetation (referring here to natural vegetation, including trees, shrubs, grasses etc., which is not disturbed by human activities) plays a key role in maintaining MCBs' ecological functions [10,11]. Vegetation can increase sediment deposition by reducing overflow rate, which in turn could expand or elevate MCBs [12], while the roots of vegetation can stabilize MCBs by reducing soil erosion during floods [13]. Therefore, understanding vegetation dynamic patterns in MCBs is important for predicting MCB evolutions in river systems.…”

Section: Introductionmentioning

confidence: 99%

Impacts of Dam Operation on Vegetation Dynamics of Mid-Channel Bars in the Mid-Lower Yangtze River, China

et al. 2021

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Vegetation dynamics on mid-channel bars (MCBs) is essential for supporting ecosystem functions and associated services in river systems, especially in dammed large rivers. Generally, there are two possible changing patterns that vegetation of MCBs downstream a dam would experience. On one hand, the vegetation area may shrink because of a decrease in the MCB area in the post-dam period, which has been observed in many rivers around the world. On the other hand, the MCB vegetation area may expand because flood disturbances would be weakened by dam operation. However, little evidence has been reported to clarify such confusion. Therefore, vegetation dynamics of MCBs in the mid-lower Yangtze River downstream the Three Gorges Dam (TGD; the world’s largest dam) is selected as a case study to address the issue. Using long-term (1987–2017) Landsat archive images, this study reveals the spatiotemporal variations of vegetation area change intensities (VACIs; indicated by dynamic trends) on MCBs in the mid-lower Yangtze River. Results show that an overall VACI in the post-dam period (2003–2017) is about three times faster than that in the pre-dam period (1987–2002). In other words, the rate of vegetation colonization accelerated after the TGD operation began in 2003. Moreover, the VACIs in the post-dam period are size dependent, where large size MCBs are likely to gain higher VACIs: Small-sized MCBs (0.33 km2/yr), medium-sized MCBs (1.23 km2/yr), large-sized MCBs (1.49 km2/yr). In addition, VACIs of individual MCBs in the post-dam period are distance dependent, where the further a MCB was from the TGD, the higher the VACI. It is also suggested that the weakened flood disturbances in the post-dam could explain the rapid vegetation growth and colonization. This work is not only beneficial for managing and protecting MCBs downstream the TGD after its operation, but is also helpful in understanding vegetation dynamics of MCBs in other dammed river systems around the world.

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