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Physics of estuaries and coastal seas
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Vegetation Competition Observed by High Resolution Remote Sensing Images Within an Estuarine Saltmarsh
P-P1-17-S
Silong Huang* , Second Institute of Oceanography, SOA, Hangzhou, China
Yining Chen, Second Institute of Oceanography, SOA, Hangzhou, China
Tinglu Cai, Second Institute of Oceanography, SOA, Hangzhou, China
Presenter Email: throne0824@hotmail.com |
| The tidal flat of the Andong Shoal is a typical mudflat expanding rapidly towards the sea. The upper part of this tidal flat is covered by a mature saltmarsh which has developed over the last decade after embankment. The evolution of the saltmarsh on the Andong Shoal is mainly determined by the competition and succession of the exotic species Spartina alterniflora and the native species Scirpus mariqueter. Therefore, in this study, we attempt to investigate the temporal and large-scale spatial variations of the exotic and native species under competition, over a period of rapid saltmarsh development. Three high resolution (<1m) remote sensing images were collected, during the period from 2016 to 2018, in order to investigate the spatial and temporal variations of Scirpus mariqueter and Spartina alterniflora within this area. Professional software packages, such as ENVI and ArcGIS, were used to analyze and further interpret the images, after the calibration using field survey data. The results showed that the total area of the studied saltmarsh increased from 2016 to 2018, at a mean rate of 161.5 m a-1. The upper marsh was mainly occupied by Spartina alterniflora and the vegetation area increased, at a rate of 1.585 km2 a-1. Scirpus mariqueter originally covered the middle to lower marsh in 2016. However, due to the competitive stress of Spartina alterniflora, the area of Scirpus mariqueter decreased over this period, at a rate of 1.245 km2 a-1, although the seaward edge of Scirpus mariqueter was still expanding. Overall, the expansion rate of Spartina alterniflora is two times of that of Scirpus mariqueter and this resulted in the succession of the middle marsh, from Scirpus mariqueter to Spartina alterniflora. The observation of the spatial patterns over two-year period also indicated a bimodal pattern for Spartina alterniflora: this exotic species expand both at the upper marsh and the seaward edge of the saltmarsh. The upper marsh expansion of Spartina alterniflora is mainly caused by the lateral expansion of rhizome, whilst the expansion at the edge is associated with seed diffusion and settling driven by tidal hydrodynamics. |
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