Plant Population Dynamics in a Degraded Coastal Wetland and Implications for the Carbon Cycle

Abstract

Habitat destruction caused by human activities is threatening wetland plants. Based on Landsat 5 TM, Landsat 8 OLI, and Google Earth images, we analysed the spatiotemporal dynamics of plant populations in a degraded wetland in the Minjiang River Estuary from 2009 to 2019. Field survey records, tasselled cap transformation, and supervised classification were used for the image interpretation. The results indicate that the plant habitat area decreased by 42.1% over these 10 years. Consequently, the distribution area of each dominant species declined, and the proportion of total vegetated area in the habitat decreased from 53.1% to 32.6%. Moreover, the dominance relations of the species changed from Spartina alterniflora > Phragmites australis > Cyperus malaccensis > Scirpus triqueter to P. australis > S. alterniflora > C. malaccensis > S. triqueter. We predict that the vegetation landscape in the wetland will be composed exclusively of P. australis and S. alterniflora if habitat destruction continues. Finally, our research shows that the NPCS (net plant carbon sequestration) and PCS (plant carbon stock) in the wetland and the average values of methane flux, NPCS, PCS, and SOCS (sediment organic carbon stock) in the vegetated area have all decreased due to plant population declines.