Abstract
Water regime is regarded as the primary factor influencing the vegetation distribution in natural wetland ecosystems. However, the effect of water regime change induced by large-scale hydraulic engineering on vegetation distribution is still unclear. In this study, multi-temporal TM/ETM+/OLI images and hydrological data from 1995 to 2015 were used to elucidate how the change in water regime influenced the vegetation distribution in the East Dongting Lake (EDTL), especially after the operation of the Three Gorges Dam (TGD) in 2003. Using unsupervised and supervised classification methods, three types of land cover were identified in the study area: Water and Mudflat, Grass, and Reed and Forest. Results showed that the total vegetation area in EDTL increased by approximately 78 km2 during 1995–2015. The areas of Reed and Forest and Grass exhibited a contrasting trend, dramatic increase in Reed and Forest but sharp decrease in Grass, particularly after the operation of TGD. The lowest distribution elevations of Grass and Reed and Forest decreased by 0.61 and 0.52 m, respectively. As a result of water level variation, submergence duration increased at 20–21 m and 28 m elevations (1–13 days), but significantly decreased at 22–27 m and 29–30 m elevations (-3 to -31 days). The submergence duration of Grass and Reed and Forest was 246 and 177 days, respectively. This study indicated that wetland vegetation pattern significantly changed after the operation of TGD, mainly as a result of changes in submergence condition. Submergence duration might be an effective indicator to predict the shift of vegetation distribution in EDTL, and which could provide scientific guidance for vegetation restoration and wetland management in this lake.
Highlights
Wetland is a crucial component of the earth’s landscape and is considered as one of the most diverse and productive ecosystems on the planet (Kingsford, 2000; Rosenberg et al, 2000; Tockner and Stanford, 2002)
Water level is considered as a major factor influencing the development of wetlands and an intuitive indicator to assess the changes of vegetation distribution, since water level fluctuation strongly affects the growth and survival of vegetation (Casanova and Brock, 2000; Johansson and Nilsson, 2002; Coops et al, 2003)
Zonation is a general response of wetland vegetation to regular water level fluctuation
Summary
Wetland is a crucial component of the earth’s landscape and is considered as one of the most diverse and productive ecosystems on the planet (Kingsford, 2000; Rosenberg et al, 2000; Tockner and Stanford, 2002). Variations in water regime, such as the frequency, duration, magnitude, and timing of flooding, can transform some key environmental factors for the development of downstream wetlands (Poff et al, 1997) These changes directly or indirectly impact wetland structure and community dynamics (Miller and Zedler, 2003; Zedler and Kercher, 2005; Fraser and Miletti, 2008; Todd et al, 2010), sometimes even resulted in the disappearance of flood-dependent vegetation (Auble et al, 1994; Taylor et al, 1996; Arthington and Pusey, 2003). The pattern of vegetation distribution appears to be unclear when water level is variable
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