Changes of Vegetation Distribution in the East Dongting Lake After the Operation of the Three Gorges Dam, China

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.

Role of Flooding Patterns in the Biomass Production of Vegetation in a Typical Herbaceous Wetland, Poyang Lake Wetland, China

“…We think this phenomenon can be attributed primarily to the higher adaptability of wetland vegetation to AID than its adaptability to IDU. For example, the study by Hu et al (2018) in the Dongting Lake wetland revealed that the distribution elevations of wetland vegetation varied to some extent in different years, although their annual inundation duration was relatively constant. It also indicated that IDU may be a better indicator to predict changes in vegetation production in response to wetland flooding patterns.…”

Flood Monitoring in Vegetated Areas Using Multitemporal Sentinel-1 Data: Impact of Time Series Features

“…Therefore, a single time series feature with the highest contribution was used for the classification for deriving the desired classes. This identification step is performed automatically by Since the TFV type is high grassland and reed (Figure 5b) [64], which is similar to the structure of some crops (rice, wheat), it is assumed that the vegetation can be penetrated by the C-band data [10,65]. Therefore, it is expected that the increase in backscatter values will occur at the time of the flood in the VV polarization due to their sensitivity to the double impact effect.…”

Factors controlling <i>Carex brevicuspis</i> leaf litter decomposition and its contribution to surface soil organic carbon pool at different water levels

“…Peng et al (2005) reported that the organic carbon density in Dongting Lake wetland soil at 1 m depth was 127.3 ± 36.1 t hm −2 , and the carbon density in the 0-30 cm topsoil was 46.5 ± 19.7 t hm −2 . Carex brevicuspis is a dominant species in the Dongting Lake wetland and has large carbon reserves (∼ 6.5 × 10 6 t yr −1 ) (Kang et al, 2009). However, due to the dam construction upstream of Dongting Lake, the water regime has varied considerably (early water withdrawal and decline of groundwater in non-flood season) in recent years, leading to a significant carbon loss in this floodplain wetland (Hu et al, 2018;Deng et al, 2018).…”