Impact of Climate Change on Vegetation Coverage in Marsh Wetland of the Tibetan Plateau

Abstract:

As the Earth’s third pole, the Tibet Plateau has a large area of marsh wetland. Marsh wetland plays a key role in providing wildlife habitat and protecting biodiversity in the Tibet Plateau. Vegetation is an important component of marsh ecosystem, and the conditions of marsh vegetation have important effects on wetland function. As a crucial biophysical parameter for monitoring vegetation conditions, fractional vegetation cover (FVC) has been widely used in detecting the dynamics of vegetation coverage and analyzing the impact of global change on vegetation in wetland ecosystems. In the context of global climate change, understanding the responses of wetland FVC to climate change in the Tibet Plateau can provide useful information for the prediction of wetland vegetation and the conservation of wetland in this region. Based on the climate data and Moderate Resolution Imaging Spectrometer Normalized Difference Vegetation Index data, this study calculated the FVC using the pixel dimidiate model and investigated the impact of climate change on vegetation coverage in marsh wetland of the Tibetan Plateau during 2000-2019. We found that the mean growing season (May to September) FVC of marsh wetland over the entire Tibetan Plateau has increased by 0.21% per year during the past 20 years. The most obvious increase of FVC was found in the northeast of the Tibet Plateau. Correlation analysis results showed that precipitation had a weak effect on the FVC in marshes of the Tibetan Plateau. Increasing growing season precipitation could slightly increase the FVC of seasonal marshes, but decrease the FVC of inland salt marshes in the Tibetan Plateau. The FVC of marsh wetland in the Tibetan Plateau was significantly affected by surface air temperature, and warming temperatures could obviously increase the vegetation coverage of marshes. In addition, we found asymmetric impacts of daytime maximum temperature (Tmax) and night-time minimum temperature (Tmin) on the FVC of marshes in the Tibetan Plateau. Compared with growing season Tmax, growing season Tmin had a larger positive effect on the FVC of marshes in the Tibetan Plateau. Given the global asymmetric warming of daytime and night-time temperature, we should pay more attention to this asymmetric impact of Tmax and Tmin on vegetation in marsh wetland of the Tibet Plateau.