Monitoring the Invasion of Spartina alterniflora from 1993 to 2014 with Landsat TM and SPOT 6 Satellite Data in Yueqing Bay, China

Abstract

The exotic plant Spartina alterniflora was introduced to Yueqing Bay more than 20 years ago for tidal land reclamation and as a defense against typhoons, but it has rapidly expanded and caused enormous ecological consequences. Mapping the spread and distribution of S. alterniflora is the first step toward understanding the factors that determine the population expansion patterns. Remote sensing is a promising tool to monitor the expansion of S. alterniflora. Twelve Landsat TM images and Support Vector Machine (SVM) were used to delineate the invasion of S. alterniflora from 1993 to 2009, and SPOT 6 images and Object-Based Image Analysis (OBIA) were used to map the distribution of S. alterniflora in 2014. In situ data and Unmanned Aerial Vehicle (UAV) images were used as supplementary data. S. alterniflora spread rapidly in Yueqing Bay over the past 21 years. Between 1993 and 2009, the area of S. alterniflora increased by 608 times (from 4 to 2432 ha). The rapid expansion of S. alterniflora covered almost all of the bare mudflats around the mangrove forests and the cultivated mudflats. However, from 2009 to 2014, the rate of expansion of S. alterniflora began to slow down in Yueqing Bay, and the total area of S. alterniflora in Yantian decreased by 275 ha. These phenomena can be explained by the landscape changes and ecological niches. Through the expansion of S. alterniflora, it was found that the ecological significance and environmental impact of S. alterniflora was different in different regions in Yueqing Bay. The conservation plans for Yueqing Bay should consider both the positive and negative effects of S. alterniflora, and the governmental policy should be based on the different circumstances of the regions.

Genetic admixture accelerates invasion via provisioning rapid adaptive evolution

“…Bigger pies in (a) and (b) shows the relative frequencies of the haplotypes. The haplotypes from additional three sites in the Gulf of Mexico were from the literature as cited TA B L E 1 The sampling locations, time of introductions (Li et al, 2009;Wang et al, 2015;Xia, Zhao, Yang, & An, 2015;Xu & Zhuo, 1985;Zhang et al, 2017) Note: The sample sizes are the number of sampled clones per population for the (north/mid-/south) gardens and alternative experiments. The regions within the invasive range are differentiated according to the differentiation among geographic, climatic and tide range variables ( Figure 1 and Figure S2), and the regions within the native range are defined following Blum et al (2007) and Bernik et al (2016).…”

Monitoring the Invasion of Spartina alterniflora Using Multi-source High-resolution Imagery in the Zhangjiang Estuary, China

“…alterniflora, as an invasive plant, has both positive and negative effects in the coastal areas of China [12,49]. For example, a 4000-m-long dike in Yueqing Bay was seriously damaged by a big typhoon in 1994, whereas 600 m of an 800-m-long dike in Wenling, close to Yueqing Bay, that was covered by dense S. alterniflora, remained in good condition [21]. In Jiuduansha, because of the high proliferation ability and competitive advantage, S. alterniflora inhibited the growth of other plant species [50].…”

Mapping Above-Ground Biomass of Winter Oilseed Rape Using High Spatial Resolution Satellite Data at Parcel Scale under Waterlogging Conditions

“…Moreover, remote sensing techniques, as well as multispectral reflectance, can provide quantitative information about the water status of many agricultural crops [17,18]. Since the first satellite was launched in 1972, a fair amount of available remote sensing datasets and images have become the basic tools for land cover mapping, environmental monitoring, and ecological process scaling from stand to regional and global levels [19,20]. Meanwhile, time series observation is particularly important for monitoring seasonal changes in plant growth and development and for studying canopy function [21].…”