Expansion and Management Implications of Invasive Alien <i>Spartina alterniflora</i> in Yancheng Salt Marshes, China

Abstract

Improved understanding of the spatial dynamics of invasive plant species is critical for effective land management and control of future invasion. The Yancheng National Nature Reserve (YNNR), an internationally important wetland, has the largest distribution of alien Spartina alterniflora in China. This alien plant was intentionally introduced for erosion prevention and dike protection in China. However, it became an aggressive competitor with native salt marsh plants in the coastal regions in China. High resolution imagery, SPOT-5, was used to map plant communities including invasive species in the south core zone of YNNR with the natural ecosystem of salt marshes in 2003, 2005 and 2008. The fuzzy set assessment method significantly improved the classification accuracies over the conventional error matrix, i.e., from 73.8%, 73.5% and 81.4% to 91.5%, 91.6% and 93.4% in 2003, 2005 and 2008, respectively. It shows a great potential for mapping invasive plant species. Phragmites australis and S. alterniflora were the most accurately mapped classes, and sparse and dense Suaeda glauca were the least accurately mapped. From 2003 to 2008, S. alterniflora increased 28.8% from 1664.1 to 2142.6 ha in area size, and more than 2.5 times from 742 to 2608 patches. The highest increase in patch number occurred within the interval between 2001 and 3000 m from the eastern baseline. This increase was dominated by small patches with area less than 200 m 2 . During the study period, the mean spread width was 405 ± 80.7 m in the original large patch of area over 200 ha. The eastward/seaward spread was distinctively larger than the westward/landward. The results enhance the understanding of alien plant's invasion patterns and help improve conservation efforts. C. Y. Liu et al. 114

Rapid Invasion of Spartina Alterniflora in the Coastal Zone of Mainland China: Spatiotemporal Patterns and Human Prevention

“…This study highlighted that the rampant extension of S. alterniflora was not yet effectively prevented. Previous studies revealed that the two top hotspot sites of S. alterniflora invasion were the coastal areas of Yancheng in Jiangsu and the Yangtze River Estuary in Shanghai [26,27,28]. Results from this study also indicate that these two sites experienced the largest area increase of S. alterniflora (Figure 4) during the investigated 25 years.…”

Rapid Invasion of Spartina alterniflora in the Coastal Zone of Mainland China: New Observations from Landsat OLI Images

“…Remote sensing data of moderate spatial resolution are of limited utility for the detection of objects at fine or detailed scales. Definitely for S. alterniflora, Landsat images are of limited value for delimitating small and narrow patches due to their spectral uniformity, e.g., areas smaller than 1000 m 2 , especially where S. alterniflora has not gained dominance [3,11]. High-resolution satellite data or the fusion of multiple data sources that cover the long coast of mainland China, combined with new classification methods such as machine learning, are thus needed to be assessed for a more accurate monitoring of S. alterniflora invasion.…”

“…Monitoring the distribution of S. alterniflora has received extensive attention in China [3,14,23,45,46]. For mainland China, there were three studies investigated the distribution of S. alterniflora along the coast [10,12,14].…”

“…Plant invasion, as an important type of biological invasion, has emerged as a serious ecological issue, which threatens native species and affects the structure and function of ecosystems [1][2][3][4].…”

Appling the One-Class Classification Method of Maxent to Detect an Invasive Plant Spartina alterniflora with Time-Series Analysis

“…The non-native species S. alterniflora was introduced for the purposes of beach protection and siltation promotion in 1979 [7]. After the 1980s, the rapid expansion of the invasive species resulted in continuous changes in the species composition of the saltmarshes and threatened coastal environments [14], for example clogging navigation and flood control channels [7], reducing the open mud feeding habitats of shorebirds [4], competing with native plants [12] and even decreasing biodiversity [16]. It is therefore urgent to assess in detail the distribution of S. alterniflora for the purposes of invasion control and biodiversity conservation.…”