入侵种互花米草空间扩张模式识别与景观变化模拟

在3S技术支撑下,通过景观格局指数、质心变化等方法,分析2006—2015年研究区内互花米草群落的景观空间分布特征,并利用2015年高分二号影像识别出扩张模式及预测扩张趋势。结果表明:(1)近年来,互花米草沼泽向陆扩张速度大于向海扩张速度,其质心不断向陆方向移动。(2)2006—2015年,互花米草斑块密度变大,面积加权平均形状指数也相应增大为8.63,景观形状越来越复杂。(3)利用LEI和PFD识别出互花米草的3种扩张模式,边缘扩张面积远大于外部隔离扩张面积,外部隔离扩张斑块数量远多于边缘扩张和潮沟引领式扩张斑块数之和,潮沟对互花米草的向陆扩张起到引领作用。(4)利用缓冲区分析模拟互花米草向陆扩张的趋势,未来5年碱蓬沼泽的面积将减少11.45%。研究可为进一步认识互花米草入侵碱蓬沼泽机制提供科学参考。

Recognition of spatial expansion patterns of invasive Spartina alterniflora and simulation of the resulting landscape-changes

Using landscape pattern indexes and the methods of centroid position with the help of 3S technology, we examined the landscape characteristics of Spartina alterniflora and its spatial expansion patterns from 2006 to 2015, in the core area of the Yancheng National Nature Reserve (YNNR) in Jiangsu Province. Furthermore, we forecasted its expansion trends based on the GF-2 Satellite Image of 2015. Our results indicated the following:first, the recent landward expansion of the Spartina alterniflora marsh occurred at a faster speed than seaward expansion, its centroid continuously moving landward. Second, over the period from 2006 to 2015, patch density of Spartina alterniflora showed an increase. In addition, the landscape shape became more complex in the tidal flat wetland and the area weighted average shape index, correspondingly increased to 8.63. Third, three expansion patterns of Spartina alterniflora, marginal expansion (ME), external isolated expansion (EIE), and tidal creek-leading expansion (TCLE), were identified through the landscape expansion index and the patch fractal dimension. The patch areas of ME were larger than the external isolated expansion, while the patch number of EIE far exceeded the total number of ME and TCLE. Tidal creeks played a leading role in Spartina alterniflora expanding landward. Finally, based on the three expansion rates measured in our field investigation, the landward spreading trends of Spartina alterniflora marsh was simulated by using buffer analysis in ArcGIS10.2. Simulation results indicated that the area of Suaeda salsa will decrease by 11.45% in the next 5 years. The conclusions of this study will be helpful for understanding the invasive mechanism of Spartina alterniflora in the Suaeda salsa marsh.