现代黄河三角洲类圆形植被斑块时空动态遥感分析

Remote Sensing Analysis on the Spatial-temporal Dynamics of Quasi-circular Vegetation Patches in the Modern Yellow River Delta,China

斑状植被在世界范围内的干旱半干旱区、海岸滩涂均有分布。近年来,有关斑状植被形成、时空格局演替的研究受到了越来越多的关注。斑状植被分布及其时空动态是其中重要的研究方向之一,它是植被演替机制研究的基础,也是表征生态系统中植被长期变化的关键指标之一。以现代黄河三角洲类圆形植被斑块为研究对象,将其分为裸斑区、明显类圆形植被斑块区和隐性类圆形植被斑块区等三大类,通过1996、2005、2007、2010和2012年5个时相多源遥感影像的人机交互目视解译,首次给出了现代黄河三角洲这三大类区域的分布范围,在此基础上分析了其时空动态。结果表明：现代黄河三角洲类圆形植被斑块在空间分布上存在明显的梯度分布和动态演替规律,具有海域—光滩—裸斑区—明显类圆形植被斑块区—隐性类圆形植被斑块区高程梯度分布的普遍特征;类圆形植被斑块的直径、植被覆盖度、植被平均高度以及土壤全盐量可作为判别新老斑块的直观标志;10m、5～6m分辨率的多光谱图像能够较好划分3种类圆形植被斑块区,但对于斑块面积变化的测量精度仍显不足,1m甚至更高分辨率图像的运用将会弥补这一缺陷。研究结果可为将来现代黄河三角洲斑状植被格局及演替机制的深入研究提供参考。

Vegetation-patches pattern is very popular in various ecosystems all over the world, such as arid, semiarid and coastal tidal flat environments.In the recent year, researches on patchy vegetation formation, temporal and spa- tial pattern successions have been paid more and more attentions.One of them was focused on patchy vegetation distribution mapping and temporal and spatial dynamics which was basis for studying the vegetation community succession machines and was a key indicator of long-term vegetation change in the ecosystems. Patch vegetation community succession in the Yellow River Delta belongs to an allogenic primary succession.With studying this suc cession,it is easier to understand the law of the birth and development of vegetation under the natural environment and to discover the adaptation mechanism of the vegetation.This study was conducted in the Modern Yellow River Delta（MYRD）.According to the visible degrees of quasi-circular patches, the bare spot regions, quasi-circular vege- tation patch regions and hidden quasi-circular vegetation patch regions were identified and derived from 1996,2005, 2007,2010,2012 images of the MYRD by interactive visual interpretation and analysis, then the temporal and spa- tial dynamics of patchy vegetation were analyzed.The results from this paper indicated that.-1）there were obvious gradients in space and dynamics of vegetation succession in the modern Yellow River Delta, and Starting in the sea, the patchy vegetation types are sequentially sea water, tidal flats, the bare spot regions, quasi-circular vegetation patch regions, the hidden quasi-circular vegetation patch regions along the elevation gradient;2）the diameter, vege- cation cover percentage,average height of patchy vegetation and total salt content in soil could be considered as the intuitive indices for distinguishing between the new and the old patchy vegetation;3）The multispectral images with 10 m and 5～6 m spatial resolution were enough to classify these three types of quasi-circular patchy vegetations, but still unsuitable for estimation of the area of patchy vegetation which would be overcome by the images with better than 1 m spatial resolution.The results from the present researches could provide a reference for deeply stud- ying spatial pattern and succession machine of patchy vegetations in the MYRD in the future.