生物多样性 ›› 2018, Vol. 26 ›› Issue (8): 828-837.DOI: 10.17520/biods.2018089

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基于MODIS EVI时间序列的鄱阳湖湿地植被覆盖和生产力的动态变化

史林鹭1, 贾亦飞1, 左奥杰1, 马童慧1, 雷佳琳1, 雷光春1,*(), 文力2,*()   

  1. 1 北京林业大学自然保护区学院, 北京 100083
    2 澳大利亚新南威尔士州环境与遗产办公室, 悉尼 2141
  • 收稿日期:2018-03-29 接受日期:2018-08-24 出版日期:2018-08-20 发布日期:2018-09-27
  • 通讯作者: 雷光春,文力
  • 作者简介:# 共同第一作者
  • 基金资助:
    国家重点研发项目(2017YFC0405303)和国家自然科学基金(41471072)

Dynamic change of vegetation cover and productivity of Poyang Lake wetland based on MODIS EVI time series

Linlu Shi1, Yifei Jia1, Aojie Zuo1, Tonghui Ma1, Jialin Lei1, Guangchun Lei1,*(), Li Wen2,*()   

  1. 1 School of Nature Conservation, Beijing Forestry University, Beijing 100083, China
    2 Science Division, Office of Environment and Heritage, Sydney, 2141, Australia
  • Received:2018-03-29 Accepted:2018-08-24 Online:2018-08-20 Published:2018-09-27
  • Contact: Lei Guangchun,Wen Li
  • About author:# Co-first authors

摘要:

鄱阳湖是我国最大的淡水湖, 是与长江保持自由连通的两个湖泊之一, 也是最为重要的候鸟越冬地之一, 其生境质量对全球的生物多样性保护至关重要。枯水期的鄱阳湖由众多子湖构成, 不同子湖具有不同的水文控制与管理模式, 尤其是位于长江上游的三峡大坝2006年正式运行之后, 不同水文控制模式下的子湖展现出不同的退水机制, 对退水期洲滩出露的时间与湿生植被覆盖和生产力产生了不同的影响。近年来, 遥感和生态模型在研究植被变化中应用广泛。本文以MODIS增强植被指数(enhanced vegetation index, EVI)时间序列表示地表属性, 并利用EVI时间序列模型, 建立了2000-2014年植被覆盖和生产力的时空变化趋势。在研究区内建立的网格中, 随机提取了107个斑块, 采集其每16天间隔的MODIS EVI时间序列(2000年2月至2015年4月), 将自适应Savitzky-Golay平滑算法应用于EVI时间序列分析, 提取了4个关键的植被生长指标, 即生长季开始的日期、生长季长度、生长季EVI峰值和生产力。研究结果表明: (1)具有不同水文控制模式下的湿地植被生长特征表现出显著的差异, 尤其位于自由连通子湖的植被与其他模式的子湖相比: 生长季开始的时间更晚, 生长季较短, EVI峰值较低, 并且生长季节的初级生产力较低; (2)由于水文情势的改变, 自由连通子湖2006年前后的双生长周期湿地植被的生长特征差异明显, 秋季生长季提前, 导致了生物量的过度积累, 降低了越冬雁类食源的适口性; 但位于局部水文控制子湖的湿地植被不存在这种差异。(3)自由连通与局部水文控制的子湖对鄱阳湖越冬候鸟的保护均具有十分重要的意义, 需要保证这两种类型子湖的面积, 为越冬候鸟提供更广阔的食源; 当水文情势发生改变时, 局部的水文人为控制可在一定程度上减缓鄱阳湖水情变化对湿地植被生长带来的影响。

关键词: 长时间序列, 遥感监测, 植被变化分析, TIMESAT, 水文波动, 洪泛湿地

Abstract:

Poyang Lake, the largest freshwater lake in China, is one of two lakes that maintain a natural hydrological link with the Yangtze River. The lake system is critical for biodiversity conservation globally, harboring large number of migratory waterbirds. During the dry season, Poyang Lake fragments in to numerous sub-lakes, and different sub-lakes have different hydrological control and management mode. However, the recent hydrological alternation, presumably caused by the operation of Three Gorge Dam (TGD), is threatening the ecological integrity of the lake system, especially as a wintering ground for waterbirds. A robust investigation of the effects of TGD on vegetation cover and productivity at this critical biodiversity hotspot is therefore timely, and could incorporate recent advances in remote sensing and ecological modelling. In this study, using MODIS EVI (enhanced vegetation index) time series, we investigated the spatiotemporal patterns of growth in the lake for the period of 2000-2014, which includes periods before (2000-2006) and after (2007-2014) TGD was commissioned. Firstly, we extracted 107 16-day MODIS EVI time series (February 2000 to April 2015) for 10 randomly placed transects across the lake. We then applied the adaptive Savitzky-Golay smoothing algorithm to the EVI time series, and extracted four key growth metrics, namely, the starting date of growth season, growth season length, seasonal peak EVI, and productivity index. We found significant associations between the hydrological alternation and changes in vegetation seasonality. First, we found that the vegetation growth characteristics of wetlands under different hydrological control modes showed significant differences. In particular, the vegetation located in the freely connected sub-lakes had a later start of growing season, shorter growing season, lower peak EVI value, and lower primary productivity compared to sub-lakes of other modes. Second, due to the hydrological alteration, growth characteristics of sites in freely connected sub-lakes displayed two cycles per year and differed significantly before and after 2006. The advance of the autumn growing season led to excessive accumulation of biomass, which reduced the palatability of the food of migratory geese. However, this difference does not exist in the sites located in the local controlled sub-lake. Third, free connected and local controlled sub-lakes are both important for the protection of migratory birds of Poyang Lake. It is necessary to protect areas harboring both types of sub-lakes to provide a wider food source for wintering migratory birds. Local hydrology control can, to some extent, slow down the impact of much larger scale hydrological alteration on wetland vegetation growth.

Key words: time series data, remote sensing monitoring, vegetation dynamic changes, TIMESAT, hydrological alternation, floodplain lakes