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厦门典型树种的HJ-1A/B NDVI时序数据滤波算法及物候特性

李晖1,2,彭韧超1,李万凯1,2,朱晓铃1,2,黄于同1,2,聂芹1,2*   

  1. 1厦门理工学院空间信息科学与工程系, 福建厦门 361024;2福建省空间信息工程研究中心厦门分中心, 福建厦门 361024)  
  • 出版日期:2019-11-10 发布日期:2019-11-10

Filtering algorithms of HJ-1 A/B NDVI time series data and phenology of typical tree species in Xiamen.

LI Hui1,2, PENG Ren-chao1, LI Wan-kai1,2, ZHU Xiao-ling1,2, HUANG Yu-tong1,2, NIE Qin1,2*   

  1. (1Department of Spatial Information Science and Engineering, Xiamen University of Technology, Xiamen 361024, Fujian, China; 2Spatial Information Research Center of Fujian (Xiamen Branch Center), Xiamen 361024, Fujian, China).
  • Online:2019-11-10 Published:2019-11-10

摘要: 植被指数具有明显的季节节律,归一化植被指数(Normalized Difference Vegetation Index,NDVI)时间序列可以获取地表植被物候信息,HJ-1 A/B兼具高空间分辨率和高时间分辨率的特点,为中小尺度范围树种物候特性应用与分析提供了丰富的时间序列数据。本文针对厦门市8个典型树种,选择Savizky-Glolay(S-G)滤波法和时间序列谐波分析法(Hants)对58景HJ-1 A/B NDVI曲线进行滤波重构,选用平均值、平均绝对误差和相关系数等指标对滤波结果进行定量评价,结合NDVI比率对8个树种的物候特性进行分析,最后探讨了气温和降水等气象因子对树种NDVI时序波动的影响。结果表明:S-G和Hants滤波方法均能很好地还原物候特征变化明显的植被,Hants谐波的平滑程度最好;7个树种(尾叶桉除外)的NDVI值均处于较高的水平,NDVI时序年内波动并不剧烈,双峰形态表现明显,NDVI值在5、6月达到顶峰,7、8月下降,10月达到第二个峰值,第二个峰值比第一个峰值低;8个树种的生长期持续时间较长,持续7~8个月,除尾叶桉的生长起始时间为2月底外,其他树种均在4月底进入生长期,11月生长期结束,在7月达到生长顶峰;生长期内出现生长期减缓的情况,8月出现生长谷值,生长曲线表现为双峰形态;树种的生长对7月降水量骤减有很明显的响应,不同树种的滞后期不同,生长降低的速度存在一定的差异,但大多表现为8月NDVI比率谷值。研究成果为亚热带地区HJ-1 A/B NDVI时间序列数据的滤波方法选择、典型树种物候特性及树种精细分类研究提供了一定的参考。

关键词: 阿尔拉镇, 民族乡镇, 城市化, 驱动力, 景观格局

Abstract: NDVI (Normalized Difference Vegetation Index) time series analysis can reveal the phenological changes of vegetation cover. With the characteristics of high spatial resolution and high temporal resolution, HJ-1 A/B satellite can provide abundant time series optical data for the application and analysis of phenological characteristics of tree species at the medium and small scales. In this study, we used Savizky-Glolay (S-G) filtering method and Harmonic Analysis of NDVI Time-Series (Hants) to reconstruct 58 HJ-1 NDVI time series data curves of eight typical tree species in Xiamen City. Mean value, mean absolute error and correlation coefficient were selected to quantitatively evaluate the filtered results. Phenological characteristics of the eight tree species were analyzed using NDVI ratio. We further examined the effects of meteorological factors including temperature and precipitation on NDVI time series fluctuation of the eight tree species. The results showed that both S-G and Hants filtering methods can restore the NDVI fluctuation shape of the vegetation characteristic of obvious phenological changes, with Hants filter being the best choice due to its ideal smoothness effect. The filtered NDVI curves showed that NDVI values of all the tree species except Eucalyptus urophylla were at a high level. The intra-annual fluctuation of NDVI time series was not intense, with obvious double peaks. Moreover, the NDVI values peaked firstly in May and June, and then declined in July and August. The second peak occurred in October, which was lower than the first peak. The growth period of all the species lasted for 7-8 months. Except that E. urophylla entered growth period at the end of February, the other tree species entered growth period at the end of April, ended in November, and reached the growth peak in July. In addition, tree growth was sensitive to the abrupt drop of precipitation in July. The lag period of such responses differed among tree species, with differences in the speed of growth reduction, but most of the species had low values of NDVI ratio in August. Our results provide reference for the selection of filtering methods for HJ-1 A/B NDVI time series data, characterizing the phenology of typical tree species, and fine classification of tree species in subtropical regions.

Key words: landscape pattern, ethnic township, urbanization, driving force., Aerla Town