摘 要

植被物候对气候变化高度敏感。然而，目前尚不清楚汉江中下游流域的植被物候如何随气候的变化而改变。在这项研究中，我们采用了中度分辨率成像光谱仪（MODIS）的数据（2000-2019年），研究汉江中下游流域植被的生长程度变化 ，用归一化植被指数（NDVI）表达，同时也研究了植被生长季节开始（SOS）和结束（EOS）的变化。利用统计的气候数据（2000-2019年），我们进一步分析了SOS / EOS与季节前平均气温和总降水量（定义为SOS / EOS之前30天）之间的相关性。研究结果表明：汉江中下游流域在近二十年来植被指数总体呈上升趋势，植被的时空变化存在着一定程度上的地貌分异。在年内植被指数最低的月份是二月，随后从三月开始到五月开始植被指数迅速增长，五月至八月为稳定期，植被指数基本保持恒定，从九月开始植被指数开始下降，十月十一月两个月下降幅度较大，十二月和一月下降速度逐渐趋缓。植被物候特征方面，汉江中下游流域EOS分别与十一月平均气温和十一月降水量呈正相关，SOS分别与二月平均气温和二月降水量呈负相关，SOS与EOS同降水天数无相关性。经过线性拟合，平均气温和降水量作为影响因子，植被物候特性作为因变量，拟合程度较好，表明气温和降水确实影响着植被物候特征。在植被物候的空间特征方面，不同的植被类型表现出的物候特征不尽相同。在时间特征方面，在近20年内汉江中下游流域总体植被SOS虽有波动，但总体趋势保持平稳；而EOS波动同样明显，总体却有提前的趋势，从而导致植被的生长季长度也有缩短的趋势。

关键字：汉江中下游流域，植被物候，气温，降水量，植被指数

Abstract

Vegetation phenology is highly sensitive to climate change. However, it is not clear how vegetation phenology in the middle and lower reaches of the Han River changes with climate change. In this study, we used MODIS data (2000-2019) to study the growth degree of vegetation in the middle and lower reaches of Hanjiang River, expressed by NDVI, and the changes of SOS and EOS. Using the statistical climate data (2000-2019), we further analyzed the correlation between SOS / EOS and pre seasonal average temperature and total precipitation (defined as 30 days before SOS / EOS). The results show that the vegetation index of the middle and lower reaches of Hanjiang River Basin has been on the rise in the past 20 years, and the spatiotemporal variation of vegetation is different to some extent. In the year, the lowest month of vegetation index is February, and then the vegetation index increases rapidly from March to May. From May to August, it is a stable period, and the vegetation index basically keeps constant. From September, the vegetation index begins to decline. In October and November, the decline range is relatively large, and the decline speed in December and January gradually slows down. In terms of vegetation phenology, EOS in the middle and lower reaches of Hanjiang River is positively correlated with average temperature in November and precipitation in November, and SOS is negatively correlated with average temperature in February and precipitation in February, respectively. There is no correlation between SOS and EOS and precipitation days. After linear fitting, the average temperature and precipitation are the influencing factors, and the phenological characteristics of vegetation are the dependent variables. In terms of the spatial characteristics of vegetation phenology, different vegetation types show different phenological characteristics. In terms of time characteristics, in the past 20 years, the total vegetation SOS in the middle and lower reaches of the Han River Basin has fluctuated, but the overall trend has remained stable; while the EOS fluctuation is also obvious, but the overall trend is ahead of schedule, which leads to the shortening of the growth season length of vegetation.

Key words: Hanjiang River Basin, vegetation phenology, temperature, precipitation, vegetation index

目录

1 绪论1

1.1 研究背景与目的1

1.2 国内外研究现状1

1.3 研究内容2

1.4 技术路线3

2 数据与研究方法4

2.1 研究区概况4

2.2 数据来源4

2.3 研究方法5

2.3.1 回归分析与线性拟合5

2.3.2 植被指数的计算5

2.3.3 物候特征的确定与提取6

2.3.4 物候特征与气候因素的相关分析6

3 汉江中下游植被指数分析7

3.1 汉江中下游流域植被指数年际变化趋势分析7

3.2 汉江中下游流域植被指数年内变化趋势分析7

3.3 汉江中下游流域植被指数时空变化的地貌分异8

4 汉江中下游植被物候特征分析10

4.1 植被物候变化与降水的关系10

4.2 植被物候变化与气温的关系10

4.3 植被物候变化与降水天数的关系11

4.4 植被物候与温度/降水之间的相关性11

4.5 汉江中下游流域植被物候参数的空间变化特征12

4.6 汉江中下游流域植被物候参数的时间变化特征14

5 对汉江中下游植被物候的深入思考16

5.1 灯光数据年际变化16

5.2 整个研究区域控制SOS/EOS的关键因素16

5.3 什么因素促成了SOS/EOS的趋势17

5.4 本研究的意义与局限性18

6 总结19

参考文献20

致谢21

第一章 绪论

研究背景与目的

植被物候学是对植物世界中周期性生物事件及其与环境因素（如气温和降水）的关系的研究^[1]。植被物候控制着陆地生态系统与大气之间的质量和能量交换，准确监测植被物候学对于评估植被动态与气候变化之间的相互作用至关重要^[2]。在过去的几十年中，植被春季物候学因其与全球变化的密切联系而备受关注。相比之下，对植被秋季物候学的理解是有限的，尽管它在确定植被生长期的过程中起着重要的作用，并且已发现受气候变化的影响很大^[3]。

地面观测物候数据和卫星数据是通常用于识别不同规模植被生长季节的两个主要工具。地面数据通常记录在物种层面，并用于在地方尺度上进行物种特定的物候分析。同时，卫星数据主要用于全球范围内的区域整个景观的生长期特征。已开发出各种卫星衍生的植被指数来提取植被物候指标，例如归一化植被指数（NDVI）和增强型植被指数（EVI）^[4]。