The Relationship between NDVI and Climate Factors at Different Monthly Time Scales: A Case Study of Grasslands in Inner Mongolia, China (1982–2015)

Zhifang Pei,Shibo Fang,Lei Wang,Qifei Zhang,Mingyan Wu,Wei Han,Dao Nguyen Khoi,Wunian Yang

doi:10.3390/su11247243

Abstract

There are currently only two methods (the within-growing season method and the inter-growing season method) used to analyse the normalized difference vegetation index (NDVI)–climate relationship at the monthly time scale. What are the differences between the two methods, and why do they exist? Which method is more suitable for the analysis of the relationship between them? In this study, after obtaining NDVI values (GIMMS NDVI3g) near meteorological stations and meteorological data of Inner Mongolian grasslands from 1982 to 2015, we analysed temporal changes in NDVI and climate factors, and explored the difference in Pearson correlation coefficients (R) between them via the above two analysis methods and analysed the change in R between them at multiple time scales. The research results indicated that: (1) NDVI was affected by temperature and precipitation in the area, showing periodic changes, (2) NDVI had a high value of R with climate factors in the within-growing season, while the significant correlation between them was different in different months in the inter-growing season, (3) with the increase in time series, the value of R between NDVI and climate factors showed a trend of increase in the within-growing season, while the value of R between NDVI and precipitation decreased, but then tended toward stability in the inter-growing season, and (4) when exploring the NDVI–climate relationship, we should first analyse the types of climate in the region to avoid the impacts of rain and heat occurring during the same period, and the inter-growing season method is more suitable for the analysis of the relationship between them.

Highlights

Vegetation connects the water, the soil, the atmosphere and other natural substances, and plays a vital role in the terrestrial circulation of matter and energy [1,2,3,4]
In the study, taking Inner Mongolian grassland as an example, we analysed the temporal changes in normalized difference vegetation index (NDVI) and climate factors, and explored the differences in R between them at different monthly time scales and analysed the change in R between them at multiple time scales
The main conclusions are as follows: (1) NDVI was affected by temperature and precipitation from 1982 to 2015 in the area, showing obvious periodic changes, and NDVI showed a certain time lag for climate factors

Summary

Introduction

Vegetation connects the water, the soil, the atmosphere and other natural substances, and plays a vital role in the terrestrial circulation of matter and energy [1,2,3,4]. To understand the evolution of vegetation and predict its change characteristics under future climate changes, it is very valuable to study the normalized difference vegetation index (NDVI)–climate relationship in-depth and reveal its internal relations. The existing NDVI time series data sets mainly include the SPOT (Systeme Probatoire d’ Observation de la Terre)/Vegetation NDVI, MODIS (Moderate–resolution Imaging Spectroradiometer) NDVI, and GIMMS (Global Inventory Monitoring and Modeling Studies) NDVI data sets, as well as others. These data sets have been commonly used to analyse the vegetation responses to climate on global and regional scales [20,21,22,23]

Methods

Results

Conclusion