Multi-scale Spatial Correlation Analysis Of NDVI And Environmental Factors In Northeast China Based On Wavelet Analysis

Environment and climate over the world have a high degree of spatio-temporal heterogeneity,which is characterized by the existence of multi-climatic zones along with strong intra-seasonal,seasonal,and inter-annual variability.The growth of global vegetation is related to this environment variability,although its dependence on time and space still needs to be explored.The multi scale correlation between the distribution of surface vegetation distribution and environmental factors is one of the key contents of the resource and environment monitoring research.This research can provide practical basis for regional ecological resource protection,landscape planning and forestry management.In this study,two ecological sample zones:southwest-northeast and north-south were set up to analyse the multi-scale-dependence among NDVI,precipitation,temperature,altitude,slope and aspect based on wavelet analysis method in the northeastern region of China.The wavelet analysis method was used to analyze the scale characteristics among NDVI,meteorological factors and topographic factors in the study area,the wavelet coherence analysis was used to explore the multi-scale correlation between NDVI and environmental factors.Finally,the RDA variance decomposition method was used to explain the response of NDVI to environmental factors.The results show that the wavelet energy spectrum can clearly identify the NDVI spatial scale structure.Its characteristic scales on the southwest-northeast sample zone are 4-8km,8-16km,16-50km,50-70km,the power spectrum value is the largest on the 50?70km scale,which is its main scale.The structural scale in the north-south direction is 16?32km,32?70km,70?160km,of which 70?160km is the main scale.The variability of NDVI in the southwest-northeast direction is stronger than that in the north-south direction.The wavelet coherence map can visually show the dependence relationship between NDVI and environmental factors with the change of spatial scale and spatial position.On the small scale,the topography plays a leading role in the spatial distribution of vegetation.On the large scale,the climate factor is the main factor.The comprehensive interpretation ability of topographic and climatic factors on the spatial distribution of NDVI in the southwest and northeast direction is 35%and 41%respectively.The interpretation ability of precipitation and altitude in each single environmental factor reaches 33.54%and 29.27%,of which precipitation is the primary factor.The interpretation ability of topography and climatic factors to NDVI on the north-south sample zone is 55%and 63%,and the explanation ability of temperature,altitude and precipitation is better,in order of 33.67%,30.17%and 22.25%,among which the temperature is spatially distributed dominant factor.On the small scale(0-15km),slope and aspect have the greatest influence on the NDVI distribution;on the 15-30km scale,precipitation is the dominant factor;on the 30-80km scale,NDVI distribution is common to all environmental factors dominant;on the 80-150km scale,temperature and precipitation are the most important factors for NDVI;On scales above 150km,precipitation is the main control factor for vegetation growth.