Investigation of Urbanization Effects on Land Surface Phenology in Northeast China during 2001–2015

Rui Yao,Hongfu Liu,Zigeng Niu,Lunche Wang,Xian Guo,Xin Huang

doi:10.3390/rs9010066

Abstract

The urbanization effects on land surface phenology (LSP) have been investigated by many studies, but few studies have focused on the temporal variations of urbanization effects on LSP. In this study, we used the Moderate-resolution Imaging Spectroradiometer (MODIS) Enhanced Vegetation Index (EVI), MODIS Land Surface Temperature (LST) data and China’s Land Use/Cover Datasets (CLUDs) to investigate the temporal variations of urban heat island intensity (UHII) and urbanization effects on LSP in Northeast China during 2001–2015. LST and phenology differences between urban and rural areas represented the urban heat island intensity and urbanization effects on LSP, respectively. A Mann–Kendall nonparametric test and Sen’s slope were used to evaluate the trends of urbanization effects on LSP and urban heat island intensity. The results indicated that the average LSP during 2001–2015 was characterized by high spatial heterogeneity. The start of the growing season (SOS) in old urban areas had become earlier and earlier compared to rural areas, and the differences in SOS between urbanized areas and rural areas changed greatly during 2001–2015 (−0.79 days/year, p < 0.01). Meanwhile, the length of the growing season (LOS) in urban and adjacent areas had become increasingly longer than rural areas, especially in urbanized areas (0.92 days/year, p < 0.01), but the differences in the end of the growing season (EOS) between urban and adjacent areas did not change significantly. Next, the UHII increased in spring and autumn during the whole study period. Moreover, the correlation analysis indicated that the increasing urban heat island intensity in spring contributed greatly to the increases of urbanization effects on SOS, but the increasing urban heat island intensity in autumn did not lead to the increases of urbanization effects on EOS in Northeast China.

Highlights

Urbanization refers to the historical process of gradual transformation of the traditional agricultural-based rural society to the non-agricultural-based modern urban society
2001–2015 in this study were similar to that of Zhao et al, where the glaobal inventory modelling and and mapping studies (IMMS) NDVI3g data were used to study the variations of land surface phenology (LSP) in Northeast mapping studies (IMMS) NDVI3g data were used to study the variations of LSP in Northeast China
The results suggested that the great changes of urbanization effects (UEs) on start of the growing season (SOS) were mainly attributed to the increasing urban heat island intensity (UHII) in spring

Summary

Introduction

Urbanization refers to the historical process of gradual transformation of the traditional agricultural-based rural society to the non-agricultural-based modern urban society. Urbanization can be explained from the perspectives of demography, geography, sociology, economics and so on. From the perspective of demography, the speed of urbanization is accelerating around the world. The proportion of the urban population in the world was 30% in 1952, 47% in 2001, 50% in Remote Sens. Urbanization can bring out a series of environmental and social issues, e.g., land use/land cover changes, urban heat island (UHI), air pollution, hydro-system changes, and land surface phenology (LSP) changes [3], and this urbanization related nature and social phenomena have profound impacts on human life. It is essential to study the magnitude, temporal variations and mechanisms of the urbanization effects (UEs) on the terrestrial ecosystems [4]

Methods

Results

Discussion

Conclusion