Forest Changes by Precipitation Zones in Northern China after the Three-North Shelterbelt Forest Program in China

Han Li,Yan Zhou,Zhichao Li,Fu Xu,Yuanwei Qin,Nanshan You,Bangqian Chen,Hui Zhou,Jinwei Dong,Xiangming Xiao

doi:10.3390/rs13040543

Abstract

China launched the Three-North Shelterbelt Forest Program (TNSFP) in 1978 in northern China to combat desertification and dust storms, but it is still controversial in ecologically fragile arid and semi-arid areas, which is partly due to the uncertainties of monitoring of the spatial-temporal changes of forest distribution. In this study, we aim to provide an overall retrospect of the forest changes (i.e., forest gain and forest loss) in northern China during 2007–2017, and to analyze the forest changes in different precipitation zones. We first generated annual forest maps at 30 m spatial resolution during 2007–2017 in northern China through integrating Landsat and PALSAR/PALSAR-2 data. We found the PALSAR/Landsat-based forest maps outperform other four existing products (i.e., JAXA F/NF, FROM-GLC, GlobeLand30, and NLCD-China) from either PALSAR or Landsat data, with a higher overall accuracy 96% ± 1%. The spatial-temporal analyses of forests showed a substantial forest expansion from 316,898 ± 34,537 km2 in 2007 to 384,568 ± 35,855 km2 in 2017 in the central and eastern areas. We found a higher forest loss rate (i.e., 35%) in the precipitation zones with the annual mean precipitation less than 400 mm (i.e., the arid and semi-arid areas) comparing to that (i.e., 25%) in the zones with more than 400 mm (i.e., the humid areas), which suggests the lower surviving rate in the drylands. This study provides satellite-based evidence for the forest changes in different precipitation zones, and suggests that the likely impacts of precipitation on afforestation effectiveness should be considered in future implementation of ecological restoration projects like TNSFP.

Highlights

China has made important contributions to the world’s greening pattern through afforestation and ecological engineering projects [1,2,3]
Our study aims to provide an overall retrospect of the forest changes attempts to address the following question: How does the forest changes (i.e., forest gain in northern China from 2007 to 2017 and and forest loss) in different precipitation zones? It includes three parts: attempts to address the following question: How does the forest changes
Accurate information on the forest spatial-temporal changes and its association with natural environmental conditions are critical for supporting forest management

Summary

Introduction

China has made important contributions to the world’s greening pattern through afforestation and ecological engineering projects [1,2,3]. China has invested about 7129 million dollars for the TNSFP, the accumulated forestation area has reached 30 million hectares until 2018, and the rate of forest coverage has increased from 5.05% in 1979 to 13.57% in 2018 in northern China [8]. Information on the forest distribution spatial-temporal changes is vital for forest management. Since 1949, the overall surviving rate of trees in the arid and semi-arid regions in northern China was only 15% [13]. Information on spatial-temporal changes of forests distribution in northern China is still unclear, especially in different precipitation zones in recent years. Given the great environmental impacts of ecological engineering projects in northern China, it is crucial to acquire detailed and timely information of forest gain as well as forest loss, especially in the recent period that would be helpful for decision-making in forest management and continuous implementation of the project

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Discussion

Conclusion