Reconstructing Long‐Term Forest Cover in China by Fusing National Forest Inventory and 20 Land Use and Land Cover Data Sets

Abstract

As one of the most important terrestrial carbon sinks, forests play a critical role in regulating global and regional carbon budgets (Houghton & Nassikas, 2018;Le Noë et al., 2021). Previous studies have estimated a global forest sink of 2.4 Pg C yr −1 for 1990 to 2007 (Pan et al., 2011), which contributes a large fraction of the entire terrestrial sink globally (Friedlingstein et al., 2020). The Chinese government has committed to reaching carbon neutrality by 2060 (NDRC, 2021), which means the various ecosystem carbon sinks and carbon capture and storage need to offset all fossil fuel CO 2 emissions (Rogelj et al., 2015). In China, forest ecosystems also dominate the terrestrial carbon sink, contributing 80% of terrestrial carbon sinks and 39% of terrestrial carbon stocks while providing a least 2.97 Pg C of potential carbon sequestration for 2010 to 2030 (Fang et al., 2018;Tang et al., 2018). In addition, the identification of forest types is also important for simulating carbon sinks because ecosystem models set different model parameters for various forest types (Houghton et al., 1983). For example, the leaf turnover rate

Reconstructing Long‐Term Forest Age of China by Combining Forest Inventories, Satellite‐Based Forest Age and Forest Cover Data Sets

“…This study aims to reconstruct China forest age data set (CFAD) from 1980 to 2015 at 5-year intervals by merging a global forest age map in 2010 (i.e., MPI-BGC forest age) and China forest cover datasets (CFCD). The MPI-BGC data set provides global forest age distribution in 2010 (Besnard et al, 2021a; see Section 3.2), whereas the CFCD data set provides forest cover maps of China from 1980 to 2015 at 5-year intervals (Xia, Xia, Chen, et al, 2023; see Sections 2.3 and 3.2). Based on these two datasets, the methods used for the reconstruction of forest age were allocated after division of the datasets into three cases (Figure 1) as described below.…”

“…The forest cover maps in China from 1980 to 2015 in 5-year intervals were produced by integrating the existing 20 land cover datasets and provincial forest areas datasets from the second to ninth forest inventory (Xia, Xia, Chen, et al, 2023). The spatially explicit forest type maps were reconstructed using the consistency of multiple forest cover datasets with the forest areas of each province as reference.…”

“…Another important data set for this study is the forest coverage dynamic data set (CFCD) produced by Xia, Xia, Chen, et al (2023), which updates the forest coverage in 5 years intervals. However, afforestation takes place every year, and thus the CFCD data set cannot indicate annual variations of forest age due to newly planted forest (National Forestry and Grassland Administration, 2020).…”

“…However, it should be noticed that the deforestation has occurred simultaneously with afforestation. For example, in 1990s, there are 5.75 × 10 4 km 2 yr −1 forest gain, and 1.94 × 10 4 km 2 yr −1 forest loss (Xia, Xia, Chen, et al, 2023). The historic forest age cannot be deduced by the current forest age by subtracting the differences of 2 years, and the current forest age datasets fail to represent historical changes in forest demography.…”

“…The open access global scale Max Planck Institute for Biogeochemistry (MPI-BGC) forest age data in 2010, which was recently developed by Besnard et al (2021a), is an ideal choice for the forest age map of China. High quality forest cover maps of China from 1980 to 2015 at five years intervals were produced in our previous study using a multi-forest cover products fusion algorithm with constraint of long-term forest areas inventory data (Xia, Xia, Chen, et al, 2023). Based on these two datasets, the major objectives of this study were to (a) develop a method for the construction of longterm forest age datasets for China; (b) examine the accuracy of the newly generated forest age datasets, and (c) illustrate the spatial and temporal patterns of changes in China's forest age.…”