Mapping forest disturbance and recovery for ecological security improvement on the Qinghai-Tibet Plateau: A case study from Three Parallel Rivers Region

It is also necessary to enhance ecological security shelter in the Three Parallel Rivers Region (TPRR) with the Nu-Salween, Lancang-Mekong and Jinsha Rivers which is the key area of biodiversity hotspot on the Qinghai-Tibet Plateau. Mapping spatio-temporal patterns of forest disturbance and recovery is prerequisites for planning effective policies by policy-makers to maintain local sustainable development. Multi-source remote sensing data is useful for long-term spatial analysis of forest disturbance and recovery. We used LandTrendr algorithm on the Google Earth Engine platform (GEE), sample migration and random forest classification methods to classify forest types and to detect forest changes (disturbance and recovery) from 1990 to 2020 in the TPRR. Results showed that: (1) total area of forest disturbance was 2107.0 km2, accounting for 8.0% of the forest area in 1990. Since 2000, except in 2006 and 2010, the area of forest recovery was always higher than the area of forest disturbance; (2) proportion of forest disturbance in Honglaxueshan national nature reserve (HLXS NNR), Baimaxueshan national nature reserve (BMXS NNR), Laojunshan scenic spots (LJS SS), Yunlongtianchi national nature reserve (YLTC NNR), Yunling provincial nature reserve (YL PNR) and outside of protected areas (OPA) was 3.0%, 6.1%, 5.5%, 10%, 15.6% and 8.3%, respectively. Percentage of forest recovery was 6.2% in the whole study area, and 6.7% outside of protected areas. Proportion of forest recovery was 1.7%, 2.3%, 3.3%, 12.4% and 10.0% in HLXS NNR, BMXS NNR, LJS SS, YL PNR and YLTC NNR, respectively; (3) duration of forest disturbance was mainly concentrated in 1–3 years with a total area of 1632.9 km2, accounted for 77.5% of total area of forest disturbance. Duration of forest recovery was less volatile which was mainly concentrated in 2–13 years, with an area of 957.2 km2, accounted for 58.8% of total area of forest recovery; (4) recovery area of pine forest was the largest, with an area of 850.2 km2, accounted for 52.2% of the total forest recovery area in the study area. Based on mapping forest distribution and recovery, this research can support the decision-making of local governments on ecological conservation and is of benefit to ecological security improvement in the TPRR.