Reconstruction of stand-replacement disturbance and stand age of Chinese fir plantation based on a Landsat time series in Huitong County, Hunan

We constructed a relatively complete annual time series of Landsat archived data of Huitong County, Hunan Province from 1986 to 2016, and detected the dynamics of each forest pixel by calculating and analyzing the annual Integrated Forest Z-cores in order to obtain historical disturbance information. We mapped stand age in the study area by establishing a statistical relationship between historical disturbance information and field-measured stand ages. The results showed that: (1) The area of Chinese fir plantations was 7.67×10⁴ hectares, which was mainly distributed in the regions with the slope steepness less than 25°; (2) The disturbance of Chinese fir plantations mostly occurred before 1996. The highest loss of Chinese fir plantation area caused by the disturbance occurred mainly during 1987-1992, accounting for 17.54% of the total area. The area of disturbed Chinese fir plantation gradually declined after 2000, while the area of forest recovered from disturbance increased rapidly during the same period. About 42% of Chinese fir plantations were recovered from disturbances during the past 15 years, which were mostly located along the major transportation routes and the rivers; (3) Mature and intermediate-aged Chinese fir plantations occupied the majority of forest landscape, covering about 47% and 15% respectively. In contrast, young, near-mature, and over-mature Chinese fir plantations covered 15%, 3%, and 6%, respectively. Our results suggested that remote sensing time-series data could be used to effectively retrieve stand age distribution of regional plantation forest. Our results provide critical information for the management of local forest resources.