species diversity patterns data in northeastern china

We have established an extensive forest inventory network (FIN) across the entire MTF region since 2017. We implemented a systematic sampling scheme so that FIN sample plots are evenly distributed with an approximately 30-km distance between any two nearest plots (except that for a total of 50 plots, of which original locations fall outside natural forest range, alternative distances ranging from 20 to 60 km (with a mean of 30 km) have been applied so that actual plot locations are within a natural forest area). Therefore, each FIN sample plot represents 30 km × 30 km (900 km²) of forest area. FIN consists of a total of 456 permanent sample plots, each circular in shape with a 17.85-m radius and 0.1 ha in size. Within each permanent sample plot, we georeferenced, tagged, and recorded species name, dbh, total height, crown width, and crown length of all free-standing woody stems with a diameter at breast height (dbh) greater than 6 cm. In addition, we also recorded the elevation, slope, aspect, and soil depth at the plot center for each plot. In these FIN sample plots, a total of 36,107 individual trees and 74 tree species were recorded. Across all the FIN sample plots, the number of tree species (<i>S</i>) varied from 1 to 20 (Fig. 1a), and tree species evenness (<i>E</i>) from 0.25 to 1.00 (Fig. 1b).