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 (S) varied from 1 to 20 (Fig. 1a), and tree
species evenness (E) from 0.25 to 1.00 (Fig. 1b).

自2017年起，我们在整个MTF区域构建了一套覆盖范围广泛的森林调查网络（Forest Inventory Network, FIN）。我们采用系统抽样方案，使得FIN调查样地均匀分布，相邻样地间距约为30公里；但针对总计50个原始位置位于天然林范围外的样地，我们采用了20至60公里不等的替代间距（平均间距为30公里），以确保实际样地位置处于天然林区内。因此，每个FIN调查样地代表面积为30公里×30公里（即900平方千米）的森林区域。该森林调查网络总计包含456个永久样地，每个样地为圆形，半径17.85米，面积0.1公顷。在每个永久样地内，我们对所有胸径（diameter at breast height, dbh）大于6厘米的独立木本茎干进行了地理配准、标记，并记录了其物种名称、胸径、总高度、冠幅和冠长。此外，我们还记录了每个样地的样地中心处的海拔、坡度、坡向和土壤厚度。本森林调查网络的样地中共记录了36107株树木，隶属于74个树种。所有FIN样地的树种数量（S）介于1至20之间（图1a），树种均匀度（E）介于0.25至1.00之间（图1b）。