Scale dependent structuring of spatial diversity in two temperate forest communities

• A large proportion of diversity accumulators were found in two research plots.
• Diversity accumulators dominated at all scales from 0 to 50 m in MF plot.
• Accumulators dominated at short ranges, while neutrals beyond 25m in OGF plot.

The data were collected in two large stem-mapped observational studies, showing similar species and size distributions but different topography, in northeastern China. Both experiments are located in temperate conifer and broadleaved mixed forests. One is a mature secondary forest (MF, 42 ha), the other is an old-growth forest (OGF, 30 ha). Based on the modified Individual Species–Area Relationship (mISAR) concept, tree species acting as diversity accumulators or repellers were identified in the two study areas. A large proportion of diversity accumulators were found, especially at distances closer than 10 m. Diversity accumulators dominated at distances between 0 and 50 m in the MF plot. In the OGF experiment, accumulators dominated at short ranges (<25 m), while both accumulators and neutrals dominated beyond 25 m. Little difference in the proportion of diversity accumulators was found between the homogeneous and the heterogeneous null models. Small proportions of significant diversity repellers were found under both the homogeneous and heterogeneous null models. When assessing the overall fit of the empirical mISAR curves at distances of 0–20 m under the heterogeneous model, almost all species significantly accumulated local diversity at some scales in MF (97%) and OGF (93%). Less than one-fifth of all species were significant repellers (MF: 19% and OGF: 17%). Most of the species acted as diversity accumulators in the two temperate forests. This implies that species diversity in our study areas is spatially structured by positive interspecific associations (e.g. facilitation).