Diversity effects and compensatory dynamics drive productivity and stability in temperate old-growth forests

Understanding mechanisms stabilizing ecosystem functions, such as primary production, is crucial for forecasting global environmental responses. While biological diversity is expected to enhance stability through compensatory reactions to environmental changes, empirical evidence is lacking, especially in old-growth forests vital for biodiversity conservation and climate change mitigation. Moreover, whether increased niche complementarity and stronger intraspecific than interspecific competition are key mechanisms promoting compensatory dynamics and stabilizing ecosystem functions in diverse forests remains unexplored. This study investigates productivity and stability in temperate old-growth forests over 20 years at community and individual levels. Analyzing 4,380 trees in a 4-hectare plot in northern Japan with over 35 tree species, structural equation models evaluated the effects of biodiversity and average asynchrony in species fluctuations (compensatory dynamics) on productivity st..., The study was conducted within a 4-hectare plot (200 × 200 meters, divided into 1,600 5 x 5 m quadrats) established in 1996 in an old-growth stand within the 2,715-hectare Tomakomai Experimental Forest. All trees exceeding a height of 1.3 meters were tagged, and their girth at breast height of 1.3 m (GBH) was measured in 1996, 1998, 2000, 2002, 2004, 2006, 2009, 2012, and 2015. To comprehend their impact on average productivity and temporal stability, we investigated various factors, including taxonomic, phylogenetic, and functional (structural) diversity, compensatory dynamics (species asynchrony), stand density, and aboveground biomass. These associations were examined at a resolution of 100 m2 by dividing the 4 ha plot into 400 quadrats, each measuring 10 m by 10 m (local communities).
The average productivity of community biomass in each quadrat was determined by analyzing changes in stand basal area increments from 1996 to 2015 (the sum of individual tree BAI calculated from remeas..., , # Diversity effects and compensatory dynamics drive productivity and stability in temperate old-growth forests

[https://doi.org/10.5061/dryad.612jm64cf](https://doi.org/10.5061/dryad.612jm64cf)

Data on multiple facets of diversity effects and compensatory dynamics on productivity and stability in temperate old-growth forests in Hokkaido, Northern Japan

#### Description of the data and file structure

Study site: Data were gathered in the Tomakomai Experimental Forest of Hokkaido University (established in 1904), situated in a natural mixed temperate forest in Hokkaido, northern Japan (42°43.4'N, 141°34.2'E, 99 m a.s.l.), 70 km south of Sapporo.

Study area: The study was conducted within a 4-hectare plot (200 × 200 meters, divided into 1,600 5 x 5 m quadrats) established in 1996 in an old-growth stand within the 2,715-hectare Tomakomai Experimental Forest.

Tree measurement: All trees exceeding 1.3 meters were tagged, and their girth at breast height of 1.3 m (GBH) was measured in 1...