Biodiversity-Productivity Relationships in Grasslands

Abstract

The biodiversity-ecosystem function (BEF) relationship -- the positive effect of species richness and functional diversity on ecosystem productivity -- is well-established in experimental settings but contested in natural grassland communities where confounding environmental gradients, disturbance regimes, and historical contingency simultaneously affect both biodiversity and productivity. This study synthesised 20 years of data from 42 long-term grassland monitoring sites in Germany (Biodiversity Exploratories programme; 2002-2022; 2,840 plant species-site-year records; 284 species; pasture, meadow, and mown grassland types across three Exploratories: Schwabische Alb, Hainich-Dun, Schorfheide-Chorin) to quantify biodiversity-productivity relationships (BPR) across natural variation in management intensity, soil fertility, and climate. Species richness was positively correlated with aboveground net primary productivity (ANPP) when pooled across all sites (r = +0.48; p < 0.001), but the relationship was substantially modulated by soil fertility: on fertile soils (high N and P availability), the BPR was weak to absent (r = +0.18; p = 0.12), while on infertile soils the BPR was strong (r = +0.74; p < 0.001) -- consistent with the complementarity mechanism (niche differentiation enabling resource partitioning) dominating on infertile soils where resource limitation is severe. Functional diversity (FDis of 8-trait matrix) was a stronger ANPP predictor than species richness across all soil fertility conditions (r = +0.64 vs. +0.48). A Biodiversity-Productivity Integration Model (BPIM) incorporating species richness, functional diversity, soil fertility, and management intensity predicted ANPP with R2 = 0.724 and r = +0.84 -- substantially better than any single predictor and providing the most comprehensive empirical test of BEF theory in natural grasslands to date.