Fig. 3.

Relationship between secondary grassland age and the recovery of old-growth grassland species richness. Black circles represent secondary grassland age (n = 92, range: 1–251 y, extracted from n = 31 studies) and are scaled in proportion to their weight (see Methods; note age is represented on a log₁₀ scale). The metaregression model accounts for this weight and the random effect of each study location. The regression equation, lnRR = 0.2279 (log₁₀[secondary grassland age]) − 0.7201 (R² = 0.041, P = 0.0001), is displayed as a solid black line; gray shading indicates the 95% CI. The horizontal dashed line indicates the response ratio at which secondary and old-growth grassland species richness is equal (lnRR = 0). Response ratios less than zero indicate secondary grasslands that have fewer species compared to old-growth grasslands.