C4 grass share rose while legume mass fell in 35 Cedar Creek plots assigned 16 species, 2001–2005 versus 2017–2021

We tested changes in biomass composition in 35 fixed Cedar Creek grassland plots assigned 16 species in 1994. Mean C4 grass share of planted biomass rose from 46.3% in 2001–2005 to 57.9% in 2017–2021. The change was 11.7 percentage points. Its nominal 95% paired plot interval was 8.3 to 15.1 points. A joint plot and two-year-block interval was 0.4 to 23.0 points. Mean legume biomass fell from 132.6 to 55.0 grams per square metre. Lupinus perennis accounted for 98.5% of this net legume mass decrease. Mean C4 biomass was also lower, from 150.1 to 128.4 grams per square metre, but its change was uncertain when years were resampled. Species changes differed within groups. The test did not establish convergence among plots: mean pairwise Bray–Curtis distance rose from 0.365 to 0.412, with a joint change interval of −0.018 to +0.104. The share shift remained with other year windows and an all-live-biomass denominator. This is a descriptive extension of earlier work on this experiment. Changes in clipped area, seasonal sampling, management, and shared weather limit interpretation. The study does not identify a cause or prove local species loss. The package includes unchanged source data, provenance, code, results, figures, and an independent check of 13,300 biomass values.

grassland · species composition · Cedar Creek · C4 grasses · legumes · long-term experiment · Lupinus perennis · biomass · reproducible ecology