About 45% of recorded annual quadrat changes involved taxa present in both six-quadrat lists at 45 NEON sites, 2013–2024

A recorded plant loss in a small quadrat need not be a loss from its larger plot. We tested this distinction in NEON RELEASE-2026 plant records from 2013 to 2024. Six fixed 1 m2 quadrats gave 7,689 annual plot pairs at 45 sites. Taxa present in both six-quadrat lists accounted for 45.3% of recorded quadrat gains and losses, with equal site weights. The central 95% range from joint site and three-year calendar resampling was 42.1–48.6%. Among taxa found in both lists, observed same-quadrat retention was 81.9%. Independent uniform placement with the observed occupancy counts held fixed predicted 56.4%. The excess was 25.5 percentage points, with a resampling range of 23.3–27.6 points. All 45 site estimates were positive. In 2,409 matched annual pairs with complete 400 m2 lists, 69.3% of quadrat losses involved taxa still recorded in the full plot, compared with 44.8% in the six quadrats. Genus-level event accounting gave a larger persistent share than species-level accounting. These results show repeat spatial structure and an effect of sampled area on the meaning of recorded losses. They do not establish biological extinction, plant movement, or a climate effect. The package has the unchanged source data, provenance, code, event tables, figures, and independent checks.

plant communities · NEON · temporal turnover · sampling area · spatial persistence · reproducible ecology