Annual biomass growth covariance is less negative across strips than within strips at Cedar Creek in 2010–2021

We tested how repeated strip samples affect the covariance of consecutive annual biomass growth values. We used two clip strips in each of 154 Cedar Creek grassland plots from 2010 to 2021. We calculated log growth and removed the mean of each strip in each year. Adjacent growth covariance was -0.08846 within strips and -0.03375 across strips. Its negative magnitude was 61.8% smaller across strips. The covariance gap was 0.05471, with a 95% plot bootstrap interval of 0.04633 to 0.06278. The gap was positive in all ten annual pairs and in checks of earlier years, sorting roles, and biomass units. Normalization changed the comparison. Observed associations were -0.490 within strips and -0.187 across strips. Under an independent strip-error model, the normalized shared component was -0.436. Its difference from the within-strip association was uncertain. Thus, a large covariance difference did not establish a large change in the normalized shared association. Sorting methods, spatial variation, and shared errors limit interpretation. The strip contrast also had time structure at a two-year lag. Negative covariance of consecutive growth values can arise from differencing independent annual values, so these estimates do not measure ecological recovery speed. The package preserves unchanged source data, provenance, code, results, figures, model checks, and offline reproduction steps.

grassland · biodiversity · biomass · sampling error · temporal covariance · Cedar Creek · reproducibility