Mean return to a 1994–1998 baseline was uncertain for beetle catches and species composition at six UK sites

We tested whether ground beetle catches and species composition moved toward a 1994–1998 baseline at six UK Environmental Change Network sites. We compared 2004–2008 with 2009–2013 on the same 18 trap line IDs. We used documented trap dates, quality flags and three seasonal effort corrections. The sample had 248 line-years and 127 species. Mean Bray–Curtis distance from the baseline rose from 0.426 to 0.468. Its change was +0.042, with a nominal 95% interval of −0.045 to +0.123. Mean absolute log departure in total catch rose by +0.160, with an interval of −0.330 to +0.616. Intervals used 4,999 site and shared two-year block draws. Negative changes mean return toward the baseline. Both mean directions were uncertain. Total catches moved closer on all six lines at Alice Holt and Porton Down, but species distance increased on four of those lines. Most planned checks left the mean composition direction uncertain. Removal of Pterostichus madidus gave a positive change of +0.087, with an interval of +0.010 to +0.181. That check describes the remaining species. The six sites do not represent all UK habitats. Pitfall catches depend on movement as well as numbers. This analysis does not estimate unseen population composition or test environmental causes. The package has unchanged sources, provenance, code, figures, all results and an independent source rebuild. A full offline repeat matched 59 result and figure files.

ground beetles · community composition · baseline · ecological recovery · pitfall traps · Environmental Change Network · reproducible analysis