Twenty-one year pairs did not show a clear seasonal difference in plant concentration on 32 Portal quadrats

We tested whether recorded annual plants were more spatially concentrated in winter or summer on 32 fixed quadrats at Portal, Arizona. We used two plots that have always been controls and PortalData 6.117.0. There were 21 matched years with at least two annual plants in each season from 1989 to 2023, with 69,839 plants. Mean Morisita concentration was 4.120 in winter and 3.225 in summer. The mean winter minus summer difference was +0.895, with a nominal 95% three-year calendar-block interval of -2.119 to +4.153. These records did not establish a seasonal difference or equal concentration. One winter had two plants in one quadrat. Removing that year changed the mean contrast to -0.570. Requiring at least 20 plants per season gave -0.333 in 18 years. Checks without Erodium, with named taxa, within plots and with other block lengths also left the difference unresolved. Exact random thinning gave an unresolved winter occupancy advantage of 1.384 quadrats. The result concerns sampled plants at one spatial grain and site. It does not identify a climate cause. The package preserves source bytes, provenance, a complete count grid, sampled zeros, missing-census records, results, figures and code. Independent aggregation and known-model checks passed, and a full rerun reproduced every numerical result file.

annual plants · spatial concentration · Morisita index · seasonality · Portal Project · quadrat sampling · reproducibility · null result