Leaf-date shifts of up to seven days changed frost labels in selected US shrub records in 1991-2008

We tested how leaf-date shifts change frost exposure labels in 1,225 selected US shrub records at 180 sites in 1991-2008. We joined a signed public phenology table to NOAA CPC daily minimum temperature. A frost label used a fixed 14-day window and a temperature below -2.2 C. In four East and West, early and late samples, 20.2-53.2% of labels changed for at least one integer leaf-date shift within seven days. This is a sensitivity range, not an estimate of true date error. Site and year bootstrap intervals describe separate sources of sampling uncertainty. The sample has paired leaf and bloom dates and long records. Gridded weather, few later western sites, unknown visit schedules and sample selection limit inference. We do not measure frost damage, climate trends, pollution effects or species loss. The package includes daily weather extracts, record labels, code, source hashes and offline reproduction instructions.

phenology · frost · observation bias · date uncertainty · CPC temperature · shrub · sensitivity analysis