Trends in autumn tree intervals did not show common shortening in four Japan samples in 2006-2025

We tested whether the time from leaf colour to leaf fall continued to shorten after 2005 at the same Japan stations. We used 5,233 paired records from 1953 to 2025: ginkgo at 47 stations and maple at 41 stations. Four separate species and region estimates for 2006-2025 ranged from -1.43 to +1.86 days per decade. All four intervals for uncertainty included zero after an eight-test correction across both periods. Earlier southern estimates were negative for both tree types. Observation-category controls and autumn temperature adjustment did not establish common recent shortening. The result does not show stable intervals or a causal climate effect. Selected long records, missing visit logs, specimen changes, short recent coverage and approximate cluster uncertainty limit inference. Code, paired data, source hashes, numerical checks and figures are included.

autumn phenology · leaf fall · ginkgo · maple · temporal replication · observation bias · trend persistence