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q-bio.PE · Populations and Evolutionstat.AP · Applicationsphysics.ao-ph · Atmospheric and Oceanic Physics

Cherry, wisteria and ginkgo dates at Japanese stations became 0.7–1.1 days/°C more temperature-sensitive after 1986 than heat-sum models predict; a changed heat requirement does not explain this

Question: did the apparent temperature sensitivity (days per °C) of spring phenology at Japan Meteorological Agency (JMA) stations change between 1953–1986 and 1987–2025, do heat-sum models with the same temperatures predict the change, and which model part must change to reproduce it? This is an independent replication of [citation 1], [citation 3] and [citation 2], with a new decomposition. Data: JMA records (regular species) for 8 spring events at 33–82 stations; daily station temperature from GHCN-Daily, with 6,415 gap station-months filled from JMA daily pages and each month anchored to the official JMA monthly mean. Method: per-station OLS slope of event day on the 60-day pre-event mean temperature, for observed days and for days from forcing-only (thermal-time) and two chill-forcing models fitted by grid search with one requirement per station. Uncertainty: year resampling shared by all stations and a permutation test over random year partitions. Results: for cherry first flowering, cherry full bloom, ginkgo budburst and wisteria flowering, the observed sensitivity became 0.73–1.04 days/°C stronger, while the forcing-only model predicted −0.08 to +0.14. Observed minus model: −0.86 (95% year CI −1.50 to −0.27), −0.72 (−1.32 to 0.02), −1.06 (−1.73 to −0.11) and −1.06 (−1.61 to −0.39); permutation p 0.002, 0.017, 0.013, 0.005 (Holm over 8 events: 0.016, 0.085, 0.078, 0.035). Mulberry, azalea, dandelion and ume showed no significant difference. The result held for 30–90-day windows, detrending, control for earlier temperature, official monthly temperature and a neighbour-station instrument. Its size depends on the split year, and moving-window curves are not monotonic. New: a period-specific heat requirement reproduced none of the change (−0.06 to +0.13 days/°C), so a requirement change (for example, from less chilling) cannot explain it in these models. A period-specific base temperature reproduced 36–120% of it; the shift was identified only for wisteria (−5 to +1 °C; year CI of shift 1 to 15 °C). Also: the forcing-only model explains weaker cherry sensitivity at warmer stations (observed gradient +0.41, model +0.36 days/°C per °C), but not the absent gradient for ginkgo, wisteria and mulberry; chill terms cut cherry cross-validated error by 12–17%. Limits: one urban reference plant per station, simple grid models, most events end in 2020, cause not identified.

phenology · temperature sensitivity · thermal time · growing degree days · chilling · cherry blossom · Japan Meteorological Agency · replication · climate change · budburst · non-stationarity

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References

9
  1. Spring plant phenology at 81 Japanese weather stations became more sensitive to temperature from 1953–1986 to 1987–2020, while fixed thermal-time models predict less sensitivity sci:sha256:a372304ce3a1aadd55322628f187e2740d8c2ae143952729f53d47badda6abbb

    [Legacy relation: reproduces] Main finding (cherry, wisteria and ginkgo became more sensitive after 1986 than fixed thermal-time models predict) reproduced with independent temperature assembly, wider model grid and year-level resampling.

  2. supportsThe excess spring temperature sensitivity at Japanese stations over a thermal-time model continued in 2002–2025, did not increase with local warming, and came with stronger winter-warmth delays sci:sha256:377b6e9d9adc390e48ed3097a3b592c9b91f22740685552404fd2da4d1bfa354

    We also find that the station-level excess does not correlate with station winter warming, and that winter warmth delays events at warm stations more than heat-sum models predict.

  3. supportsSpring phenology temperature sensitivity at Japanese weather stations did not decrease in 1953–2025 beyond a forcing-only model, which also explains lower cherry sensitivity at warmer stations sci:sha256:a30b18e0b9dbed22d7ae3539df648fe0cae472a7014dbd9770521051485120f2

    We also find that a forcing-only model explains the weaker cherry sensitivity at warmer stations, and that cherry sensitivity in moving windows was strongest near 1995-2005.

  4. A heat-sum model fitted to year-to-year variation predicts 84% of the spatial flowering gradient of clonal Somei-yoshino cherry at 81 Japanese stations in 1953–2025; adding chilling gives 94–98% sci:sha256:f14cf93db545148c4932132945c22334891b263a6b2f0de9e0e09cae65eb4ded

    Related result: a chill-dependent requirement improves cherry predictions; our cross-validation agrees.

  5. usesEarlier budburst did not cause earlier autumn yellowing or leaf fall in the same ginkgo and mulberry trees at Japanese weather stations in 1953–2020 when autumn temperature is controlled sci:sha256:11f49f6ad83249631ee87728c5812f778dc56e0d8946e8e047891f31291f2783

    We use the JMA phenology zip and GHCN-Daily station files retained with this work (shared dataset sha256-eded9775...).

  6. doi:10.1111/gcb.15746

    Heat-sum arithmetic predicts declining linear sensitivity with warming; the hypothesis we test.

  7. doi:10.1038/nature15402

    Reported declining sensitivity of European leaf-out.

  8. doi:10.1016/j.agrformet.2023.109571

    Chilling and forcing effects on Japanese cherry bloom across latitude.

  9. usesdoi:10.1175/JTECH-D-11-00103.1

    GHCN-Daily station temperature.

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