Morel Signal

What This App Is

Graph-first seasonal view using modeled weather and soil data from Open-Meteo forecast and historical datasets [2,3]. Set your location using the map picker (click or drag the pin, or enter coordinates directly). Location and season settings are saved between sessions. Use Reset settings in Settings to return location and season controls to defaults.

What The Two Graphs Show

Two views answer different questions:

• Soil Temp Context: current-year views show recent modeled soil-temperature history plus short-range forecast context; prior-year views show historical Open-Meteo soil-temperature data only. A soil-depth selector lets you choose between the 6 cm / 0-7 cm archive (2.36 in) and 18 cm / 7-28 cm archive (7.09 in) layer pairs, plus a `6 cm and 18 cm average` proxy that combines both shallow layers. All can include thaw-window shading and rainfall-event bars for context [2,3].
• Season Progression: cumulative modeled soil degree-days above 32°F in the season window, compared against a published Missouri/Buscot onset reference band from field observations [1,6]. This drives Onset Band Position.

Soil Temp Logic

For the current season, the soil chart combines recent Open-Meteo historical data with the available forecast horizon [2,3]. Solid line is historical data; dashed segment is forecast context. For prior years, the chart uses historical data only and marks the selected season year on the x-axis. The 32°F line marks the degree-day baseline used for accumulation, not a standalone fruiting threshold. These values are environmental context (not the same as the cumulative degree-day reference band).

The soil-depth setting includes two direct layer pairs plus a `6 cm and 18 cm average` proxy: 6 cm / 0-7 cm archive (2.36 in) and 18 cm / 7-28 cm archive (7.09 in) are direct options, and the average proxy combines the 6 cm and 18 cm shallow layers as a derived estimate of roughly 12 cm (4.72 in). The deeper 54 cm option is not exposed in this app.

• Show thaw-window shading: highlights continuous runs where modeled soil stays above 32°F, capped at 30 days. A visible border on a shaded region means the thaw window hit the 30-day cap. The cap is a readability proxy loosely aligned with the 30-day antecedent-weather timescale in [1], not a proven thaw-duration trigger.
• Show rainfall events: daily rain bars in inches for both history and forecast. The summary metric counts recent events above 10 mm because [1] linked morel abundance to that threshold in the 30 days before fruiting.

Why 30 days? There is no definitive paper showing that exactly 30 consecutive thawed-soil days is a biological trigger by itself. In this app, 30 days is a literature-informed display window: [1] found a 30-day antecedent rain signal for abundance. The cap only affects thaw-window shading; it does not stop degree-day accumulation or change the season window.

Season Progression Logic

Uses a default window of Jan 1 to Jun 30 and accumulates modeled soil degree-days above 32°F within that window. Select a season year in Settings to review current or historical seasons. Optional custom start and end dates are available under Advanced Season Settings. Historical views mark Season end instead of Today. The running total is compared to the published Missouri/Buscot onset reference band from the morel literature [1,6].

• Onset Band Position = Pre-Range: below roughly 365 F-days
• Onset Band Position = In Range: roughly 365 to 580 F-days
• Onset Band Position = Beyond Onset Range: above roughly 580 F-days (not a hard season-ending signal)

What Is Research-Backed vs Heuristic

• More supported: cumulative soil warming matters for onset timing; the 365 to 580 F-day band is the main published reference in this app [1], with a related 424 to 580 F-day observation reported by Buscot [6].
• More supported: recent rain events above 10 mm matter for abundance in [1], especially over the 30 days before fruiting.
• Heuristic: thaw-window shading.
• Context only: rainfall bars and soil trace overlays provide environmental context; they are not direct onset calculations.
• Data limitation: this app uses modeled soil temperature from Open-Meteo, not direct in-ground sensor readings [2,3].
• Scope limitation: species, latitude, elevation, aspect, host trees, and local soils can shift fruiting timing; this app does not model those factors directly.

References

• [1] Mihail, Bruhn, and Bonello (2007), Spatial and temporal patterns of morel fruiting. Main field-study anchor for soil temperature and rain-event logic. DOI, ScienceDirect
• [2] Open-Meteo Forecast API docs. Source for the live forecast and recent weather data used by this app. Forecast Docs
• [3] Open-Meteo Historical Weather API docs. Source for historical weather variables including humidity, dew point, precipitation, and soil temperature layers. Historical Docs
• [6] Buscot (1989), Field observations on growth and development of Morchella rotunda and Mitrophora semilibera in relation to forest soil temperature. Earlier soil-temperature degree-day field observation cited by [1]. DOI