Grow a virtual tree one annual ring at a time using a simplified, real dendroclimatology growth model. Set each year's temperature and precipitation, or auto-generate a synthetic multi-decade climate record, and watch Liebig's law of the minimum decide how wide each ring becomes.
A Vaganov–Shashkin-style limiting-factor model: ring width = maxWidth × min(temperature response, moisture response). Whichever factor is scarcest that year controls growth — Liebig's law of the minimum.
Adjust the precipitation and temperature sliders and click "Grow this year's ring", or press "Auto-generate history" to watch decades of rings appear from a randomly generated climate record.
Bristlecone pines can live over 4,800 years, and dendrochronologists cross-date overlapping ring patterns from living and dead wood to build climate chronologies stretching back more than 12,000 years.
Each year a tree in a seasonal climate lays down one growth ring: a pale, low-density earlywood band formed early in the growing season, capped by a darker, denser latewood band as growth slows toward autumn. Because exactly one ring normally forms per year, the sequence of ring widths going outward from the pith at the centre is effectively a year-by-year diary of the tree's growing conditions — narrow rings mark stressful years, wide rings mark favourable ones.
This simulation implements a simplified version of the process-based growth models used in real dendroclimatology (in the tradition of the Vaganov–Shashkin model). Two response curves, one for temperature and one for moisture, each range from 0 (fully limiting) to 1 (optimal). Liebig's law of the minimum then sets that year's ring width from whichever curve is lower — a warm year with a drought still produces a thin ring, because moisture, not temperature, is the bottleneck.
Scientists use exactly this kind of ring-width record — built from real trees rather than sliders — for dendroclimatology: reconstructing centuries of temperature and rainfall before instrumental records began, cross-dating archaeological timber and dead wood against living trees to date it precisely, and studying historical droughts, wildfires and volcanic winters preserved in the ring pattern.
Why do trees in this simulation form one ring per year?
In seasonal climates, cambial growth (the layer of cells just under the bark) is active during the warm, wet growing season and dormant through winter or drought. That on/off cycle produces exactly one light earlywood-to-dark latewood couplet per year, which is why counting rings out from the pith gives the tree's age and why each ring can be tied to a specific year.
Why do narrow rings mean the tree was stressed?
Ring width in this model is proportional to how favourable the limiting factor was that year. A narrow ring means temperature, moisture, or both were far from the optimal range — a cold growing season, a drought, or both — so the tree could only add a thin layer of new wood before conditions cut growth short.
What actually controls growth in this model?
Liebig's law of the minimum: ring width equals the maximum possible width multiplied by the smaller of the temperature response and the moisture response for that year. Growth is never averaged between the two factors — whichever one is furthest from ideal single-handedly caps that year's ring, exactly as in real process-based tree-growth models.
Cross-dating is the technique of matching the distinctive pattern of wide and narrow rings in one piece of wood to the same pattern in another, overlapping sample. By chaining together living trees, old stumps, building timbers and buried logs whose ring patterns overlap in time, dendrochronologists build a single continuous, precisely-dated chronology that can stretch back thousands of years beyond any one tree's lifespan.
Great Basin bristlecone pines grow extremely slowly at high, harsh, dry elevations, which produces very dense, decay-resistant wood and keeps competitors and fire away. Some living individuals are over 4,800 years old, and dead wood from the same groves survives for millennia more, giving dendroclimatologists an exceptionally long, well-preserved ring record from a single species in a single region.
Real dendroclimatologists measure ring widths (and sometimes wood density or isotope chemistry) from many trees at a site, cross-date and average them into a chronology, then statistically calibrate that chronology against the short instrumental climate record to reconstruct temperature or precipitation for centuries before thermometers and rain gauges existed. The limiting-factor logic in this simulation is a simplified version of the process models used to interpret those chronologies.
It captures the two most important real mechanisms — a temperature response curve, a moisture response curve, and Liebig's law of the minimum combining them — which is the same core logic used in process-based models like Vaganov–Shashkin. It omits many real complications (soil depth, prior-year carryover, species differences, light and CO2 effects), so treat it as an illustrative model rather than a calibrated scientific instrument.