Phenophase · senescence August 2026
The first wetting rain reaches the soil in McDonald Forest
Twelve point four millimetres of rain on 31 August ended a forty-seven day dry spell and put water into the top ten centimetres of soil for the first time since July. Bracken on the ridge went from green to half brown in three days.
| Date | Place | McDonald-Dunn Research Forest, Benton County, Oregon | Weather | 14°C · overcast, steady rain for six hours · Wind SW 3 m/s |
|---|
Forty-seven days without rain is not a record here, but it is enough to make the first real storm an event. It rained steadily from 04:20 to 10:40, and by the time I walked in, the litter had changed colour.
What the gauge and the trowel say
- Rainfall: 12.4 mm in six hours, all of it gentle, with no more than 2 mm in any ten-minute period. That last number is the one that matters for infiltration.
- Soil at 10 cm under the litter: dry and crumbly 40 m in from the road, then visibly dark and able to hold a shape by the third handful. Water had reached 8 to 11 cm into mineral soil in the four pits I dug, and the depth followed the slope rather than the tree cover.
- Soil temperature at the same depth: 15.2°C before the rain on 28 August, 13.8°C on 31 August. Six hours of rain took more heat out of the ground than a week of cold nights had.
- The creek was up and running clear. Since mid-July it had been a series of pools.
What changed on the ridge
The bracken was green when I last walked this line on 26 August. Three days later, ten fronds in each of three plots showed browning from the tip down, on average about a third of each frond. The fern is not browned by the rain; it browns because the season is over, and the rain is the signal the plant responds to.
The first mushrooms were up, which is the other half of the same story: eleven Douglas-fir suillus within two metres of a fir trunk and four fly agaric buttons on the north slope. Neither species was visible on 26 August. Two ensatinas were under the same piece of bark, and an American dipper was singing in the creek, the first I have heard here since May.
One caution that belongs in every autumn note: I record mushrooms because they are the visible result of soil water, not because I eat them. Nothing in this journal is a foraging guide, and the fly agaric is a mushroom that kills people who trust a photograph.
What to check next time
- Re-read the same four soil pits after the next rain to see whether water reaches 20 cm.
- Count mushrooms along the same 20 m transect every visit; the shape of the flush is the interesting number, not the peak.
- Note how many days the creek takes to run clear after each storm. That is the sediment coming off the road.
Observed
| Scientific name | Vernacular | Count | Note |
|---|---|---|---|
| Pteridium aquilinum | bracken fern | 30 | ten fronds in each of three plots, all browning from the tip down |
| Amanita muscaria | fly agaric | 4 | four buttons pushing up through the litter on the north slope |
| Suillus caerulescens | Douglas-fir suillus | 11 | eleven, all within 2 m of a fir trunk |
| Ensatina eschscholtzii | ensatina | 2 | two under the same piece of bark, the first salamanders since May |
| Cinclus mexicanus | American dipper | 1 | one in the creek, singing |
Reflection
Rain is the one variable I cannot measure by looking at it. A gauge, a thermometer and a trowel cost me fifteen minutes a visit, and without them this note would be a paragraph about how good the forest smelled.
Kit carried
- rain gauge
- soil thermometer
- trowel
- 10x hand lens
- Rite in the Rain notebook
- 2H pencil
- steel rule