Letts Lake site in the Experimental Network for Assisted Migration and Establishment Silviculture (ENAMES)
The Letts Lake site, part of the Experimental Network for Assisted Migration and Establishment Silviculture (ENAMES) study, has been established in the Mendocino National Forest to test assisted population migration of Douglas-fir, as well as the effect of planting configuration on seedling survival and growth. The site burned during the 2018 Ranch Fire and was planted in 2024.
Landowner: U.S. Forest Service
Location: Mendocino National Forest, Grindstone Ranger District
Nearest town: Fouts Springs, CA
Planted species: Douglas-fir (Pseudotsuga menziesii)
Site history: This site, next to a lake and a high-use campground, burned in the 2018 Ranch Fire. Prior to the fire, the stand was Coast Range mixed conifers and was actively managed due to its proximity to the campground. This area is part of a larger research initiative and hosts many other research projects.
Site characteristics: The site is on a ridge at an elevation of 4600 ft, facing south-southwest on one side and north-northeast on the other, with a gentle slope of 10–20°. The soils are shallow to deep gravelly loams formed in alluvium and colluvium from metamorphosed igneous, sedimentary, metasedimentary, and metavolcanic rocks. The mean annual temperature is 54 °F (coldest month 39 °F, warmest month 73 °F) and mean annual precipitation is 1259 mm (39 mm as snow).
Planting date: Spring 2024
Contact person:
Radoslaw Glebocki, Silviculturist, Mendocino National Forest, Grindstone Ranger District
Stacy Drury, Research Ecologist, Pacific Southwest Research Station
Jessica Wright, Research Geneticist, Pacific Southwest Research Station
Christopher Looney, Research Forester, Pacific Southwest Research Station
Pre-planting site conditions from the Letts Lake site. Photo by Kara Sanghera.
View from the Letts Lake site. Photo by Kara Sanghera.
Management objectives and other considerations: Since the site is next to a campground and very visible to the public, which generally does not approve of monocultures, ponderosa pine selected by the local silviculturist will be interplanted at 20% with the Douglas-fir. The silvicultural treatments were chosen to test ideas presented by Forest Service Research Ecologist Malcolm North about cluster planting to more quickly move toward a natural forest condition. The site has a ridge in the middle with 16 acres of gentle sloping terrain on either side. This provides an opportunity to replicate treatments on the same substrate but two different aspects, a more southerly/warm one and a more northerly/cool one.
Site preparation: All dead trees were removed from the site prior to planting.
Pre-planting site conditions: The site was cleared of trees and snags; some stumps remained.
Assisted migration treatments: The team used the Climate-Adapted Seed Tool to choose four planted seed sources (see table below).
Climate period
| Seed origin | Seed source elevation (ft) | Mean cold month temperature (°C) | Summer heat-moisture index |
Historical/local (1961-1990) | CA Seed Zone 372 (Mendocino National Forest) | 3500-3500 | 4.31 | 199.2 |
Early-century (2011-2040) | CA Seed Zone 372 (Mendocino National Forest) | 3500-4000 | 4.58 | 240.9 |
Mid-century (2041-2070) | CA Seed Zone 302 (Klamath National Forest) | 2500-3000 | 5.55 | 239.2 |
Late-century (2017-2100) | CA Seed Zone 521 (Shasta National Forest) | 2000-2500 | 6.19 | 227.8 |
Silvicultural treatments: Four treatments: uniform vs cluster planting; hot vs cool landform aspect.
Planting density: Contract crews planted 176 trees per acre.
Seedling stock type: Styro 10-D (large containerized stock.)
Monitoring: The site will be monitored to track and compare seedling survival among seed sources and silvicultural treatments. Measurements are planned for 1, 5, 10, and 15 years after planting.
The site may also serve as a demonstration plot for managers to visit and visually compare seed source performance.
Year 1 results
In the graphs below, bars with same letter (for example, a) indicate no significant difference among seed sources/climate scenarios. Different letters (such as a vs b) indicate a significant difference based on latest measurements.
Seedling survival was not measured at this site during the first round of measurements.
Figure 1. Seedling diameter by seed source 1 year after planting at the Letts Lake site.
Figure 2. Seedling growth by seed source 1 year after planting at the Letts Lake site.