Hammerhorn site in the Experimental Network for Assisted Migration and Establishment Silviculture (ENAMES)
The Hammerhorn 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 2020 August Complex Fire and was planted in 2024.
Pre-planting site conditions at the Hammerhorn site. Photo by Christopher Looney.
Landowner: U.S. Forest Service
Location: Mendocino National Forest, Upper Lake Ranger District
Nearest town: Reeves Place, CA
Species: Douglas-fir (Pseudotsuga menziesii)
Site history: The original plant community was Sierra mixed conifer, comprised mostly of Douglas-fir and ponderosa pine, with small components of sugar pine and incense cedar. The area was harvested for timber in 1980, and likely once or twice before then. This site burned during the 2020 August complex.
Site characteristics: The site is at an elevation of 3500 ft and faces south-southwest, with a slope of 8–15°. The soils are moderately deep, well drained soils derived from residuum from sandstone and shale. The mean annual temperature is 52 °F (coldest month 38 °F, warmest month 69 °F) and mean annual precipitation is 1466 mm (69 mm as snow).
Planting date: 2024
Contact person:
Gary Urdahl, Silviculturist, Mendocino National Forest, Upper Lake 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
Management objectives and other considerations: The site is next to a well-used campground frequented by school field trips. This provides a great opportunity for demonstration plots and educational signage about assisted migration. Because of the high visibility of the site and public dislike of monocultures and plantations, 80% site was planted with Douglas-fir and 20% was interplanted with ponderosa pine. The silviculturist selected and provided the ponderosa pine seedlings. All experimental treatments will focus on 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 towards a natural forest condition.
Site preparation: None. This site was completely cleared in the fire.
Pre-planting site conditions: No remaining overstory; minimal understory vegetation.
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 340 (Mendocino/Trinity National Forests) | 3000-3500 | 4.31 | 199.2 |
Early-century (2011-2040) | CA Seed Zone 526 (Eldorado National Forest) | 3500-4000 | 4.58 | 240.9 |
Mid-century (2041-2070) | CA Seed Zone 525 (Tahoe National Forest) | 2500-3000 | 5.55 | 239.2 |
Late-century (2017-2100) | CA Seed Zone 524 (Plumas/Lassen National Forest) | 2000-2500 | 6.19 | 227.8 |
Silvicultural treatments: Two treatments: uniform vs cluster planting.
Planting density: Contract crews planted 200 trees per acre.
Seedling stocktype: 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.
Figure 1. Seedling survival for the different seed sources 1 year after planting at the Hammerhorn site.
Figure 2. Seedling diameter by seed source 1 year after planting at the Hammerhorn site.
Figure 3. Seedling growth by seed source 1 year after planting at the Hammerhorn site.
Silviculture: The spaced treatment had significantly higher survival than the clumped treatment
Silviculture-climate interactions: None
Notes: Survival measured to a maximum of 50% (50 trees)