Summit Trail site in the Experimental Network for Assisted Migration and Establishment Silviculture (ENAMES)

Summit Trail site 3D map showing experimental plots color-coded by the climate scenario each seed source is adapted to. Map by Laura Gonzalez Mantecon.

Land manager: Confederated Tribes of the Colville Reservation.

Nearest town: Keller, WA.

Species: Western larch (Larix occidentalis).

Site history: This site, historically a conifer stand managed primarily for timber production, burned with high intensity during the 2021 Summit Trail Fire.

Site characteristics: The site is at an elevation of 4,900 ft and faces west-southwest, with a gentle slope of 6–15°.  The soils are very deep, well-drained silt loams formed in colluvium and residuum from granitic rock, with a mantle of volcanic ash. The mean annual temperature is 28 °F (coldest month: 14 °F; warmest month: 50 °F) and mean annual precipitation is 1079 mm (710 mm of which is snow).

Planting date: Spring 2025.  

Contact person:

Spus Wilder, Acting Assistant Forest Manager and Forester, San Poil Silvicultural District; Confederated Tribes of the Colville Reservation Forestry Department, Bureau of Indian Affairs.

Robert Slesak, Research Forester, USDA Forest Service, Pacific Northwest Research Station. 

The Summit Trail site during planting. Photo by Mekeilah Aguilar.

 

A newly planted Western Larch seedling at the Summit Trails site. Photo by Rob Slesak.

Pre-planting site conditions at the Summit Trail site. Photo by Laura Gonzalez Mantecon.

Management objectives and other considerations: The main objective for this site is to reestablish a productive and resilient timber stand, as well as providing erosion control and wildlife habitat.

The combination of elevation, precipitation, and soil type make this study block a good candidate to test planting Western larch. Larch is a highly desirable species for planting following a disturbance for both economic and ecological reasons: First, it is a strong conifer competitor following a disturbance, and we wish to embolden this trait through artificial regeneration. Second, it is also highly fire tolerant, even in a non-merchantable plantation state, which helps us protect our planting investment.

Our recent post-planting survival counts indicate that Western larch has had the lowest survival rates out of all the species that we plant (larch, ponderosa pine, and Douglas-fir). Unlike ponderosa pine plantings, higher or lower survival did not seem to be tied to elevation or precipitation amounts that year. This seems to indicate that seedling size and type may play more of a role in Western larch artificial regeneration survival, which is why we chose to test seedling stock type for this site.

In general, Western larch is at the edge of its range on most of the Colville Reservation, a fact that is only going to be exacerbated by climate change.  Western larch is the poster child for needing help through assisted migration, and this study can hopefully provide a step in the right direction to help it remain on the landscape.

Site preparation: Excavator piling with a follow-up vegetation control treatment (mechanical or chemical, to be determined).

Pre-planting site conditions: Some midsize burned snags remained at the site, but no live trees. The ground was largely clear, with some woody debris and herbaceous regeneration, including fireweed (Chamaenerion angustifolium) and lupine (Lupinus polyphyllus). Live conifers in adjacent areas could promote some natural regeneration, but no seedlings were visible.

Experimental design: A randomized complete block with four replications per treatment applied to 0.5-acre plots.

Assisted migration treatments: The team used the Seedlot Selection Tool to choose four planted seed sources (see table below). 

Seed source locations matching historical and predicted future climates for the Summit Trail site. Map by Scout Dahms-May.

Silvicultural treatments: Three different stock types (see below).

Planting density: Operational contract crews will plant 300 trees per ac.

Seedling stock type: Containerized stock (Styro 6, Styro 10, Styro 2A [211A]).

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.