Josh Chenoweth, Olympic National Park. His crew is replanting the reservoirs to recreate as a natural forest for salmon.
There has been no dam removal project to date this large, with this much sediment, so we don’t have much to go on in regards to revegetation success.
The plan for revegetation includes a seven year installation plan and more than 400,00 plants and more than 7,000 lbs of seed to sow with a six year monitoring plan.
One year of planting so far. Planting season is Nov through March.
Planted more than 30,000 native trees, shrubs and herbaceous plants in Lake Mills, 49 different species.
Conditions faced with revegetation:
With the reservoirs lowered, it creates a valley environment. They are dealing with a layer of fine sediment – pure silt and clay – which is a unique substrait for plants to try and survive in.
Another variable – where is the seed coming from to regenerate the sites? It’s going to come from the shoreline, via wind. The park is allowing the shoreline (the area between the reservoir and forest) to reseed on its own.
An exposed terrace in Lake Mills showed the levels of material, from original forest soils to pure silt and clay, fine sands and the coarse delta material (coarse sand and gravel).
Another planting site was pure fine sediment about 4-5 feet thick.
It’s a little early to talk about survival. Thimbleberry looks good but the Doug Fir is mortality significant.
Seeding has been done at Lake Aldwell. Very successful and allowing a quick cover of grasses on the exposed reseviors.
Biggest concern is the invasive plant species, in both reservoirs. but primarily in Lake Aldwell. 13 of our 33 invasive species of concern have appeared, such as Herb Robert.
Lake Aldwell web cam is a good way to watch the revegetation progress. In the upper right hand corner of the web cam screen was a green patch that was a group of non-native reed canary grasses but was treated with herbicide so now it’s brown.
Below that terrace is positive native regeneration – willow, cottonwood and alder have been found just a few feet away from the reed canary grass. It all depends on when the site was exposed and this was in summer 2011. So, the willow seed came down and regenerated and have this amazing growth.
Work in this area has included counting plants and they counted 50,000 woody plants per acre.
Overall, natural regeneration is sporadic. There are not a lot of sites where it’s happening but it also depends on where it’s happening on the exposed reservoir sites.
It’s all tied to water – where is there the most water? Area with a lot of moisture has good regeneration; those that do not have less success.