I report here on recent developments on breeding resistant trees. These include both promising results from decades-long efforts and also a promising start to addressing a new challenge.
These programs have benefited from major commitments by the USDA Forest Service. I hope they encourage similar commitments for other priority species – such as those named by the CAPTURE program.
Port-Orford cedar – ready to be planted in the forest!
Scientists who have been working for decades to breed seedlings of Port-Orford cedar (POC) trees resistant to the root rot caused by Phytophthora lateralis https://www.dontmovefirewood.org/pest_pathogen/port-orford-cedar-root-disease-html/now say that they have seedlings ready for planting in the forest. They made this case in a webinar in late February. It can be viewed here. The full webinar runs somewhat over two hours.
The scientist who led early studies of POC and the root disease, Don Zobel, Professor Emeritus, Oregon State University, described the ecological requirements that should guide planting programs. POC produces high-calcium litter. It grows from the sea coast to 1950 meters elevation, on sand dunes, fens, soils with hardpans; mafic & ultramafic rocks (serptentines) and fertile soils on some sedimentary rocks. POC is less shade tolerant than western hemlock but more fire tolerant. It can form a secondary canopy under Douglas-fir and supercede other conifers when fire occurs repeatedly. The tree needs surface water, e.g., seepages and stream sides; but the water must be flowing, not stagnant. Seedlings are especially vulnerable to drying during winter.
[I posted a separate blog about other trees native to this region, including serpentine soils, here.]
One purpose of the webinar was to encourage owners and managers of lands within POC’s historic range (see the map under Dr. Zobel’s presentation) to begin planting the species in appropriate sites. With this in mind, Dr. Zobel emphasized criteria for selecting sites:
- Climates in coastal areas of the range are less likely to change under climate change
- Quartenary marine terraces are the best geologic type; Lookingglass and Roseburg geologic types are also acceptable
- Availability of water during summer, e.g., streamside and seepage areas. Try planting beneath alder. However, avoid interior valley stream corridors if the soils are not ultramafic. And avoid stagnant water.
Dr. Zobel also says one should plant pathogen-resistant genotypes and pay attention to local genetic varieties (which have largely been determined).
Dr. Richard Sniezko of the USFS Dorena Genetic Resource Center described the Center’s 30-year effort to find and exploit resistance to the pathogen. Funding has come from the USFS Forest Health Protection program, other parts of the USFS, and the Bureau of Land Management (BLM). The goal all along has been to produce seedlings for restoration to the forest – meaning not just resistant to the pathogen but also adapted to various local conditions. The program can now provide resistant seedlings in large quantities for planting by landowners and public land managers.
Dr. Sniezko emphasizes that success depends on engagement of four sets of people: research by university scientists; application of that research and development of propagule growing methods by the Dorena Center; support from USFS leaders to continue the program; involvement of land managers who choose to plant the resistant seedlings.
USFS and BLM staff described efforts to determine where POC grows on land under their management, the status of disease in those areas, and efforts to slow the spread of the disease, especially along roadsides and as result of timber or engineering projects. Some of this sanitation work has been funded by USFS Forest Health Protection program — not the National Forest System.
Richard Sniezko stated that the seedlings’ quantitative disease resistance means that some seedlings will die. He expects 40-50% survival of seedlings from many of the breeding zones. This is well above the level of resistance in un-improved populations.
Both BLM and the Rogue-River-Siskiyou National Forest have planted tens of thousands of resistant seedlings in recent years and plan to continue. Funding provided by COVID-19 legislation might allow increased effort. [See Dr. Sniezko’s presentation on the webinar for photos from some plantings.]
Norma Kline of the Oregon State University extension program has distributed more than 10,000 seedlings to small/non-industrial landowners. Many of the recipients shared seedlings with neighbors or are coordinating their planting over a large area. They were motivated primarily by conservation concerns. Her monitoring showed that the POC seedlings survived but did not thrive under dense tanoak canopy. They did well in competition with grass in areas near the coast where there was more moisture. They also did well under Douglasfir as long as there was dappled sunlight.
The non-governmental organization American Forests is likely to participate actively in the planting effort.
In an email to me, Dr. Sniezko asks that people who have planted POC outside its native range inform him where the tree(s) is/are thriving. This information would enhance scientists’ understanding of the species’ environmental tolerances.
Posted by Faith Campbell
We welcome comments that supplement or correct factual information, suggest new approaches, or promote thoughtful consideration. We post comments that disagree with us — but not those we judge to be not civil or inflammatory.
For a detailed discussion of the policies and practices that have allowed these pests to enter and spread – and that do not promote effective restoration strategies – review the Fading Forests report at http://treeimprovement.utk.edu/FadingForests.htm
This is a great article , and it warms my heart knowing that great strides have been taking to combat the fungus that has taken such a toll on the Port Orford cedar, good job folks.
My question is how long does the fungus live on the host tree and is there a danger of using the dead tree for lumber and it spreading to none effected trees, does it staying in the soil, or dies with the tree?
According to forest pathologists, the pathogen stays in the soil and roots of the infected trees. Because of how easily the disease is transmitted with mud on equipment or boots, experts have urged great caution, including not salvaging diseased trees.