Open4st Short and Long Term Regional Field Trial Strategies

Aspen trees have the widest natural range of any tree species in North America ("Aspen"). They provide significant commercial, wildlife and aesthetic value and don't require replanting as they re-grow from the roots after a fire or harvest. This characteristic allows some aspens to survive thousands of years ("Pando" Tree) and store significant amounts of carbon in their roots. A Canadian research study on the long term soil carbon patterns of small tooth aspens (P. tremuloidies) found that aspens grown on 40-year rotations on good sites may sequester several times as much carbon per year as old-growth forests ("Carbon storage in Lake States aspen ecosystems").

This capability may establish tree plantations with less resource inputs and environmental impact. The re-generated growth may provide synergistic benefits for timber, wildlife and a natural fire barrier ("Aspen Ecology"). The open4st team is also developing high value strains of figured aspen. These clones could enhance existing aspen markets including rustic wood paneling with locally grown options as opposed to imported and endangered figured woods. Unlike other poplars, native aspens don't easily propagate from dormant stem cuttings so they are not typically planted. We have developed diverse hybrid aspen strains that root well from dormant stem cuttings, allowing elite individuals to be planted on a wider scale.

The primary Open4st goal is to develop and test vigorous, high value aspens that can root over 80% from 8” dormant stem cuttings, have at least 50% native aspen with reduced seed germination rates to help prevent gene flow with native aspen populations. Important scored traits include nursery vigor/survival, leaf issues, adventitious rooting, number of 12" cuttings and plus trees. Details of the Open4st program are outlined on the online Open4st site and the document, Low-Resource Aspen Breeding and Nursery Selection Strategies. The 2018 Open4st Project Summary describes the 2018 nursery, recent field trials and participation in the 2018 Woodycrops international conference. Plant materials produced by Open4st are released under the Public Domain via the Open4st Disclaimer and Copyright.

The general short term strategy is to plant a large number of clones represented by a relatively small number of trees across several sites and years. This would allow about 20 - 30 clones to be field tested and archived along with additional family and species combinations. The long term strategy involves the inverse by planting a relatively large number of trees per clone using desirable materials from previous trials. Later, promising selections could be re-tested by cooperators, improved within a breeding program then transition the project to an industrial partner

Short Term Strategy

• Short Term Testing Strategy: It was observed that planting nursery grown 7' tall stock field planted and pruned to 5' resulted in some top heavy trees with upper stems that droop over the entire tree. This is likely the result of the thinner nursery stem diameters when grown at close spacings and vigorous field growth on fertile sites. These large 1-0 trees are somewhat difficult to grow in the nursery and may be limited to areas with longer growing seasons. Planting large 1-0 7' rooted stock may provide a one year growing start and planting with 14" cuttings have the opposite effect with a slower start. However, planting shorter cuttings is operationally more efficient from a storage and handling perspective and may produce field trees with more balanced root to shoot ratios. Going forward, the Open4st team will investigate low-resource methods to grow 14" dormant cuttings with 1.5' or 3' semi-transparent woven textile tree tubes (see: Multi-Stage Aspen Planting Strategies). Additionally, in 2018 there were 337 25xr F1 P. x rouleauiana seedlings that will require several years of nursery testing for important traits. It is expected that by 2022 there should be a sufficient number of 25xr 14" field grade cuttings and cultural processes to begin regional short term field trials

  • Primary Trial Design: Plant about 20 clones on 3 sites with 12 trees per clone on each site. Each site could consist of 3 4-tree square randomized plots in 3 blocks with trees spaced on 10’ x 10’ spacing with 14” dormant cuttings having DN34 and TxE control materials. Each cutting would be protected with a woven fabric tree sleeve and weed control per the cooperators requirements (see: Multi-Stage Aspen Planting Strategies). First year survival rates will be measured and recorded. The first year dead trees may be replaced and recorded with the same 14” dormant cuttings in the following Spring.

  • Plant Materials: Between 2019 and 2022, the Open4st team will be nursery and local field testing a number of materials including 150 full sib P. grandidentata, 337 25xr F1 P. x rouleauiana seedlings and about 34 clones with previous nursery testing (see: vw_2018_8_stock_summary). The expectation is to select 20 to 30 clones with an assortment of desirable traits for later regional field trials.

  • Duration: The short term strategy field trials could span two to three years. The second and third years could involve a mix of about 20 clones from the McGovern/Bender aspen archives along with nursery tested selections from the 25xr F1 P. x rouleauiana family and 6xgg P. grandidentata seedlings.

Long Term Strategy

• • Primary Trial Design: Plant about 10 clones on 3 sites with 24 trees per clone on each site. Each site could consist of 6 4-tree square randomized plots in 6 blocks with trees spaced on 10’ x 10’ spacing with 14” dormant cuttings with DN34 and TxE control materials. Each cutting would be protected with a woven fabric tree sleeve and weed control per the cooperators requirements. First year survival rates will be measured and recorded. The first year dead trees may be replaced and recorded with the same 14” dormant cuttings in the following Spring.

  • Plant Materials: The materials could be based on selections from the earlier short term field trials.

  • Potential Sites: The sites could be determined based on the short term trial results and current needs at that time.

  • Duration: The long term strategy trials could span two to three years.

  • Michigan - Archive Planting - This planting would transition from stool cutting production to a longer term archive of the best materials. The least desirable clones would be removed leaving room for the best to produce flowers for breeding or later whole tree sampling. Any changes would be recorded.

  • Tree Breeding: Aspens can start flowering at around age 4-5. The long term strategy could exploit F1 and F2 backcross breeding opportunities with improved selections from the earlier plantings, McGovern archive sites and native aspen populations.

  • Project Transition: The Open4st project supports public domain materials and the free flow of information. The long term strategy should enable interested industrial partners to take ownership of the Open4st materials and processes for future generations.

  • Funding: This paper describes a high level project spanning several partners. Funding and specific project details should be investigated among interested parties that are able to participate.