Post date: Nov 01, 2019 7:6:45 PM
Abstract
The 2019 Open4st project investigated nursery, field, figured wood and r4st database strategies to prepare for regional field trials with select hybrid aspen materials. The 2019 nursery season propagated 8" and 14" dormant stem cuttings with various treatments and variable length tree shelters. A total of 1796 seedlings, dormant cuttings and rooted 1-0 stock were planted in the 2019 Bell nursery having a 57% overall survival rate (1027 trees). There were 243 trees planted on 3 archive field sites in 2019. The material was a mix of 1-0, 14” dormant cuttings (DC) and 14” 1-0 root pruned cuttings referred to as “ministools” (MS). Field trees were also protected with variable length shelters similar to the nursery. There were 82 aspen clones tested for figured wood via the split wood test with 7 clones (8.5%) identified as having a mean undulation figured rate of 2 or higher (3 is highest). Five figured aspen clones have been carried forward in the 2019 nursery and over 60 new clones will be tested for figure in 2020. The online r4st database was upgraded and simplifying the reporting process for easier reading and maintenance. The importance of establishing regional field trials is explained in the 2018 document, “Low-Resource Aspen Breeding and Nursery Selection Strategies”, which also provides a historical project perspective. These 2019 tests were statistically non-significant "Proof of Concept" (POC) pilot tests to investigate if further testing is warranted.
The tentative 2020 strategy is to field plant about 30 clones consisting of the top 20 2019 nursery selections and 10 previous elite clones on two local sites using 1.5’ and 3’ protective tree sleeves. These 30 clones will also be ramped up in the 2020/2021 nursery to produce about 40 trees per clone by 2022 (~1200 total trees). These 14” ministool 1-0 materials could available in the Spring of 2022 for field trials at one to three locations depending on resources and the clonal trial design. These diverse aspen materials represent about 9 different families, hybrids and pure species.
2019 Bell Nursery Summary
The 2019 Bell nursery had a good growing season despite excessive rainfall. A total of 1796 seedlings, dormant cuttings and rooted 1-0 stock were planted in the 2019 Bell nursery having a 57% overall survival rate (1027 trees). Below are key nursery highlights:
2019 Bell Nursery Context: Most of the 2019 Bell Nursery cutting material was planted on 4/27/2019 in about a 1000 square foot composted, roto-tilled nursery (40' x 16' and 20' x 20') planted in similar configuration to previous years. The ramet cuttings were 8" or 14" long with diameters ranging from 6 mm to ~14 mm. All material was cut from heeled in whips in mid March, banded with their planting label and stored in a refrigerator at 30 degrees F. until Spring planting. The 8" dormant cutting (DC) material was planted in 11 rows with 30" centers having dual rows of cuttings 4" apart and cuttings planted 5 to 6 inches apart in each row. The internal 4" between the rows was covered with Miracle Gro Sphagnum Peat Moss, which had some plant food and absorbed water easily. The area between the double rows was treated with glyphosate to control mid-summer weeds. The nursery was irrigated as needed with a 9' tall sprinkler. The P. grandidentata (GxG) and P. x wettsteinii (TxE) 1-0 stock was planted in the North edge row to allow direct access to "jet spray" water on the back side of leaves infected with aphids and spider mites that severely impacted only these species in past years. This year was extremely wet, which likely lowered the spider mite infection. Damage from the heavy rains was reduced by the North to South rows following site drainage and a deep trench along the North edge.
Bell Nursery Replications: The 2019 Bell nursery was planted via 22 test plots or replications as used in the r4st database column “replication_nbr”. These replications may simply replicate a test clone from another row or a have a completely different test. See: 2019 Nursery Summary by Replication Number.
Bell Nursery "leaf_score" Metric: Some of the 25xr P. × rouleauiana family materials have had a chlorotic leaf condition since the seedlings were produced in 2016. This is likely a genetic condition since it has been consistently observed on specific clones at consistent annual rates. These leaf conditions were tracked with a 1 to 5 “leaf_score” metric (5 is excellent) on the Bell nursery and open4st field sites. There are 30 primary clones selected in the 2019 nursery, which may be be field planted in 2020. Eighteen of these clones (60%) belong to the 25xr family and had a 5 leaf score with no observable leaf issues.
2019 Nursery Selection Types: The 2019 nursery season propagated 8" dormant cuttings for 180 25xr family clones at 5” or 6” spacings to maximize 1-0 stock diameter for optimal testing and selection of clones with potential figured wood. There were 32 clones selected as “Primary Elite” and 6 figured wood selections that will likely be considered for field testing in 2020.
Dormant Cutting IBA Rooting POC Test: Test replication number 17 compared survival of 100 8” dormant cuttings for 8 clones at 6” spacing. One row (“iba30”) was dipped in Hormex #30 rooting powder (3% IBA) that appeared to work well in the past but was purchased in 1995 and was likely stale. The associated control side row had no IBA treatment. The mean overall survival rate for the IBA treated cuttings was 48% and 52% for the untreated control cuttings. See: nursery_30iba_rooting_2019.sql. While the results are not significant and the IBA was likely defective, it shows the need for future nursery propagation tests for these variable and more difficult to root clones.
Nursery Stapled Fabric Sleeve POC Test: Test replication number 18 observed 2 aspen clones planted in the nursery as 14” dormant cuttings with 1’, 1.5’ and 3’ stapled white fabric tree sleeves that were pruned back to the top of each sleeve on 6/2 and 8/13. This test was needed to understand the impact of pruning (or browse) during the growing season. While this was a small POC test having 9 test trees, it was worthwhile to note several observations:
Five of the 6 sleeved cuttings survived and re-grew 9” to 29” after the final 8/13 pruning.
The regrowth and general vigor was higher for the 3’ sleeves perhaps due to their higher biomass capacity constrained by their sleeves.
The sleeved tests had smaller leaves (about 4”) versus 8” for leaves on standard nursery grown 1-0 stock.
More tests with larger numbers is needed.
Observe P. deltoides Rooting Patterns: Investigate the variation of dormant cutting rooting patterns in a native P. deltoides population and compare them to Open4st aspen hybrid rooting patterns that use P. alba for most of the rooting traits. A set of these clones will be observed for basal and/or adventitious rooting and if that pattern affects clonal rooting propagation rates. About one quart of open pollinated P. deltoides seed/cotton was collected on 6/10/19 under several large cottonwood trees and about 300 seeds were sown directly outdoors on 6/21/19. The tilled and raised seedbed was top dressed with washed sand and a shade cloth covering the South half of the bed. The seedlings were thinned on 8/1/19 with 103 seedlings surviving by 9/17 having heights ranging from 4” to 39” and a mean height of about 24”. See 2019 1xdw P. deltoides data. By 9/3/19 All of the seedlings were heavily infected with rust, however the nearby aspen hybrids had clean leaves. These seedlings will be grown another year in the nursery then propagate 6 dormant cuttings per clone to observe rooting patterns. In summary, the P. deltoides leaf issues and slow growth were similar to growing native P. grandidentata in this Bell nursery. See 2019 P deltoides OP Seedling Photos.
2019 Open4st Field Summary
There were 243 trees planted on 3 non-replicated field sites in 2019 North of Grand Rapids, MI. The material was a mix of stock types including 1-0, 14” dormant cuttings (DC) and 14” 1-0 root pruned cuttings referred to as “ministools” (MS) and P. grandidentata 1-1 seedlings (see: 2019 Post Sites by Stock Types). There were 43 different clones planted with an 87% overall survival rate a site mean height of 54 cm (see: 2019 Post Sites Summary). See site photos: North Post and South Post. Below are key 2019 field highlights:
Planted 14" ministools with white fabric sleeves (POC): All field trees were protected with 1’, 1.5’ and 3’ stapled white fabric tree sleeves that were exposed to rabbits, deer mice and voles. We have observed that large 1-0 aspen stock with ½” DBH were more difficult to plant, tended to rock in the soil and became top heavy for some fast growing clones. We have also observed that heavy deer browsing on unprotected aspens resulted in a multi-stemmed tree that was set back but typically not killed. Planting 14” rooted ministools with tree sleeves may be more robust, provide better survival than unrooted cuttings and a better root to shoot ratio than tall, slender 1-0 stock. Producing 14" ministools are also desirable from an operational standpoint, since the source cuttings can be cut from the upper ministool 1-0 stems avoiding expensive land and time resources to plant and maintain stool beds. See: 2019 Field Sleeve Test Photos.
Compared clone 25r23 with cuttings vs ministools: It was interesting to note the one year performance of clone 25r23 on this site with 3 different stock types (1-0, 14” dormant cuttings and 14” ministools) all having 100% survival. The 14” rooted ministools had more robust performance than the 14” dormant cuttings. The 13 ministools had twice the mean one year height and 2 feet of 12” field grade cuttings versus 0 feet for the 7 trees with dormant cutting stock. This is evident by observing these materials with pink ribbons on a site having 12 25r23 ministools (and this foreground photo) planted near 2 25r23 dormant cutting trees. This difference makes sense since the unrooted dormant cuttings must use resources to establish roots whereas the ministools have some roots.
Deer Browse Observations: Deer had browsed some trees across all 3 sites and almost all of the control clone DN34 trees were browsed, however none were killed. Deer appeared to browse some random aspens and rarely more than two times on the same tree. Overall, the 1.5’ and 3’ shelters appear to adequately protect the tree in the first growing season. It will be interesting to see how the different sizes protect against deer damage (browse and rubbing) and damaged tree forms in later years. We will be using both the 1.5’ and 3’ tree sleeves in future field tests.
2019 Woven Textile Weed Barrier POC: Conducted a small POC test investigating an alternative, non-chemical weed control option via black woven textile weed barrier. The 2019 test consisted of planting 15 14" dormant cuttings at 8' x 8' spacings using a 6" gas augered planting holes, 3' stapled fabric sleeves and 1.5' x 24" black woven textile fabric secured to the ground with 4 12" bamboo corner stakes. See all PostSE1 site photos, a sample weed barrier photo and related data: Weed Barrier POC Test 2019. High level observations below:
The Western 7 rows had lower survival rate perhaps due to soil fertility or drainage differences.
There were 12 weed barrier test clones, 15 planted, 7 survived, 45% survival rate, mean 16.2 cm height.
There were 14 total PostSE1 site clones, 102 planted, 86 survived, 84% survival rate, mean height of 35.6 cm.
The weed barrier trees had almost half the survival and growth rate.
The weed barrier trees started fairly good in the Spring but started failing during the hot and dry July days.
Conclusion: It would appear that the weed barrier trees under performed the other trees on this site, however, this POC test was too small and unreplicated for conclusive results. A future replicated, multi-site test might investigate using a 2' x 2' weed barrier using 14" 1-0 rooted ministool stock. Installing these weed barriers is difficult, time consuming and downright painful for old knees.
Field Trial Master Summary Table Data: This r4tst online database table lists summary statistical data for all open4st plantings grouped by the clone names with the number of sites, years planted and number of stock types. It also includes the summary data, "avg_field_cuttings_ft" column for the mean 12" field cuttings per tree and the "sites_plustree_survival_score" metric which employs a weighted formula to gauge clonal performance across a variety of sites, plus tree scores and survival rates. The general formula is as follows: "number of sites * 3) + (sum of plus trees * 2) + (survival rate * 5)". The need for this field was driven to help understand the un-replicated nature of the trials at this early stage. Hopefully, future replicated regional field trial data will be provide a clearer picture of the clone and site interactions.