Work Package 2c “Mixture configuration” plots
This trial will investigate the impact of alternative configurations of broadleaf crop and shelter mixtures. The trial is designed for the medium-term to the point of removal of the shelter species. A number of sites, located throughout the country, will be established using species and configurations that exhibit promise from WP2a. A Randomised Complete Block Design will be used with six treatments where possible and three replicates. Each trial site that includes all six treatments (see Figure 2) will be in excess of 1.5 ha, allowing for open space for access, and enclosed by deer fencing to ensure longevity of the trials. Examples of individual plot designs are provided below (Figure 3). Site and cost restrictions may lead to a limitation in the number of treatments that can be installed on a site.
Figure 4. Proposed site layout of "Mixture configuration" trial sites
Figure 5. Possible designs for the "Mixture configuration" plots using oak as an example. Going clockwise starting top left: pure broadleaf crop; alternate lines; 5/3 bands; shelterwells; 3/3 bands
Since the beginning of the project, the recommended spacing for the afforestation of oak as increased from 0.75 m × 2 m to 1.5 m × 2 m. A “mixture configuration” trial was established during the 2012-13 planting season at Teagasc Johnstown Castle Research Centre, Co Wexford that uses the new spacing. The trial is planted with oak (Quercus robur) and birch (Betula pubescens), both from native provenances. The trial has three treatments and three replicates. All trees are planted at 2 m × 1.5 m spacing (3,300 stems/ha). The treatments are:
- pure oak control
- oak:birch 3:3 banded mixture
- shelterwells with 12 m centres and consisting of 9 oak per shelterwell.
See Figure 6.
Figure 6. Mixture configuration trial design planted in Johnstown Castle during 2012-13 planting season. o = oak; b = birch
During the coming years the trial will be monitored and used to investigate whether birch can be a suitable nurse for oak and, if it can, which of the two nursing mixture being trialled is the more advantageous.