Treestock performance on coastal sandy sites

Stock type selection greatly affects the establishment and initial growth of a new plantation, especially on harsh sites. The two main stock types used in plantation forestry are bareroot and container-grown seedlings. Container seedlings have lower establishment risks on dry or sandy sites or out of season planting. Container seedlings have less transplant shock because there is virtually no root disturbance during lifting, packing, transport, and right through to planting. Containers also come with their own "packed lunch of nutrients" to promote quick establishment and faster new growth.

In a recent study we compared the performance of bareroot and container seedlings on a sandy coastal forestry site. Seedlings from the same CP seedlot were raised in a bareroot nursery and in PF Olsen’s container nursery. A field trial was established in 2016 in Tangimoana Forest, on a coastal sandy site, using seedlings from both treestock types. Seedling height and root collar diameter were measured at the time of planting. Mortality, tree height, root collar diameter and tree health were assessed again one year (403 days) after planting.

The mortality rate one year after planting was low, (less than 4%) and the difference in mortality rate between container and bareroot seedlings was statistically insignificant. The bareroot seedlings were slightly taller and bigger than the container seedlings at the time of planting. Tree height, 403-days after planting increased 2.4-fold for bareroot seedlings and 3.3-fold for container seedlings (Figure 1). Root collar diameter increased 4.6-fold for bareroot seedlings and 7.7-fold for container seedlings in the same period (Figure 2). The differences in height and root collar diameter growth between the two treestock types were statistically highly significant. There was no significant difference in tree health between the two treestock types, but more container trees had an “excellent” health rating (34.9%) than bareroot trees (29.7%)


Figure 1. Comparison on the height growth between bareroot and containerised seedlings

Figure 2. Comparison on the root collar diameter growth between bareroot and containerised seedlings

In summary, on a coastal sandy site, where water holding potential in the soil is poor, container-grown seedlings showed significantly better early growth. This is because the root system of container seedlings can maintain higher water and nutrient holding capacity. Container seedlings provide an opportunity for forest managers to achieve a better establishment result when planting Pinus radiata on sandy or drought stressed sites. PF Olsen produces container seedlings at its south Auckland nursery. It supplies container seedlings to forest owners throughout New Zealand. For enquiries about container seedlings order, please contact Dawn Lewis on 07-9217205 or email dawn.lewis@pfolsen.com.

The trial was a collaboration between PF Olsen Ltd and Ernslaw One Ltd. For more information, please contact Dr. Wei-Young Wang wei-young.wang@pfolsen.com.