With estimates of survival as low as 50 percent, the success rate for interior spruce plantations on brush-prone sites is giving cause for concern. Failure in most cases is attributed to the inability of the planted trees to compete with other vegetation. There are a number of means by which plantation failure.due to this cause can be reduced. These include:
1. suppress competing vegetation by pre-planting site treatments (e.g. burning, or mechanical preparation);
2. post-planting weed control measures (e.g. mechanical weeding, or herbicide application);
3. modify soil ,conditions so as to improve tree growth in relation to the ,growth of other vegetation (e.g. rotovation or mounding); and
4. increase the size and vigor of the planting stock used.
With regards to alternative No. 4 recent trials have shown that one-year-old interior spruce plugs, from 20 cubic inch containers (PSB 615) are superior, both in size and in initial growth rate to all spruce stock types currently used in B.C. The results of these trials are summarized here and some of their implications noted.
The study included three experimental plantations; two on low elevation sites in the Prince George Forest Region; and one at a high elevation in the Nelson Forest Region. The first season growth of one-year-old interior spruce seedlings from PSB 615 containers greatly exceeded that of 2+0 bare root stock, the interior spruce stock type most commonly used in B.C. Mean first season height growth in the plugs ranged from 12 cm to 17 cm versus about 5 cm in the bare root trees. Mean height at the end of the first growing season varied from 38 cm to 53 cm for the plugs, and from 17 cm to 27 cm for the bare root stock. In one of the plantations, seven other stock types were also planted (3+0, 1 1/2+1/2, 2+1, 2+2 bare root, and 211, 313 and 415 plugs), Not one of these stock types challenged the 615 plugs either in first season shoot extension, or in height at the end of the first growing season.
In all plantations fertilization at planting improved foliage color at the end of the first growing season. This was especially evident for the plug stock. Fertilization also increased first season shoot extension of the plugs, but not of the bare root trees.
Second year performance has been observed in only one plantation. In that case the plugs continued to out grow the 2+0 bare root stock both in height and in stem volume.
Shoot extension in both stock types was less in the second year than in the first. This fall down in height growth was at least partially counteracted by fertilization at planting. Second year shoot extension of the bare root trees was doubled by fertilization, that of the plugs tripled. Stem volume at the end of the second growing season was only slightly increased by fertilization at planting in the case of the bare root trees; however, in the plugs it was more than doubled. At the end of the second season, the stem volume of the bare root trees equalled that of the plugs when first planted. During the first two seasons, stem volume of the fertilized plugs increased 10 times; that of the fertilized bare root trees only five times.
Compared with the 2+0 bare root trees, the 615 plug seedlings were much bushier in form. In this they resemble naturally-established trees. Shoot tip wilt due to infection by Sirococcus strobilinus was observed in one plantation. The cause of a high incidence of shoot tip die back (25%) in another plantation was not definitely determined.
The relatively high failure rate for interior spruce plantations in some parts of the Province has been attributed to the inability of the planted trees to compete with other vegetation. The observations reported here indicate that the early growth of planted spruce can be greatly influenced by stock type. In particular, of the stock types that can be made available at present, large plugs have the greatest early gro ...
BC Forest Service - Research Division. 1982. The potential of large plug stock in the establishment of interior spruce plantations. British Columbia Ministry of Forests, Lands, Natural Resource Operations and Rural Development. Research Memo (FLNRORD). RM51
Topic: FLNRORD Research Program
Keywords: FLNRORD, Research Memo, British Columbia
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