MANAGEMENT NOTES Number 8

Transcription

1 MANAGEMENT NOTES Number 8 PLANTING WHITE PINE AND RED SPRUCE WITH SHELTER/SHADE Preliminary results by William M. Glen, 1993 INTRODUCTION The forests of Prince Edward Island have been subject to selective cutting or high grading for at least the past 270 years. Now many stands contain a few good trees and a large volume of poor quality material. To replace these stands with more desirable species and quality by clearcutting, replanting and follow up maintenance is expensive and in many cases the areas to be treated are small, making this approach impractical. This paper describes the results from a number of plantings which were done using the existing stands' shelter as an alternative. The history of each stand is documented and results to date are recorded. While these sites were not established as experiments, comparisons with other planting sites were available in most situations, and the results from them are very relevant to current discussions. SOFTWOOD STAND UNDER PLANTINGS Two locations are described where white spruce (Picea glauca (Moench) Voss) growing on former agricultural land was thinned and underplanted. They are at Bonshaw in Queens County on the property of the author (Universal Transverse Mercator grid 'UTM' 4723/1165) and at Orwell, Queens County on the MacPhail Homestead property (UTM 5137/1118). Bonshaw In the fall of 1983 an old field white spruce stand growing on a west facing slope was thinned (approximately 40% basal area removal) and a small portion of it was clearcut. The stand was a result of natural regeneration circa 1940 and contained 95% white spruce and 5% other species including white pine (Pinus strobus L.) and hardwood. In the spring of 1984 the small clearcut (patch cut, 500 m 2 ) and the thinned stand were planted with white pine supplied by the P.E.I. Forest Service nursery at Upton Road. The stand was thinned a second time in 1991 with minimal damage to the pine. The pine have been manually released from the other regenerating species as required. This has been very minimal but has been done every two years. The patch cut received a treatment of herbicide (glyphosate) to control the raspberries in This is a publication of the P.E.I. Dept of Energy and Forestry, Forestry Division, P.O Charlottetown, P.E.I. C1A 7N8

2 No damage has been done by the white pine weevil (Pissodes strobi Peck) or snowshoe hare (Lepus americanus (Erxleben)), locally known as rabbits, to any of the planted trees. The planting was broken down into five areas, the patch cut, two strips (former racks or extraction trails) approximately five metres wide, and two blocks of the stand which were underplanted. Measurements were done on thirty trees in each area except the two strips which had 28 each. The measurements were taken in mid August 1994 after height growth had stopped. Figure I gives an overview of the average heights plus and minus one standard deviation for each area. Table 1 provides the numerical data on the measurements and a visual assessment of the crown closure of the overstory. Figure I

3 Table 1 Height of white pine under planted 1984 in Bonshaw old field white spruce site established circa 1940 and thinned 1983 and 1991 Site 11 growing seasons height in cm Crown Minimum Maximum Std Deviation Average Closure patch cut % strip cut % strip cut % underplanting % underplanting % Orwell In the winter of 1979/80 an old field white spruce stand growing on former agricultural land in front of the MacPhail homestead (then MacPhail Provincial Park), had the dead understorey trees removed from it. As no live trees were removed by this treatment, the canopy of the stand was not broken so light reaching the forest floor was limited. The stand had naturally regenerated circa 1940 and was mature at the time of the operation. In 1983 the stand was underplanted with white pine and red spruce (Picea rubens Sarg.) obtained from the Nova Scotia Department of Lands and Forests nursery at Lawrencetown. The stand received no further treatment until recently when the stand was further underplanted by the 'MacPhail Ecological Woodlot Project' being run by the Environmental Coalition of Prince Edward Island under the supervision of Garry Schnieder. It was however, subject to spruce budworm (Choristoneura fumiferana Clemens) attacks and has been subject to the old field white spruce mortality syndrome. As a result, the crown health has declined markedly over the period and the forest floor is now receiving considerably more light than in The tree sizes were small and no weevil damage was noted. Table 2 reports the results of measurements of thirty trees of each species.

4 Table 2 Height of white pine and red spruce planted 1983 MacPhail Homestead old field white spruce site established circa 1940 Species 12 growing seasons height in cm Crown Minimum Maximum Std Deviation Average Closure underplanting W. pine % R. spruce % The planted stock have been subject to severe and continued browse by snowshoe hares. The lack of light has been particularly detrimental to the white pine. Where the white pine are now in a more open area due to overstory mortality they have grown to heights of 200 cm plus. HARDWOOD STAND UNDERPLANTINGS Three locations are described where hardwood stands were thinned and underplanted. They are at Bonshaw in Queens County on the property of the author; Brudenell, Kings County on the Brudenell Provincial Park property and at Afton Road on a property managed by the P.E.I. Forestry Service. Bonshaw In 1987/88 a tolerant hardwood stand established circa 1930 was thinned. The stand was composed of red maple (Acer rubrum L.), sugar maple (A. saccharum Marsh.), striped maple (A. pennsylvanicum L.), white birch (Betula papyrifera Marsh.), and yellow birch (B. alleghaniensis Britton). In the spring of 1991 two areas were underplanted with white pine supplied by the P.E.I. Forestry Service (crop number 91111). A few trees (<5%) have since been browsed by snowshoe hares. Table 3 shows the height growth as of August, 1994.

5 Table 3 Height of white pine planted 1991 in Bonshaw tolerant hardwood site established circa 1930 and thinned 1987/8 Site 4 growing seasons height in cm Crown Minimum Maximum Std Deviation Average Closure underplanting site % site % (Site 1, UTM 4721/1163; site 2, UTM 4719/1163) Brudenell-underplanting site 1 In 1982 a mixed wood stand of red maple, poplar (Populus tremuloides Michx.), balsam fir (Abies balsamea (L.)Mill.), and white birch was thinned as part of the 'ENFOR' thinning studies (UTM 5308/1180). This stand was underplanted in 1983 with white pine obtained from the Nova Scotia Department of Lands and Forests nursery at Lawrencetown. No follow up work has been done to this site since the planting. Weevil damage was not noted or expected due to the small diameter of the terminal leaders of the trees. Browse by hares has been a particular problem with this site. The measurements are shown in Table 4 and Figure 2. Brudenell-underplanting site 2 In 1983 another mixedwood stand of red maple, balsam fir, and grey birch (Betula populifolia Marsh.) was harvested (UTM 5296/1169). Most of the area was clearcut but part of it was very heavily thinned with only 20%-40% crown closure left. White pine and red spruce (both from N.S. L. & F.) were planted in the 'dappled' shade left on the site. By 1994 the crown closure had increased to 50-60% and the crowns of the remaining overstory are now an impediment to the height growth of many of the white pine. The pine have been subject to low to moderate levels of weevilling over the past few years. The current level of attack is 17.5%. The few red spruce have reached an average height of cm (minimum 62 cm, maximum 201 cm, standard deviation 64.7 cm). Brudenell-old field Some of the same stock used in the underplantings was established in a small section of abandoned farmland (UTM 5316/1175). These trees have grown well but have been subject to higher levels of weevilling. The current level of attack is 23.3%. This planting provides a comparison for the other sites at Brudenell and MacPhail that were planted with the same stock.

6 Brudenell Patch cuts In 1980 a series of small patch cuts were created in a mixed stand of larch (Larix laricina (DuRoi) K. Koch) and white spruce approximately 14 metres in height growing on former agricultural land naturally regenerated circa 1940 (UTM 5298/1172). Two of these cuts had a small number of white pine planted in them. The stock was wildings lifted from the Findlayson Point area near Murray Harbour, P.E.I. (UTM 5334/975) One cut approximately 10 metres square was planted at a spacing of 1.8 by 1.8 metres. The other cut was larger, about 1,000 m 2 and the pine were planted in partial shade in two rows along the southern face at the same spacing. No follow up maintenance has been done and competition in the larger cut has reduced the growth of some trees. Browse from snowshoe hares has been notable and has kept a number of the trees small but this has not been problematic as most of the pine have now out grown the reach of the hares. No weevil damage was found in these patch cuts. Table 4 Height of white pine planted 1980 and 1983 in Brudenell on various site types Site 15 or 12 growing seasons height in cm Crown Minimum Maximum Std Deviation Average Closure patch cut py % Underplanting 1- py % Old field py % Underplanting 2- py % (Patch cut UTM 5298/1172, Underplanting 1 UTM 5308/1180; old field UTM 5316/1175; underplanting 2, 5296/1169)

7 Figure 2 Afton Road In 1980 an area of ericaceous barren that was regenerating to poplar, red maple, white and grey birch was site prepared using a 'C & H' plough (UTM 5060/1358). This created furrows on approximately 2.4 metre centres with planting microsites each side of the furrow centre approximately one metre from the centre. The area between the prepared strips was undisturbed. Black spruce seedlings were planted in the prepared area but survival was poor. The vegetation in the undisturbed strips soon overtopped the prepared area. White pine seedings from the P.E.I. Forestry Service Nursery at Upton Road were planted to replace the black spruce in The overstory was thinned circa 1984 and again circa Recent observations show that the overstory crown closure was about 60% but an understory of hazel (Corylus cornuta (Marsh.), alder (Alnus B. Ehrh.) and other shrubs was 100%. These two canopy layers have reduced the growth of the pine and kept the size within reach of the snowshoe hares. Measurements taken in early September showed a mean height of cm with a standard deviation of cm. This lack of height was due to repeated browse by the snowshoe hares. A few pine planted next to the access road have outgrown the hares and had reached heights of four metres CONCLUSIONS The 1983 white pine plantings at MacPhail and Brudenell provide a reasonable indication of the variation in growth that can be expected from the species. The old field site provides an

8 indication of the maximum rate of growth and the other sites, the amount of reduction that can be expected under differing light conditions. The 1984 plantings in Bonshaw also provide similar results. Figure 3 provides a comparison of annual height growth versus the overstory crown closure of the site. Figure 3 Based on these plantings white pine and red spruce have shown that they can survive in heavy shade for periods of up to 12 years with little growth. The amount of crown closure or shade under which they are growing appears to be critical to their subsequent growth. Based on these observations a maximum crown closure of 65% is recommended for reasonable growth of white pine underplantings. For continued acceptable growth, maintenance of a crown closure of less than 65% will require on going effort or other factors (i.e. mortality). If the overstory crown closure increases to more than 65% the reduced growth rate of the planted material makes them more susceptible to on going damage by the snowshoe hares. The Afton Road site provides a good example of the result. The patch cuts examined did not have any damage from the white pine weevil and may offer a more maintenance free way of successfully establishing white pine. (The red spruce sample size was too small to draw any conclusions but are reported here for further reference.)