Planting density

Planting density has large potential impacts on amount, size and value of timber harvested from managed forests and on biological and technical rotation lengths.

Effects of Spacing Paper Birch–Mixedwood Stands in Central British Columbia - EN29

This extension note describes two studies that have been established in the central interior of British Columbia to provide information on the effects of thinning paper birch on growth of understorey conifers. Paper birch is found throughout the British Columbia interior. It is also found in pure stands and in mixture with conifers across a broad range of sites in the Interior Cedar–Hemlock, Sub-Boreal Spruce, and Boreal White and Black Spruce zones. In the past, paper birch was largely ignored during conifer harvesting and reviled in conifer plantations. Recent recognition of the contribution of broadleaf trees to biodiversity and site productivity and opportunities for the commercial utilization of broadleaves has stimulated interest in managing mixedwoods in British Columbia. Current utilization of paper birch is low in British Columbia (less than 10% of potential, province-wide) but there are opportunities to manufacture birch veneer, plywood, and lumber products for markets in the United States and Pacific Rim countries.

Clumpy Spacing, Juvenile Spacing Douglas-fir into Clumps to Imitate Natural Stand Structure - EN32

Drybelt Douglas-fir is a moderately shade-tolerant species that grows in multi-aged stands on dry sites in the southern Interior of British Columbia. These stands may include aspen and scattered or patchy lodgepole pine as well as the Douglas-fir in distinct or mixed layers. Stand structure between and within stands often varies greatly. These drybelt stands have high timber values and, if well managed, can provide opportunities for regular February 1999.

Growth and Survival of Douglas-fir and Western Redcedar Planted at Different Densities and Species Mixtures - TR44

Survival and height, diameter at breast height (dbh), volume, and crown growth of Douglas-fir and western redcedar in a mixed plantation were measured 14 years after planting. As expected, Douglas-fir had faster early growth than western redcedar and average dbh, volume, and crown area of the stand increased as the proportion of Douglas-fir in the stand increased. However, the average growth of Douglas-fir and western redcedar was not significantly different when grown in a pure stand compared to being grown in a mixed stand. Average growth of either species was also not significantly different at densities of 500, 1000, or 2000 stems per hectare. Consequently, at this young age, the effect of the species mixtures on growth was likely due to different early growth rates rather than from differences between interspecific and intraspecific competition. This experiment will help to determine the long-term outcomes of different stand mixtures in producing timber volume.

The Effects of Plantation Density on the Growth and Yield of Lodgepole Pine: 20-year Results - EN102

The effects of plantation density (espacement) on the growth and yield of lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.) are reported 20 growing seasons after planting. Five densities (500, 1000, 1500, 2000, and 2500 trees per hectare) were established on plots in central British Columbia. Both individual-tree and per-hectare data were analyzed. With the exceptions of mean height, periodic height growth, and survival, espacement had a statistically significant effect on all of the characteristics examined. Although this report provides only short-term information on the effects of espacement, it does indicate the need to optimize individual-tree growth rates with levels of growing stock in order to maximize yield per unit area.

Effects of Planting Density on Yellow-cedar and Western Redcedar Growth - EN101

An espacement (planting density) trial was established in the Coastal Western Hemlock biogeoclimatic zone in 1988. Two species, yellow-cedar (Chamaecyparis nootkatensis) and western redcedar (Thuja plicata), were planted at densities of 240, 480, 720, 1090, 1680, and 2990 stems per ha (sph) at two sites for each species. After 21 years, height, diameter at breast height (dbh), height to the lowest live branch, and height to the base of the live crown were not significantly different across the treatments. However, general trends were becoming apparent. Height and dbh growth were slower at the denser spacings for western redcedar. For yellow-cedar, height and dbh growth were similar at all spacings except at the 2990 sph spacing, which showed slower growth. The effect of spacing was more pronounced on dbh than on height. There was a trend of an increasing height to the base of the live crown and height to the lowest live branch as density increased for western redcedar. There was no trend for height to the lowest live branch and to the base of the live crown for yellow-cedar. Future measurements on this trial may yield definitive results and provide guidance on managing western redcedar and yellow-cedar.

Effects of High Plantation Densities on the Growth and Yield of Lodgepole Pine - TR115

The effects of high plantation densities (espacement) on the growth and yield of lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.) are reported over a 34-year period. Seven densities ranging from 2500 to 160000 trees per hectare were established on plots in the Central Interior of British Columbia. This study was designed to investigate the height repression of lodgepole pine that has been observed with high densities established post-wildfire. A variety of statistical tests provided strong evidence of a general height reduction with increasing treatment density and stand density (post-mortality) compounded by age. Stand dominant height was described using top height (the height of the largest-diameter tree in a treatment plot) and site height (the height of the tallest 5% of the trees in a plot). Treatment-level top-height and site-height measures were found to be similar only when density was >10000 stems per hectare (sph). Site heights were greater than top heights when density was <10000 sph. Nonlinear segmented regression estimates suggested threshold repression densities of around 11000 and 8000 sph, respectively, for top height and site height at age 15. Treatment density trajectories indicated that all plots were following known stand mortality dynamics. Total stand volumes were found to increase with increasing density with no indication of declining stand productivity at high treatment densities.

The Effects of Planting Density on the Growth and Yield of Lodgepole Pine, Interior Spruce, Interior Douglas-Fir, and Western Larch: 16- to 26-Year Results from EP964 - TR98

Long-term monitoring of planting density trials provides critical information about the effects of planting density on the growth, development, and yield of conifer plantations. Experimental Project 964 (EP964), which was established in the Interior of British Columbia by the B.C. Ministry of Forests between 1985 and 2000, comprises 26 standardized planting density installations distributed over nine forest districts and four biogeoclimatic zones. The installations include four commercial conifer species laid out using five planting density treatments. The installations with this Experimental Project have now been monitored for about 16-26 years since planting.

In this project, we analyzed data for 17 EP964 installations planted with interior lodgepole pine, interior Douglas-fir, interior spruce, and western larch. We focussed our analyses to answer three questions of interest to forest managers that concern: (1) the consistency of planting density effects on the growth and yield for particular tree species; (2) the optimal planting density to achieve the highest timber value per area for particular timber products; and (3) the forest health effects of planting density on pine mortality.