Pine Spacing Trial Research Articles

Correction: Managing plantation density through initial spacing and commercial thinning: yield results from a 60-year-old red pine spacing trial experiment

Correction: Managing plantation density through initial spacing and commercial thinning: yield results from a 60-year-old red pine spacing trial experiment

Managing plantation density through initial spacing and commercial thinning: yield results from a 60-year-old red pine spacing trial experiment

We report on a 60-year-old red pine (Pinus resinosa Aiton) spacing trial experiment located in Ontario, Canada, that included the combinations between six initial spacings (from 1.2 to 3.0 m) and the presence or absence of a commercial thinning (CT) regime, as well as their impacts on quadratic mean diameter (QMD) and stand volume yield. The CT regime, initiated at age 30, targeted a residual basal area (BA) of 38 m2·ha−1after each of four entries. Without thinning, as initial spacing increased, QMD increased; gross and net volume production peaked in the 2.1–2.4 m spacings. With thinning, similar trends with spacing were evident for QMD, although piece sizes were larger and differences between spacings were lower. The immediate increase of mean tree size caused by tree selection explained most of the differences in QMD between thinned and unthinned plots. Thinning to a common target BA resulted in similar standing volume across spacings. Cumulative gross yield was similar between spacings of <2.1 m for both thinned and unthinned stands and decreased for thinned plots for wider spacings. Greater net volume production in thinned stands with the narrower spacings confirmed that mortality was captured. Lower gross and net production for wider spacings suggested that thinning resulted in underutilized growing space.

Crown-rise and crown-length dynamics: application to loblolly pine

The original crown-rise model estimates the average height of a crown-base in an even-aged mono-species stand of trees. We have elaborated this model to reduce bias and prediction error, and to also provide crownbase estimates for individual trees. Results for the latter agree with a theory of branch death based on resource availability and allocation. We use the improved model to estimate the growth and stem-profile development of a mean-tree in an even-aged stand of loblolly pine. Predictions show good agreement with data from a loblolly pine spacing trial.

Forage Production Potential in a Ponderosa Pine Stand: Effects of Tree Spacing on Understorey Plants after 45 Years

We examined the development of understorey forage plant communities in relation to tree density in an experimental ponderosa pine (Pinus ponderosa) stand. We used a 45-year-old ponderosa pine spacing trial near Westwold, British Columbia, Canada, with five spacing treatments (1.22, 2.44, 3.66, 4.88, and 6.10 m) to sample understorey biomass and diversity, with a focus on pinegrass (Calamagrostis rubescens) and rough fescue (Festuca campestris)—two regionally important forage grasses. We predicted that there would be a positive correlation between tree spacing and understorey biomass and a compositional shift from pinegrass to rough fescue under increased tree spacing. We found that rough fescue, the preferred forage species, grew only under tree spacings equal to or greater than 3.66 m, with the greatest biomass at 4.88 and 6.10 m spacings, whereas pinegrass was equally abundant under all spacings. We believe that silvopasture principles could be applied to similar ponderosa pine stands to optimize and maintain both timber and forage productivity.

Rotation-Age Results from a Loblolly Pine Spacing Trial

Rotation-Age Results from a Loblolly Pine Spacing Trial

Does Row Orientation Affect the Growth of Loblolly Pine Plantations?

Abstract Analysis of covariance methods applied to long-term loblolly pine spacing trial growth data showed that the orientation of rows with regard to a particular azimuth direction had no significant impact on either basal area or dominant height growth through the age of 20 years. Results were consistent for a range of planting densities and spacings and across a range of ages that included very young ages before crown closure. These results suggest that for loblolly pine growing in the Piedmont and Coastal Plain areas of Virginia and North Carolina, the selection of row orientation at plantation establishment can be made based on criteria other than growth.

Biomass partitioning in a miniature-scale loblolly pine spacing trial

Stand conditions influence the partitioning of biomass to stem, needle, branch, and root components. Using data from 4- to 6-year-old loblolly pine ( Pinus taeda L.) trees grown in a miniature-scale spacing trial, this study determined the effect of initial spacing on the biomass partitioning of loblolly pine. Multivariate analysis of variance procedures concluded that row and column spacing did not have a significant effect on the relative amount of biomass among tree components. Root/shoot and height/diameter ratios, however, differed across densities, indicating that allometric-based partitioning tradeoffs occurred. Results from the miniature-scale trees showed trends similar to those observed with mature-sized trees at operational spatial scales. Stem and woody roots were 70% and 14% of total mass, respectively. Since these trees were physiologically young at the time of harvest, the allocation of mass to needle continued to be a priority, accounting for 10% of the total mass. Initial planting spacing did not directly affect partitioning patterns; however, allometric ratios offered some evidence that partitioning may have changed between above- and below-ground tree components. This analysis offers insight into using principles from similarity analysis to analytically relate biomass partitioning from miniature to operational spatial scales.

Estimating individual tree leaf area in loblolly pine plantations using LiDAR-derived measurements of height and crown dimensions

Accurate estimates of leaf area index (LAI) could provide useful information to forest managers, but due to difficulties in measurement, leaf area is rarely used in decision-making. A reliable approach to remotely estimating LAI would greatly facilitate its use in forest management. This study investigated the potential for using small-footprint LiDAR, a laser-based remote sensing tool capable of characterizing the vertical structure of forest vegetation, to generate estimates of individual tree leaf area based on LiDAR-derived estimates of tree height and crown dimensions. At a 16-year-old loblolly pine spacing trial in Mississippi, LiDAR-derived estimates of leaf area based on height and crown diameter were on average within 0.1 m 2 of ground-based estimates for trees on plots initially planted at a 1.5 m × 1.5 m spacing. For trees on plots originally planted at square spacings of 2.4 m and 3.0 m, LiDAR-based leaf area estimates were below ground-based estimates by 5.8 m 2 and 14.5 m 2, respectively. At a study site in Texas, LiDAR-derived estimates of leaf area for 4-year-old loblolly pine were, on average, within 0.4 m 2 of ground-based estimates. Errors in leaf area estimates were largely due to the inability to generate accurate LiDAR-based estimates of crown dimensions. Tree heights were accurately estimated with LiDAR at both locations, but crown diameter and vertical crown dimensions at the Mississippi site were underestimated on average by 21% and 3%, respectively.

Patterns of Survival, Damage, and Growth for Western White Pine in a 16-Year-Old Spacing Trial in Western Washington

Abstract Information about effects of planted spacing on growth and development of western white pine is scant because white pine blister rust disease has severely limited the survival of trees in young plantations. In the early 1980s, we established a western white pine spacing trial in the southern Cascades of Washington, using seedlings from a seedlot comprised primarily of open-pollinated seed from trees screened and certified as resistant to white pine blister rust. Initial square spacings ranged from 2 to 6 m; treatment plots were 0.4 ha in size and were replicated three times (six times for the 3 m spacing). Permanent measurement plots were installed at age 8, and the lower portion of all stems was pruned in the 10th growing season to reduce blister rust infections. The plots were remeasured at ages 11 and 16. Sixteen years after planting, survival averaged 80%; most mortality was associated with blister rust, but the rate of new infections and mortality diminished substantially between ages 11 and 16; 71% of the planted trees were free of blister rust at age 16. Trees averaged 8.4 m tall (ranging from 7.6 m in the 2 m spacing to 8.8 m in the 4 and 5 m spacings) and 12.7 cm dbh (10.3 in the 2 m spacing to 14.0 cm in the 5 m spacing). Periodic annual growth from 11 to 16 yr in the three wider spacings averaged 0.7 m in height and 1.0 cm in diameter. Antler rubbing by elk caused substantial damage to stems, but wounds on most trees were overgrown in 2 to 4 yr. Rub damage did not appear directly related to spacing but rather to stem diameter, with damage limited primarily to stems >6 and <15 cm. Early growth rates in this trial were much greater than those attained in older, natural stands (as inferred from site index curves and yield tables) and in progeny tests and other young silvicultural trials planted elsewhere. We believe rust-resistant stock of western white pine merits greater consideration for planting in the Douglas-fir region. West. J. Appl. For. 18(1):35–43>.

Effect of intra-specific competition on tree architecture and aboveground dry matter allocation in Scots pine

The study was carried out in a 25 year old Scots pine spacing trial, established with grafted clones at four different spacings. The oven-dry weight of the different aboveground parts of the tree (i.e. stem, large and small branches, needles and cones) was assessed separately. With closer spacing, the relative proportion of cones and of large branches per tree decreased, while the dry matter increment allocated to stemwood increased gradually from 11.7 to 28.5 percent. Without competition, the dry matter allocated to cones was nearly similar to that of current stemwood increment. On a unit area basis, the dry matter weight allocated to cones did not change significantly at different density levels and remained between 0.6 and 1.0 tonnes per ha. The highest total biomass per unit area was measured at maximum stand density (98.2 t/ha), where stem number is regulated by natural mortality (self-thinning). A slightly positive effect of competition on height growth was detectable only when the trees were young. The results show the plasticity of Scots pine architecture in relation to spacing in the early phases of stand development.

Basal Area Growth and Crown Closure in a Loblolly Pine Spacing Trial

Abstract Data collected after each of the first 13 yr since planting of a loblolly pine spacing trial were used to study relationships between basal area growth and crown closure. Crown closure and crown competition factor at the inflection age of cumulative basal area growth were examined on 192 plots of varying initial density and rectangularity at four sites in the Piedmont and the Atlantic Coastal Plain. Inflection age increased with initial growing space, but at a decreasing rate, presumably approaching some maximum value that would be realized in the absence of all competition. The inflection generally occurred earlier on study sites with the highest site index values, but exceptions to this trend were observed. The degree of crown closure at the inflection age increased with planting density, but did not depend in a meaningful way on the site index of the study sites. Crown competition factor at the inflection age increased with planting density, but also increased with site index. Rectangularity did not significantly affect the inflection age, but it did reduce the level of crown closure at that age. A test for the effect of rectangularity on crown competition factor was inconclusive. For. Sci. 45(1):35-44.

Impact of Heavy Glaze in a Loblolly Pine Spacing Trial

Abstract In March 1994, a severe ice storm badly damaged an 11-yr-old loblolly pine spacing study in central Virginia. After the storm, trees in the spacing trials were categorized into one of five stem and top damage classes. Analysis of variance procedures indicated no significant relationship between stem and top damage and spacing or density. Forked trees were found to be more susceptible to ice damage than single-stemmed trees. At an individual tree level, strong correlations were found between diameter and height and the type (stem bending or top breakage) and severity of damage. Prediction equations were developed for estimating the probability of five levels of stem bending and top breakage based on a proportional odds model. South. J. Appl. For. 20(3):151-155.

Efficiency of Early Selections for Stem Volume and Predictions of Size Distributions of Selections in a Red Pine Spacing Trial

Abstract Simulated phenotypic selections for superior stem volume at age 34 were carried out in a red pine spacing trial between age 10 and age 34. The efficiency of selections increased exponentially with selection age and with diminishing initial spacing. Interactions between spacing, age, and the intensity of selection modified the overall efficiency of early selections. The probability that a tree would remain in a given relative size class during a 2-or 4-year-period increased with age when the initial spacing was less than 2.1 m. Wider spacings induced a decline in these probabilities. Realistic predictions of future size class distributions of trees selected for superior size at age 10 were generated from a maximum of 4 years growth information with the help of Markov chains (transition probability matrices). Age 34 standardized means of early selections could be estimated within 2% from a quadratic response surface with age, spacing, and selection intensity (%-select) as independent variables. For breeding purposes, selections at age 10 appeared more attractive than later selections. Predictions of age 10 to age 34 years correlations of stem volume based on these Markov chains produced realistic results for plantations planted at a 3.0 m square spacing and closer. For. Sci. 37(2):593-612.

Honduras Pine Spacing Trial Results in Puerto Rico

Abstract Puerto Rico has one of the oldest, continuously measured spacing trials of Honduras pine (Pinus caribaea mor. hondurensis) in existence. At 18 to 20 years, mean survival for all the trial sites except one that suffered hurricane damage in 1979 was 82%. Survival was not related to the triangular spacing treatments of 5, 7, 10, and 14 feet. But spacing did influence diameter growth at all four sites and affected height growth at all but one site Each site had trees ≥100 feet tall at 18 to 20 years; on the two best sites, individual trees reached 90 feet by 12 years. At close spacings, mean annual height increments peaked at 4.0 to 4.5 years on two sites and at 7.2 years on the other two sites. Mean annual diameter increments peaked even earlier, at 3.0 to 3.5 years on the two good sites and at 6.0 years on the two poorer sites. Early effects of competition in reducing both mean annual height and diameter growth, particularly at close spacings, have several managerial implications. The most striking are: (1) underestimating site quality or site index if growth assessments are made only in dense stands, and (2) significant loss of wood volume over long rotations when managers fail to time thinnings before mean annual height and diameter increments decrease.