Ring Specific Gravity Research Articles

Regional variation in wood specific gravity of planted loblolly pine in the United States

Loblolly pine ( Pinus taeda L.) is the most important plantation species in the southeastern United States and specific gravity (SG) is its most important wood quality trait. Analysis of annual ring SG of breast height (1.37 m) increment cores from 3957 trees representing 147 plantations across the species natural range showed that ring SG increases with increasing age and varies significantly among physiographic regions. The South Atlantic and Gulf regions had the highest ring SGs, while the Hilly and Piedmont regions had the lowest. Based on ring SG, the juvenile period averages 4.3 years, followed by 8.6 years of transition wood, with mature wood produced by year 13. Whole-core mean SG was significantly higher in the South Atlantic (0.486) compared with the other regions (mean = 0.455), which were not statistically different from each other. Trees from the South Atlantic have significantly higher whole-core SG because they contain significantly more latewood (40.1%) compared with trees growing in other regions (33.8%). Maps indicate that stands in the South Atlantic and Gulf regions have the highest SG at a given age. Stands growing on the northern and western fringe of the natural range of loblolly pine have the lowest whole-core SG.

Long-term growth and ecophysiological responses of a southeastern Oklahoma loblolly pine plantation to early rotation thinning

A thinning levels study was initiated in a 9-year-old loblolly pine ( Pinus taeda L.) plantation containing 26.6 m 2 ha −1 basal area during the spring of 1984 in southeastern Oklahoma. Thinning treatments consisted of (1) three control plots (BA100), (2) three plots thinned to approximately 50% of the original basal area (BA50) and (3) three plots that were thinned to 25% of the original basal area (BA25). In 1987 the BA50 and BA25 plots were both rethinned to a basal area of 12 m 2 ha −1. No other thinnings were done through age 24. The control plots have attained a basal area of 45.3 m 2 ha −1 and basal area is now starting to decline. The BA25 and BA50 plots have basal areas between 34 and 35 m 2 ha −1. Mortality has averaged about 90 trees ha −1 per year from age 10 to age 24 on the control plot, declining from 2078 trees ha −1 at age 10 to 827 trees ha −1 at age 24. Mortality losses in the BA25 and BA50 plots have been only 3.2–7.7 trees ha −1 per year over the entire study period. Cumulative stem biomass lost to mortality was 10.5, 16.0 and 61 Mg ha −1, respectively, for the BA25, BA50 and BA100 treatments. Cumulative standing live biomass at age 24 in the BA100 treatment is 132 Mg ha −1. Cumulative standing live biomass in the BA25 and BA50 treatments at age 24 is 86 and 79%, respectively, of that observed in the BA100 treatment. These results suggest wide ranges of residual stand densities left after an early thinning will produce a high percentage of the potential total maximum standing stem biomass. Diameter distributions at age 24 show only 33% of the trees in the BA100 treatments have the dimensions to be sawtimber (≥30 cm) but 92 and 95% of the trees in the BA25 and BA50, respectively, are sawtimber dimension or larger. Mean annual stem biomass production (MAI) of the BA100 treatment is 7.5 Mg ha −1 per year at age 24. MAI of the thinned treatments is about 5.1 Mg ha −1 per year and is converging to that of the BA100 treatment. The basis for this convergence is not that the live trees in the BA100 treatment are producing live biomass less rapidly than the thinned plots, but that mortality losses in the BA100 plot are much higher. Current annual stemwood production in all treatments is often limited by the severe summer droughts that occur in this region. The wide variations in weather experienced at this site also result in variations in earlywood:latewood ratio and ring specific gravity.

Long term growth responses of loblolly pine to optimal nutrient and water resource availability

A factorial combination of four treatments (control (CW), optimal growing season water availability (IW), optimum nutrient availability (FW), and combined optimum water and nutrient availability (FIW)) in four replications were initiated in an 8-year-old Pinus taeda stand growing on a droughty, nutrient-poor, sandy site in Scotland County, NC and maintained for 9 years. Results for the first 4 years after treatment initiation at this study were first reported by Albaugh et al. [For. Sci. 44 (1998) 317]. The site is primarily nutrient limited and all measured stand parameters (height, basal area, leaf area index, live crown length, stem mass accumulation, current annual stem mass increment) were increased with fertilization throughout the study period. Irrigation effects were also positive for these parameters but the increases were much smaller than those found with fertilization. For example, 9 years after treatment initiation, standing stem mass was increased 100 and 25% by fertilization and irrigation, respectively, while current annual increment of stem biomass production was increased 119 and 23% by fertilization and irrigation, respectively. Interestingly, stem density (stems ha −1) was not significantly affected by treatment in any year of the study. Growth efficiency (stem mass increment per unit leaf area index) was 1.9 Mg ha −1 per year per LAI for CW and influenced by treatment with IW, FW, and FIW achieving growth efficiencies of 2.4, 2.7 and 2.9 Mg ha −1 per year per LAI, respectively. Growth efficiency appeared to be relatively stable in the last 4 years of the study. Ring specific gravity was measured in the third, fourth, and fifth years after treatment initiation. An average reduction in ring specific gravity of 7.5% was observed with fertilization while irrigation had little effect on specific gravity in any year measured. The continuation of high growth rates with no observable growth decline in the treated stands throughout the 9-year study may be a function of the age of the stands when treatments were initiated (8 years), the very poor initial nutrient and moisture availability, and/or the application of an ongoing optimum nutrient regime at the site. The fertilized plots are now at or near an age and a size when a commercial harvest would be feasible. For the stand conditions at this site, then, the optimum nutrient availability plots have achieved high productivity throughout the economic life of the stand without measurable declines in stand productivity.

Modeling Thinning Effects on Ring Specific Gravity of Loblolly Pine (Pinus taeda L.)

Abstract Effects of thinning on ring specific gravity in loblolly pine trees were examined in a regional trial in the southeastern United States. The thinning study consisted of two treatment levels (30% and 50% of the basal area removed) and a control. Thinning did not alter the proportion of the annual ring in earlywood or latewood and thus did not affect ring specific gravity. There was regional variation in average ring specific gravity, with trees from the Coastal Plain having higher ring specific gravity than trees from the Piedmont or the Highlands. Within the Coastal Plain, trees in the Gulf Coastal Plain tended to have higher average ring specific gravity than trees in the Atlantic Coastal Plain. A ring specific gravity prediction model was developed based on ring position, tree, stand, and site attributes. Much of the variation in ring specific gravity was due to within-tree variation; consequently, stand and site factors accounted for a limited proportion of variation in ring specific gravity. As the within-tree observations used in the study tended to be correlated, a direct covariance modeling approach was used to account for the correlation among observations. For. Sci. 44(2):212-223.

Variation of ring width and specific gravity within trees from unthinned Sitka spruce spacing rial in Clocaenog, North Wales

Summary The aim of this work was to quantify patterns of change in ring width and specific gravity within trees of Picea sitchensis with ring number across juvenile and mature wood, in relation to height in tree, original spacing, and crown dimensions. Five trees were sampled from each of three plots on a 52-year-old unthinned spacing trial at Clocaenog, North Wales. The ring width of wood produced in early decades of the plantation was most strongly correlated with original spacing, while that produced in later decades was more strongly correlated with branch diameters of the upper crown. In later decades, trees originally at the widest spacing had higher specific gravity than those originally at closer spacing, presumably associated with self-thinning of the narrower-spaced unthinned plots. Differences in amount of juvenile wood between spacing plots were less marked than those reported from the same plots when harvested 7 years earlier; it is suggested that as trees surviving after self-thinning are likely to be those with a competitive advantage from an early stage, differences between plots in amounts of juvenile wood may become less apparent in trees harvested later in the rotation than in those sampled earlier. Underlying patterns of variation in ring width and specific gravity across the tree were found to be modified by a progressive drift with height in the tree. Linear regressions between specific gravity and ring width also varied in a systematic way; the intercept and slope of these regressions tended to increase with ring number from the pith, and with height in tree at a specified ring number. Equations are given as a basis for quantifying these trends, but more data are needed from other sites to determine the extent to which these equations represent trends inherent to cambial and apical ageing, as distinct from influence of changing environment around the trees.

Within-tree variation in wood production and wood quality in sycamore (Acerpseudoplatanus): its relation to crown characteristics

To quantify patterns of wood formation in sycamore (Acerpseudoplatanus L.), the seasonal progress of wood production and structure was followed systematically throughout the outer growth sheath of the main stem and major branches. These data were considered in relation to the profile of leaf dry weight down through the crown in 8- and 12-year-old trees at stages before and after canopy closure, respectively. Mature fibre production was earliest towards the tips of the branches of the midcrown, and spread basipetally along the branches. In the main stem, mature fibre production was earliest at the tip and spread down the tree, taking about 10 days to reach the base of both pre- and post-canopy closure trees. In the stem, later fibre production down the tree was offset by later cessation of fibre maturation basally. Branch data suggested that the pattern of cessation may depend on the branch position, because cessation was latest at the base of the upper branches and at the tip of the lower branches. The maximum rate of fibre production was in the upper stem, several internodes higher than the internode bearing maximum leaf dry weight. Despite this, ring width increased down the stem, presumably as a result of the increased duration of fibre production and increased cell size. Within growth rings, vessel size remained nearly constant before declining sharply towards the end of the ring. Trees with narrower growth rings tended to have more of their ring occupied by declining vessel size suggesting a slight inverse relationship between ring width and specific gravity. Specific gravity increased down the outer growth sheath of the stem, and this increase was associated with systematic trends in fibre and vessel dimensions, together with changes in the relative proportions by area of the different tissues. Although some anatomical characters appeared to vary with the profile of the crown, others appeared to be independent of crown profile.

THE EFFECT ON VARIATIONS IN DECAY OF MOISTURE CONTENT AND RATE OF GROWTH IN SUBALPINE SPRUCE

The moisture content in subalpine spruce was highest in overstory trees and lowest in understory trees, and it was higher in trees on a moist site than in trees of similar vigor classes on a dry site. Moisture contents of 10% of saturation for the more vigorous trees on the moist site and 7% of saturation for the less vigorous trees on the dry site represented a statistically significant difference which appeared to restrict the development of heartwood fungi to the wetter trees. A similar difference in the moisture content existed between the 1.5-ft. and the 20-ft. level of the trees, the occurrence of fungi being restricted to the wetter basal portion of the stems. In the laboratory, infection did not take place in test blocks at moisture contents lower than 8% of saturation. It is suggested that the threshold moisture content for infection in the trees occurs around the 7 to 8% saturation level. In the laboratory tests a difference in the moisture content of 3.4% of saturation in wood resulted in a statistically significant difference in the rate of decay by Coniophora puteana (Schum. ex Fr.) Karst., but differences in ring frequency and specific gravity in the test pieces corresponding to the differences between these properties in the living trees did not appreciably affect the decay rate. There was no evidence that variations in the distribution of decay-promoting or decay-retarding substances occurred in the trees from the two sites.