Stem Radius Research Articles

Estimation of the aerial biomass of weedy shrubs by regression methods: Studies on Adhatoda vasica

Estimation of above-ground biomass of Adhatoda vasica on a fresh-weight basis has been done, using observed weight ( W 0) as dependent variable and basal radius ( p) of stem just above ground and height ( H) of plant as independent variables, through linear regression techniques. Basal radius indicated an almost linear relationship with weight, while height appeared to be a redundant factor. The best estimates were obtained using the equation W 0= bp 2 × H+ C, though reasonably accurate estimation can be done also through equation W 0= bp+ C, where C is the regression constant. Adhatoda exhibited fairly uniform distribution of moisture content along the height.

Stresses in, and the shape of, tree stems in forest monoculture

The mechanistic theory of the shape of tree stems, that is the variation in stem radius with height, assumes that the stem is a tapered vertical beam of circular cross-section fixed rigidly at ground level and subjected to vertical forces due to the weight of the stem and crown and horizontal forces due to wind. The theory then holds that the stem is shaped so that the maximum bending stress acting at any point along the stem is constant. Most support for this theory has come from empirical observation of the shape of tree stems. In this work, a model is proposed to estimate directly the bending stress acting at any point along a tree stem. It includes a model of the wind profile within the forest canopy which can be used to estimate forces acting on tree crowns. The model is applied to a monoculture of Eucalyptus regnans F. Muell and the results compared to those from an earlier model which also predicts stress but assumes a constant wind profile through the canopy. It is concluded that stress is constant along stems, above their butt swell, if the wind profile is constant but is increasingly less so as the wind profile becomes steeper. The possibility of applying this model to predict changes in stem shape with age and changed stand circumstances, such as those that result from thinning, is discussed.

Quantification of Douglas-fir growth losses caused by western spruce budworm defoliation using stem analysis

Periodic growth and volume losses in Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) trees in one stand defoliated four times in their lifetime by western spruce budworm (Choristoneuraoccidentalis (Freeman)) are reported. Losses were calculated by comparing periodic growth for the years of reduced ring increment with potential growth estimated using the IMPACT growth loss program. Proportional losses in stem radius and cross-sectional area remained approximately constant or declined slightly from tree top to base; losses differed at all stem levels among the infestations. Average gross volume losses per tree relative to the potential volume the trees should have reached at the end of each loss period were 17, 15, 8, and 13% for the 1920's, 1940's, 1950's, and 1970's infestations, respectively. In the last infestation, losses ranged from 9% in trees defoliated from 1 to 50%, to 18% in trees defoliated 91–100%. Cumulative tree volume losses, calculated by adjusting growth during all loss periods to their potential values, were estimated to be 44% of the potential volume the trees should have reached by 1977 had the trees never been defoliated. On a per hectare basis, the 1970's infestation in this stand caused an estimated 60 m3 (18%) loss, comprising 40 m3 (12%) owing to tree mortality and 20 m3 (6%) of growth deficit in the surviving trees.

Applicability of Growth Equations to the Growth of Trees in Stem Radius (III)

Applicability of Growth Equations to the Growth of Trees in Stem Radius (III)

Applicability of Growth Equations to the Growth of Trees in Stem Radius (II)

Applicability of Growth Equations to the Growth of Trees in Stem Radius (II)

Time lags in the water relations of Sitka spruce

Time series analysis is used to estimate the time lags between diurnal changes in the transpiration rate, shoot water potential and stem radius of early pole-stage Sitka spruce. In July 1974 data were collected hourly over 7 consecutive days on shoot water potential, stem radius changes at several heights in three trees and lengths of leading shoots in two trees. In July/August 1976 shoot water potentials were measured at four positions in the canopy, stem radius changes at two heights on a single tree and leading shoot lengths on two trees. In the 1st year transpiration rate was estimated using the Penman-Monteith equation and in the second year by an eddy-correlation/energy balance method. Time series of data were divided by a moving average technique into Trend or Periodic and Random contributions. Power spectral analysis was then used to investigate the relative importance of periodic and random changes while Serial Cross-Correlation was used to find the time lags between appropriate series. Variations in stem radius at different heights in a single tree were found to be well correlated and in phase as were such changes at the same height in different trees. Water potentials in leading shoots and at the trunk, both at two heights, were all found to be in phase. Transpiration rate and shoot water potential changes were found to be in phase while changes in stem radius at the base of the canopy lagged up to 3 h behind these. A simple resistance-capacitance analogue of water flow in Sitka spruce is proposed as a result of these relationships.

Control by Indole-3-Acetic Acid of Wood Production in Pinus radiata D. Don Segments in Culture

The effect of indole-3-acetic acid (IAA) on stem radius growth, tracheid lumen diameter, and tracheid wall thickness in P. radiata was investigated. Stem segments from trees that normally produce high-density wood and from trees that normally produce low-density wood were grown in vitro at a number of IAA concentrations between 0 and 20 mg l-1. Maximum increase in stem radius and maximum tracheid lumen diameter were found at IAA concentrations of 6-10 mg l-1. Tracheid wall thickness increased approximately linearly as IAA concentration was increased up to 20 mg l-1. Absolute differences in radial stem increase and in cell lumen diameter between the high- and the low-density stems were greatest at IAA concentrations of 4-10 mg l-1. At low or high IAA concentrations, absolute differences between the clones in their stem radial increase and in their tracheid lumen diameter were small. Proportional differences between the clones in these two factors were greatest at IAA concentrations of 10 mg l-1. Clonal differences in the tracheid wall volume per unit stem volume could account for the differences in wood density only at IAA concentrations of 4-10 mg l-1.

Frost Rings Formed in 14-m Tall Red Pine

In codominant and suppressed trees in two red pine (Pinus resinosa Ait.) plantations in Simcoe County, Ontario, frost rings had formed at the start of most annual rings in the two internodes below the current leader until the trees were nearly 14-m tall. None occurred in the current shoot growth or below the sixth internode. They seldom formed when the stem radius (inside bark) exceeded 2 cm.

Effects of environmental factors on estimated daily radial growth ofPinus resinosa andBetula papyrifera

Relations between estimated daily radial growth of red pine (Pinus resinosa) and white birch (Betula papyrifera) trees and various environmental factors were studied in northern Wisconsin. Daily variations in stem radius, which reflected an irreversible cambial growth component as well as superimposed shrinkage and swelling of stems, were recorded with dendrographs and daily radial growth was estimated with trend lines connecting midpoints between daily maximum and minimum stem radii. Orthogonalized regression analysis was used to isolate individual effects despite intercorrelations between the variables. Regression models were developed on 9 independent variables: rainfall (log P, n), minimum temperature (Tmin, n; Tmin 2, n), average daily relative humidity (Ra, n), maximum saturation deficit with a one-day lag (Vmax, n−1), minimum temperature with a two-day lag (Tmin, n−2), percent soil moisture (log M150), time trend (Day2) and autocorrelation (y, n−1). These factors explained 81% of the variation in estimated daily radial growth of birch. They also explained 78% of the variation in growth of pine at the wettest site (lower slope) and 64% at the driest site (upper slope). As soil and plant water stress intensified up the slope, radial growth of pine was inhibited and the direct relation between growth and environmental factors was progressively weakened while the autocorrelation factor became dominant. Rainfall (log P, n) was the most important factor influencing radial growth, reflecting the paramount importance of cell turgor in the cambial zone.

Diurnal and Seasonal Changes in Water Balance of Acer saccharum and Betula papyrifera

AbstractDiurnal and seasonal changes in plant water potential, leaf diffusion resistance, and stem radial changes of Acer saccharum and Betula papyrifera trees were studied in northern Wisconsin during the 1974 and 1975 growing seasons. Water potential decreased during the day, following relatively high values in the morning, and increased in the late afternoon and evening. Diurnal patterns and actual values of water potential varied with species, soil water availability, and factors influencing transpiration (e.g., solar radiation, vapor pressure deficit, and transpiration flux density). When plant water deficits were not severe, leaf resistance of both species was rather stable during the day. During severe droughts, however, leaf resistance increased (stomata closed) during the day when light intensity was high. Leaf resistance at high light intensity was higher in Acer than in Betula. Stomatal closure with decreasing light intensity varied between species and among Acer trees. Tree stems of both species shrank during the day, as internal water deficits developed, and they expanded as trees rehydrated during the night. Stems of Acer shrank more than those of Betula. The amount of daily stem shrinkage increased as the season progressed if the trees were not under severe water deficits. During severe droughts the amount of diurnal stem shrinkage decreased. Shrinkage of stems lagged behind water potential changes by 1 to 2 h in Acer and less than 1 h in Betula. The relationship between stem radius and leaf water potential was not constant throughout the growing season.

DAILY PATTERNS OF SHOOT ELONGATION IN PINUS RADIATA AND EUCALYPTUS REGNANS

SUMMARYDiurnal patterns of shoot elongation, obtained by mechanical growth recorders, were compared with those of leaf elongation and stem radius; the relationships of these to environmental factors were studied in the field and in growth chambers.In sunny weather, minimal elongation (or shrinkage) occurred during the mornings, and maximal elongation rates during late afternoons. On rainy days, elongation patterns tended to be undefined.The observed patterns appeared related to diurnal changes in water balance, air temperature and light. There was no evidence of an endogenous rhythm. Rising evaporative demand during sunny mornings resulted in contractions in shoot and leaf lengths and in the thickness of the stem live bark. Re‐expansion occurred in the evening and at night, or during the day when evaporative demand was reduced by cloud cover and rain. Shoots also contracted on frosty nights, but expanded rapidly following thawing early in the mornings. Temperature also positively influenced growth (i.e. irreversible increase in size). Light appeared to inhibit shoot growth in the mornings, but this effect was confounded with the tendency of shoots to shrink in length due to dehydration.Since growth and reversible changes in shoot length often occurred simultaneously in different portions of the same shoot and since the zones of reversible change and growth overlapped, the measurement and analysis of hourly growth responses can be complicated; a distinction must therefore be made between growth (which is irreversible) and elongation (which may include both growth and reversible changes in shoot length).

The Shape of Plant Stems

Based on experiment, functional relationships are found that give, with considerable precision, the loading, the normal stress and the radius as a function of stem height. Using the functional relationship for the loading and for the normal stress, a theoretical expression for the radius distribution in the stem and for the volume of the stem is developed. By optimizing the total volume of the stem with respect to the stress parameter a and using the functional relationship for the loading, a theoretical (optimal) stress distribution and a theoretical (optimal) radius are found. These particular distributions lead to a minimumvolume stem. Experiments with plants having different load functions show that the actual values of the normal stress and radius agree with the theoretical (minimum-volume) predictions. INTRODUCTION Sequoia gigantea! Standing near this largest of all living things leads to astonishment and then to speculation, for some at least. An engineer might ask: Why does the stem grow in such a shape? How does the load affect the shape? These questions can be applied to all plants, and this paper attempts to answer them for some singlestemmed plants (Markwardt, 1930; Markwardt and Wilson, 1935). The following abbreviations are used throughout: A, area of cross section, ft2; C, constant of integration; E, Young's modulus in compression, lbf/ft2; F, total load of plant from the tip [L] to x, lbf; L, height of stem from datum, ft; k, number of stem segments; r, radius of stem, ft; x, height above datum, ft; V, volume of stem from the tip [L] to x, ft3; Vt, total volume of the stem, ft3; W, distributed load of plant, lbf/ft; Y, vertical displacement, ft; a, stress parameter, dimensionless; ,B, radius parameter, dimensionless; y, load parameter, dimensionless; A, difference operator; a, nominal normal stress, lbf/ft2. EXPERIMENTAL OBSERVATION S Plants of the type that have a single stem were examined to determine the loading, the normal stress and the radius as a function of stem height and, further, to see if some approximating functions could describe the measured values of these properties with precision. Using the definition o(x) F (x) L .JL W(x)dx (2.1) A (x) A (x) where a(x) = nominal normal stress, lbf/ft2 F (x) = total load of the plant from the tip [L] to x, lbf A(x) = 7r r2(x) = area of cross section of stem, ft2 x = height above datum, ft W (x) = distributed load of the plant, lbf/ft r(x) radius of stem, ft measurements on three types of plant were taken. 371 This content downloaded from 207.46.13.80 on Thu, 11 Aug 2016 06:26:47 UTC All use subject to http://about.jstor.org/terms 372 THE AMERICAN MIDLAND NAT URALIST 86(2) Figure 1 shows a typical plot of the three properties F (x), a(x) and r(x). In the figure, the point of maximum normal stress defines the separation between the root and the stem. This paper deals with the stem only. It was found that the three properties could be represented closely on this basis, by the functional relationships F(x) = F. (1x ) (2.2) u(X) = uo(1X a (2.3) and r(x) Xr (1 X I, (2.4) Specifically, each plant to be measured experimentally was cut off at the ground, and the total load of the plant and diam of the cut were measured and the nominal normal stress ul computed. Starting in the root-flare region, a series of small cuts were made, and with the ith cut the total load of the plant and the diam of the cut were measured, and the nominal nonnal stress ui computed. This process was continued until un = un+1, and the neighborhood of the maximum normal

Monitoring Cotton Plant Stem Radius as an Indication of Water Stress1

AbstractCotton plant water stress was monitored continuously during a drying cycle by measuring microchanges in plant stem radius with a linear variable displacement transducer (LVDT). Plant stem contraction was directly related to the degree of leaf water stress, and plant stem radius was very responsive to changes in the energy load at the evaporating surface. The LVDT provided a stable, trouble‐free method for monitoring relative plant water stress under field conditions without destroying plant tissue.

TREE FORM: DEFINITION, INTERPOLATION, EXTRAPOLATION

Definition of tree form requires numerous measurements of height and stem radius or diameter distributed over the entire tree stem. Further definition may involve a graphic plot of stem profile, an analytic expression of radius as a polynomial or rational polynomial function of distance from apex, or the direct numeric evaluation of the major integrals of tree form (length, surface, volume). Linear, quadratic, or harmonic interpolation over short intervals can assume a monotonic one-parameter function without introducing serious error. Extrapolation should employ a two-parameter function passing through the origin and based on three measured pairs of coordinates. Appropriate surface and volume integrals are given for the convex right hyperbola (XY−QX+PY=O) and the concave parabola (Y2+QX−PY=O).