Open-grown Trees Research Articles

Leaf water relations and anatomy of a tropical rainforest tree species vary with crown position.

Leaf water potentials, osmotic properties and structural characteristics were examined in the Australian tropical rainforest tree species, Castanospermum australe. These features were compared for individuals growing in the understorey and canopy of the undisturbed forest and in an open pasture from which the forest had been cleared. Leaf water potentials during the day declined to significantly lower values in the open-grown and canopy trees than in the understorey trees. During most of the day the opengrown tree experienced the lowest water potentials. These differences were paralleled by significant differences in tissue osmotic properties. The tissue osmotic potential at full hydration was lowest in the open-grown tree (-1.80 MPa), intermediate in the canopy trees (-1.38 MPa), and highest in the understorey trees (-0.80 MPa). As a result, the degree to which high and positive turgor pressures were maintained as water potentials declined was highest in the open-grown tree, intermediate in the canopy trees, and lowest in the understorey trees. The differences in tissue osmotic properties between individuals in the three crown positions were paralleled, in turn, by differences in leaf structual characteristics. Relative to leaves of the canopy and open-grown trees, leaves of the understorey trees had significantly larger epidermal cells with thinner cell walls, larger specific leaf areas and turgid weight: dry weight ratios, and a higher proportion of intercellular air space.

Agroforestry: An economic appraisal of the benefits of intercropping trees with grassland in Lowland Britain

A mathematical model simulating the effect of intercropping trees (ash) with grassland on wood production, grass yields and output of sheepmeat is described. Using the model, an assessment has been made of the implications of varying the density and the planting pattern of the trees on the combined income from the sale of wood and livestock over a number of years. The resultant incomes have been compared with that from an equivalent unafforested area to assess the likely economic implications of intercropping trees with grass. At a discount rate of 5%, the indications are that combining wood and sheepmeat production on the same area could be financially attractive. At higher discount rates, the economic attraction of growing trees is more dependent on an increase in timber prices relative to those prevailing at present. However, given the large number of assumptions necessitated by the limited availability of data and in the absence of any means of validating the model, extreme care is needed in interpreting the results. Confident economic projections of the value of intercropping trees with grass await further experimental work on appropriate growth models for open-grown trees, light interception, tree rooting patterns and water uptake of tree roots.

Peroxidase Allozyme Differentiation among Successional Stands of Ponderosa Pine

Genetic variation of a peroxidase locus from mature ponderosa pine needles has been surveyed among four successional stands on the Shanahan Mesa near Boulder, Colorado. The recent colonization of this mesa by ponderosa pine can be documented by historical reports and tree cores. Allozyme differentiation was observed on the Shanahan Mesa between two recently colonized, open-grown stands and a shaded secondary growth stand, which parallels patterns of differentiation found in nearby mountain populations. At a transitional stand in the middle of the mesa, genetic differences also occurred between older open-grown trees and shaded younger trees. Environmental effects from canopy closure appear to have affected peroxidase differentiation among these successional stands.

Composition of an isolated prairie in central Ontario

A remarkable prairie outlier was recently discovered in central Ontario. The site had about 1.6 ha of open prairie surrounded by 11 ha of Quercus rubra – Pinus strobus savanna. The savanna had a density of about 27 huge, open-grown trees per hectare (11 per acre). The vegetation of the prairie opening comprised four zones ranging from a dry sand barrens to a mesic to wet-mesic prairie arrayed on a gentle slope. The major dominants overall were Sorghastrum nutans, Andropogon scoparius, Danthonia spicata, Lespedeza capitata, Desmodium canadense, Aster azureus, Monarda fistulosa, Solidago nemoralis, Aster sagittifolius, Equisetum hyemale, Car ex rugosperma, and Panicum linearifolium. The site had a rich flora of 115 species, of which more than one-third were listed as prevalent or modal species of Wisconsin prairies and related communities, occurring more than 800 km to the west. In addition, about 15% of the species in the prairie opening were regionally rare and three, Carex richardsonii, Lespedeza intermedia, and Scirpus clintonii, were considered rare in Ontario.

Biology of an Ash Borer, Podosesia syringae,1 in Green Ash in Mississippi

By tunneling in the trunks of green ash and other species of Oleaceae, larvae of Podosesia syringae (Harris) damage trees grown for timber and ornamental purposes. Open-grown trees are more heavily infested than those in dense stands. Life history studies revealed that moth emergence is heaviest during spring and occurs earliest from stems of smallest diameter. Females call, mate, and begin ovipositing on the day of emergence. They deposit ca. 400 eggs, mostly during the first 2 days. Larval galleries extend inward in the sapwood, then turn upward and back to the surface; they range from 7 to 32 cm in length. Woodpeckers, most important of the natural enemies, captured 67–81 % of the larvae in a young stand.

Biology and Damage of the Hickory Borer, Goes pulcher, in Hickory and Pecan

Goes pulcher (Haldeman), one of the most important insect borers of hickory and pecan, occurs throughout the eastern United States. In central Mississippi adults emerge during May and June and deposit eggs singly in niches between the bark and sapwood. A life cycle requires 3-5 years. Borer attacks occur on trunks 2-14 cm diam, and at heights up to 4.8 m. Tunnels extend horizontally or obliquely upward into the stem for 2-5 cm, vertically for 6-12 cm, then horizontally back to the surface. Open-grown trees and those near openings within young stands appear to be most heavily attacked. The weakened stems are predisposed to breakage and to invasion by stain and decay fungi and by ants. Natural mortality is caused largely by heavy predation.

Frost Damage to White Spruce Buds

Unopened buds of white spruce (Piceaglauca (Moench) Voss) were damaged by late spring frost. At time of death of the apical meristem the buds were not ready for flushing. As expected on the basis of ground frosts, there was more damage among shorter trees than among taller trees, and more damage among open-grown trees than among understory trees.

Crown Shape in Open- and Forest-Grown Balsam Fir and Black Spruce

Crown-radius equations developed from measurements taken on open-grown balsam fir and black spruce were applied to forest-grown trees of the same species. For that part of the crown considered to be growing free of aerial competition, radii were estimated to within ±1.5 ft (±45.7 cm) at the 5% significance level. It was concluded that those portions of balsam fir and black spruce crowns estimated to be growing free of aerial competition are not significantly different from similar portions of open-grown trees of the same height and species. Coefficients and related statistics for the general crown-radius equation, CR = a1 L + a2LH + a3L2/H + a4L2, are given.

Ecology of the Cone Moth Laspeyresia toreuta1 in Pinus banksiana Stands

Laspeyresia toreuta (Grote) is a cone moth reported from 6 species of pine. This study was made in Pinus banksiana stands in Baraga County, Mich. Laspeyresia toreuta has a univoltine life cycle in which 11 months are spent inside the cone in larval and pupal stages and 1 month as adults. For the years 1962–66 the cone infestation rates in the study area were 78, 55, 14, 56, and 10%, respectively. Cones on open-grown trees with branches to the ground were most heavily infested. Cones lower in the trees had more insects than higher cones. Low-density stands contained more insects than high-density stands. South-facing cones in some years contained more insects than north-facing cones. The size of the cone crop varied tremendously and affected L. toreuta population size. Intraspecific competition was an important mortality factor. Extended diapause was observed in from 2 to 15% of all 5th-instar larvae. Parasites killed from 30 to 50% of all larvae.

DEVELOPMENT AND TESTING OF STAND MODELS FOR DOUGLAS FIR AND LODGEPOLE PINE

Methods used in the development and testing of stand models for Douglas fir and lodgepole pine are described briefly. Influence of spacings from 3.3 to 19.8 feet on number of trees per acre, basal area per acre, and average d.b.h. is shown graphically for Douglas fir. The importance of knowing distribution as well as amount of mortality is stressed and illustrated. Use of the model for studying thinning is described.Study of a lodgepole pine model, which also includes tree height and volume per acre, suggests that the general approach based on crown width and d.b.h. of open-grown trees could be applied to other species. Because of the ease and speed of manipulation of these models they could become an important operational and research technique.

The chemical composition of foliage as an index of nutritional status in red pine (Pinus resinosa Ait)

Near terminal foliage was sampled from 26 young, open-grown trees in each of three red pine plots on a potassium deficient site. The plots were respectively control, trees fertilized with potassium in the nursery and trees fertilized with potassium in the field. Multiple regressions relating tree height and leader length to foliar concentrations of sodium, potassium, calcium, magnesium, manganese, phosphorus, nitrogen, and silica were calculated to test Leyton's hypothesis that only deficient nutrients would be significantly related to growth in such equation. The hypothesis was supported by the pooled data and by the data from the trees fertilized in the nursery but not from the other two plots. The different elements were interrelated in the leaves so that results of multiple regression analyses were strongly influenced both by the combination of regressor variables used as well as by which one of a number of interrelated growth measurements was used as dependent variable. The closeness of correlation between variables and the chances of incorrect predictions appear to increase with severity of deficiency. However it was possible to relate leader length to foliar potassium in all three plots by one second-order polynomial regression which accounted for 66 per cent of the observed variation in leader length. The data confirmed the conclusion of Stoneet al. that excellent growth of red pine is possible when there is 450 mg/100 g of potassium in current-year red pine needles. Variations of some other factor which may be either external (site) or internal (genetic) is believed to be contributing to the variations in leader growth on this site.

THE SUPPRESSION OF GROWTH RINGS IN JACK PINE IN RELATION TO DEFOLIATION BY THE SWAINE JACK-PINE SAWFLY

An investigation of the radial growth of jack pine (Pinus banksiana Lamb.) defoliated by the Swaine jack-pine sawfly (Neodiprion swainei Midd.) disclosed that growth rings were discontinuous and missing in cross-sectional disks from severely damaged trees. In young and open-grown trees with dead tops, the incidence of such deficiencies in radial growth was especially high in disks from upper regions of the stems, in the vicinity of the dead tops; radial growth was suspended for 1 year and subsequently resumed in disks from the lower regions of some stems. Cambial inactivity was more generalized in trees from an old and dense stand and it was detected in disks representing major portions of some of the stems sampled; the death of some trees followed 2 to 6 years of cambial inactivity in disks cut at various heights along their entire stems. Growth deficiencies in the young stand were clearly effects of severe sawfly defoliation. Data from the old, dense stand indicated that sawfly defoliation had perhaps merely hastened the gradual deterioration of the stand in which intertree competition was intense.

THE VASCULAR CAMBIUM AND RADIAL GROWTH IN THUJA OCCIDENTALIS L

The vascular cambium, to use the term in the general sense as designation for the entire meristem producing secondary xylem and phloem, consists of the self-perpetuating uniseriate initiating layer and the derived tissue mother cells. In the dormant condition the cambium in the stems of mature trees is one to four, usually two to three, cells wide. The one to three tangential tiers of cells toward the xylem are made up of xylem mother cells, and the single tier next the phloem is composed of initial cells. On reactivation all cambial cells expand radially. Periclinal divisions soon follow, usually according to a sequence in which the xylem mother cells in the tier contiguous to the late wood are the first to divide and the initial cells last, although some variation occurs. The zone of periclinal division rapidly widens to 100-300 μ in vigorous open-grown trees, the center of activity during this vernal surge of growth clearly being among the dividing and redividing xylem mother cells. Thereafter, from mid-June to August, a continued decline in cell production follows as the zone of xylem mother cells decreases from many tangential rows to few. The initiating layer becomes relatively more important as the center of cell generation, and toward the end of the growing season the initial cells undergo those changes which modify the cellular pattern of the cambium and hence of the derived tissues. Phloem development begins later than that of xylem, and at the end of May the new phloem varies from none to four cells as compared with a xylemward production of 30-60 cells in vigorous trees. Phloem expansion continues at a more or less steady rate from June to the termination of cambial activity in August or early September. The annual phloem increments vary less in width than those of xylem.