Stages Of Tree Development Research Articles

Microbial biomass C and N, and mineralizable-N, in litter and mineral soil under Pinus radiata on a coastal sand: Influence of stand age and harvest management

Microbial biomass C and N, and anaerobically mineralizable-N, were measured in the litter and mineral soil (0–10 cm and 10–20 cm depth) of Pinus radiata plantations in two trials on a nitrogen-deficient coastal sand. The trials comprised (a) stands of different age (1 to 33 years), with five of the seven stands studied being second rotation, and (b) a harvest-management trial, with stands established after different harvesting treatments of the first-rotation trees and understorey development controlled by manual weeding and chemical sprays. The harvest-management stands were sampled in the fifth year after the second-rotation establishment. In the stands of different age, the levels of microbial biomass C and N, and also mineralizable-N, in the litter and mineral soil showed no relationship with tree age and were similar to those in the oldest (33 years) stands of P. radiata. In the harvesting trial, five years after establishment of the second rotation, levels of microbial N and mineralizable-N in the litter and mineral soil were generally lowest where whole trees and the original forest floor had been removed; they were higher in associated plots in which the original forest floor had been removed but fertilizer N was regularly applied. No marked differences were then found between the other harvest treatments, viz. whole-tree harvest, stem-only harvest with slash remaining on site, and stem-only harvest plus extra added slash materials. In each trial, levels of microbial C and N and mineralizable-N were closely related to total C, and especially total N, in 0–10 cm depth mineral soil, but not generally in litter. Respiratory measurements strongly suggest that the microbial populations in mineral soil had a high metabolic activity. On an area basis in the harvest-management trial, total tree N and microbial N in the litter and mineral soil were lowest in stands where the original forest floor had been removed. In this particular treatment, microbial N in the litter plus mineral soil (0–20 cm depth) after five years of second-rotation growth comprised 7.3% of the total ecosystem N; values in the other treatments ranged between 5.6 and 6.0%. Our results emphasise the importance of slash and litter, and probably volunteer shrubs and herbaceous under-storey species, in conserving pools of potentially available N during the early stages of tree development.

Pear, Prebloom Applications of Insegar for Control of Pear Psylla, 1991

Abstract Mature bearing pear trees were sprayed with air carrier equipment applying 400 gal per acre to test prebloom applications of Insegar for control of PP. Plots consisted of unreplicated blocks of 1/2 acre or larger. Treatments were applied at delayed dormant (20 Mar) and at clusterbud (8 Apr) stages of tree development. Additional sprays applied to the entire orchard during the growing season included Dimilin 25% WP 1 lb/acre plus superior type oil 1 gal/acre on May 31, Guthion 35% WP 2.5 lb/acre plus Vendex 4 L 2 pt/acre on 11 Jul and Guthion 35% WP 2 lb/acre plus Mitac 50% WP 3 lb/acre on 31 Jul. Treatments were evaluated by adult, egg, and nymph counts on several dates after treatment. Adults were counted by the limb tap method. Early season eggs and nymphs were counted on fruiting spurs collected at random from test plots and examined under magnification in the laboratory. Later egg and nymph samples were counted from 2 50-leaf samples per plot. Leaf samples consisted of the proximal leaf, distal leaf, and 3 leaves from the middle of 10 terminal shoots. Leaves were brushed and resulting slides were examined under magnification. PP russet was rated according to US grade standards for fresh market 'Bartlett' and 'd'Anjou' pears on 2 samples of 25 mature fruit per plot. Factors of fruit quality including firmness, soluble solids, and size were evaluated from 2 10-fruit samples per plot at normal harvest maturity. Fruit and foliage were examined for phytotoxicity after each spray.

Apple, Concentrate Acaricide Evaluation Experiment, 1991

Abstract Treatments were applied to single-tree plots in a randomized block design consisting of 3 replicates of 'Yorking' and 2 replicates of 'Golden Delicious'. The trees were planted to a spacing of 20 × 20 ft and were 18-yr-old. Experimental sprays were applied with a Myers Mity Mist sprayer calibrated to deliver 100 GPA at 2 mph, with the exception of HHE-3736 70 WG and Savey 50 WP which were applied with a handgun from a truck-mounted John Bean sprayer equipped with a 35 gal/min pump at 4.2 gallons of spray/tree. Pre-bloom sprays were applied at the half-inch green stage of tree development (8 Apr) for Sun 6 E Oil and the Apollo treatments and at pink (17 Apr) for AC-801757 20 EC. Post-bloom sprays were applied based on the following thresholds of motile mites/leaf: 5-10 for AC-801757 following Sun 6 E Oil, 5 for Kelthane 50 WP, and 3-5 for HHE-3736 70 WG and Savey 50 WP. Kelthane sprays were delayed due to extraneous circumstances. General sprays of fungicides (Benlate, Captan, Nova, and Thiram) were made at 1-2 week intervals throughout the experiment. Insecticides (Guthion and Lannate) were applied at 1-2 week intervals beginning with petal-fall in early May. Effectiveness of the treatments against mites was evaluated by counts at approximately weekly intervals during the season on samples of 25 leaves/tree, 125 leaves/treatment. The predator, S. punctum was observed by making 3 minute counts of adults and larvae around the periphery of the trees. Russet ratings are based on 30 Golden Delicious apples/replicate, 60/treatment. Fruits were rated as 0 (no russet), 1 (raised lenticels), 2 (1-10% russeted surface), 3 (11-25% russeted surface), 4 (26-50% russeted surface), or 5 (>51% russeted surface). Possible ranges are 0-30 (none to raised lenticels), 31-60 (raised lenticels to 1-10% russeted surface), 61-90 (1-10% to 11-25% russeted surface), 91-120 (11-25% to 26-50% russeted surface), and 121-150 (26-50% to >51% russeted surface)

Regrowth Response of London Plane Injected with Dikegulac at Different Stages of Tree Development

Three-year-old London plane (Platanus acerfolia) trees pruned at 5 different stages of plant development were injected with dikegulac [2,3:4,6-bis-0)1-methylethylidene)- 0(-L-xylo-2-hexulorfuranosonic acid)]. At the end of the growing season, sprout length, number of new sprouts, and phytotoxicity were determined. Maximum growth reduction with minimum foliar damage was obtained on injected trees pruned at half-leaf development stage. Even though greater growth reduction was obtained on injected trees pruned at fullleaf development stage, the phytotoxicity was unacceptable.

Scheduling and resource allocation in a food service system

Scheduling and resource allocation in a food service system

Influence of Reflectant and Shade Material on Light Distribution in Mature ‘Delicious’ Apple Trees1

Abstract Diffuse light within the tree canopy of mature red strain of ‘Delicious’ apple trees (Malus domestica (Borkh.)) was increased throughout the 1978 growing season with under-tree reflectors and decreased by overtree shade material. Three all season light integrating methods were well correlated (Yellow Springs total radiometer, Lambda quantum sensor, Cain integrator). The Lambda quantum sensor used at intervals showed daily quantity of light reflected was dependent on climatic conditions, time of day, and stage of tree development. Neither reflectors nor shade altered spectral quality. Leaf cross sections, as an indicator of light exposure, showed gross morphological differences between shaded and check leaves but not between reflector and check leaves.

SEQUENTIAL CHANGES IN RATE OF ANTICLINAL DIVISION, CAMBIAL CELL LENGTH, AND RING WIDTH IN THE GROWTH OF CONIFEROUS TREES

The early growth of a tree is marked by a widening of the annual increments, a deceleration in rate of multiplicative (anticlinal) division of fusiform cambial cells, and an increase in cell length. Distance outward from the pith at which maximation in cell size occurs, and subsequent trends in cell dimensions, are apparently modified by rate of growth. Continuation of a uniform ring width through the middle to late years favors comparative constancy in rate of anticlinal division and cell size during that stage of tree development. Reduction in amount of annual increment in the late growth to the width optimal for cell extension, about 1 mm, induces a delayed and probably heightened maximation in cell length. Continued lessening in radial growth to an annual accretion of 0.5 mm or less, with the onset of senility, results in acceleration in rate of multiplicative division and reduction in cell length.

Behavior and Control of the Grape Mealybug on Pear

The grape mealybug, Pseudococcus maritimus (Ehrhorn), is a chronic pest of pears which became a serious problem in several pear-growing areas in 1960 and 1961. Biology studies showed that the over wintering crawlers invaded and fed upon tissue in the fruit buds from the period of bud crack until petal fall. After this time, the mealy bugs migrated to the base of sucker shoots where rough bark provided protection. Because the insects are exposed within the open fruit buds, a spray timed at the cluster bud stage of tree development is preferred. Spray trials were conducted at the dormant, cluster bud, and petal fall periods on Bartlett pears. The results indicated that parathion or Diazinon® ( O,O -diethyl O -(2-isopropyl-4-methyl-6-pyrimidinyl) phosphorothioate) at a dosage of 2 pounds 25% per 100 gallons or a 1 pound dosage combined with either oil or a welting agent provided the best control. Dormant oil combined with lime sulfur, polysulfide, dinitrophenol, and dimethoate did not provide acceptable control. Zectran® (4-dimethylamino- 3,5 -xylyl methylcarbamate) and Dilan (a mixture of I part of 1,1-bis( p -chlorophenyl)-2-nitropropane (Prolan) and 2 parts of 1,1-bis( p -chlorophenyl)-2-nitrobutane (Bulan)) reduced meal. bugs. but were less effective than either parathion or Diazinon.