Treewidth Research Articles

Corridor Health Survey, of the Upper Lachlan Catchment, Central West, New South Wales.

A major survey of stream corridor health was undertaken in the upper Lachlan Catchment. The survey provides a benchmark assessment of the riverine environment condition. The following attributes were examined: reach environments, channel habitat, cross-section analysis, bank condition and composition, bed and bar condition, riparian vegetation (presence and structure), aquatic habitat analysis, scenic, recreational and conservation values. This paper outlines some of the prelimin~ results related to the assessment of riverine vegetation in this catchment an area of approximately 35 000 km. The survey found that 77% of the riparian vegetation was highly degraded, 10% in poor condition, 4% moderate and 3% in good condition. Six percent of the upper catchment's riparian vegetation was in pristine condition, mostly confined to tributaries of the Abercrombie River. The average width of the riparian zone in the Upper Lachlan Catchment is 12.2 m. This approximates to one or possibly two mature tree widths (species dependant). Trees are generally confined to the banks of water courses and there is very little diversity, structural or species, in the shrub and ground cover understorey. Some implications for platypus conservation are discussed.

Performance of maize, beans and ginger as intercrops in Paulownia plantations in China

Yield, morphology and specific leaf weight of summer crops maize, beans and ginger were studied in relation to tree proximity and PAR transmissivity in a 7-year old plantation of Paulownia elongata grown at a spacing of 15 m x 5 m in Eastern China. The yield of beans and maize was significantly reduced, compared to controls, at all positions relative to the trees. This yield depression was particularly marked at positions closest to the trees. Beans grown at 2 m from the trees had reduced height and specific leaf weight. These crops would yield more at wider tree row spacings. Ginger gave high yields when intercropped and is an ideal shade crop for these systems. Further research is required on optimisation using a bioeconomic approach. Further agronomic, physiological and biochemical work is required on ginger and other economic members of its family as these appear to have compatibility with dense agroforestry plantings.

On bounded treewidth duality of graphs

On bounded treewidth duality of graphs

Timber quality after thinning from above and below in stands of Pinus sylvestris

Timber quality and logging damage after different thinning types in Scots pine (Pinus sylvestris L.) stands were studied in a field experiment in north Sweden. Thinning operations were mechanized and carried out according to normal Swedish practise. The treatments were thinning from below and thinning from above. The quality of the residual stand was evaluated using variables such as diameter of the thickest branch, stem taper, annual ring width, straightness and lean of trees. The only variables showing differences between treatments were lean of tree and stem straightness. No difference in the frequency of trees with logging damage was found. The conclusion of this study is that differences between thinning types in first thinning may be evened out when carried out as in commercial forestry due to extraction of strip road and damaged trees. Consequently, differences in timber quality and logging damage in the residual stand may be small.

Purkinje cell dendritic arbors in chick embryos following chronic treatment with an N‐methyl‐D‐aspartate receptor antagonist

The normal development of Purkinje cell dendrites is dependent on afferent innervation. To investigate the role of neuronal activity in Purkinje cell dendritic development, chick embryos were chronically treated with a potent, selective, and systemically active competitive N-methyl-D-aspartate (NMDA) receptor antagonist, NPC 12626. The NMDA receptor was chosen as a target for pharmacological blockade because of the importance of the NMDA receptor in synaptic plasticity and stabilization in development. Chick embryos were given daily injections of NPC 12626 (25 to 100 mg/kg) from embryonic day 14 (E14) to E17. The initial injections of NPC 12626 dramatically blocked embryo movements, but activity levels partially recovered following subsequent injections. Embryo movements were reduced by 24% at the end of the experiment. Embryos were killed on E18, and their brains processed for Golgi-Cox staining. The morphology of Golgi-stained Purkinje cells in drug-treated embryos was similar to control embryos. Morphometric analysis showed, however, that chronic treatment with NPC 12626 resulted in a 19% reduction in Purkinje cell dendritic tree area and a 13% reduction in the number of dendritic branch points. The overall width and height of the drug-treated dendritic trees were not significantly different from controls, suggesting that NPC 12626 reduced Purkinje cell dendritic area by interfering with branch formation. The volume of the granule cell layer and the heights of the molecular and external granule cell layers was not reduced, suggesting that NPC 12626 treatment did not simply delay development. These results suggest that activation of the NMDA receptor may mediate the afferent-target interactions in the cerebellum that regulate the elaboration of Purkinje cell dendrites.

Quickly Excluding a Planar Graph

In an earlier paper, the first two authors proved that for any planar graph H, every graph with no minor isomorphic to H has bounded tree width; but the bound given there was enormous. Here we prove a much better bound. We also improve the best known bound on the tree-width of planar graphs with no minor isomorphic to a g × g grid.

An empirical evaluation of a three-dimensional crown model for predicting volume growth

A three-dimensional geometric model of crown competition was developed which can be used for empirical distance-dependent individual-tree models or biologically based process models. The crown model calculates the shape of a subject tree's crown based on the positions of its competitors' crowns and the rules of competition. It is necessary to use a crown profile equation to use the crown model. The crown profile equation was estimated from the crown width of open-grown trees at the base of the live crown. Ten replicates of a loblolly pine ( Pinus taeda L.) progeny study planted in a variable density Nelder's wheel layout re-measured annually from Ages 6 to 10 and at Age 12 were used for the analysis. The use of two different rules of competition and two different methods of calculating crown volume, surface area, and exposed surface area resulted in eight different estimates related to the geometry of each crown. The relationships of the natural logarithm of periodic annual wood volume growth of different time lengths were fit to geometric estimates generated from the crown model. These relationships were compared with crown length and wood volume relationships to evaluate the utility of the three-dimensional crown model. Exposed surface area of the crown was the best predictor of volume growth produced by the crown model. Wood volume was the single best predictor of growth until Age 9, when exposed surface area became superior. The best model of all possible models was wood volume, exposed surface area, and surface area. Wood volume, exposed surface area, and total surface area length accounted for 1–11% more of the variability than crown length and wood volume. This indicated that the crown model offered benefits over the use of the raw data. The relative performance of the crown model compared with wood volume and crown length improved as competition increased. The crown model appears to offer potential for growth and yield modeling; it must be further evaluated, however, for use in mature stands.

Patrones de cítricas y tamaño del árbol y rendimiento de seis clones de Valencia

Se realizaron experimentos en la Estación Experimental en Adjuntas, en la zona central montañosa de Puerto Rico, para determinar el efecto de cuatro patrones sobre el crecimiento y la producción de seis clones de china Valencia. Se constataron diferencias notables entre clones en cuanto al tamaño de las frutas, pero también se observaron diferencias significativas en cuanto a porcentaje de cascara, número de semillas por fruta y características del jugo. Se obtuvo una mayor producción en todos los clones cuando se usó la mandarina Cleopatra como patrón. Hubo diferencia significativa entre los clones 3164 y 3264 en cuanto a producción total de frutas. No hubo diferencias significativas en eficiencia de rendimiento durante el primer año de cosecha informado, pero los patrones mandarina Cleopatra y naranja agria produjeron árboles más altos y con mayor volumen de copa. Se encontraron diferencias significativas entre clones para patrones específicos en cuanto a altura, amplitud y volumen de copa, producción total de frutas y rendimiento.

On the chordality of a graph

AbstractThe chordality of a graph G = (V, E) is defined as the minimum k such that we can write E = E1 ∩ … ∩ Ek with each (V, Ei) a chordal graph. We present several results bounding the value of this generalization of boxicity. Our principal result is that the chordality of a graph is at most its tree width. In particular, series‐parallel graphs have chordality at most 2. Potential strengthenings of this statement fail in that there are planar graphs with chordality 3 and series‐parallel graphs with boxicity 3. © 1993 John Wiley & Sons, Inc.

ROOTSTOCK AFFECTS TREE GROWTH AND PRUNING REQUIREMENT

As part of the NC-140 rootstock evaluation trials, `Starkspur Supreme Delicious' on 18 rootstocks planted in 1984 were evaluated for growth and pruning requirement. After 9 seasons, trees on the P.22 produced the smallest trees, 1.1 m width and 1.7 m height. The stocks P.16, P.2 and Bud.9 produced trees 2.0-2.2 m wide and 2.1-2.6 m tall. Trees on MAC.39, C.6, MAC 1, M.26 EMLA P.1, BUD.490, M.7 EMLA, CG.24, and domestic seedling were 2.9-3.4 m wide and 3.7-4.3 m tall. The largest trees were on P.18 and M.4; 3.6 m wide and 4.2 m tall. Dormant pruning time in two seasons significantly increased at an exponential rate with increasing tree width and height. An asymptote for maximum pruning time had an x-axis intersection at approximately 2.7 m tree height. Pruning time per tree significantly increased in a linear manner with increasing trunk cross section. When pruning time was calculated on a per hectare basis, trees planted at 1460 to 2000 trees/ha required less pruning time than when planted at ≤ 750 tr/ha or ≥ 4000 tr/ha. Trees on P.16, P.2, Bud.9 and C.6 required the least pruning per unit of fruit production.

Limit distributions for queues and random rooted trees

In this paper several limit theorems are proved for the fluctuations of the queue size during the initial busy period of a queuing process with one server. These theorems are used to find the solutions of various problems connected with the heights and widths of random rooted trees.

Prospects for Using Eucalyptus camaldulensis Dehn. in Mixture with Agriculture Crops

SYNOPSIS Eucalyptus camaldulensis was planted in the same field with Zea mays, Phaseolus vulgaris, Arachis hypogaea and Manihot esculenta, at Makoka in Zomba. Plot size was held constant at 0,02 ha, while tree espacement varied between 1,8 × 1,8; 1,8 × 3,6; 2,7 × 2,7 and 2,7 × 5,4. Trees in the same plots with A. hypogaea and M. esculenta had better volume production than those in the same plot with P. vulgaris and Z. mays. The presence of these agricultural crops did not significantly affect tree diameter and tree height. Varying tree espacement, however, had a significant effect on tree diameter and volume production. In terms of agricultural crop yields, plots with wider tree espacement gave greater crop yields than narrower tree espacement.

Electrodeposit tree patterns in linear cells: Experiment and computer models

Fractal tree patterns are generated experimentally in electrodeposits of CuSO 4 in thin linear cells with relatively high voltages (15–30 V across two copper electrodes of separation 3.8 cm). The tree separations, tree widths and heights, and tree statistics are analysed. Tree pattern from two-dimensional computer models, the three-directions biased random walk (BRW) model and the dielectric breakdown model (DBM) with probability cut-off, are produced. The BRW model compares very well with our experimental data. There is a minimum in the N m versus m curve where N m is the number of trees with mass m. For m small, N m ∼ m −τ with 0 < τ < 1, in contrast to the DLA result that 1 < τ < 2. The fractal dimension of the tree D varies linearly with the fractal dimension of the walker D w , which also differs from the DLA results of Matsushita et al. The DBM with cut-off gives trees with too much ramification compared to the experimental results, and fails to produce the sharp structure transition lines observed in previous electrodeposit experiments.

Growth velocity of electrochemical deposition and its concentration dependence

The structure and stational growth velocity of electrochemical deposits grown from one-dimensional seeds were studied as a function of electrolyte concentration. The growth velocity of zinc metal leaves was found to be independent of the concentration of zinc ions respectively from 0.003 to 0.008 mol/ℓ and from 0.010 to 0.018 mol/ℓ for a fixed potential of 15 V. In this concentration range the local structure remains fractal, but the width of trees and the separation between the trees depends strongly on the concentration. The local structure suddenly changes from fractal to dendritic structure with backbones at 0.020 mol/ℓ. The dicrepancy between the experimental results and the velocity selection mechanism based on DLA is discussed.

Noise-reduced diffusion-limited deposition

To investigate the role of fluctuations in diffusion-limited growth the authors apply the noise reduction algorithm to the problem of two-dimensional deposition on a substrate consisting of a straight line. The authors consider the scaling of the height and the width of trees growing on the square lattice. For the sizes studied they find two length scales characterised by different exponents depending on the noise reduction parameter m. Using these exponents the effective fractal dimension Deff of trees is calculated and for m>>1 they obtain Deff approximately=1.57. The density profile in the direction of growth and the scaling properties of the lateral correlation function are also determined.

Electronic Measurement of Tree Canopy Volume

ABSTRACT AN electronic tree canopy volume measurement system was developed. The system was based on commercial ultrasonic range transducers with novel digital interface circuitry. The measurement system and a microcomputer were mounted on an orchard air-blast sprayer for testing. Calibration tests with ideal targets found system error to be < 2% at mid range (2.6 m). Field tests in apple and peach orchards at different stages of leaf development found the system to measure tree width and extension with <10% average error and high precision. Tests at ground speeds of 2, 4 and 6 km/h found no significant effect on system performance due to ground speed.

Effects of Wild Pigs on Beech Growth in Great Smoky Mountains National Park

Growth of trees in 9 high-elevation American beech (Fagus grandifolia) gaps in Great Smoky Mountains National Park (GSMNP) was examined from June to August 1982, for impact from rooting by wild pigs (Sus scrofa). Beech trees exhibited significantly greater shoot elongation (F2,6 = 7.71, P < 0.05) with increased exposure to rooting by wild pigs; however, tests for changes in radial increment (F,, = 5.42, P < 0.10) were not as significant due to confounding effects from elevation and stand age. Annular-ring widths of trees from young stands demonstrated greater variation in growth for years with pigs present compared to years before pigs inhabited the sites. Comparable changes were not observed for older stands. The growth responses of trees observed probably resulted from an enhanced nutrient mobilization in soils disturbed by pigs. J. WILDL. MANAGE. 50(4):655-659 Distribution of the wild pig has expanded to all continents as a direct consequence of introduction by man (Tisdell 1982). Wild pigs are abundant in several regions of the United States (Wood and Barrett 1979) and now occupy 13 areas managed by the U.S. National Park Service (Singer 1981). Impacts caused by the rooting of wild pigs are varied and, depending on the local situation, have been viewed as either detrimental or beneficial (Tisdell 1982). A management objective of national parks is to conserve native species in their natural environments. The presence of exotic wild pigs threatens the achievement of such an objective for GSMNP. Wild pigs in GSMNP have caused changes in herbaceous vegetation (Bratton 1974, 1975; Howe and Bratton 1976) and soils (Lacki and Lancia 1983, Singer et al. 1984). Rooting by wild pigs is known to damage tree roots and increase the amount of sprouting or root suckering (Huff 1977), but the responses by overstory components in forests of GSMNP have not been examined. To fully assess the implications of a resident population of wild pigs in GSMNP, the impact of these animals on all ecosystem components needs to be quantified. The objective of our study was to determine the effect of rooting by wild pigs on tree growth in the most disturbed forests of GSMNP. Our research was funded by the Natl. Park Serv. (NPS) through Uplands Res. Lab., GSMNP (NPS Contract X5460-0-2592) and, in part, by a Theodore Roosevelt Mem. Fund Grant to the senior author. This is Contrib. 10249 from the N. C. Agric. Res. Serv. journal series. We are indebted to R. J. Fredrickson and W. M. Whiteside for field assistance and to L. A. Nelson, K. H. Pollock, and W. L. Hafley of the Deps. Stat. and For. at North Carolina State Univ. for statistical advice. We are grateful to N. H. Shrimpton for measuring increment cores. We thank Uplands Res. Lab. and the Resour. Manage. Sect. GSMNP, and the Deps. For. and Zool. at North Carolina State Univ. for logistic support. Comments and suggestions were provided by C. L. Campbell, C. B. Davey, P. D. Doerr, J. D. Hair, R. Lea, and P. M. Vitousek.

Riverflow reconstruction from tree rings in southern Britain

AbstractRing widths of oak trees (Quercus petraea Liebl. and Quercus robur L.) from a network of seven sites in southern Britain and northern France are used to reconstruct riverflow for three river catchments in southern Britain. These dendrohydrological reconstructions, made using a principal components regression technique, are the first such reconstructions in Europe. The results are statistically significant, and the stability of the regression models is verified using independent data. The reconstructions are more reliable for low flow events; a finding which is potentially useful for water resource planning. The reconstructions indicate a possible increase in the frequency of extreme low flows over the period 1755–1859, compared to 1860–1979, which although not of conclusive statistical significance, warrants further investigation.

Peach Rootstock Influence on Foliar and Dormant Stem Nutrient Content

Abstract Foliar and dormant shoot nutrient content and tree survival of ‘Loring’ and ‘Redhaven’ peach [Prunus persica (L.) Batsch] on 8 seedling rootstocks (Lovell, Halford, Harrow W-208, NA8, Nemagard, Siberian C, NC NRL-4, and NC 152-AI-2) were determined during 2 seasons. Foliar Ca levels of both ‘Loring’ and ‘Redhaven’ peach trees were lower on Siberian C rootstock than on any other rootstock in the study. Dormant stem Ca levels were lower when cultivars were on Siberian C rootstock than when on most other rootstocks. Cultivars on Siberian C had lower foliar K levels than most other scion/rootstock combinations. Some differences in foliar and stem N, P, Mg, and Mn levels were evident; however, these differences generally were small and inconsistent. After 6 years in the orchard, greatest tree loss occurred with ‘Loring’ on Siberian C and ‘Redhaven’ on Siberian C or NA-8. Other rootstocks did not affect tree survival of either cultivar. Tree width was smallest with Siberian C rootstock, but few differences in trunk circumference and tree height were observed.

The effects of tree spacing, herbicide management and width of grass alleys on phosphorus concentrations in Golden Delicious apple fruits

SummaryIn 1973, 5-year-old Golden Delicious trees on M.9 rootstock widely spaced within rows in herbicide strip management produced fruit with higher P concentrations than those from closely spaced trees, but this pattern was reversed in subsequent years. Wider alleys also increased P concentrations in most years and this effect persisted after conversion to overall herbicide management in 1977. The combined effects of between-row and within-row spacing and management resulted in large differences (15 to 20%) in fruit P concentrations in 1980 and 1981.