Proper Tree Research Articles

Integrating Classical Biological Control with Plant Health in the Urban Forest

Classical biological control is defined as a process of identification and introduction of natural enemies of pest species for the purpose of reducing the population size of the damaging species. Introduction of a parasitic wasp and a predaceous beetle has reduced populations of the ash whitef ly by 10,00-fold in landscape trees in California. It is hoped that similar introductions of parasitic wasps to control the eucalyptus longhorned borer will be successful in reducing tree mortality. However, choosing the proper species of Eucalyptus for site conditions, proper water management to maintain optimum tree vigor, and proper tree maintenance will reduce the risk of attack by this borer. Plant health care is critical to enhance tree resistance and limit tree susceptibility. The combination of maintaining vigorous tree growth and limiting the number of insect pests in the environment through the action of natural enemies provides a long-term approach to tree protection.

State Regulation of Utility Arboriculture

The role of state governments in regulating utility arboriculture is primarily for the purpose of protecting and maintaining the aesthetics of public roadways for the traveling public. The utility service companies can realize benefits as the state becomes active in promoting proper tree care standards within utility clearance space requirements. Maryland's Roadside Tree Program is administered to foster cooperation between property owners, local jurisdictions, utility services and other state agencies in the care of trees within the public rights-of-way.

Targets for Proper Tree Care

Proper tree care starts with a thorough understanding of trees and the many treatments used to help trees stay attractive, safe, and healthy. In the real working world of trees, it is almost impossible to do all the needed treatments perfectly all the time. A professional arborist must know what proper tree care is. Each part of each procedure for proper tree care becomes a target. I believe that the degree of professionalism of an arborist centers about knowing where the targets are, and how to hit them. The clearer the targets are to you, the better your chances of hitting them more often. I try here to clarify further some of the targets for proper tree care.

Rots and Rods

Trees with internal rot, or crotches likely to split, can be helped by proper bracing. Although the holes made for the bracing materials are wounds, and wounds start the processes that can lead to rot, the braces can extend the time that trees with rot and weak crotches can remain safe, attractive, and healthy. An understanding of how rots develop and how rods should be properly installed will help the ar­ borist to maximize the benefits of proper tree bracing and to minimize the injury caused by the new wounds required for the bracing materials. Some basic information on the develop­ ment of tree rots and installation of bracing materials is given.

Formulation of state equations for RLC networks with modified proper trees

A new procedure for formulating the state equations for RLC circuits without proper trees is presented. This method would force the network to have a proper tree; thus, obviating the necessity of finding the inverse of a general L, C matrix (a matrix which is not diagonal), and saving the memory and time requirements for computer implementation.

Topological Model for a Three-Phase Converter

The purpose of this article is to develop an efficient model for the analysis of a three-phase converter. An algorithm for the generation of a modified proper tree and fundamental cutset matrix from a network graph is developed, which utilizes much less computer storage space and computation time compared to the classical methods. A three-phase rectifier bridge with its associated protective circuits is considered and the results obtained from the developed technique are discussed.

The A-matrix of linear passive reciprocal networks

The explicit form of Bashkow's A-matrix is obtained for RLCM networks containing ideal transformers. The constraints introduced are handled by associating with each transformer a magnetic graph; the transformer constraint equations then become associated with cutsets and loops of this graph. Necessary conditions on the topology of RLCT networks for the existence of a unique solution are derived, and the concept of a maximal proper tree is introduced. Starting from a maximal proper tree, the explicit form of the A-matrix is obtained by showing that the constraint equations for an RLCMT network can be written in a similar form to those for an RLCM network. This enables the elimination process, derived earlier for the RLCM case, to be extended to the RLCMT case.