Potential Failure of A Decayed Tree Under Wind Loading

Trees with decayed wood that are subject to moderate winds often collapse and cause property damage or injury and death to people. The purpose of this paper is to describe a decision-making aid to help identify a tree that may fail in the forest or be a potential hazard in the city. A tree may fail when the probability of radial shear cracks developing for a given wind load is sufficiently high.Mathematical models are used to estimate the constant wind force on trees and to evaluate the cracking and collapse mechanisms under this loading. The physical dimensions are used to determine the wind force or drag on the tree, and the amount of decay in the tree is used to determine its ability to resist this load. Owing to uncertainties associated with accurately measuring and modeling a decayed tree, estimating the wind load, and specifying the wood strength of a tree species, reliability analysis is used to assess the potential risk of failure. Coupling this information with meteorological data for the largest wind speed value expected at the tree site and the topography of the tree site completes the analysis of potential failure. Case studies of balsam fir trees with the same exterior diameters but with different dimensions of decay columns, tree weights, tree heights, and wind speed conditions are analyzed and compared

A Macroscopic and Microscopic Study of Compartmentalization and Wound Closure after Mechanical Wounding of Black Walnut Trees

Compartmentalization is a concept developed to explain tree response to injury. To study this concept, uniform mechanical wounds were made in fifty black walnut trees. Each tree was wounded at two different heights, 0.5 and 1.4 m, and at two different times, fall (November 1975) and spring (March 1976). The amount of wound closure was noted after one complete growing season, as were several macro- and microscopic characteristics of compartmentalization. Wound closure and compartmentalization were separate responses. Most of the wounds were closed after a single season's growth.The eight trees with one or more open wounds were among the smallest and slowest growing trees in the study. This suggests a positive relationship between growth rate and wound closure, but statistically the relationship was not significant. Wood discoloration was the most prominent wound-related defect. Greater volumes of discolored wood were associated with fall wounds than with spring wounds. Similarly, fall and spring upper wounds were associated with larger volumes of discolored wood than their lower counterparts. Prior fertilizer treatments had no effect on wound closure or compartmentalization. The compartmentalization of wound-affected wood in black walnut agrees with the generalized model of compartmentalization of decay in trees (CODIT). The outer tangential and lateral compartment walls are the strongest, and the inner tangential and top and bottom compartment walls are the weakest and most easily overcome by invading microorganisms. The initial wood discoloration process did not appear to be associated with microorganism activity. Effective compartmentalization was positively correlated with growth rate. Some results of this study suggest that the relative ability to compartmentalize is under genetic control

Effect of logging wounds on diameter growth of beech (Fagus orientalis Lipsky) trees following selection cutting in Caspian forests of Iran

Background Logging damage to residual trees during selection cutting may lead to serious economic losses in terms of both timber quality and diameter growth reduction. In this study, we investigated the effect of logging operations on residual tree damage and the consequence of injuries on diameter growth in an uneven-aged mixed forest dominated by beech (Fagus orientalis Lipsky)