Snow damage in Australian pine plantations

Abstract

In June 1981 heavy falls of wet snow with air temperatures near 0°C and strong winds caused extraordinary damage in both pine plantations and native eucalypt forests in much of southeastern Australia, especially at altitudes between 700 m and 1200 m. Using data from a thinning trial, inventory plots, forestry records and extensive inspections of plantations and arboreta, a study was made of this damage to identify types, incidence and mechanisms of damage in Pinus radiata plantations, and their silvicultural implications.The most widespread but least injurious types of snow damage were the bending and breakage of branches. Uprooting was important in only one plantation. The main damage was the bending or breakage of stems. Some 500 ha of pine plantations have had to be salvaged by clearfelling and a further 1700 ha by heavy thinning, most of them about 15-30 m tall.Snow damage toP. radiata stems was found to be influenced by: (a) bending moments (due to imbalance of the loaded crowns and lean of the tree), (b) the height/diameter (HID) ratio of the stems, (c) the shelter enjoyed by the trees below the general canopy, (d) the height/spacing ratio (and hence the chance of one tree falling on another), (e) selective removal of the weaker, less stable individuals of the stand, (f) effects of growing space on diameter growth and hence HID ratios, and (g) effects of age on HID ratios and the intrinsic strength of the wood. Comparisons are made with other species.It is concluded that the HID ratio provides a valuable indication of the risk of snow damage, and that this risk can be largely controlled by spacing-thinning strategies. In plantations of P. radiata, trees should be allowed as much growing space from an early age as is compatible with other constraints; they should be established at no more than I 000 stems/ha and thinned by removal of the more slender trees before the dominants exceed 20 m in height.

Snow damage in eucalypt forests

“…The patterns of damage to the stems of such eucalypts were similar to those recorded in the pine plantations (Cremer et al 1983). The incidence of bent and broken stems was simiDownloaded by [New York University] larly influenced by the slenderness of the stems, the lean of the trees, the imbalance of the crowns, and the proximity between trees (the chance of one tree collapsing on and bringing down its neighbours).…”

“…The damage to the eucalypts was examined by walking some 50 to 100 km in the mountain forests in the ACT, NSW and Victoria, and by driving for hundreds of kilometers through the forests. The paper complements a more detailed study made of snow damage in pine plantations (Cremer et al 1983), in which the incidence of snow damage is examined in relation to tree characteristics.…”

Effects of phenotypic selection on height-diameter ratio of Norway spruce and Scots pine in Sweden

“…Given the significant negative correlation detected between breeding values of height-diameter ratios and height and diameter for Scots pine and Norway spruce, the breeding programs for these species need to select for other traits in order to avoid reductions in the height-diameter ratio in improved material. However, maintaining the same height-diameter ratio as unimproved material may not necessarily be optimal, as there may be sound silvicultural and commercial reasons for adjusting it (Cremer et al 1983;Lohmander and Helles 1987;Harrington and DeBell 1996).…”

“…In Swedish conditions, genetic differences in stem slenderness might justify adjustments of (for example) the diameter-height models presented by Fahlvik and Nyström (2006). Furthermore, stem slenderness is often used to determine tree stability and susceptibility to windthrow and snow damage (Cremer et al 1983;Lohmander and Helles 1987;Harrington and DeBell 1996). In a study on five tree species in Canada, Wang et al (1998) found that stem slenderness was negatively correlated with tree diameter at breast height (dbh), height, crown length and age, but positively correlated with stand density, species composition, and site index.…”

<b>Statistical Analysis of Tree-Forest Damage by Snow and Wind:Logistic Regression Model for Tree damage and Cox Regression for Tree Surviv</b><b>al </b>

“…Figure 1 shows a trunk-bending scenario in Toyama, Japan. The degree of snow damage depends on several factors, including forest stand and geographic characteristics (Cremer et al, 1983;Kato and Nakatani, 2000;Jalkanen and Mattila, 2000). In our analysis candidate variables include geographic elements such as slope aspect, and forest stand attributes such as stand age and average tree height.…”