Snow Damage Research Articles

Logistic regression models for wind and snow damage in northern Finland based on the National Forest Inventory data

The susceptibility of forest stands to wind and snow damage was predicted with basic logistic regression models from a large systematic sample and with conditional logistic regression from a smaller matched study. Data was from the 8th National Forest Inventory, recorded in northern Finland during 1992–1994. The current investigation adds to previous studies by considering the role of individual explanatory variables more closely, instead of only predicting the absolute risk. From both, the basic logistic and the matched models, we obtain odds ratios for explanatory variables, which estimate the so called relative risk; i.e. increase in the damage risk by a particular factor. In our study, matching by cluster or municipality was used to control the possible effects of stochastic local factors that were not quantified, such as wind and snow conditions, on the odds ratios. According to the basic logistic regression model, the susceptibility of a stand to wind damage was increased by: large mean diameter, high stand age, seed-tree cutting, special cutting (cutting for ditches, roads or power lines, or sanitation cutting after damage), and decreasing temperature sum. Significant exposure factors for snow damage were: decreasing temperature sums, elevation >200 m a.s.l., conifer-dominance, mineral soil, undrained, unthinned, development stage pole stand and no proximity to stand edge. The distribution of damaged stands at the landscape level could not be predicted well with the basic logistic regression model, since it is only concerned with the susceptibility component of the probability, and not the occurrence of the damaging agents; i.e. unfavourable weather. Odds ratios can be used as an alternative to probabilities for comparing the damage risks related to combinations of exposure factors from site, stand and forest management. The matched approach showed promise as an alternative method for modelling the odds ratios. The results suggest that matching was useful for wind damage, but less so for snow damage. If the incidence of winds can be taken into account in some way, as with the matched model, the effect of exposure factors on damage risk can be estimated more precisely. Wind damage is a more stochastic phenomenon than snow damage: at least in northern Finland, snow damage may be more tied to more regularly occurring climatic factors at the site than wind damage. Consequently, the basic logistic regression model where these can be included as explanatory variables was better for snow damage than the matched model.

Extent of abiotic damage and its relation to defoliation of conifers in Finland

Data from the eighth National Forest Inventory (NFI) and annual surveys of the vitality of forests was used in this study. Abiotic damage (wind, snow, frost or edaphic factors) was present on 8.4% of forest land, on 1.68 million hectares during 1986–1994. It decreased the silvicultural quality of the stand in 5.2% of forest land. Abiotic damage was more frequent in northern than in southern Finland. Especially snow damage was important in northern Finland in Scots pine stands. The defoliation of conifers and various damage forms showed significant co-occurrence. Temporal and spatial patterns were evident in the occurrence and importance of different causal agents. Abiotic damage increased the defoliation in Picea abies more than in Pinus sylvestris, but in the latter species the damage was locally more severe. Sudden changes in defoliation were related to abiotic and biotic damage, and the effect of these injuries can be so remarkable that they mask the possible trend in defoliation. The analysis of these injuries may aid monitoring of forest condition by simplifying interpretation of national and regional patterns of forest damage.

An approach for estimating resistance of Japanese cedar to snow accretion damage

Snow accretion damage to Japanese cedar ( Cryptomeria japonica D. DON) plantations is common in Japan. It is necessary to evolve an index as a measure of resistance for trees to the damage for silvicultural treatments (thinning, pruning, etc.), aiming at reducing the damage. Nakatani et al. [Nakatani, H., 1991. J. Toyama Forestry For. Prod. Res. Center 4, 1–54] proposed an approach to calculate critical snowfall as a new index for measuring resistance to the damage on an individual tree and indicate an amount of snowfall causing the damage that is based on physical characteristics, e.g. the stem form, the elasticity of the wood, the degree of support for the tree by the roots and the distribution of foliage within the tree crown. In this study, we (1) developed the Nakatani’s approach to calculate the critical snowfall of an individual tree by using empirical equations to estimate those physical characteristics from basic parameters of a tree, e.g. tree height, stem diameter and age, and (2) evaluated the approach based on model computation. This new approach was useful in discriminating between damaged and undamaged trees at damaged stands without considering wind influence. Furthermore, the resistance of tree to the snow damage tended to increase with increasing stem diameter and age and decreasing tree height. This new approach provided a useful index to evaluate the effects of thinning and pruning to the snow damage. It was found to be necessary to hasten the diameter growth of tree by planting trees with wider spacing and thinning trees in order to reduce the snow accretion damage. The resistance of a single tree to snow damage increased immediately after heavier pruning and increased with the rise in tree height or age for similar removal ratio of foliage.

Risk of Snow Damage in Unmanaged and Managed Stands of Scots Pine, Norway Spruce and Birch

The aim of this study was to assess the risk of snow damage to trees in unmanaged and managed stands of Scots pine (Pinus sylvestris L.), Norway spruce [Picea abies (L.) Karst.] and birch (Betula spp.) over a rotation. The risk assessment was based on the prediction of critical snow loads in interaction with the windspeed at which trees can be expected to break or be uprooted, and on the frequency of long-term extremes of precipitation and of suitable temperature conditions for the accumulation of snow on the tree crowns. The Scots pine stands were found to be more susceptible to snow damage than the others, and an unmanaged stand of Scots pine to be more susceptible to break and uproot than a managed one. Correspondingly, an unmanaged stand of Norway spruce was more susceptible to stem breakage than a managed one, but less susceptible to uprooting. Neither unmanaged nor managed birch stands were likely to suffer any kind of snow damage. The susceptibility of unmanaged stands is caused by low tapering of the trees. Based on the frequency of long-term extremes in precipitation at the temperatures needed for snow accumulation on tree crowns, critical snow loads of 10-19, 20-29 and 30-39 kg m-2 occurred 19.3, 3.3 and 1.3 times in a decade in southern Finland. Critical snow loads of 10-19, 20-29, 30-39 and 60-69 kg m-2 occurred in northern Finland 17.0, 6.3, 1.7 and 0.3 times in a decade.

Crown snow damages of Pinus thunbergii in south coast of Akita Prefecture

Crown snow damages of <i>Pinus thunbergii</i> in south coast of Akita Prefecture

Effect of Melt Water as the Factor of Snow Damage and the Torelance Mechanism on Faba Beans

Effect of Melt Water as the Factor of Snow Damage and the Torelance Mechanism on Faba Beans

Climate risks and age-related damage probabilities – effects on the economically optimal rotation length for forest stand management in Japan

We estimated the damage probability according to age class and major climatic disasters based on ‘Statistical Yearbook of National Forest Insurance’ from 1960 to 1996. The probability of snow damage is high for young stands, then gradually decreases with age. On the other hand, the risk of wind damage gradually increases with age. Decisions about rotation age should be based on the distribution of damage probability with stand age. Risk of damage has two contradictory effects on the optimal rotation period; one is that the rotation-shortening effect caused by risk of damage around harvest age; another is the rotation-extending effect due to decrease of rent by the risk of damage through the raising period. Change of optimal rotation depends on the relative magnitude of these effects. We examine this by calculating land expectation value (LEV) using a simulation model with the empirical damage probability, price and cost. Change of the optimal rotation period obtained from the national average damage probability is not significant. However, the optimal rotation is shorter in high wind risk areas and is longer in high snow risk areas. It is because the damage probability for a mature stand is high in the case of wind and low in the case of snow. In addition, the extent of decrease in LEV is smaller for wind than for snow. The results of simulation based on empirical data confirm that the optimal rotation period can become either shorter or longer through incorporating risk in decision making, depending on the damage probability distribution with stand age.

A mechanistic model for assessing the risk of wind and snow damage to single trees and stands of Scots pine, Norway spruce, and birch

A mechanistic model for assessing the risk of wind and snow damage to single trees and stands of Scots pine (Pinus sylvestris L.), Norway spruce (Picea abies (L.) Karst.), and birch (Betula spp.) is presented. The model predicts the critical turning moment and wind speed at which the trees will be uprooted or break at forest margins. The resistance to uprooting is predicted using the estimate of the root-soil plate weight to derive a resistive moment, while the resistance to stem breakage relies on values for the modulus of rupture determined for different species of timber. A tree is assumed to be uprooted if the total turning moment exceeds the support provided by the root-soil plate anchorage. Similarly, a tree is assumed to break if the breaking stress acting on the stem exceeds a critical value of the modulus of rupture. The model is in general quite sensitive to parameter changes, which partly results from the location in the forest to which it was designed to apply (the stand edge). The predictions of the critical turning moments needed to uproot and break trees nevertheless give a good agreement on average with the Finnish tree-pulling data for Scots pine, Norway spruce, and birch.

Modelling the risk of snow damage to forests under short-term snow loading

Regression models are developed to assess the risk of snow damage to Scots pine ( Pinus sylvestris L.), Norway spruce ( Picea abies (L.) Karst) and birch ( Betula spp.) stands based on simulated data, employing a mechanistic wind and snow damage model developed by Peltola et al., 1998a. The risk is predicted in terms of the critical windspeed needed to cause stem breakage and uprooting of trees at forest edges under short-term snow loading. Separate regression models are developed for each tree species using stem taper (breast height diameter of stem relative to tree height, d 1.3/ h), stand density, snow loading and distance from the stand edge as variables, and a general model for stem breakage and uprooting is also proposed having tree species as an additional dummy variable. The overall risk of stem breakage and uprooting is shown to increase with snow loading and decrease with increasing stem taper and stand density for all three tree species, although Scots pines and Norway spruces are predicted to be much more susceptible to snow damage than birches, which, being leafless, had much less crown area for snow attachment and wind loading. The greatest susceptibility to stem breakage and uprooting is seen at the stand edge, where the risk due to wind loading is much greater than inside the stand. Under these circumstances, slightly tapering Scots pines and Norway spruces are found to be the most vulnerable under a snow load of 60 kg m −2, suffering damage at windspeeds of <9 m s −1 at a constant height of 10 m above the ground, i.e. these windspeeds enhance the risk, whereas higher speeds can be expected to dislodge the snow from the crowns. Birches will only exceptionally be broken and uprooted at windspeeds of <9 m s −1 according to the models developed here. Since the general models give rise to somewhat greater residuals compared with the simulated data than do the single tree species models, it seems that the latter will give more reliable predictions of the risk of snow damage. The models could be useful when discussing the risk of snow damage in connection with alternative forms of stand management, especially in high risk areas, enabling high-risk trees to be removed during thinning.

Influence of Snow Melt Water on the Content of Mineral Nutrients in the Leaves of Broad Bean (Vicia faba L.) under Snow Cover with Reference to Snow Damage.

The content and distribution of potassium (K) and calcium (Ca) in the leaves of broad bean during the snow cover period were investigated to clarify the role of snow melt water in snow damage. The experiments were carried out under the conditions where air temperature was usually above 0°C and snow had been melting during the snow cover period. The melt water with an average pH of 4.4 contained CL-, SO42- and NO3-. The plants were cultivated in open fields or inside tunnels covered with non-woven fabric to decrease the quantity of melting water. Most of the plants in the open fields were damaged after 52 days of snow cover, but the plants inside the tunnel were hardly damaged. The K content in the leaves decreased under snow cover in both plots and the decrease in open field plots was greater than that in the tunnel plots. On the other hand, Ca content decreased only in the open field plots. The observations of leaves after snow melting with an Electron Prove Micro X-ray Analyzer revealed that the content of K in the necrotized part of the leaf was lower than that in the healthy part. From these results, we concluded that the minerals i leaves were leached out by continuous out by continuous snow melt water and the melt water is one of the factors enhancing the snow damage.

A mechanistic model for assessing the risk of wind and snow damage to single trees and stands of Scots pine, Norway spruce, and birch

A mechanistic model for assessing the risk of wind and snow damage to single trees and stands of Scots pine (Pinus sylvestris L.), Norway spruce (Picea abies (L.) Karst.), and birch (Betula spp.) is presented. The model predicts the critical turning moment and wind speed at which the trees will be uprooted or break at forest margins. The resistance to uprooting is predicted using the estimate of the root-soil plate weight to derive a resistive moment, while the resistance to stem breakage relies on values for the modulus of rupture determined for different species of timber. A tree is assumed to be uprooted if the total turning moment exceeds the support provided by the root-soil plate anchorage. Similarly, a tree is assumed to break if the breaking stress acting on the stem exceeds a critical value of the modulus of rupture. The model is in general quite sensitive to parameter changes, which partly results from the location in the forest to which it was designed to apply (the stand edge). The predictions of the critical turning moments needed to uproot and break trees nevertheless give a good agreement on average with the Finnish tree-pulling data for Scots pine, Norway spruce, and birch.

An examination of tolerance to the shade environment for candidates of resistant tree to the snow damage in Yamagata Prefecture

An examination of tolerance to the shade environment for candidates of resistant tree to the snow damage in Yamagata Prefecture

Modelling probability of snow and wind damage using tree, stand, and site characteristics from Pinus sylvestris sample plots

The risk of damage on trees from snow and wind was modelled using tree, stand, and site characteristics from 286 permanent Scots pine (Pinus sylvestris L.) sample plots within the Swedish National Forest Inventory. Three logistic risk assessment models were developed for the county of Västerbotten in the boreal zone of Sweden. The best model, using tree, stand, and site variables, correctly classified 81.1% of the undamaged and 81.8% of the damaged plots. The model over‐predicted the proportion of damaged plots (21.3%), compared to the observed proportion of 3.8%. When evaluating the models using temporary plots from Västerbotten, the model using tree, stand, and site variables showed the best overall predictability. When applied in southern Sweden, the models developed for Västerbotten showed poor predictability. The study shows possibilities for correctly classifying the overall susceptibility to damage from snow and wind if the models are used within their limits.

Effects of thinning on snow damage in Pinus sylvestris L.

The extraordinary damage caused by snow on January 1996 in Scots pine stands in the Sistema Central (Central Spain) are analysed. Data from two thinning experiences carried out in 44 and 60 years old stands have been used. Damage was greater in the crown thinning and control treatment (no thinning plots), compared with low thinning plots. Results clearly show a decrease on snow damage with increasing low thinning intensity. The effects of low thinning on stand stability is related with the lower growing stock, the removal of smaller and suppresed trees, and the lower risk of damage of the remaining stand. The individual susceptibility to snow damage decreases with decreasing height-diameter ratio, increasing diameter, and increasing lenght of green crown.

Model computations on the critical combination of snow loading and windspeed for snow damage of scots pine, Norway spruce and Birch sp. at stand edge

Model computations were made on the critical combination of snow loading and windspeed for snow damage of Scots pine ( Pinus sylvestris L.), Norway spruce ( Picea abies Karst.) and birch sp. ( Betula sp.) at the newly formed stand edge with varying tree height and stem taper using the model developed by H. Peltola, S. Kellomäki and H. Väisänen (1996, HWIND: A Mechanistic Model for Wind and Snow Damage of Scotts Pine, Norway Spruce and Birch sp.) for the mechanism of wind and snow damage. In the computations, the total turning moment arising from the wind and snow load and from the bending of stem and crown was calculated along with the breaking stress of the stem and root anchorage. Windspeed variation within the crown and the vertical distribution of snow, stem and crown weight were also taken into account. According to computations, the critical combination of snow and wind loading for stem breakage and uprooting of trees was caused mainly by accumulation of snow on tree crowns, rather than by wind, which did, however, increase the risk of damage. The risk of damage increased along with stem taper decrease or tree height increase for all tree species studied. However, Scots pine and Norway spruce were found much more susceptible to snow damage than birch, which (being leafless) had much less crown area for snow attachment and wind loading. The trees most likely to suffer stem breakage were slightly tapering Scots pines and Norway spruces with tapers of 1:120 for varying tree heights of 12–20 m under short-term snow loading of 60 kg m −2, i.e. they would have suffered stem breakage under windspeeds of less than 9 m s −1 above the tree canopy top. Respectively, even Scots pine and Norway spruce with tapers of 1:100 were at risk of stem breakage through sustained snow loading of 60 kg m −2. In addition, even snow loads of 20–40 kg m −2 were found big enough to cause stem breakage of these trees with stem tapers of 1:120 during sustained snow loading. Correspondingly, similar pines and spruces with stem tapers of 1:120 were found to even more liable to be uprooted during conditions of unfrozen soil than of having their stem broken by short-term snow loading of 20–60 kg m −2, i.e. less windspeed was needed to cause uprooting. However, pines and spruces with tapers of 1:80 were not at risk for stem breakage and uprooting. This was because snow would have more probably been dislodged from the tree crowns by windspeeds greater than 9 ms −1 which are needed to worsen the damage. Nor would very slender birch without leaves have suffered stem breakage or uprooting under any circumstances with windspeeds of less than 9 ms −1.

Relationship between Physiological and Ecological Traits and Snow Mold Damage in Winter Wheat Varieties (Triticum aestivum L.).

コムギの雪害はそのほとんどが雪腐病の発生に起因しており,その被害程度には積雪下における植物体の生理的活性程度が大きく影響する。耐雪性品種の育種に資するため根雪前及び積雪下での生理・生態的形質の変化と雪腐病被害との関係を秋播コムギ45品種を用いて検討した.1992-1993年には冠部比率,乾物率,LT50による耐凍度を根雪前に調査したほか特に代表的な1O品種については茎葉重,乾物率,耐凍度,暗黒下再生量を根雪前と積雪下70日目に測定し,比較した。さらに1993-1994年には全品種の耐凍度を根雪前と積雪下95日目に測定するとともに雪腐病被害程度を調査した。茎葉重や乾物率では根雪前と積雪下70日目に有意な相関があったが耐凍度や暗黒化再生量では有意でなかった。また乾物率,耐凍度,暗黒化再生量の相互間に根雪前には有意な相関は認められなかったが,積雪下では有意な正の相関が認められた。これらの原因としてP.I.173438,Niederndorferberg,Haunsberg,農林62号などの耐雪型品種が根雪前では乾物率が高いにもかかわらず耐凍度が劣り積雪下では耐凍度や暗黒化再生量の減少が少ないためで,耐凍度や暗黒化再生量は積雪下における植物体の生理的活性の指標として有用であった。雷腐病被害程度と耐凍度及び暗黒化再生量の関係も同様に根雪前には有意でなかったが積雪下で有意となった。一方乾物率は積雪下で10品種一様に減少した結果,雪腐病被害程度との相関が根雪前(r=-0.618)においても積雪下70日目(r=-0.879***)においても調査形質中最も高かった。耐凍型品種が高い乾物率と優れた耐凍度を示し冠部比率が50%近くその叢生はロゼット型を示したのに対し,耐雪型品種は高い乾物率でありながら耐凍度は相対的に低く冠部比率が35%前後でその叢生は直立していた。

屋根雪の滑雪制御に関する基礎的考察

The effectiveness of roof snow control by sliding mechanism on the sloped roof is widely recognized, but many problems are remained to systemize the techniques on removing roof snow.This paper presents fundamental study on the factors; characteristics of roof snow damage, regional characteristics of the damage, methods of removing roof snow, the frame on the systemization of roof snow control, and the state of studies on roof snow behavior, that are required in the systemization of the techniques on roof snow control.From the study, it is clarified that the techniques on roof snow control should be supported by prediction technique and countermeasure technique against to the roof snow damage. The prediction technique is required to know roof snow behavior and damages occurred by roof snow. The systemization of roof snow control is strongly required in deep snow area of Japan. Furthermore it is required to organize the knowledge obtained by observational, experimental, or analytical approach.

Factors affecting snow damage of trees with particular reference to European conditions.

Factors affecting snow damage of trees with particular reference to European conditions.

Wind and snow damage in a thinning and fertilization experiment in Picea abies in southern Sweden

Summary Changes in susceptibilit y to wind and snow damage due to thinning and fertilization were examined in even aged Norway spruce (Picea abies (L.) Karst.) stands in southern Sweden. The stands are part of a nationwide experiment to investigate growth and yield following different thinning and fertilization regimes established between 1966 and 1983. The material used in this study included 16 replications of seven treatments. The treatments were: three levels of thinning from below (20-70 per cent); 20 per cent thinning from above; thinning from below in combination with N and NP fertilization (thinning percentage 25—28 per cent); and unthinned control. The stands have been censused twice for damage during an average period of 12 years. The degree of wind and snow induced damage varied between 9 and 20 per cent of the basal area increment produced during the observation period. For treatments with high basal area removal, the highest relative number of trees damaged by wind occured during the first period after thinning. The densest stands (i.e. unthinned controls and stands thinned from above) showed a high proportion of snow damage throughout the observation period. The block effect was in general more significant than the effect of treatments on damage level. When analysing the influence of the block effect (i.e. of site and stand characteristics) on damage level, wind damage was best predicted by stand basal area left after thinning and stand age, while snow damage was best predicted by latitude, altitude, site index, and stand age. On average the tested site and stand characteristics explained 17 per cent of the variation in wind damage and 36 per cent in snow damage.

Snow damage and efficacy of pruning of planted Fraxinus mandshurica var. japonica

Snow damage and efficacy of pruning of planted Fraxinus mandshurica var. japonica