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Is there a need for additional safe work practices for work taking place in stands of dead Pine? Lewynsky, Martin Apr 30, 2011

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Is there a need for additional safe work practices for work taking place in stands of dead Pine? Frst 497 Martin Lewynsky April 2011  Primary advisor: Stephen Mitchell Secondary advisor: Kevin Lyons  Abstract In the interior of British Columbia forest harvesting is taking place in the 16.3 million hectares of lodgepole pine forest affected by the mountain pine beetle (Dendroctonus ponderosa) (MFML, 2008). In this paper I looked into the types and amount of work with associated hazards that are occurring in these stands. Hazards include whole and partial tree failure both of which can occur in any phase of the harvesting process. I then looked at how applicable the current wildlife/danger tree assessment method in stands comprised mainly of dead lodgepole pine. The assessment method was found to not be practical for use in these stands in its traditional form. I also looked at how hazards in these stands change over time. I found that checking and drying in the wood may be an important factor in partial tree failure. From my findings I came up with a few recommendations for forest companies with employees working in dead pine stands. One is a switch to a stand level risk assessment rather than single tree risk assessment for dead pine stands. Second the creation of a wind cut-off speed specific to stands of dead pine. Keywords: Lodgepole pine, ponderosa pine, mountain pine beetle, danger tree, blow down, wind throw, checking, saprot, whole tree failure, partial tree failure, hazards, snag.  1  Table of Contents Introduction ................................................................................................................................................. 3 The current mountain pine beetle situation in the province of British Columbia ................................ 3 Types of hazards posed to workers in dead lodgepole pine stands......................................................... 4 Is British Columbia’s Wildlife/danger tree assessment process effective for use in Beetle killed Pine stands?.......................................................................................................................................................... 6 Beetle killed pine degradation and susceptibility to wind throw over time ........................................... 7 Wildlife tree patches ................................................................................................................................... 9 Dead pine trees in populated and recreational areas ............................................................................... 9 Assessing decay in standing trees in the field ......................................................................................... 10 My thoughts and observations working in dead pine stands ................................................................ 10 Discussion .................................................................................................................................................. 12 Recommendations .................................................................................................................................... 13 Literature cited.......................................................................................................................................... 14 Figures............................................................................................................................................................ Figure: 1Frequency distributions of time-since-death of fallen sample trees killed by mountain pine beetle (A), and years to fall of the same trees (B). Date of fall was determined by dating scars on live adjacent trees damaged when the beetle-killed tree fell over.................................................................... 8 Figure 2: Fallen beetle killed lodgepole pine broken off near the ground ............................................... 9  2  Introduction In recent years the mountain pine beetle has left 16.3 million hectares of dead lodgepole pine forests across the province of British Columbia (MFML, 2008). The forest industry has responded to this by increasing harvest rates to salvage the dead pine stands while they are still economically viable. Over time the dead pine trees begin to decay and lose the durability they held as standing trees. As these dead trees become weaker they pose a danger to anyone working around them. Increased forestry activities in these areas means that worker exposure to these danger trees will be higher than ever before. To evaluate of the level of worker exposure I will first take a look at the current amount of harvesting in dead pine stands as well as likely amounts in the coming years. Knowing how dead lodgepole pine degrades over time will also give an idea of how far into the future we will be salvage harvesting from the current mountain pine beetle epidemic. There are many types of work activities that go on in the forest from pre-harvest planning to post harvest silvicultural activities. Hazards will likely vary between each activity phase of an operation so this is what I will look at next. From here I will begin to look at British Columbia’s danger tree assessment process to determine its practicality and applicability for use in stands of dead lodgepole pine. Pine species affected by the mountain pine beetle are also found in populated areas so I will briefly look at the related hazards and how they differ from those in the forest industry. As worked in stands of dead lodgepole pine I will finish by discussing my thoughts and observations plus relating them to findings from research papers. I will then end by discussing what I have found and give my recommendations.  The current mountain pine beetle outbreak in the province of British Columbia From the current mountain pine beetle epidemic it is estimated that a cumulative total of 675 million cubic meters of timber have been affected since the outbreak began (MFML, 2010). Stands killed by mountain pine beetle are deemed to have commercial value up to 15 years after tree death (Kadla, et al. 2008). To salvage the dead pine in these stands before the 15 year mark the annual allowable cut in British Columbia has been temporarily raised and government programs have been created to encourage harvesting in dead pine stands. The BC government has increased the provincial annual allowable cut (AAC) by 6.2 million cubic metres in an effort to capture value from beetle-kill timber (NRC, 2004). While a poor market has made it difficult to take advantage of the AAC increase, government initiatives have helped forest companies continue to salvage the dead pine. The stumpage rate on dead lodgepole pine was brought down to the minimum, and Forests for Tomorrow has helped to reduce the costs of harvesting. Forests for Tomorrow is a program developed by the BC government to improve future timber supply. The program was introduced by the government in 2005 with an initial amount of $161M allocated over four years and it is anticipated to have a 3  $53.9M annual budget in future years (FFT, 2008). After an area is logged the licensee is required to plant and regenerate the area. For dead lodgepole pine stands if the area is deemed to be non-satisfactorily restocked in the understory then Forests for Tomorrow will pay for the post harvest planting (Mathewson, 2009). Growth of the current mountain pine beetle epidemic peaked in 2004, though the area of beetle attack continued to increase up to 2009 (NRC, 2011). While the rate of attack is decreasing, the epidemic is not over yet and will continue for a number of years into the future. Pine trees killed in the future will still then have a 15 year shelf life so salvage from the current epidemic will likely go on far into the future. In dry ecosystems it is evident that standing dead trees will not experience decay for many years (estimated 15-20 years) (Lewis, Hartley, 2006). The mountain pine beetle epidemic is also present in Alberta and in a number of north western states in the US. Since the outbreak has jumped over the Rocky Mountains it may get into the jack pine of the boreal forest. If the mountain pine beetle does get into the jack pine there are concerns regarding the potential of spread across the boreal forest (Shor, et al, 2009). If this happens then the epidemic will carry on long into the future. The hazards of working in these dead pine stands will then also be present in the other provinces with the boreal forest.  Types of hazards posed to workers in dead lodgepole pine stands As mentioned earlier, beetle killed pine stands are deemed to have a shelf life of up to 15 years (Trent et al., 2006). With the large volume of dead timber in the province it is likely that forest harvesting in these stands will occur right up to the 15 year mark. Under certain circumstances, these degrading trees can pose a real safety risk to workers—from falling branches to whole trees toppling over (Rakoch, Hawkins, 2006). Due to the wide variety of stand conditions that are affected by many variables such as time since death and site specific characteristics there are many hazards associated with standing dead trees. As well, hazards to workers will vary based on the phase of the operation that they are a part of. When standing dead trees start to decay they become unable to support themselves. Trees will lose their branches, tops and fall down completely when they are subjected to forces applied to them that are greater than the level of strain they are able to withstand. Trees are subjected to forces from gravity, wind and other trees that they come into contact with. Whole tree failure creates a danger zone greater than the height of the tree. The tree’s danger zone is the area around a danger tree where it poses a threat to people. If the tree is on sloped ground it may slide and roll, extending the danger zone. Whole tree failure is likely to be more of an issue in open areas where the trees are fully exposed to wind. In closed-in stands trees shield each other from the wind so wind speeds below the forest canopy will be lower. Partial tree failure includes dislodged tree tops, branches, slabs and chunks. During wind events, trees in a closed in stand come into contact with each other. In stands of dead pine where the tops are dry 4  and brittle these tree to tree contacts are more likely to cause breakage than in stands of live trees. The danger zone for partial tree failure depends on tree lean and ground slope. As crowns become larger, the force exerted on them by the wind increases; and as trees become taller, turning moment increases with the length of the lever arm (tree height) (Harris, 1999). Over time dead trees will begin to lose their foliage. When the trees lose their foliage their crowns become smaller and therefore force exerted on them from wind will decrease over time. A decrease in the force exerted on a tree will make it less susceptible to blow down. In the first few years after tree death when the trees still have their foliage they will also still have strength properties similar to when they were alive. Tree blow down while the trees still have full crowns will likely be similar to when they were still alive. Since they will be less susceptible to blow down once they have lost their foliage they will be able to remain standing for a longer period of time. Over time these standing dead trees decay especially in the roots which are what gives them there standing support. As the tree roots become more decayed and weaker the trees become more likely to fall down and not just during high wind events as would be the case in stands of living trees. The first workers to enter a site of proposed harvesting are people associated with the planning phase. Types of work that take place in the planning (pre harvest) phase include block boundary and road location, timber cruising and silvicultural planning. These activities involve workers walking through the forest and don’t involve the use of heavy machinery. Workers are surrounded by standing dead trees and are subject to hazards from all directions. Top and branch failure due to wind will likely be the greater hazards in this situation. Workers in the harvesting phase will be subject to the same as those in the planning faze but likely to a greater extent. Heavy machinery adds an additional set of forces that will be acting on the trees. Ground vibration due to machine operation, air movement in the case of a helicopter, or tree contact by a person, machine, log, or operating line may induce tree failure (Toupin, Filip, Erket, Barger, 2008). Dead trees that have been standing for many years will be very susceptible to tree failure from machinery activity. During the Cariboo Plateau outbreak it was found that the likelihood of log breakage when felling and handling killed pine trees increased with time since death (Lewis, Hartley, 2006). After heavy wind events, large amounts of dead pine forest may blow down even though the wood is still in a utilizable state and economically viable to harvest for a short period of time. Very little is known about decay in wood from a utilization perspective, though decay increases rapidly once the trees are on the ground (Lewis, Hartley, 2006). Downed trees in heavy blow down areas will be stacked and cause pressure loads on one another. Cutting through these trees may result in a pressure release which can be hard to predict and very dangerous (Sentrony, 2010). Post Harvest includes a range of activities including site preparation, tree planting and stand tending which may go on for many years after harvesting takes place. These activities will take place in areas cleared from logging, though workers will still be exposed to trees left behind in 5  retention patches and trees in the surrounding forest at the edges of the block. Leave trees and trees at the edge of the block are now fully exposed to wind.  Is British Columbia’s Wildlife/danger tree assessment process effective for use in Beetle killed Pine stands? In British Columbia a group called the Wildlife Tree Committee (WTC) has developed a wildlife/danger tree assessment procedure to provide a higher standard of worker safety. The WTC was formed in 1985 and is a committee composed of representatives from the provincial ministry of forests, mines and lands, the ministry of environment, worksafe BC, industry and labour as well as public interest groups (MFML, 2010). By definition a tree being labelled a “dangerous tree” means that it is a hazard to a worker due to its location, its physical damage, overhead conditions, deterioration of its limbs, stem or root system or any combination of these conditions (WSBC, 2008). A danger tree can be of any size and be live or dead. The assessment procedure involves taking note of features and conditions of the tree in question as well as the surrounding area and documenting all of the relevant information. Once all the required data is collected the tree is given a danger rating class and a wildlife tree value. The assessment is performed by an individual who has taken a wildlife/dangerous tree assessor’s course. The disturbance caused by trees being felled has the potential to dislodge defective parts in nearby trees – tops and limbs, portions of trees or whole trees can collapse. Other activities include yarding and loading, mechanical site preparation, road construction and use of helicopters (WorkSafe BC, 2008). In this paper I ask the question: Is the wildlife/dangerous tree assessment program appropriate for use in stands where nearly every tree in the stand has the potential to be a dangerous tree? Clearly an assessment of each tree in the stand prior to commencing work is not practical. This would be very time consuming and costly. Beetle kill pine salvage operations are already performed on a very tight budget. In 2005 Cooper and Associates based out of Prince George, BC did a study to evaluate the effectiveness of the wildlife/danger tree assessment procedures in mountain pine beetle killed and fire damaged stands. For the study, a total of 36 plots were located in dead pine stands throughout central BC. Out of the 321 trees that were assessed they confirmed that only 7 (2% of the population) were confirmed to be dangerous. While this study does confirm that dangerous trees are found in dead pine stands it does not show that the system is practical for use in all dead pine stands. As well this study did not show how these stands change over time. Knowing which trees are dangerous in a stand is most important so workers know which areas to avoid or take the necessary precautions. 6  In a healthy forest stand potential danger trees can be singled out for assessment. In stands where all of the trees are dead they all have the potential to be dangerous. While the majority of the trees in the stand may not be dangerous they make it much harder to locate the ones that are. Ideally we’d like to know where the dangerous trees are located in the stand but since this can’t be done practically at least knowing the increased level of danger working in dead pine stands may be better than nothing. While the wildlife/danger tree assessment program may not be effective in beetle killed pine stands in the manor that it was intended, it may still be an effective tool.  Beetle killed pine degradation and susceptibility to wind throw over time Over time dead lodgepole pine trees will degrade due to a variety of natural factors. As the trees rot they lose their strength properties and are unable to support themselves causing them to become danger trees until they eventually fall. The wildlife/danger tree assessment may not be practical for use in individual stands, though it can be an effective tool to better understand beetle killed pine stands overall. From their data, Cooper and associates (2005) found trends that showed how tree danger related to age and site variations. The trends are what would be expected, though the study gives greater details. The rate of decay for lodgepole pine varies from site to site as well different parts of the tree will decay at different rates from site to site. Root decay is much more prevalent in sites with higher moisture as well as stands nearing the age of ten. As the wood degrades the trees become more susceptible to wind throw. A few studies have examined deterioration of beetle-killed wood over time, using samples from the current outbreak in British Columbia (Lewis 2006, Trent 2006). There are many causes of strength degradation in dead wood. These include checking, sap rot and wood borer activity. Checks are cracks that form in the trunk of the tree. As the dead trees dry out the wood shrinks and the checks form. Trees in dryer sites are more prone to checking than trees in moist site. The checks in the tree then lead to additional drying. When lodgepole pine dries out it becomes lighter and much more brittle. Dry wood is more prone to breakage than wood that is green (Magnussen, Harrison, 2008). Lewis, Thompson, Hartley, Pasca (2006) found in their study that the greatest amount of checking occurred in the middle section of the tree trunk and that the top section had minimal checking. Since the wood in top receives significantly less checking it will dry much slower. This means that a heavier top is sitting on a light and brittle middle section. Saprot fungi and ambrosia beetles became established during the first 2 years post-mortality (Lewis, Thompson 2009). Indicated by depth of saprot penetration, saprot may be initiated sooner higher along the stem; however, as time advances, the depth of penetration at lower locations along the stem surpasses those at higher locations (Lewis, et al, 2006). Shortly after death, the trees will still have higher moisture content in their stems. Over time the stems dry out 7  through the roots and low portion of the trunk will remain moist by receiving moisture from the surrounding soil. The blue stain fungi that is transported by the mountain pine beetle and is found in the wood of all trees that have been attacked has been found to cause no detectable strength losses. After the trees are dead and their defences are no longer functioning and wood boring insects begin to invade the wood. In a study of wood borer damage to trees killed by the mountain pine beetle it was found that 29% of the trees had wood borer damage two years after mortality, and more than 50% of the trees had wood borer damage three year after mortality (Lewis, Thompson, Hartly, Pasca, 2006). Wood boring insects generally carry wood decaying fungal spores that germinate in the wood when brought in by the insects. The fungi partially break down the wood making it easier for the wood boring insects to bore into the trees. Strength loss will likely be greater in trees that have been infected with wood borers due to the introduction of additional wood degrading fungi into the trees as well as the damage from the insects boring through the wood.  Figure 1: Frequency distributions of time-since-death of fallen sample trees killed by mountain pine beetle (A), and years to fall of the same trees (B). Date of fall was determined by dating scars on live adjacent trees damaged when the beetle-killed tree fell over (Lewis, Thompson 2009).  Wind throw within the 1-5 year time period since tree death is fairly low (figure 1) and that significant amounts of wind throw starts to occur as the time since death approaches the 10 year mark. These graphs give show an average over a wide range of site types. Site specific fall down rates varied between moisture regimes dry, mesic and wet. In 1998 Preisler and Mitchell conducted a study done on fall rates of lodgepole pine trees killed by mountain pine beetle in thinned and un-thinned stands. In their study they found that snags began falling three years after death in thinned stands and five years in un-thinned stands. In thinned stands, 50% were down in eight years and 90% were down in 12 years. In un-thinned stands, 50% were down in 9 years and 8  90% were down in 14 years. These numbers closely resemble the findings of Lewis and Thompson in their study from 2009. Priesler and Mitchell (1998) also found that all beetle-killed trees broke off at the ground when they fell (eg. Figure 2). This means that the lower trunk of the trees were a weaker point than the roots in the ground. The results of both of these studies are averages from samples taken on a variety of site conditions. When looking at different site conditions blow down occurred sooner after death in areas that had higher moisture than sites that were dryer.  Wildlife tree patches It is standard practice to retain single or patches of trees throughout a harvest area for wildlife value. If dead trees are left in the open they almost certain to blow down and lose much of their wildlife value as well as pose a threat to silviculture workers that may be working in the area. Stubbed trees are retained snags or trees cut down to a height of 5m or less to meet workers compensation board requirements (Harris, 2001). Stubbed trees are much less susceptible to blow down and provide a safer alternative to leaving whole dead trees.  Figure 2: Fallen beetle pilled lodgepole pine broken off near the ground.  Dead pine trees in populated and recreational areas While the main focus of this paper was to look at worker safety in the forest industry, recreationalists also spend a lot of time in these forests. As well lodgepole and ponderosa pine are very common in populated areas around the interior of BC. In populated areas, dead trees are usually removed as the trees will eventually fall down and potentially cause damage. There are government programs in place to mitigate the post-beetle impact (NRC, 2007). In parks and other recreational sites simply removing the trees may not be the best option. Dead trees hold 9  much ecological value and provide habitat for many wildlife species. As well it may be too costly to remove them and the recreational value of the area may be lost if they are removed. Parks Canada policy considers that native insects and diseases are natural ecological processes that should be allowed to proceed without interference if possible. However, where insects or disease pose a serious threat to provincial lands, intervention may occur (Parks Canada, 2009). The forest service, as well as many forest companies has built recreation/camp sites in their timber areas. These sites may be closed to the public if they are deemed unsafe or they may remove the danger trees.  Assessing decay in standing trees in the field Through visual inspection alone it can be difficult to determine the level of decay throughout a standing dead tree. Internal decay may even occur on live trees even when they look perfectly normal on their exterior. Lawday and Hodges (2000) performed a study on using stress waves for detecting decay in standing trees. Their method involved inserting two screws into the tree, one with an attached accelerometer and the other to be struck by a calibrated hammer. While this method was found to be affective in detecting decay it is not time efficient. Another method is using ultrasonic sound waves. Ultrasonic devices use a sound wave sent through a tree to a receiver (USFS, 2010). This method only detects decay in the lower bowl of the tree and not the entire stem. A more straight forward method is to cut down and destructively sample the tree. This may be very time consuming, though it is the best way to determine decay throughout the entire tree.  My thoughts and observations working in dead pine stands Over the past few years I have been worked for a forestry consulting company as well as a forest licensee. Two of the summers spent with the consulting company were spent working almost entirely in dead lodgepole pine stands. In the summer of 2007 I worked in forests near Chetwynd, Tumbler Ridge, Dawson Creek and Fort St. James. My work included cut block boundary and road traversing, timber cruising and other tasks. I also spent one shift locating beetle attacked pine trees for removal in northern Alberta. In the summer of 2009 I was based out of Kamloops and worked in the surrounding areas including Clearwater, Ashcroft and Cache Creek. My work included locating cut block roads and boundary as well as other surveying tasks. Many of the contracts that we worked on were with the Forests for Tomorrow program. I have also spent two summers working on the BC coast. One with the consulting company and one with a forest licensee: working in both second and original growth timber. The forests I worked in around Chetwynd were green attack and one year old red attack. Although my knowledge of the danger tree rating system is minimal, these trees seemed to be in 10  similar structural condition to living trees. The forests I worked in around Fort St. James were still in the red attack stage, though had been attacked a few years earlier. In both regions the trees had not began to fall in whole tree failure from wind throw. While in Fort St. James I experienced two days of stormy weather with fairly high wind speeds. During these wind events there was significant tree to tree contact. When gusts came through the forest, broken branches literally rained to the forest floor. As well I witnessed multiple tree tops break off and fall to the ground. The size of the top section that fell were not of significantly large size, though if one were to strike a worker would likely cause serious damage and potentially death. During my summer in Kamloops I worked in dead pine stands that ranged from age class five to age class eight. Although I did not work in forests containing ponderosa pine I did drive through semi-open areas that contained beetle killed ponderosa pine daily. Throughout this summer I did not experience any days with considerable wind speeds while in the forest. As a result I did not observe these stands while under the applied forces of wind and tree to tree contact. What I did observe was that the majority of the beetle killed ponderosa pine in the more open areas had already blown down. All of the blown over ponderosa pine trees broke off about 10-30cm from the ground. Though, ponderosa pine in open areas is not of much concern for forestry workers. Another observation was that all of the lodgepole pine had significant checking. In fact the checking was so bad that in most of the areas the wood was destined to be pulp or hog fuel as it was too checked to cut boards from. Due to the large amounts of checking the wood in these stands will dry out significantly fast and become brittle affecting stability. As mentioned previously Lewis, Thompson, Hartley, Pasca (2006) found that the greatest amount of checking in dead lodgepole pine trees occurs in the middle section with next to none in the top section. Since checking results in faster drying, a likely outcome of this is a heavy top sitting on a light and brittle middle section. This data correlates to what I observed while working near Fort St. James. While the main sections of the trees seemed to be structurally sound the tops were breaking off at a much more frequent rate than would be expected in a stand of living trees. This may have been attributed to the fact that the tops would contain more sapwood which decays at a faster rate than heartwood (Mitchell, 2011). Going between working on the coast and the interior there were no additional safety requirements or recommendations for working in dead pine stands. While there were work cut off’s for high levels of wind and rain, the wind cut off was not lowered for work in dead stands of pine. On the coast it was a requirement to wear caulk boots and a hard hat. While in the interior these were both considered optional.  11  Discussion In the interior of British Columbia there is currently a large amount of forest harvesting going on in stands that have a large component of dead lodgepole pine. This will continue into the future for as long as it is economically viable. Over time the dead lodgepole pine trees begin to break down and have the potential to become hazardous to people that spend time in these forests. From falling branches to whole tree failures dead pine trees pose a real safety risk to workers in these forests. Since lodgepole pine has found to hold commercial value for many years after tree death work in these stands has been and is likely to continue to take place in them. Due to the fact that the majority of the trees in the stand of beetle killed pine have the potential to be a danger tree the current wildlife/danger tree assessment method is not practical for use in its traditional form. In standard practice a potentially dangerous tree would be given a thorough assessment by a qualified individual. Since the assessment is performed visually from the ground it is impossible to determine how stable the top portion of the tree is unless there are visual defects. For an individual tree there may only be a small chance that it has a weak top while appearing normal. Though, the chance of this increases drastically when considering an entire stand. Locating and assessing danger trees is done in the pre-harvest phase so workers are exposed to these trees throughout the process. It seems a though marking danger trees is aimed towards safety for the harvesting phase, though from my experience there are significant hazards during all phases of operation in stands of dead lodgepole pine. Manning, Deans and Rowe (2005) recommend ceasing work when wind velocities reach 20 km/h in stands dead for more than 15 years in moist or wetter sites. They did not give any other recommendations regarding ceasing work at certain wind speed velocities. I believe that this is not adequate as they only took whole tree failure into consideration and based their recommendations solely on their finding from the wildlife/danger tree assessment method. Over time dead lodgepole pine trees become less able to support themselves and are more likely to fail in part or in whole during wind events. Whole tree failure seems likely to be the result of decay in the roots or lower portion of the tree bowl. Partial tree failure seems to be more likely to result from checking and drying causing the wood to become more brittle.  12  Recommendations Until more is known about the time frame of fall-down for beetle-killed trees, safety planning is essential to ensure that workers are not exposed to the hazards of danger trees in these stands (Rakochy, Hawkins, 2006). Safety requirements alone will not prevent accidents and injuries from occurring. Workers need to be made aware of the hazards in the work place so they can make their own judgement calls while in the field. From my research and personal observations I have come up with a few recommendations for companies with employees working dead pine stands to increase the level of safety. Stand level rather than single tree risk assessment. Hard hats to be worn at all times working in stands containing dead pine. Creation of a wind cut-off speed specific to stands of dead pine. Provide sufficient information of hazards and dangers of working in stands of dead pine to workers. Due to the limitations of research done on stands of dead lodgepole pine I am unable to recommend a specific wind velocity as a cut off for work. A stand level survey using random sampling could be used to determine the stand level danger tree risk. This could be incorporated into other types of surveys such as timber cruising.  13  Literature cited Ministry of Forests, Mines and Lands. Mountain Pine Beetle Faq’s. Government of British Columbia. February 2008. Source: http://www.for.gov.bc.ca/hfp/mountain_pine_beetle/faq.htm#6 Work Safe BC, Forestry Operations and similar Activities. May 2008. Source: http://www2.worksafebc.com/Publications/OHSRegulation/Part26.asp#SectionNumber:26.1 Ministry of Forests, Mines and Lands. Wildlife Tree Committee of British Columbia. Government of British Columbia. February 2008. Source: http://www.for.gov.bc.ca/hfp/values/wildlife/WLT/index.htm E. Todd Manning, A. Deans, D. Rowe Manning. An Assessment of Tree Condition and Worker Safety Concerns in Mountain Pine Beetle-killed and Fire-damaged Lodgepole Pine Stands in Central Interior British Columbia. Cooper and Associates Northern Interior Office, Prince George, BC. December 2005. M. Sentrony. Personal communication. June 2010. T. Trent, V Lawrence, K Woo. A wood and fibre quality-deterioration model for mountain pine beetle-killed trees by biogeoclimatic subzone. Natural Resources Canada. Canadian Forest service. Victoria BC. October 2006. Lewis, K.J.; Thompson, D 2009.Change in wood quality and fall rate of trees up to ten years after death from mountain pine beetle. Natural Resources Canada, Canadian Forest Service, Pacific Forestry Centre, Victoria, BC. Mountain Pine Beetle Working Paper 2008-30. 30 p. R. Toupin, G. Filip, T. Erkert, M. Barger 2008. Field guide for Danger Tree Identification and Response. United States Department of Agriculture, forest service pacific northwest region, united states department of interior, Bureau of Land Mangagement. Work Safe BC. Wildlife/Dangerous Trees Awareness: a safety guide for logging operations. February 2008. S. Magnussen, D. Harrison 2008. Assessing the shelf life attributes of mountain pine beetlekilled trees. Natural Resources Canada. Canadian Forest Service. Pacific Forestry Centre. Victoria, BC. J. Kadla, F. Lam, I Zaturecky. Chemical, mechanical, and durability properties of mountain pine beetle infested timber. Mountain Pine Beetle program. Natural Resources Canada. Canadian Forest Service. Pacific Forestry Centre. Victoria, BC. February 2008.  14  A.S. Harris. Wind in the forests of Southeast Alaska and Guides for Reducing Damage. United States Department of Agriculture. Pacific northwest Research Station. Forestry Sciences Laboratory. Juneau Alaska. July 1999. Natural Resources Canada. Mountain Pine Beetle Initiative Epidemic Risk Reduction and Value Capture Research and Development Strategy. Canadian Forest Service. Victoria BC. April 2004. Forests for Tomorrow. What is the Forests for Tomorrow Program?. Ministry of Forests. Government of British Columbia. 2008 Source: http://forestsfortomorrow.com/fft/home/whatforests-tomorrow-program Natural Resources Canada. Sustainability indicators: Mountain pine beetle. Canadian forest Service. Victoria BC. July 2010.Source: http://canadaforests.nrcan.gc.ca/indicator/mountain pinebeetle T.L Shore, A. Fall, C. Burnett, W.G. Riel. Characterization of the Jack Pine Forests of Wester Canada for Susceptibility to Infestation by the Mountain Pine Beetle. National Resources Canada. Canadian Forest Service. Pacific Forestry Centre. Victoria BC. April 2009. K. Lewis, D. Thompson, I. Hartley, S. Pasca. Wood decay and Degradation in standing lodgepole pine (Pinus contorta var. Latifolia Engelm.) killed by mountain pine beetle (Dendroctonus ponderosa Hopkins: Coleoptera). Natural Resources Canada. Canadian Forest Service. November 2006. Mitchell, R.G.; Preisler, H.K. Fall rate of lodgepole pine killed by the mountain pine beetle in central Oregon. Western Journal of Applied Forestry 13(1): 23-26. 1998. Natural Resources Canada. Federal Mountain Pine Beetle Program Hazard Tree Removal from Municipal Lands. Municipal Forestlands Element. July 2007 Parks Canada. Yoho National Park of Canada: An old Tree Problem. National parks of Canada. October 2009. K.J. Lewis, I.D. Hartley. Rate of deterioration, degrade, and fall of trees killed by mountain pine beetle. BC Journal of Ecosystems and Management. Forrex Forest Research Extension Partnership. February 2006. P. Rakochy, C. Hawkins. Wildlife/danger tree assessment in unharvested stands attacked by mountain pine beetle in the central interior of British Columbia. BC Journal of Ecosystems and Management. Prince George BC. May 2006. B. Harris. Observations on the use of stubs by wild birds: A 10-year update. B.C. Journal of Ecosystems and Management. Southern Interior Forest Extension and Research Partnership. Penticton BC. 2001. 15  C. Mathewson. Personal communication. May 2009. S. Mitchell. Personal communication. March 2011. G. Lawday, P.A. Hodges. The analytical use of stress waves for the detection of decay in standing trees. Institute of Chartered Foresters. Buckinghamshire Chilterns University College. High Wycombe Bucks England. 2000. United states forest service. Evaluation of Decay Detection Equipment in Standing Trees. United States Department of Agriculture. Technology and Development Program. 2010. Source: http://www.fs.fed.us/t-d/programs/im/tree_decay/tree_decay_detect_equip.shtml  16  


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