Roundheaded Pine Beetle Epidemic: Coconino National Forest Flagstaff, Arizona

Transcription

1 Roundheaded Pine Beetle Epidemic: Coconino National Forest Flagstaff, Arizona Brian Jeske Undergraduate Thesis: Environmental Science 1

2 Abstract Flagstaff, Arizona has one of the largest ponderosa forests in the U.S that consists of 1.8 million acres. The Coconino National Forest extends from western New Mexico to north-central Arizona, and he area is currently being attacked by numerous anthropogenic stresses that are killing the pondersoa pine trees. This study examines the Coconino National Forest, there are many different stresses that are now killing the trees. This study examines stress is the roundheaded pine beetle that is negatively impacting this forest structure of the ponderosa pine (Pinus pondersoa) forest. Roundheaded pine beetles are shiny dark-brown to black insects that attacks the ponderosa pine trees by eating into the moist tissue of the tree, soon enough stressing out the tree and leaving a snag behind. After examining the results Diameter at Breast Height (dbh) and Lean were significant. This sub-study is part of a larger study done on snags killed by bark beetles and wildlife use of snags, which includes the Coconino and Kaibab National Forest. It was funded by a grant from the Natural Science Foundation given to Joy Mast (Carthage College) and Carol Cambers (Northern Arizona University). Therefore, this study examines factors that influence whether or not a tree is susceptible to roundheaded pine beetle attacks. Introduction Understanding how the recent infestation of pine beetles is interacting with other stresses in the ponderosa pine forest will improve management and preservation of these ecosystems. As a part of a larger study, by Joy Mast (Carthage College) and Carol Chambers (Northern Arizona University), which examines snags killed by bark beetles and wildlife use of snags that included Coconino and Kaibab National Forest that is funded by the Natural Science Foundation, this study examined evidence of roundheaded pine beetles (Dendroctonus adjunctus) attacks in the Coconino National Forest. Coconino National Forest consists of 1.8 million acres of land on the Colorado plateau near Flagstaff Arizona. The landscape ranges from ponderosa pines (Pinus ponderosa), desert, flatlands, and alpine tundra to ancient volcanic peaks (Covington 1997). There are many different kinds of stresses that are affecting the forest, but more closely looking at the attacks of the roundhead pine beetle. Roundhead bark beetles chew through the bark and dig a chamber in to the moist tissue of the tree below the bark (Cain and Costa 2

3 1990). These attacks that tend to develop in poor sites and ridge tops of slopes (Massey, 1977) have led to thousands of ponderosa pine trees being killed due to the infestation. Therefore, this study examines what influences whether or not a tree is susceptible to beetle attacks. Background/Literature Review Northern Arizona has the largest ponderosa pine forest in the world, extending from western New Mexico to north-central Arizona (Friederici 2003) (Map 1). Flagstaff, Arizona, was first settled by the Euro-American in the 1870 s (Friederici 2003). The city is growing rapidly with a population of more than 65,338 people as of Coconino National Forest was originally established in 1898, which at that time was called the San Francisco Mountains National Forest Reserve (Covington 1997). Later in 1908, it was merged with the surrendering lands to later become the Coconino National Forest. The Coconino National forest is made up of 1.8 million acres with many species of tree. At the lower elevations on drier sites, these include Gambel oak (Quercs gambelii), New Mexico locust (Robinia neomexicana), junipers (Juniperus spp.) and piñon pine (Pinus edulis). At the higher elevations with more moisture, species include quaking aspen (Populus tremuloides), Douglas-fir (Pseudotsuga menziesii), white fir (Abies concolor), Engelmann spruce (Picea engelmannii), limber pine (Pinus flexilis) and ponderosa pine (Pinus ponderosa) (Mast 1999). Prior to Euro-American settlement, the forest structure and composition was most influenced by frequent low- intensity surface fires, climate cycles (especially droughts) and insect outbreaks (Swetnam and Bentancourt 1998). Incidence of insect breakout has increased however; as population increases these natural fires have been suppressed, resulting in an increased understory density (Furniss 3

4 and Carolin 1977). Influences as a result of this increase forest density on the ecosystem have impacted over 100,000 acres of damaged podersona trees due to pine beetle attacks in late summer and fall of 2002 (DeGomez 2004). The main outbreak that this study focused on is the native roundhead pine beetle, which attacks ponderosa pine trees by eating into the trees moist tissue killing the tree. Roundhead pine beetle woodborer adults could be over one inch in size with antennae s usually longer than the body, which gives them an alternate name of longhorned beetles. Once male beetles enter the chamber, mating soon takes place (Furniss and Carolin 1977). Female beetles then dig tunnels in the inner tree bark that can be up too 25 to 50 mm (Furniss and Carolin 1977). Eggs produced by the female are laid individually within the chambers. They then look like fleshy, cylindrical and elongated grubs. Most of the roundhead pine beetles complete their life cycle in one year, although ten percent of the brood may take two years (Lucht 1974). The greatest outbreak of these newly developed beetles emerges in late October and early November. The evidence of roundhead pine beetle attacks on the remaining dead-standing tree include brownish-red colored sap that drips down from the snag. These beetles can kill up to 50 percent of conifer forest (Lucht 1974). The roundhead pine beetles previous studies (Lucht, 1974) often select ponderosa pine trees that have been weakened and are already fighting an environmental stress. These stresses could either be the climate such as droughts or other diseases. Flagstaff has four-season climate with an average temperature of 26 C in the summer and 7 Cin the winter. Flagstaff has an annual precipitation of 22 inches per year with a range of 9 to 39 inches during the summer and an average of 97 inches of snow annually. During the summer time from mid July to mid September, Flagstaff has a monsoon season. The four 4

5 driest years since 1951 were 1956, 1996, 2000 and 2002 (Gatewood, 1962). The period 1996 to the present was a server drought for northern Arizona, which stressed out the trees causing them to die. Climate is an important influence in the southwestern ponderosa pine seed production, germination and seedling establishment (Pearson 1923). Ponderosa pine forests in northern Arizona become susceptible to bark beetle outbreak due to below normal winter precipitation and also normally dry conditions during May and June (DeGomez, 2004). In moisture levels in the fall/winter were 6.9 below normal leaving to a death of millions of trees in 2002 (DeGomez 2004). Compared to precipitation levels during the fall/winter of the were 2.3 and 2.4 inches below normal (DeGomez 2004). Due to the below normal moisture and precipitation levels, over-wintering beetles were able to emerge and significantly increase tree mortally compared to prior to In 2003, air photos determined that the ponderosa forest showed the greatest number of acres affected. Damage levels will depend on the weather patterns throughout the years to come. If the weather patterns continue, the ponderosa forest can become one on the most damaged forests in the world due to pine bark beetles. Not only does climate have a factor in stressing out trees, but also diseases play a major factor on a trees life. The most serious disease in the ponderosa forest is the dwarf mistletoe. Southwestern dwarf mistletoe (Arceuthobium vaginatum) (an invasive species) is becoming a critical disease agent that is widespread throughout the southwestern pine forest. This disease ranges from the Arizona to New Mexico, Colorado, southern Utah, and east to west Texas (Hawksworth and Shaw 1987). Nearly 40 percent of the commercial ponderosa pine types throughout the Southwest are affected by dwarf 5

6 mistletoe (Maffei, 1989), but can be higher in percent affected. Dwarf mistletoe can affect ponderosa forests in many ways, including reduced growth, diameter, height and volume of growth. They do not affect the total height or volume until the dwarf mistletoe reaches the canopy of the tree. Also, the dwarf mistletoe increases the mortality rate. The infection by the ponderosa pine dwarf mistletoe, particularly when severe, accelerates tree mortality (Korstain and Long 1922). In addition, dwarf mistletoe will reduce the cone and seed production when affected. In a previous study, Korstain and Long (1922) found that in Arizona there was about a 75 percent less seed production from the ponderosa pine that had been affected compared to uninfected tree. Historical data for Arizona and New Mexico indicates that 1 to 2 percent of the ponderosa pines were attacked by mistletoe, although some areas experienced heavier infestations (Woodsey 1911; Wilson and Tkacz 1993). Since dwarf mistletoe stresses pines, ponderosa pines that are heavily infected with dwarf mistletoe are often then attacked and killed by secondary bark beetles (Parker 1979; Stevens and Hawksworth 1970, 1984). Although ponderosa pines are affected by climate and disease, they also are impacted by fire suppression. The number of old ponderosa pine trees in the southwest forest has fallen since settlement, partly because of an increase in logging, but also from increases in competition from dense young trees (Sutherland 1991). The Southwestern forests are experiencing more intense canopy fires, including areas where bark beetle and drought killed trees (DeGomez 2004). Numerous, low-intensity fires are the natural disturbance for northern ponderosa pine forest. But because the forest too dense, fires are climbing up younger trees and burning the crowns of canopies One benefit from having prescribed fires is that older ponderosa pine increased in volume, basal area, and height 6

7 growth especially when competition was reduced because other trees were killed out due to the fire (Morries and Mowat, 1958, Cooper, 1960, Weaver 1967). A study of long-term ponderosa pine growth that had prescribed burns in northern Arizona found that prescribed fires every four to six years would reduce the forests fuel loads without reducing the long-term growth of the tree (Peterson 1994). Trees compete with each other for soil resources, in particularly water and nitrogen (Mast 1999). If the forest becomes so dense that young trees are slowing the growth down of older individuals, older trees become more susceptible to disease and secondary bark beetle infections. This is not just happening in the Coconino National forest, but also throughout the western U.S. This leads me to believe that the difference between ponderosa pines killed by roundhead pine beetles opposed to other factors are influenced by tree condition, tree density, and plot location (topography). Hence I hypothesize that in tree condition, beetle attacks will have more of an impact on larger more mature trees when having to compete with new saplings. Tree density, is expected to influence beetle outbreaks so that beetle attacks will be greater in areas with higher amount of trees making it easier for bark beetles to move tree to tree. Also I expected that beetles would favor trees on slopes given that the tree is already being stress rather then on flat ground. Beetle attacks are also expected to be found in less trees facing north due to higher moisture in the air, which would not give the trees the stress of drought. Experimental Procedure/ Field Methods Field experiments took place during the summer of 2008 in the Coconino National Forest in Flagstaff, Arizona. Three plots that contained snags that had been 7

8 attacked by roundhead pine beetle were sampled (Figure 1). Within each 1 ha plot, snags were examined for signs of roundhead pine beetle attack. Roundhead pine beetle attacks produce a reddish brown dust on the bark. Once the research team found these snags, protocols were then applied for tree condition, tree density and site condition (Chambers and Mast, 2005) Protocols for tree condition consisted of size, which is measured by diameter at breast height (dbh) (had to be greater then 10 cm in diameter). Dbh was taken at breast height (1.4 meters above the ground) in centimeters. Height of tree was found using a range finder standing either 15.5 meters away or 32.5 (higher the tree, greater the distance you had to stand). Once the distance was determined, the height of the snag was taken in meters with a clinometer. Clinometer measures vertical angles, tree height and slope. For each snag, top condition was recorded as either intact or broken. Limbs were also counted if greater 10 cm in diameter and greater then 30 cm in length. The last protocol for tree condition was lean that was measured using a clinometer to determine the degree lean of the snag perpendicular to the ground. Tree density was determined by looking at live and dead trees around each snag using a BAF prism. Live (BA alive) and (BA dead) trees around the snag were found. Site condition of plots included the slope of the land and aspect of the tree. Slope of the snag was calculated by the percent average from 20 meters up slope and 20 meters down slope using a clinometer. The aspect of the dead snag was determined by looking at the direction the snag faces in degrees (0 to 359) with a compass. (Figure 1) Study sites in Coconino National Forest (Google Earth Image 2007) 8

9 Qu ic k Tim e and a d ec o m pres s or are needed to see this picture. Sites where located off of forest road 151 off of highway 180. Sites were located on a single-track road running along side of Hochderffer Hills, Flagstaff Arizona. Results We tagged and measured a total of 426 snags, consisting of 318 beetle killed and 108 non-beetle killed snags within the Coconino National Forest. This was over a total of three individual plots combined into one data sheet. The results when using (T<=t) twotail T-test assuming equal variance were then looked at in the overall data to see if there was any significance. In the overall data, there was only significance in dbh and lean (Table 1). Dbh for beetle killed averaged cm with a range of 60cm (Figure 2). Dbh for non-beetle killed had an average of 18.16cm with a range of 40.1cm (Figure 2). However, when looking at lean, which had a significant P-value, beetle killed averaged 5.54 with a range of 26 (Figure 3). Non-beetle killed lean averaged with a range of 56 (Figure 3). 9

10 Beetle-killed and non-beetle killed snags were differently impacted by dbh (P= , Table 1) and lean (P= , Table 1). This meant that larger snags tended to have been more often influenced by beetle attacks then did smaller snags. Trees that were in an upright position found out to be less impacted by beetle attack then trees that were leaning. I suspected that if you were to look at the plots individually, that there could be a difference in significant P-values that weren t shown in the overall data table. Plot 1, consisted of 212 snags tagged total, with 155 being beetle killed and 57 being non-beetle killed snags. The results when using (T<=t) two-tail test assuming equal variances showed that lean and aspect were significant. Lean for beetle killed averaged 5.66 with a range of 26 (Figure 4). Non-beetle killed averaged 9.81 with a range of 50 (Figure 4). Lean had a significant P-value of (P=0.0003, Table 2). This meant beetles attacks favored straighter trees rather then trees that were already leaning. Aspect also had a significant P-value (P=0.0213,Table 2). Aspect ranged from 120, and even though aspect had a statistical significance, its not ecological significant to trees. Plot 2, consisted of 174 snags tagged total, with 140 being beetle killed and 37 being non-beetle killed snags. Results from plot 2 varied from overall data giving significance to BA alive, POTR (aspen). Results also showed that dbh and lean were again significant to using (T<=t) two-tail test assuming equal variances. Dbh for beetle killed averaged 22.18cm with a range of 26.60cm (Figure 5). While dbh for non-beetle killed averaged 15.5 having a range of 16cm (Figure 5). Beetle killed and non-beetle killed P-value was (P=4.4634E-8, Table 3). Lean had an average for beetle killed of 5.72 with a range of 60 (Figure 6). Non-beetle killed for lean averaged with a 10

11 range of 56 (Figure 6). Beetle killed and non-beetle killed P-value was (P=0.0009, Table 3). Tree density for BA alive, showed POTR (aspen) to have a average of 8.28 beetle killed with a range of 90 (Figure 7). Non-beetle killed had an average of with a range of 170 (Figure 7). Beetle killed and non-beetle killed P-value was (P= , Table 3). Plot 3, consisted of 37 total tagged snags, 23 being beetle killed and 14 being nonbeetle killed. Plot 3 had significances in lean and aspect using (T<=t) two-tail test assuming equal variances. Lean averaged for beetle killed to be 3.63 with having a range of 30 (Figure 8). Non-beetle killed snags for lean averaged with having a range of 45 (Figure 8). Beetle killed and non-beetle killed P-value was (P=0.0171, Table 4). Aspect also had a significant P-value (P=0.0109). Aspect ranged from 42 in beetle killed snags and 34 in non-beetle killed snags. Discussion Roundheaded pine beetle outbreaks are becoming a major factor in killing trees in the Coconino National Forest. After examining the results tree condition was examined at first to determine whether beetle attacks will have more of an impact on larger more mature trees. Dbh (diameter at breast height) and lean were the two major factors, which supported my hypothesis and showed significance in using (T<=t) two-tail test of similar difference. Each of these two protocols that were implemented in the research showed the P- value to be less then Dbh was significant in plot two and in the overall data, with lean being significant in each individual plot and overall data. I was not surprised in finding that dbh was significant because larger more mature trees need more nutrients and water to survive, which leaves them more open to be attacked by roundheaded pine 11

12 beetle. Having the tree stressed out in competing for nutrients in its ecosystem, this leaves the tree weakened and susceptible to bark beetle damage that could lead to possible mortality. For lean, however, I was surprised to find out that lean was greater in nonbeetle killed snags rather then beetle killed snags. I suspected that lean would be influence by beetle killed, due to making it easier for the beetles to transfer from tree to tree. This leads me to believe that lean could be post-death. Post-death means that after the tree is already killed, mainly by other factors, it then started to lean. For an example, an increase in high winds could have uprooted the tree giving this tree a different mortality even before roundheaded pine beetle attack the snag. Tree density, which was suspected, would be higher in locations with lots of trees giving bark beetle attacks to be greater, was not significant. Results showed only in table 3, plot 2, aspen had a significant P- valve, which was less then 0.05, but not in the overall data table. Non-beetle killed vs. beetle killed had a greater mean value, but overall there were fewer aspen in beetle killed. Less aspen in this plot means that there was more of a pure stand of ponderosa pine, which increased bark beetle spread and severity. Finally, site condition was the last protocols studied in this research. Under site condition we focus on percent slope and aspect to see if there was any significance when comparing non-beetle killed to beetle killed. Site condition for slope, suspected to find that beetle attacks would be more likely affected trees on a slope then on flat ground. Looking at the data, you can determine that there was no significance P- valve and this hypothesis was not supported. Slope, however did not show stress to the tree, unlike how I thought it would in having the tree more susceptible to bark beetle attacks. Aspect, which was thought to have beetle attacks, found less in trees facing north also was not 12

13 supported. Even thought in plot one and two there was a statistical significance P- valves, it is not ecological significant to trees and their mortality. Since there were more plots researched in the summer of 2008, which included the Kaibab Lake National Forest, this should have been included to give more of a statistical analyst into each hypothesis. Also when looking at more areas to compare, I only focus on three plots within the Coconino National Forest, which consists of 1.8 million acres. Having such a huge National Forest, there could be many areas affected by roundheaded pine beetle that were not sampled. Having more plots within the Coconino National Forest would give a better insight in determining how bark beetle spread and the mortality of trees. Even thought this was a sub-study off a main study done by Joy Mast and Carol Chambers, there are plots from the summer of 2007, which include different National Forest that are experiencing the same epidemic. This National Forest includes Turkey Hills and Sunset Crater. Including these National Forests within this study would also give a more of a direct answer in asking questions such as tree condition, tree density and site condition in how each play a factor in bark beetle attacks. Conclusion The importance to understanding what variety of characteristics of trees roundheaded pine beetles are attacking, brings of greater concern in knowing the role of this ecosystem. This ecosystem in the Coconino National Forest has a heavy density of trees and is experiencing dramatic changes. Having fire suppression take command in this National Forest, it is now taking a toll in killing over 100,000 acres tress from disease outbreaks, competition for nutrients, and now more recently of concern, bark beetle attacks. After studying and finding out that bark beetles do favor larger, more mature 13

14 trees, this means that this forest is being altered in a whole different way. Altered in meaning, bark beetles are found attacking fewer, and younger trees that are giving them a chance to out compete larger, more mature trees in the ecosystem. The whole forest structure will change with having new saplings come in and start to grow. Instead of having a older forest with more mature trees, this will be a newer forest with young sapling trees. My findings were only a snap shot of what could be done on a much more larger scale. There must be several areas within the Coconino National Forest of were bark beetle outbreaks are happening or happened. I only touch the base of were bark beetles outbreaks occurred. Because this was only a snap shot of looking at this epidemic of beetle outbreaks, the next step would be to include Kaibab Lake, Turkey Hills and Sunset Crater to get direct result when looking at tree condition, tree density and site condition. Acknowledgments I thank Dr. Joy Mast (Carthage College) and Carol Chambers (Northern Arizona University) for allowing me do a sub-study of their main study, which also included the nesting of birds. Also thank Dr. Tracy Gartner for constant reviews and improving my thesis as an undergraduate. (Map 1) 14

15 Distribution map of Ponderosa Pines in the West/Southwest of the United States 15

16 Table 1 Overall data for tree condition, top condition and tree density of the Coconino National Forest Preserve. Means and standard deviation for characteristics of snags in three 1-ha plots for beetle killed vs. non-beetle killed trees. OVERALL Variableª Beetle Killed Non-Beetle Killed n= 318 n= 108 Mean St. Dev. Mean St. Dev. P Tree Condition DBH (cm) Height (m) Top Condition (%) Intact Broken Limbs (#) Lean ( ) Tree Density BA alive PIPO POTR PIFL BA Dead PIPO POTR PIFL Site Condition Slope (%) Aspect ( ) Beetle killed vs. non-beetle killed in n is the number of snags measured in plots. P is probability (T<=t) two-tail test assuming equal variances (beetle killed vs. non-beetled killed). ª Dbh is diameter at breast height, intact and broke was looked at top condition of the snag, number of dead limbs (number of dead limbs >10cm diameter and >30cm length, lean (degree of snag lean from perpendicular to ground), percent slope averaged from two directions at 20 m from each snag, aspect (degrees) of slope on which the snag stood by using the natural line of travel that water would follow, basal area (using 20 BAF prism) of live and dead trees surrounding each snag. 16

17 Lean Dbh (cm) Jeske Diameter at Breat Height (DBH) Non-Beetle Killed Beetle Killed Figure 2 Dbh was averaged from plots 1, 2 and 3 this consisting of either Non-Beetle Killed snags or Beetle Killed snags. Non-Beetle Killed mean ± standard deviation Beetle Killed mean ± standard deviation Lean of Snag ( ) Non-Beetle Killed Beetle Killed Figure 3 Lean was averaged from plots 1, 2 and 3 this consisting of either Non-Beetle Killed snags or Beetle Killed snags. Non- Beetle Killed mean ± standard deviation Beetle Killed mean 5.53 ± standard deviation

18 Table 2 Plot 1 data for tree condition, top condition and tree density of the Coconino National Forest Preserve. Means and standard deviation for characteristics of snags in plot 1, 1-ha plot for beetle killed vs. non-beetle killed trees. PLOT 1 Variableª Beetle Killed Non-Beetle Killed n= 155 n= 57 Mean St. Dev. Mean St. Dev. P Tree Condition DBH (cm) Height (m) Top Condition (%) Intact Broken Limbs (#) Lean ( ) Tree Density BA alive PIPO POTR PIFL BA Dead PIPO POTR Site Condition Slope (%) Aspect ( ) Beetle killed vs. non-beetle killed in n is the number of snags measured in plots. P is probability (T<=t) two-tail test assuming equal variances (beetle killed vs. non-beetled killed). ª Dbh is diameter at breast height, intact and broke was looked at top condition of the snag, number of dead limbs (number of dead limbs >10cm diameter and >30cm length, lean (degree of snag lean from perpendicular to ground), percent slope averaged from two directions at 20 m from each snag, aspect (degrees) of slope on which the snag stood by using the natural line of travel that water would follow, basal area (using 20 BAF prism) of live and dead trees surrounding each snag. 18

19 Lean Jeske Lean of Snag ( ) NoniBeetle Killed Beetle Killed Figure 4 Lean was averaged from plot 1 consisting of either Non-Beetle Killed snags or Beetle Killed snags. Non- Beetle Killed mean 9.81 ± standard deviation Beetle Killed mean 5.66 ± standard deviation

20 Table 3 Plot 2 data for tree condition, top condition and tree density of the Coconino National Forest Preserve. Means and standard deviation for characteristics of snags in plot 2, 1-ha plot for beetle killed vs. non-beetle killed trees. PLOT 2 Variableª Beetle Killed Non-Beetle Killed n= 140 n= 37 Mean St. Dev. Mean St. Dev. P Tree Condition DBH (cm) E-8 Height (m) Top Condition (%) Intact Broken Limbs (#) Lean ( ) Tree Density BA alive PIPO POTR PIFL BA Dead PIPO POTR Site Condition Slope (%) Aspect ( ) Beetle killed vs. non-beetle killed in n is the number of snags measured in plots. P is probability (T<=t) two-tail test assuming equal variances (beetle killed vs. non-beetled killed). ª Dbh is diameter at breast height, intact and broke was looked at top condition of the snag, number of dead limbs (number of dead limbs >10cm diameter and >30cm length, lean (degree of snag lean from perpendicular to ground), percent slope averaged from two directions at 20 m from each snag, aspect (degrees) of slope on which the snag stood by using the natural line of travel that water would follow, basal area (using 20 BAF prism) of live and dead trees surrounding each snag. 20

21 Lean Dbh (cm2) Jeske Diameter at Breast Height (DBH) Non-Beetle Killed Beetle Killed Figure 5 Dbh was averaged from plot 2 consisting of either Non-Beetle Killed snags or Beetle Killed snags. Non- Beetle Killed mean ± standard deviation Beetle Killed mean ± standard deviation Lean of Snag ( ) Non-Beetle Killed Beetle Killed Figure 6 Lean was averaged from plot 2 consisting of either Non-Beetle Killed snags or Beetle Killed snags. Non- Beetle Killed mean ± standard deviation Beetle Killed mean 5.69 ± standard deviation

22 Average Jeske BA alive: POTR Non-Beetle Killed Beetle Killed Figure 7 BA alive: POTR was averaged from plot 2 consisting of either Non-Beetle Killed snags or Beetle Killed snags. Non- Beetle Killed mean ± standard deviation Beetle Killed mean 8.29 ± standard deviation

23 Table 4 Plot 3 data for tree condition, top condition and tree density of the Coconino National Forest Preserve. Means and standard deviation for characteristics of snags in plot 3, 1-ha plot for beetle killed vs. non-beetle killed trees. PLOT 3 Variableª Beetle Killed Non-Beetle Killed n= 23 n= 14 Mean St. Dev. Mean St. Dev. P Tree Condition DBH (cm) Height (m) Top Condition (%) Intact Broken Limbs (#) Lean ( ) Tree Density BA alive PIPO PIFL BA Dead PIPO PIFL Site Condition Slope (%) Aspect ( ) Beetle killed vs. non-beetle killed in n is the number of snags measured in plots. P is probability (T<=t) two-tail test assuming equal variances (beetle killed vs. non-beetled killed). ª Dbh is diameter at breast height, intact and broke was looked at top condition of the snag, number of dead limbs (number of dead limbs >10cm diameter and >30cm length, lean (degree of snag lean from perpendicular to ground), percent slope averaged from two directions at 20 m from each snag, aspect (degrees) of slope on which the snag stood by using the natural line of travel that water would follow, basal area (using 20 BAF prism) of live and dead trees surrounding each snag. 23

24 Lean Jeske Lean of Snag ( ) Non-Beetle Killed Beetle Killed Figure 8 Lean was averaged from plot 3 consisting of either Non-Beetle Killed snags or Beetle Killed snags. Non-Beetle Killed mean ± standard deviation Beetle Killed mean 3.65 ± standard deviation Work Sited 24

25 1. Cooper, C. F. "Ecological Monographs." Changes in vegetation, structure and growth of southwestern pine forests since white settlement (1960). 2. Covington, W. W., P. Z. Fule, M. M. Moore, S. C. Hart, T. E. Kolb, J. N. Mast, S. S. Sackett, and M. R. Wagner. "Journal of Forestry." Restoring ecosystem health in ponderosa pine forest of the southwest 95 (1997): Friederici, Peter. Ecological Restoration of Southwestern Ponderosa Pine Forest. Washington, D.C.: Island P, Furniss, R. L., and V. M. Caroline. "USDA Forest Service." Western Forest Insects (1977). 5. Gatewood, J. S., A. Wilson, H. E. Thomas, and L. R. Kister. "U.S Geological Survey Professional Paper." General effects of drought on water resources of the Southwest 372 ( ): B1-B Gatewood, J. S. "Geological Survey Professional Paper." The meteorologic phenomenon of drought in the Southwest 372 (1962): A1-A Hawksworth, G. F., and G. C. Shaw. Damage and Control of Major Diseases of Ponderosa Pine (1987): Korstian, F. C., and W. H. Long. "USDA Agricultural Bulletin 1112." The western yellow pine mistletoe: Effects on growth and suggestions for control (1922): Lucht, D. D. "Forest Insect & Disease Leaflet 155 Forest Service U.S. Department of Agriculture." Roundheaded Pine Beetle (1974). 10. Maffei, M. H. "Southwestern dwarf mistletoe damage to multi-aged ponderosa pine stands." Diss. Colorado State, Abstract. (1989): Massey, C. L., D. D. Lucht, and J. M. Schmid. Forest insects and disease leaflet 155. Washington, D.C.: USDA Forest Service, Massey, C. L. "Forest Insects & Disease Leaflet 155 Forest Service U.S. Department of Agriculture." Roundheaded Pine Beetle. 13. Mast, J. N., P. Z. Fule, M. M. Moore, W. W. Covington, and A. Waltz. "Ecological Applications." Restoration of presettlement age structure of an Arizona ponderosa pine forest 29 (1997): Morris, G. W., and E. L. Mowat. "Journal of Forestry." Some effects of thinning a ponderosa pine thicket with a prescribed fire (1958). 15. Parker, L. D. "USDA Forest Service, Southwestern Region." Integrated pest management guide in ponderosa pine (1979): Pearson, G. A. "U.S. Forest Service Bulletin 1105." Natural reproduction of western yellow pine in the Southwest (1923). 17. Peterson, L. D., S. S. Sackett, L. J. Robinson, and S. M. Haase. "International Journal of Wildland Fire." The effects of repeated prescribed burning of Pinus Ponderosa growth (1994): Stevens, E. R., and G. F. Hawksworth. "USDA Forest Service General Technical Report." Insect-dwarf mistletoe associations: an update (1984): Stevens, E. R., and G. F. Hawksworth. "USDA Forest Service Research Paper." Insects and mites associated with dwarf mistletoes (1970). 25

26 20. Sutherland, K. E., and W. W. Covington. "Forest Ecology and Management." A model of ponderosa pine growth response to prescribed burning (1991). 21. Swetnam, T. W., and J. L. Betancourt. "Journal of Climate." Mesoscale Disturbance and Ecological Response to Decadal Climatic Variability in the American Southwest 11 (1998). 22. United States Forest Service. Arizona State Land Department. "For Immediate Release: Pine Beetle Outbreak in Arizona." Press release. Flagstaff, Arizona. 23 June Weaver, H. Proceeding of the Tall Timbers Fire Ecology Conference, Aug Fire and its relationship to ponderosa pine White, S. A. "Ecology." Presettlement Regeneration Patterns in a Southwestern Ponderosa Pine Stand 66 (1985): Wilson, L. J., and M. B. Tkacz. "USDA Forest Service." Status of insects and pathogens in the Southwest: Implications for forest health (1993). 26. Woolsey, S. T. "USDA Forest Service Bulletin." Western yellow pine in Arizona and New Mexico (1911). 26