Geo Alpine Treeline in the American West
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Geo Alpine Treeline in the American West

Course Number: COMP 006d, Fall 2008

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Influences of Geomorphology and Geology on Alpine Treeline in the American West More Important Than Climatic Influences? by David R. Butler* Department of Geography Texas State University-San Marcos San Marcos, TX 78666-4616 * corresponding author e-mail: db25@txstate.edu phone: 512-245-7977 fax : 512-245-8353 George P. Malanson Department of Geography University of Iowa Iowa City, IA 52242 Stephen J. Walsh...

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of Influences Geomorphology and Geology on Alpine Treeline in the American West More Important Than Climatic Influences? by David R. Butler* Department of Geography Texas State University-San Marcos San Marcos, TX 78666-4616 * corresponding author e-mail: db25@txstate.edu phone: 512-245-7977 fax : 512-245-8353 George P. Malanson Department of Geography University of Iowa Iowa City, IA 52242 Stephen J. Walsh Department of Geography University of North Carolina Chapel Hill, NC 27599-3220 Daniel B. Fagre U.S. Geological Survey Glacier Field Station Glacier National Park West Glacier, MT 58836 1 Abstract The spatial distribution and pattern of alpine treeline in the American West reflect the overarching influences of geological history, lithology and structure, and geomorphic processes and landforms. These influences occur at spatial scales ranging from the continental scale to fine scale processes and landforms at the slope scale. Past geomorphic influences, particularly Pleistocene glaciation, have also left their impact on treeline, and treelines across the west are still adjusting to post-Pleistocene conditions. Digging by animals illustrates a slope-scale set of processes that impact treeline and that should be examined in detail in future studies to facilitate a better understanding of where individual tree seedlings become established. Key words: alpine treeline, geomorphic facilitation, geologic control, biogeomorphology, ecotone, Rocky Mountains, American West 2 Introduction Alpine treeline in the American West is the ecotone between coniferous forest at lower elevations and alpine tundra or bare bedrock above. Conventional wisdom in studies of alpine treeline in the west and elsewhere states that alpine treeline is primarily a result of some aspect of climatic or edaphic control (e.g., temperature, length of growing season, length of snow cover, soil temperature, or soil moisture, to mention some of the most commonly cited variables [see Holtmeier, 2003, for a magisterial coverage of climatic factors affecting treeline]). We assert here, however, that the impact of geology and geomorphology must first be examined as primary determinants of the location and pattern of alpine treeline, rather than climate. This assertion may be expressed most clearly as follows: climate is subservient to the role of geology and geomorphology across both spatial and temporal scales as a determinant of alpine treeline in the American West. This perspective on the importance of geomorphology and geology has also been mentioned by Holtmeier (2003) and Holtmeier and Broll (2005), although not to the extent that we assert here. They recognize three fundamental types of treeline: climatic, orographic, and anthropogenic (which we explicitly do not address here). Orographic treeline (Holtmeier [2003] prefers the term timberline) is always located more or less far below the elevation to which the forest would advance at the given climatic conditions (Holtmeier (2003), p. 25), and is induced by steep rocky trough walls, talus cones, slope debris and avalanche chutes (p. 25). This perspective on the role of geomorphic conditions and disturbances goes partway to our perspective, but does not go 3 sufficiently far, because even climatic treelines illustrate, through the fine-scale patterns of seedling distribution, the role of geomorphic processes and landform patterns. Inherent geological conditions also strongly influence treeline locations and patterns, and also frequently trump climate as the primary causal control on those locations and patterns. Kruckeberg (2002) asserts in effect that all plant distributions are the result of geological control, and although we do not go that far in our perspective on the role of geomorphology and geology as treeline determinants, our position is closer to his than that of Holtmeier. As Wiegand et al. (2006, 880) noted, treeline features are not arbitrary but . there is a clear signal in the pattern which allows for inference of the underlying processes. We assert that those underlying processes are geomorphic and geologic. Spatial and Temporal Scales at Treeline A consideration of scale is critical to our position on geomorphology and geology at treeline. Most studies of treeline have focused on the plants themselves rather than on the broader pattern. Even global scale analyses have been about global patterns of temperature influences on individual plant physiology (e.g., ). Malanson et al. (here) have emphasized multiple scale interactions, but primarily examine how affects at finer scales influence patterns at coarser scales, not vice versa. While we also consider finer scales, we take a somewhat inverted approach and consider the scale question from the perspective of what constraints coarser scale phenomena impose on finer scale process and pattern relations. The importance of coarse scale constraints can affect what happens to individual plants if one follows the constraints down the hierarchy. 4 In their examination of the Western Cordillera of North America, Malanson and Butler (2002) identified four spatial scales of significance for the study of mountains there the continental scale, the mountain range scale, a within-range scale, and a withinvalley scale. Here, we compress and slightly revise these into three scales of note: the continental-to-range scale, the within-range scale, and the slope scale, the latter term better encompassing the finer processes and landforms associated with local issues of alpine treeline. We examine each of these in sequence below, with specific examples of where treeline conditions are at least moderated, if not outright controlled, by geology and geomorphology. Issues of temporal rates of change at treeline are also addressed where appropriate. Our examples are taken from mountain ranges throughout the American West (Table 1), many of which serve as primary and secondary sites for the U.S. Geological Surveys Western Mountain Initiative program (Figure 1). Continental-to-Range Scale At the geographic scale of an individual mountain range or larger, geology trumps climate as a primary control of treeline, because plate tectonics are responsible for the very presence of the mountains (Malanson and Butler, 2002). Kruckeberg (2002, p. 87) conjectures that (m)ajor weather systems are products of the mountain systems they encounter. From that perspective, all mountain weather and climate is a function of plate tectonics, and thus all treelines are controlled by geological histories associated with each respective mountain range. This perspective does, of course, ignore the postorogenic reality of varying climates within a mountain range; yet, even with varying climates at the within-range (or finer) scale, geology and geomorphology must be 5 considered as primary treeline determinants, as described below. The overall pattern of north-south trending ranges in North America, in line with the global latitudinal energy gradient and perpendicular to the west-east precipitation gradient, determines a continental gradient in treeline elevation but also in variation in glaciation coincident or not with current treeline, and so affects the degree of variation in landforms and geomorphic processes within ranges. Within-Range Scale Within an individual range, the geologic structure and glacial history determines the spatial arrangement of major ridges and valleys (Malanson and Butler, 2002), and thus the spatial pattern of treeline. For example, on the West Spanish Peak in the Sangre de Cristo Range of Colorado (Figure 2), treeline is a function of the structure of the peak (an intrusive stock with radiating dikes) which, upon exhumation, has induced the development of a radial drainage pattern that profoundly affects the upper limits of treeline. The stream channels radiating from the rounded peak create geomorphically active sites where trees are unable to survive at elevations where adjacent ridgecrests are tree-covered. The isolated Cascade Range volcanoes are another example where the geologic structure of a stratovolcano is the primary determinant of subsequent erosion patterns, and subsequently of treeline. Lithology also serves as the primary determinant of treeline within some ranges. In the White Mountains on the Nevada-California border, the location and pattern of upper treeline is a function of the distribution of sandstone versus dolomitic limestone (Wright and Mooney, 1965; Kruckeberg, 2002) (Figure 3). On the sandstones of the 6 White Mountains, treeline is well below the climatic limits where trees may survive, but on the dolomitic sites a zone of bristlecone pine (Pinus longaeva) extend up to the climatic limits of tree growth (Figure 4). The dolomitic sites are coarse and nutrient poor, but bristlecone pine is able to survive in such harsh conditions, whereas other trees and sagebrush cannot. On adjacent areas of sandstone, bristlecone pine could survive but is out-competed there by other tree species and particularly by sagebrush (Wright and Mooney, 1965). Although not exclusive to treeline sites, Parkers work (1991, 1995) also illustrated the significant role of lithology in determining tree species distribution and density in the Sierra Nevada and southern Cascades of California. Disturbance treelines (sensu the orographic treelines of Holtmeier, 2003) at the within-range scale are also typically a function of underlying geologic control. In Glacier National Park, Montana, for example, the presence of the Lewis Overthrust fault along the eastern edge of the Park powerfully influences the location of the disturbance/orographic treeline produced by large-scale bergsturz (Figure 5) (Oelfke and Butler, 1985; Malanson and Butler, 2002). In the same area, Butler and Walsh (1990) and Butler and Malanson (1992) illustrated that lithology and geologic structure exerted primary control over the spatial distribution of snow-avalanche paths, themselves a spatially widespread form of orographic treeline in the Park. Butler and Walsh (1994) showed that debris flows in eastern Glacier National Park severely depress alpine treeline below a hypothetical climatic optimum, and Walsh et al. (1994) did the same for snowavalanche paths. Both forms of mass movement are widespread throughout the West, and act throughout the region as a geomorphic inhibiter of upward advance of treeline. 7 Within most mountain ranges in the American West, one must also note that current treeline, geomorphic processes, and soils are still adjusting to climatic change covering a variety of time scales, i.e., many ranges are in disequilibrium with current climatic conditions. The effects of the Little Ice Age are probably most prevalent at the slope scale, and are discussed below; however, at the within-range scale, many areas in the West are still adjusting to the geomorphic effects of the Pleistocene. In the Grand Tetons, for example (Figure 6), deep scouring by alpine glaciers descending to the adjacent valley floor removed surface soils and exposed bedrock that has yet to recover with sufficient soils for trees to ascend to elevations where nearby trees exist in areas of deeper soil. In such a situation, conditions are slowly improving and will allow eventual tree establishment and upward movement, but at a rate slower than at sites with better soils/edaphic conditions (Figure 7). Elsewhere, such as in parts of the Sierra Nevada and Glacier National Park, Montana, the intensity of Pleistocene glaciation produced glacial landforms such as cirque headwalls (Figure 8) that are simply not going to be invaded by trees within the foreseeable future regardless of whether the current climate would allow it (Figure 9). The current-day disturbance treeline (Butler and Walsh, 1994; Walsh et al., 1994; Butler et al., 2003) also acts to preclude upward advance of treeline under currently prevailing climatic conditions. Overall, landforms also differentiate the patterns that plants can develop within the ecotone because of differences in slope extents and angles at the right elevation range. Broad gentle slopes exist just above treeline in Rocky Mountain National Park, CO, where treeline is compressed on steeper slopes, in contrast to the east slopes of the Snowy Range in Wyoming where treeline is spread across a broad gentle slope below the main 8 peaks. The coincidence of current treeline elevation with landforms determined by past glaciation varies across all of western North America. Slope Scale At first glance, the slope scale seems to best represent the influence of climate on treeline. Locations where the upper limit of tree growth approximates a straight line (Figure 10) suggest an upper altitudinal limit to tree growth imposed by climate (although even in these cases, geomorphic processes can impose a disturbance treeline upon a climatic treeline; Figure 11). In such cases, it is posited that seedling establishment above the general horizontal treeline represents a response to changing climatic conditions (e.g., Bekker, 2005; and Zeng et al., 2007, and references therein). In some areas in the West, however, the landscape is still adjusting to the end of the Little Ice Age, and upward advance of treeline has not occurred; instead, patches of krummholz have become denser and/or taller without upward movement (Butler et al., 1994; Klasner and Fagre, 2002). Such a situation certainly could be a function of a time lag, as suggested by Malanson (1999); however, it is also feasible that the geomorphic setting in the immediate surroundings of the patches is simply inimical for survival. Conditions immediately adjacent to the established patches were not colonized for a reason, whereas the patch was. We suggest that the conditions that were not appropriate for initial establishment were associated with geomorphic and geologic conditions deleterious to seedling establishment and survival. The issue of tree seedling establishment and survival at the slope scale has been addressed in previous research of the Mountain GeoDynamics Research Group (Allen 9 and Walsh, 1996; Malanson et al., 2002, 2007; Walsh et al., 2003; Butler et al., 2003, 2004; Resler et al., 2005; Resler, 2006; Zeng and Malanson, 2006; Zeng et al., 2007). This body of work has focused particularly on the role of fine-scale geomorphic processes and landform features as facilitators of tree seedling establishment and survival. This work has illustrated that, even in locations where climate at first glance seems to be the controlling factor at treeline, fine-scale geomorphic processes and landforms ultimately dictate where a tree seedling may become successfully established; or conversely, where a seedling will find geomorphically unfavorable conditions inimical to survival. Solifluction terraces are a relatively common landform found adjacent to treeline in many ranges in the American West (Figure 12) (e.g., Hansen-Bristow and Price, 1985; Caine, 2001; Walsh et al., 2003). Solifluction treads and risers are very difficult environments on which a tree seedling attempts to become established and survive; risers are comprised of dense tundra vegetation that is difficult if not impossible for seedlings to penetrate, and treads are rocky, barren, and highly susceptible to frost heaving (Butler et al., 2004). Soil conditions and quality vary little on the solifluction treads (Malanson et al., 2002), but in general are better with higher nutrient status than in adjacent krummholz (Malanson and Butler, 1994). On the solifluction surfaces, turf exfoliation (also known by the German term Rasenabschlung) facilitates tree seedling establishment by creating fine-textured, penetrable surfaces at the base of risers (Butler et al., 2004). These sites also offer topographic protection from wind and wind-driven ice, as do randomly distributed boulders across the tundra surface, where seedling survival is enhanced (Resler et al., 2005; Resler, 2006). At this fine scale, the geomorphic 10 conditions are what may serve as an accelerator that allows upward establishment and migration of the treeline (Figure 13). It is also interesting to note that the same geomorphic process (e.g., solifluction) may operate at a different scale in ranges across the West (Figure 12), but with the same general effect on treeline. Another slope-scale group of processes that may have profound localized effects on treeline alpine location and pattern is the work of digging by animals. Grizzly bears excavate widespread surfaces on slopes in the treeline ecotone (Figure 14) (Butler, 1992; Hall and Lamont, 2003), and these excavations produce higher concentrations of forms of nitrate than in adjacent, intact meadows (Tardiff and Stanford, 1998) that may benefit tree seedlings. Clarks nutcrackers (Nucifraga columbiana) bury whitebark pine (Pinus albicaulis) seeds throughout the West from the Sierra Nevada (Tomback, 1982) to northwest Montana (Resler and Tomback, in press), and their choice of burial locations determines where whitebark pine seeds sprout. Those choices may, in turn, benefit from localized protection (facilitation) offered by slope-scale geomorphic processes and geologic settings such as at the base of solifluction terraces, rock outcrops, or boulders (Figure 12). Numerous mammals also create widespread excavations at alpine treeline through the creation of a variety of burrow structures (Figure 15) (Butler, 1995; Hall and Lamont, 2003), and their digging activities may have pronounced effects on nitrogen and carbon in soils there (Aho et al., 1998). Virtually no research has been done at present, however, concerning whether or not these excavations aid or hinder tree seedling establishment and survival. Pocket gophers (Geomyidae) in particular have been examined for the role they play in affecting soils characteristics in alpine tundra adjacent 11 to treeline (Seastedt, 2001; Sherrod and Seastedt, 2001; Forbis et al., 2004; Sherrod et al., 2005). No work exists on the roles of gopher digging, gopher mounds, or gopherinduced changes in soil characteristics as facilitators of tree seedling success at alpine treeline. Gopher mounds in Georgia (Simkin and Michener, 2004) illustrated greater longevity of longleaf pine seedlings than in the surrounding matrix, although the difference was not statistically significant. Reichman and Seabloom (2002, 45) noted that mortality of seedlings tends to be very high on gopher mounds, because of exposure to herbivores and dry soil conditions, but they were not specifically addressing tree seedlings. They also pointed out that individual seedlings that survive on mounds are larger and produce more seeds than similar plants embedded in the surrounding plant matrix. Forbis et al. (2004) illustrated that recently created gopher mounds on Niwot Ridge, CO, had lower seedling emergence and survival rates than undisturbed areas in the first five years after mound creation, but also that the mounds had higher seedling emergence density from five years to at least 20 years after disturbance. The study by Forbis et al. (2004) was carried out in alpine tundra, however, and no tree seedlings were found in their seedlings that emerged on gopher mounds. Would mounds in the immediate treeline ecotone (Figure 15) show tree seedling emergence and survival? Schtz (2005) examined the question of whether gopher digging damaged young trees on Niwot Ridge, and found no evidence that pocket gophers are responsible for visible damage on juvenile conifers there. Given the potential significance of gopher mounds as a geomorphic facilitator or inhibitor at alpine treeline, we suggest that they merit greater examination. 12 Concluding Statements We are not dismissing the concept of climatic treeline here. Indeed, horizontal, roughly straight-line, treelines such as those illustrated in Figures 10 and 11 reflect a primary climatic control. Treelines such as these typically occur in areas of relatively uniform geologic conditions, particularly in areas of homogeneous granitic lithology such as typify parts of the Sierra Nevada and Colorado Rockies where Pleistocene glacial scouring was limited in extent and severity. Such treelines are diagrammatically represented by Figure 10c, where upward advancement of treeline is neither hindered nor facilitated by geomorphic or geologic conditions. We are, however, emphasizing that treelines throughout the American West are, in many more cases than traditionally recognized, strongly controlled by geological history, geologic structure, lithology, geomorphic processes, and landforms. Furthermore, the distribution of many of the landforms that influence the location and pattern of alpine treeline are themselves directly controlled by geologic structure and lithology. Disequilibrium conditions associated with the profound impacts of Pleistocene glaciation further illustrate the significance of geomorphic processes in controlling present-day treeline. Figure 9 summarizes the situation where geologic and/or geomorphic conditions utterly preclude upward migration of treeline, and Figure 7 does so for situations where upward migration is slow, inhibited by current or past (disequilibrium) conditions, and likely not to be geographically widespread. Even at the slope scale, where a first glance may reveal a relatively uniform, horizontal treeline, we urge a closer inspection. At this scale, the specific location of present-day seedlings is likely the result of fine-scale geomorphic facilitation (sensu Butler et al., 2004, and 13 Resler et al., 2005) that allows upward migration at an accelerated rate compared to the surrounding landscape (Figure 13). The fine-scale geomorphic effects of digging by animals may serve to facilitate or inhibit seedling establishment on treeline, and the jury is still out on which situation is more likely (or if both may occur under varying, sitespecific conditions). Future research is needed to expand our knowledge of the significance of animal excavations as facilitators or inhibitors of seedling success in the alpine treeline ecotone. The relations between geology and geomorphology and the ecological processes and patterns of the treeline ecotone will also change with changing climate in any one place. If a treeline elevation shifts, it may move into an area of different landforms at the within-range scale. Of equal interest will be how changes in climate can affect slopescale processes such as solifluction and animal activity, which would then change how plants respond to the climate change. In any case, interpretation of the scale-dependent influence of geology and geomorphology is necessary to understanding treeline pattern and process. 14 Acknowledgments This paper is a Contribution of the Mountain GeoDynamics Research Group. Funding for fieldwork came from the USGS Biological Resources Division, Global Change Programs Western Mountain Initiative, through the office of Dan Fagre and the Glacier Field Station. The National Park Service provided research permits and access to Glacier, Rocky Mountain, Sequoia/Kings Canyon, Olympic, and North Cascades National Parks. Tim Seastedt organized and hosted an excellent tour of the INSTAAR facilities and landscape of Niwot Ridge, Colorado, and Nel Caine graciously shared his extensive geomorphological experience on Niwot Ridge with us. The field assistance of Dan (Cookie) Weiss, Zahao (The Wanderer) Shen, Darren (Darius, King of Persia) Grafius, and Will (Farm Boy Fred) Butler is gratefully acknowledged. Dan Weiss also produced Figure 1. 15 References Aho, K., Huntly, N., Moen, J., and Oksanen, T. (1998) Pikas (Ochotona princeps: Lagomorpha) as allogenic engineers in an alpine ecosystem. Oecologia, Vol. 114, 405-409. Allen, T.R., and Walsh, S.J. (1996) Spatial and compositional pattern of alpine treeline, Glacier National Park, Montana. Photogrammetric Engineering and Remote Sensing Vol. 62, 1261-1268. Bekker, M.F. (2005) Positive feedback between tree establishment and patterns of subalpine forest advancement, Glacier National Park, Montana, U.S.A. Arctic, Antarctic, and Alpine Research, Vol. 37, No. 1, 97-107. Butler, D.R. (1992) The grizzly bear as an erosional agent in mountainous terrain. Zeitschrift fr Geomorphologie, Vol. 36, No. 2, 179-189. Butler, D.R. (1995) Zoogeomorphology Animals as Geomorphic Agents. Cambridge, U.K.: Cambridge University Press. Butler, D.R., and Malanson, G.P. (1992) Effects of terrain on excessive travel distance by snow avalanches. Northwest Science, Vol. 66, No. 2, 77-85. Butler, D.R., Malanson, G.P., Bekker, M.P. and Resler, L.M. (2003) Lithologic, structural, and geomorphic controls on ribbon forest patterns. Geomorphology, Vol. 55, No. 1-4, 203-217. 16 Butler, D.R., Malanson, G.P., and Cairns, D.M. (1994) Stability of alpine treeline in Glacier National Park, Montana, USA. Phytocoenologia, Vol. 22, No. 4, 485500. Butler, D.R., Malanson, G.P., and Resler, L. M. (2004) Turf-banked terrace treads and risers, turf exfoliation, and possible relationships with advancing treeline. Catena, Vol. 58, No. 3, 259-274. Butler, D.R., and Walsh, S.J. (1990) Lithologic, structural, and topographic influences on snow-avalanche path location, eastern Glacier National Park, Montana. Annals of the Association of American Geographers, Vol. 80, No. 3, 362-378. Butler, D.R., and Walsh, S.J. (1994) Site characteristics of debris flows and their relationship to alpine treeline. Physical Geography, Vol. 15, No. 2, 181-199. Caine, N. (2001) Geomorphic systems of Green Lakes valley. In: Structure and Function of an Alpine Ecosystem Niwot Ridge, Colorado (W.D. Bowman and T.R. Seastedt, eds.). New York: Oxford University Press, 45-74. Forbis, T.A., Larmore, J., and Addis, E. (2004) Temporal patterns in seedling establishment on pocket gopher disturbances. Oecologia, Vol. 128, 112-121. Hall, K., and Lamont, N. (2003) Zoogeomorphology in the Alpine: some observations on abiotic-biotic interactions. Geomorphology, Vol. 55, No. 1-4, 219-234. Hansen-Bristow, K.J., and Price, L.W. (1985) Turf-banked terraces in the Olympic Mountains, Washington, U.S.A. Arctic and Alpine Research, Vol. 17, No. 3, 261270. Holtmeier, F.K. (2003) Mountain Timberlines: Ecology, Patchiness, and Dynamics. Dordrecht, The Netherlands: Kluwer. 17 Holtmeier, F.K., and Broll, G. (2005) Sensitivity and response of northern hemisphere altitudinal and polar treelines to environmental change at landscape and local scales. Global Ecology and Biogeography, Vol. 14, 395410. Klasner, F.L., and Fagre, D.B. (2002) A half century of change in alpine treeline patterns at Glacier National Park, Montana, U.S.A. Arctic, Antarctic, and Alpine Research, Vol. 34, No. 1, 49-56. Kruckeberg, A.R. (2002) Geology and Plant Life. Seattle, WA: University of Washington Press. Malanson, G.P. (1999) Considering complexity. Annals of the Association of American Geographers, Vol. 89, No. 4, 746-753. Malanson, G.P, and Butler, D.R. (1994) Tree-tundra competitive hierarchies, soil fertility gradients, and the elevation of treeline in Glacier National Park, Montana. Physical Geography, Vol. 15, No. 2, 166-180. Malanson, G.P., and Butler, D.R. (2002) The Western Cordillera. In: The Physical Geography of North America (A. Orme, ed.). Oxford, U.K.: Oxford University Press., 363-379. Malanson, G.P., Butler, D.R., and Fagre, D.B. (2007) Alpine ecosystem dynamics and change: a view from the heights. In: Sustaining Rocky Mountain Landscapes: Science, Policy and Management for the Crown of the Continent Ecosystem (T. Prato and D. Fagre, eds.). Washington, D.C.: RFF Press, 85-101. Malanson, G.P., Butler, D.R., Cairns, D.M., Welsh, T.E., and Resler, L.M. (2002) Variability in an edaphic indicator in alpine tundra. Catena, Vol. 49, No. 3, 203-215. 18 Oelfke, J.G., and Butler, D.R. (1985). Landslides along the Lewis Overthrust Fault, Glacier National Park, Montana. The Geographical Bulletin, Vol. 27, No. 1, 715. Parker, A.J. (1991) Forest/environment relationships in Lassen Volcanic National Park, California, U.S.A. Journal of Biogeography, Vol. 18, No. 5, 543-552. Parker, A.J. (1995) Comparative gradient structure and forest cover types in Lassen Volcanic and Yosemite National Parks, California. Bulletin of the Torrey Botanical Club, Vol. 122, No. 1, 58-68. Reichman, O.J., and Seabloom, E.W. (2002) The role of pocket gophers as subterranean ecosystem engineers. Trends in Ecology and Evolution, Vol. 17, No. 1, 44-49. Resler, L.M. (2006) Geomorphic controls of spatial pattern and process at alpine treeline. The Professional Geographer, Vol. 58, No. 2, 124-138. Resler, L.M., Butler, D.R., and Malanson, G.P. (2005) Topographic shelter and conifer establishment and mortality in an alpine environment, Glacier National Park, Montana. Physical Geography, Vol. 26, No. 2, 112-125. Resler, L.M., and Tomback, D.F. (in press) Blister rust prevalence in krummholz whitebark pine: implications for treeline dynamics. Arctic, Antarctic, and Alpine Research, in press. Schtz, H.-U. (2005) Pocket gopher actor under the stage. Studies on Niwot Ridge, Colorado Front Range, U.S.A. In: Mountain Ecosystems Studies in Treeline Ecology (G. Broll and B. Keplin, eds.). Berlin: Springer, 153-180. 19 Seastedt, T.R. (2001) Soils. In: Structure and Function of an Alpine Ecosystem Niwot Ridge, Colorado (W.D. Bowman and T.R. Seastedt, eds.). New York: Oxford University Press, 157-173. Sharp, R.P., and Glazner, A.F. (1997) Geology Underfoot in Death Valley and Owens Valley. Missoula, MT: Mountain Press Publishing Company. Sherrod, S.K., and Seastedt, T.R. (2001) Effects of the northern pocket gopher (Thomomys talpoides) on alpine soil characteristics, Niwot Ridge, CO. Biogeochemistry, Vol. 55, 195-218. Sherrod, S.K., Seastedt, T.R., and Walker, M.D. (2005) Northern pocket gopher (Thomomys talpoides) control of alpine plant community structure. Arctic, Antarctic, and Alpine Research, Vol. 37, No. 4, 585-590. Simkin, S.M., and Michener, W.K. (2004) Mound microclimate, nutrients and seedling survival. American Midland Naturalist, Vol. 152, No. 1, 12-24. Tardiff, S.E., and Stanford, J.A. (1998) Grizzly bear digging: effects on subalpine meadow plants in relation to mineral nitrogen availability. Ecology, Vol. 79, 2219-2228. Tomback, D.F. (1982) Dispersal of whitebark pine seeds by Clarks nutcracker: a mutualism hypothesis. Journal of Animal Ecology, Vol. 51, 451-467. Walsh, S.J., Butler, D.R., Allen, T.R., and Malanson, G.P. (1994) Influence of snow patterns and snow avalanches on the alpine treeline ecotone. Journal of Vegetation Science, Vol. 5, No. 5, 657-672. 20 Walsh, S.J., Butler, D.R., Malanson, G.P., Crews-Meyer, K.A., Messina, J.P., and Xiao, N. (2003) Mapping, modeling, and visualization of the influences of geomorphic processes on the alpine treeline ecotone, Glacier National Park, Montana, USA. Geomorphology, Vol. 53, No. 1-2, 129-145. Wiegand, T., Camarero, J.J., Rger, N., and Gutirrez, E. (2006) Abrupt population changes in treeline ecotones along smooth gradients. Journal of Ecology, Vol. 94, 880-892. Wright, R.D., and Mooney, H.A. (1965) Substrate-oriented bristlecone pine in the White Mountains of California. American Midland Naturalist, Vol. 73, No. 2, 257-284. Zeng, Y., and Malanson, G.P. (2006) Endogenous fractal dynamics at alpine treeline ecotones. Geographical Analysis, Vol. 38, 271287. Zeng, Y., Malanson, G.P., and Butler, D.R. (2007) Geomorphological limits to selforganization of alpine forest-tundra ecotone vegetation. Geomorphology, Vol. 91, No. 3-4, 378-392. 21 Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 (below) E L E V A T I O N Elevation of treeline over time with climate warming Geomorphic/geologic conditions encountered that decelerate upward migration of treeline Elevation threshold above which treeline would not likely advance without geomorphic/ geologic facilitation TIME Figure 8 Figure 9 (below) E L E V A T I O N Elevation of treeline over time with climate warming Geomorphic/geologic condition encountered that essentially precludes any upward advance of treeline, regardless of climate change TIME Figure 10 a (above), b (middle), and c (bottom) E L E V A T I O N Elevation of treeline over time with climate warming Continuing upward advance of treeline facilitated by geomorphic/geologic conditions Elevation threshold above which treeline would not likely advance without geomorphic/geologic facilitation TIME Figure 11 Figure 12 a (above) and b (below) Figure 13 Geomorphic/geologic conditions encountered that accelerate upward migration of treeline E L E V A T I O N Elevation of treeline over time with climate warming Elevation threshold above which treeline would not likely advance without geomorphic/geologic facilitation TIME Figure 14 (a, above ; b, below) Figure 15

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COMP 16001: Introduction to Scientific ProgrammingLectures: MW 12:30 1:45, Sitterson 011 Recitation: F 1:00 1:50 Haines 002 (Section number 602.) Instructor: Jack Snoeyink, Sitterson 333, snoeyink@cs.unc.edu, Office hours: Sitterson 333, TBA or b
UNC - COMP - 016
Technical Report TR06-016 (June 2006) Department of Computer Science, UNC Chapel HillTexturing FluidsVivek Kwatra1 David Adalsteinsson11 University 2 GeorgiaNipun Kwatra2Mark Carlson3Ming Lin1of North Carolina, Chapel Hill, NC Institute o
UNC - COMP - 051
COMP 051: Technology and Entrepreneurship: Propitious PartnersInstructor: Diane Pozefsky Office: 146 Brooks Hall . Phone: 962-1817 e-mail: pozefsky@cs.unc.edu Instant Message: AIM and MSN: dianepozefsky, Yahoo: dianepoz24 Office Hours: walk in any t
UNC - COMP - 101
Welcome to Comp 101!Computational Thinking1) Course Mechanics 2) Course Objectives 3) InformationI thought this course was called Computer FITnessComp101 Spring 20081/10/2008L01 - IntroductionMeet the CrewLectures: TA: Book:Leonard Mc
UNC - COMP - 101
Getting to Know Your Computer Your File System Applications Whats running on your machine Its own devices NetworkingComp 101 - Spring 20081/31/08L07 - Getting to know your computerYour File System My Computer Directories & Folders Hi
UNC - COMP - 101
You Need an Interpreter!Comp 101 - Spring 200802/28/08L10 - An InterpreterClosing the GAP Thus far, weve been struggling to speak to computers in their language, maybe its time we spoke to them in ours How high can we rasie the level of dis
UNC - COMP - 101
Your Own Web Page; Quick and Dirty Via MashupReminder: Next Quiz on 4/15Comp 101 - Spring 2008 04/03/08 L14 - Web Pages and MashupA Special Language for the Web In the early 1990s web pages were mostly described using a special purpose language
UNC - COMP - 120
COMP 120Computer Organization Spring 2006For any doubts in the following, contact Agam, Room. 023Problem Set #8 SolutionProblem 1. Simplified Shifts[A] 4 pts. Since <25:21> = 100002 = 16 We dont need LSEL signal and the MUX associated with it.
UNC - COMP - 120
Comp 120 Spring 2006Computer Abstractions and Technology1. Layer Cakes 2. Computers are translators 3. Switches and Wires (Read Chapter 1)1/17 LectureComputers Everywhere The computers we are used to- Desktops - Laptopspage 1- Embedded pr
UNC - COMP - 120
The UNIVERSITY of NORTH CAROLINA at CHAPEL HILLComp 120 Computer Organization Spring 2005 Problem Set #2 Issued Thursday, 1/27/05; Due Thursday, 2/03/05 Homework Information: Some of the problems are probably too long to be done the night before the
UNC - COMP - 120
The UNIVERSITY of NORTH CAROLINA at CHAPEL HILLComp 120 Computer Organization Spring 2005 Problem Set #4 Issued Thursday, 2/17/05; Due Thursday, 2/24/05 Homework Information: Some of the problems are probably too long to be done the night before the
UNC - COMP - 121
Enclosure 2, Attachment A CONTRACT PRICING PROPROSAL FOR COST REIMBURSEMENT CONTRACTS WITH UNIVERSITIESThe purpose of this form to provide a standard format by which the Offeror submits information in cost reimbursement contracts A. Name of Offeror
UNC - COMP - 140
First Java program JDK and EclipseDorian MillerAnnouncement Program 3Due Thursday Oct 11, 11:59pm EST Monday Oct 15, in-class, closed book/computer Important: Install Java software Collecting student ideas Midterm Friday's Recitation
UNC - COMP - 144
COMP 144 Programming Language Concepts Lecture 36: Global Optimization, Loop Improvement and ProfilingApril 22, 2002The University of North Carolina at Chapel HillCOMP 144 Programming Language ConceptsSpring 2002Lecture 36: Global Optimizati
UNC - COMP - 144
COMP 144 Programming Language Concepts Lecture 5: Syntax AnalysisJanuary 18, 2002The University of North Carolina at Chapel HillCOMP 144 Programming Language ConceptsSpring 2002Lecture 5: Syntax AnalysisFelix Hernandez-Campos HernandezJan 1
UNC - COMP - 144
COMP 144 Programming Language Concepts Lecture 2: Compilation and InterpretationJanuary 11, 2002The University of North Carolina at Chapel HillCOMP 144 Programming Language ConceptsSpring 2002Lecture 2: Compilation and InterpretationFelix H
UNC - COMP - 144
COMP 144 Programming Language Concepts Lecture 3: Lexical AnalysisJanuary 14, 2002The University of North Carolina at Chapel HillCOMP 144 Programming Language ConceptsSpring 2002Lecture 3: Lexical AnalysisFelix Hernandez-Campos HernandezJan
UNC - COMP - 145
#! /usr/local/bin/perl # # # Smart Search Administration Program # began by: Leslie Jacobson # Comp 145 - Spring 1999 # # Running this program allows the Smart Search team and any future # Smart Search administrators to maintain the database. # This
UNC - COMP - 180
The Cycle of Scholarly CommunicationA PRESENTATION BY STAN TREMBACH INLS 180-002Scholarly communication and the continuum of electronic publishing (Kling & McKim, 1999)What is an electronic publication?Articles, journals, subscriptions etc., et
UNC - COMP - 190
Recursion Arrays and File inputDorian MillerAnnouncements Happy Halloween! Homework 5 available Due Thu Nov 8, 11:59pm EST Program 4 Questions? Due Thu Nov 1, 11:59pm EST Office hours Today 3:30-4:30 Thu: 2-3 (end 3pm sharp)Program 4
UNC - COMP - 236
Texture Mapping Part 1Why Texture Map? How to do it How to do it right Spilling the beans Assignment #3 Lecture 17 Comp 236 Spring 20053/21/2005The Quest for Visual RealismLecture 172Decal TexturesThe concept is very simple!Simple OpenG
UNC - COMP - 236
Imaging and 2D TransformsLecture 3 Comp 236 Spring 2005Two-Dimensional Geometric Transforms Functions for mapping points from one place to another Geometric transforms can be applied to drawing primitives (lines, conics, triangles) pixel coord
UNC - COMP - 236
Part 2: Physically-Based Illumination ModelsRevisit OpenGLs Illumination ModelI total =lights i =1k Iaa + k dIdMax (N L), 0) + k sIsMax (N H), 0)nshineyMaxwells Eqns Cook & Torrance BRDFs Last Lecture covered on Quiz Lecture 11 Comp 23
UNC - COMP - 236
Comp236 Spring 2005 Programming Assignment #2 Due 3/1/05 (before 11:59:59pm)Objective: In this project, you will use OpenGL to render, manipulate, and animate 3-D models. Your scene should be composed of a ground plane, and at least 3 models. One m
UNC - COMP - 242
1COMP 242 Class Notes Section 3: Interprocess CommunicationReadings: Chapter 7, Comer. An operating system provides interprocess communication to allow processes to exchange information. Interprocess communication is useful for creating cooperatin
UNC - COMP - 242
1COMP 242 Class Notes Section 7: User Interface1. USER INTERFACE processes. We will now study how an operating system provides resources and services to users.So far we have seen how an operating system provides resources and services toAn ope
UNC - COMP - 242
COMP 242 Midterm Exam Spring 2006 There are 3 questions; answer all of them. If you need to make an assumption to clarify a problem, write your assumption down. Only reasonable assumptions get full credit. Explain all answers. The exam is worth 75 pt
UNC - COMP - 242
COMP 242 Final Exam Spring 2006 There are 4 questions; answer all of them. If you need to make an assumption to clarify a problem, write your assumption down. Only reasonable assumptions get full credit. Explain all answers. You have three hours to n
UNC - COMP - 250
Program design with: Arrays and classesDorian MillerAnnouncements Program 5 graded See BlackBoard for grades and solution Homework 5 Topics: reading, writing, using classes No class inheritance Due Thu Nov 29, 11:59pm EST Program 6: Java s
UNC - COMP - 254
Comp 254, Image Processing and Analysis Spring 2002, Prof. Guido Gerig Assignment 3: Hough TransformOut: Tuesday April-02-2002 Due: Tuesday April-16-2002 (theoretical and practical part) Please provide a paper copy of essential results of the practi
UNC - COMP - 254
Comp 254, Image Processing and Analysis Spring 2002, Prof. Guido Gerig SyllabusGoal: To present fundamentals for methods of processing and analysis of images using a computer. Statistical pattern recognition, multiscale shape and geometry, local to
UNC - COMP - 254
Comp 254, Image Processing and Analysis Spring 2002, Prof. Guido Gerig Assignment 2: Statistical Pattern RecognitionOut: Thursday Feb-21-2002 Due: Thursday Mar-07-2002 Required Readings: Haralick handouts, papers, Canny handout, papersI. Theoretic
UNC - COMP - 256
Motion in Computer VisionE. Scott Larsen October 29, 2001 Comp 256Motion in Computer Vision The Primary Assumption The BCCE Space-time Images Examples The Aperture Problem The Correspondence Problem (again!) Optical FlowThe Primary Assump
UNC - COMP - 256
Comp 256 Computer Vision, Fall 2001, Guido GerigCourse and Instructor Evaluation Form: End of semesterName (optional): _The instructor and the T.A. will not see forms until after final grades are turned in.This form is designed to provide an ove
UNC - COMP - 259
Water Droplet Flow on Melting IceAvneesh SudCOMP 259 Spring 2002Motivation How water droplets would flow on ice surface ? Simulate slow melting of ice Flow of water droplets on wet surfacesComp 259 Spring 2002 2Problems State Change Wate
UNC - COMP - 290
Comp 290, Fall 2006 Using Collaborative Systems to Classify Recent CSCW PapersDate Assigned: Tue Aug 29, 2004 Completion Date: Tue Sep 12Objectives: Use synchronous application sharing. Compare screen sharing with model sharing. Use asynchronous
UNC - COMP - 290
Comp 290, Fall 2004 Using Collaborative Applications to Classify Recent CSCW PapersDate Assigned: Sun Aug 29, 2004 Completion Date: Tue Sep 14Objectives: Use synchronous application sharing. Compare distributed application sharing with face-to-fa
UNC - COMP - 290
COMP 290 Midterm Exam Fall 2004 There are ve questions; answer all of them. If you need to make an assumption to clarify a problem, write your assumption down. Only reasonable assumptions get full credit. Explain all answers. You have seventy ve minu
UNC - COMP - 290
Comp 290-075 Computer Vision, Spring 2000Course and Instructor Evaluation Form: End of semesterName (optional): _The instructor and the T.A. will not see forms until after final grades are turned in.This form is designed to provide an overall as
UNC - COMP - 410
Topic: Welfare Properties of the Competitive Market Solution & of Government Interventions A. Consumer and Producer Surplus If a consumer demands and purchases q units at the price p, then the consumer surplus is the area between his/her demand curve
UNC - COMP - 411
Comp 411 Computer Orginization Fall 2007 Problem Set #1 Solutions Problem 1a) If all nucleic acids are equally likely, a 3-nucleic acid sequence can be represented with 6 bits, as such: log2 ( 444 ) = log2 ( 64 ) = 6 1 1 Given that there are 20 amin
UNC - COMP - 411
Comp 411 Computer Orginization Fall 2007 Problem Set #2 Solutions Problem 1Instruction sll $0, $0, 0 addi $4, $0, 2 add $2, $0, $4 and $3, $2, $4 ori $3, $2, 1 sra $3, $2, 8 lui $2, 0xfeed ori $2, $2, 0xface loop: bne $t0,$0,loop Hexadecimal 0x00000
UNC - COMP - 411
Comp 411 Computer Orginization Fall 2007 Problem Set #5 Solutions Problem 1In the follows answers, the black section of the circuit is the new section, while the grey section is the section that was given in the problem. a)VddA C A BB D y C D
UNC - COMP - 523
Proposal for Community Media Portal and Database for COMP 523 The Peoples Channel www.thepeopleschannel.org Contact: Chad Johnston 919.960.0088 Johnston@thepeopleschannel.org The Peoples Channel is Chapel Hills nonprofit Community Media Center and Pu
UNC - COMP - 523
John Joseph Bachir j@jjb.ccWordPress / LyceumWordPress [http:/wordpress.org] is the worlds most popular blogging system. It powers millions of blogs and websites, and gains popularity and features every day. It has an excellent API that makes it v
UNC - COMP - 633
COMP 633: High Performance Computing PRAM AlgorithmsSiddhartha Chatterjee Jan Prins Fall 2007Contents1 The PRAM model of computation 2 The Work-Time paradigm 2.1 Brents Theorem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
UNC - COMP - 633
Sep 13, 2007PA1u1-1/2COMP 633: High Performance Computing Programming Assignment 1: All-pairs n-body simulationFall 2007Assigned: Due: Thu Sep 13, 2007 Tue Oct 2, 20071. Problem Description We consider a very simple simulation of the trajecto
UNC - COMP - 633
Aug 21, 2007633 (F07) 1.1/3High Performance ComputingCOMP 633 Fall Semester 2007http:/www.cs.unc.edu/~prins/Classes/633/Meeting Times: Tue, Thu 9:30 10:45 in SN 011 (Tue Aug 21 Tue Dec 4) Instructor: Jan Prins (SN 355, Tel: 962-1913, prins@
UNC - COMP - 633
OpenMP version of 1-D diffusion program To run on topsail.unc.edu compile: execute using 8 threads: COMP 633 Fall 2007 J. Prins icc -openmp -fast -o ex1 ex1.c bsub-sizes 8
UNC - COMP - 665
WelcometoComp665Imaging, Graphics, and Vision Administra*ve Details CourseOverview Whatisasignaland whyshouldyoucare?8/29/08 Comp665Introduc*on&Signals 1Introduc2ons Me:LeonardMcMillan Whyisabioinforma*csguyteachingimaging? Whyisabioinforma
UNC - COMP - 665
The UNIVERSITY of NORTH CAROLINA at CHAPEL HILL COMP 665 Imaging, Graphics, & Vision Fall 2008Problem Set #2 Solution October 18, 20081.Self Duals (0.35 points for A~F, 0.4 points for G)Note: If you plot the real and imaginary part separately, y
UNC - COMP - 665
FourierFiltering The first Problem set is posted on the web site, and is due on 9/239/8/08Comp665FourierFiltering1FourierImpetus Therewasonemo<va<ngfactorbehindour ndingasetofEigenvectorscapableof describingawiderangeoffunc<ons Itissumme
UNC - COMP - 790
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UNC - COMP - 870
Soft Shadows using Hardware CamerasKyle Moore COMP 870The UNIVERSITY of NORTH CAROLINA at CHAPEL HILLPrevious Work Cone TracingAmanatides, J. 1984. Ray tracing with cones. In Proceedings of the 11th Annual Conference on Computer Graphics and i
UNC - COMP - 918
Comp 918: Final Project (50%) of GradeThis project has two parts. Part one is a team activity that begins with the selection of any active NSF or NIH BAA funding opportunity. Each two-person team will develop a mini proposal to include abstract, 3-5
UNC - COMP - 918
Comp 918: Patent Claims Writing AssignmentThis project has two parts: the writing of patent claims and the diagramming of those claims. First select any commonly known object, e.g., a table, radio, electronic mixer. Write three independent claims (o
UNC - COMP - 918
Course Syllabus Research Administration for Scientists COMP 918Overview: This course covers a range of topics important to any doctoral student in the sciences topics that are rarely covered in other courses. Students will learn the basics of writi
UNC - COMP - 991
Potential COMP 991 Project on Statistics of Shape, for Autistics BrainsMIDAGStephen Pizer, Kenan Professor J.S. Marron, Hawley Professor (Stats & CS)1Statistical Shape AnalysisAnswers question such asIn what ways and in what positions are a
UNC - CYTO - 720
Oral Oncology (2007) 43, 523 534available at www.sciencedirect.comjournal homepage: http:/intl.elsevierhealth.com/journals/oron/REVIEWAdvances in the biology of oral cancerP.K. Tsantoulis a, N.G. Kastrinakis a, A.D. Tourvas a, G. Laskaris b,
UNC - PATH - 162
History 162: Russia since 1861University of North Carolina, Chapel Hill, Fall Semester 2006 Instructor: Professor Donald J. Raleigh, Hamilton Hall 410, 962-8077, djr@email.unc.edu Class Meetings: T/Th, Caldwell 105, 12:30-1:45 Office Hours: Tuesday