Abstract The frequency of debris flows on Mount Rainier is increasing due to glacial retreat as a result of climate change. The intent of this investigation was to study biotic and abiotic factors of succession that are indicators of the age of debris flows in order to understand the history of debris flows that have occurred on Mount Rainier and better predict the effects of climate change. Factors were selected based on their low level of impact on the environment and being easily observable in the field. Data was collected from two debris flow prone valleys and a control section in Mount Rainier National Park during the months of October and July. Variations in O-Horizon depth, canopy coverage, soil color, soil pH level and lowest branch height were observed utilizing belt and line transects. Mathematical models were constructed for each factor to identify the factors that change over time that might be useful in predicting the age of debris flows. O-Horizon depth and canopy coverage were selected for further investigation because they are interconnected factors, display clear trends and have high R2 values (above 90%). Using the equations for the regression curves predictions were made for three previously untested sites of known ages based on the logarithmic curves. Additional data was then collected at these sites utilizing the same field methods. While canopy coverage was not found to be a reliable predictor of debris flow age, O-Horizon depth as a model was further validated.

IntroductionOn November 6th and 7th, 2006 record rainfall and snow melt combined to form debris flows, flooding and erosion that devastated both natural and recreational areas within Mount Rainier National Park. As a result, the park was closed for six months, the longest period of time of closure since World War II. It took the combined efforts of 1,500 volunteers and approximately thirty million dollars to reopen the park; however some areas remain unoperational and inaccessible and surrounding businesses reliant on tourism have yet to fully recover1. Many aspects of this disaster are indicative of the degenerative effects of climate change that have been impacting mountainous regions in recent years. Although these heavy damages were devastating, they pale in comparison to what lies ahead as global climate change pervades and Mount Rainier’s massive glaciers continue to retreat, shedding their once frozen bodies, leading to destruction in the valleys below2. The purpose of this investigation is to study the stages of succession following debris flows in order to better determine the age of debris flows that have occurred in Mount Rainier National Park. By doing so, a historical record of

Patterns of Biotic and Abiotic Factors of Succession Following Debris Flows at Mount Rainier National ParkLaura Kostad1* and Denise Thompson2

Student1, Teacher2: Orting High School, Orting, Washington 98360*Corresponding author: laurakostad@hotmail.com

IN SCHOOL ARTICLE

debris flows that have occurred in the area can be compiled to assist scientists and park personnel in planning for the protection of natural and historical resources as the park responds to the rapidly increasing effects of global climate change. Furthermore, by gaining this understanding they could more accurately address the matters of intervention, observation and estimation so as to know what to expect in the following years as the ecosystems regenerate3,4.

A debris flow is a slurry of mud and rock mixed with water that resembles concrete tumbling downslope destroying all vegetation within its path either by knocking it down or burying it. Debris flows can result from volcanic activity or as glaciers warm and retreat, due to rising temperatures. These retreating glaciers uncover sediments that provide the solid materials for debris flows. When an excess of water from a major rain storm, melting glaciers, or snowmelt flows over these exposed sediments, it carries them destructively downstream picking up more and more debris from the valley floor. As the valley slope decreases, the debris flow slows down eventually depositing meters of sediment in the streambed. Because of global climate change, debris flows are increasing in frequency in many glacial occupied valleys on Mount Rainier2,3,5,6.

The relationship existing between the amount of canopy coverage observed in a particular site and the age of a debris flow is in general that the greater the percentage of canopy coverage, the farther along the ecosystem is in terms of succession because, for example, in a climax community (the apex of succession), canopy coverage is nearly one hundred percent due to old growth coniferous trees which dominate the forest canopy and that are only present when an ecosystem has reached this point in succession. However, pioneer species such as Alder quickly colonize debris flow surfaces resulting in a narrow window of time (potentially 15-20 years) for which canopy cover would be useful as a predictor.

Vegetative destruction caused by debris flows leads to forest succession. Debris flows are considered to be a form of high level disturbance because they decimate nearly all of the vegetation in an environment and bury the soil layer under meters of sediment. When this layer is absent, an ecosystem is considered to be in primary succession. Secondary succession is regrowth in an area that retains its soil layer. When a debris flow occurs, the affected ecosystem essentially has to start over from scratch and recolonize completely starting with making a new soil layer. This is dangerous for ecosystems because rather than encouraging biodiversity, ecosystems with frequent debris flows never reach the climax community stage. Furthermore, the more biodiversity in an ecosystem, the more stable the ecosystem will

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be and the better it will be able to respond to environmental changes. Moreover, this negative cycle also opens the door for invasive species to take over and out-compete the native species during recolonization, in some cases leading to localized extinction7. Consequently, each of these factors supports the need for an increased understanding of the dynamics of debris flows and succession on Mount Rainier.

Fallen leaves and other decaying organic matter accumulate on the forest floor, covering and enriching the underlying sediments and increasing their organic content. The depth of the O-Horizon is the point at which decomposing organic material (detritus) diminishes so that the underlying layers (typically a sand or gravel layer) lack organic material. Following a debris flow, succession begins with the development of the O-Horizon during primary succession, followed by the development of plant life during secondary succession, making the depth to the O-Horizon an excellent tool for determining the stage of succession as well as age of the of a debris flow being observed.

Once a soil layer is reestablished, succession continues with a pioneer species, usually one that performs nitrogen fixation that contributes nutrients and organic materials to the recovering soil. As time progresses, pioneer species are gradually replaced by intermediate species until a climax community results7. On Mount Rainier, the first plant species to recolonize an area following a debris flow is the Red Alder (Alnus rubra), followed by the Douglas Fir (Pseudotsuga menziesii). Climax communities are dominated by a variety of evergreens including Western Hemlock (Tsuga herterophyla), Western Red Cedar (Thuga plicata) and Douglas Fir as well. Specific patterns of succession are unique to the particular ecosystem being observed and because of this; it is unreliable to take a previously developed model from one ecosystem and attempt to apply it to another. Due to many factors such as latitude, precipitation, elevation and scale of disturbance, the ecosystems between mountains in the Cascade Range differ despite their relative proximity. It is for this reason that it is impractical to take models developed for Mount St Helens (where a significant portion of successional research has been focused post 1980)8,9,10, for example, and attempt to apply them to Mount Rainier. As a result it becomes necessary to collect data from and develop models specific to Mount Rainier’s respective ecosystem to design accurate models concerning the age of debris flows and the stages of succession occurring there. Once the specific pattern of succession within existing ecosystems is understood spatially and temporally, it can be used to approximate the age of debris flows impacting similar ecosystems on Mount Rainier.

Dendrochronology (the core sampling of trees) normally would have been the first method to utilize in attempting to determine the age of debris flows11; however, due to the risk of insect infestation such as pine bark beetles, the study sites being on protected national park land and other matters concerning the trees’ and the surrounding environment’s welfare, scientists at Mount Rainier preferred that this method not be used. In addition, since alders are the first tree species to recolonize an area following a debris flow within the ecosystem studied, coring other existing species that arise in later stages of succession would provide inaccurate age data, being that the age of the individual tree would be recorded rather than the time since the debris flow occurred11. In addition, alders are generally absent in the climax community, and therefore unreliable for measuring the age of a debris flow once a climax community has been established. This led to the search for other biotic and abiotic successional factors that may be indicative of the age of debris flow—predominantly those that are non-labor intensive, easy to perform in the field, have low environmental impact and allow for immediate onsite age determination.

Other types of disturbances besides debris flows and other factors outside of the ones that I focused on in my investigation can interfere with and sometimes even invalidate data. For example, a flood is another form of disturbance that occurs frequently on Mount Rainier. During the warmer summer months, glacier and snow melt runs into the rivers that cascade down the mountain and surrounding foothills, frequently inundating the rivers’ normal banks and spreading out across the area close by. This can affect the appearance of succession as decomposing organic matter such as fallen leaves and limbs may be swept away or layers of sediment may be deposited on the surface burying the pre-existing soil layer while negligibly impacting forest vegetation. As a result, if a debris flow affected area is also prone to flooding then biotic and abiotic factors will be expressed differently.

Materials and MethodsAfter collecting data from the Tahoma Creek, Kautz Creek and Twin Firs Trail sites, models were constructed from the canopy coverage and O-Horizon depth data in Excel in order to produce an equation that could be used to predict the amount of canopy coverage and the depth to the O-Horizon in other sites. These two factors were chosen based on their interconnectedness and the consistent as well as reliable data that resulted from collection in the first three sites. The models for canopy coverage were based on 0 to 64 years and 64-500 years separately because the amount of canopy coverage leveled off by 64 years. The Tahoma Creek, Kautz Creek and Twin Firs Trail sites were selected based on their varying ages and stages of succession. Tahoma Creek was selected because of its recent history of debris flows. Kautz Creek was selected because its last debris flow occurrence is significantly older in comparison to Tahoma Creek. Twin Firs Trail served as our control site due to the fact that it has never experienced any known debris flows and its most recent disturbance was a forest fire estimated to have occurred approximately 500 years ago. Initially data was collected on the amount of canopy coverage, depth to the O-Horizon, branch height, soil color and soil pH. The data was then analyzed and it was determined that the factors of canopy coverage and depth to the O-Horizon were the most reliable of those studied. Models of succession over time of these two factors were constructed in Excel using the average data points as the framework. Predictions were then made for three new sites (Westside Road 1, Westside Road 2 and Westside Road 3) using the equations of the regression curves as determined graphically. Canopy Coverage: In each site visited, a relatively homogenous transect was located in which to collect data. Within the transect, using a tape measure, ten meters were measured in as straight line as was possible. Starting at one end of the tape measure, using a small piece of PVC pipe split into quarters at the end, the observer looked directly above them through the pipe and estimated the percentage of sky that could be seen. The data was then recorded in a data table and the process was repeated every meter for ten meters and then repeated for two more transects at each of the six sites that were visited. O-Horizon Depth: A homogenous transect was located in which to collect data. Within the transect, using a tape measure, ten

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meters was measured out in as straight a line as was possible. Beginning at zero meters, a hole was dug using a trowel until the base of the O-Horizon was reached (if present). The distance from the ground surface (ignoring detritus such as leaves and branches) to the bottom of the O-Horizon was then measured using a ruler with centimeter units and the depth was recorded in a data table. This process was repeated every meter for ten meters and repeated for three transects. Branch Height: In each of the first three sites visited (Tahoma Creek, Kautz Creek and Twin Firs Trail), a relatively homogenous area was located in which data was collected. The ten largest alder trees were then selected for measuring. The distance from the ground at the base of the tree to the lowest branch was measured in meters using a tape measure. If the lowest branch was unable to be reached by extending the arm fully upward then trigonometry was applied to determine the distance from the ground to the lowest branch. This was accomplished by measuring the distance of an observer to the base of the tree and the angle between the observer and the lowest branch using a clinometer. The height was calculated by multiplying the distance by the tangent of the angle. This process was repeated two more times in new homogenous areas at each of the six sites visited. Soil Color:In each of the first three sites visited (Tahoma Creek, Kautz Creek and Twin Firs Trail), a relatively homogenous transect was located in which to collect data, using a tape measure, ten meters was measured out in as straight and flat of a line as was possible. Detritus was cleared from the forest floor where the sample was to be taken. Beginning at one meter, using a trowel a small sample of the soil was collected. The soil color was observed and then compared to The Globe Soil Color Book 2nd Edition12 and the corresponding color code within the 10YR range was recorded in a data table. A new sample was taken every one meter from that point, for a ten meter transect. This entire process was completed for three transects at each site visited. Soil pH Number: In each of the first three test sites visited (Tahoma Creek, Kautz Creek, Twin Firs Trail) a relatively homogenous transect was located in which to collect data. Within the transect, using a tape measure, ten meters was measured out in as straight and flat of a line as was possible. Starting at one meter, detritus was cleared from the forest floor where the sample was to be taken. A two milliliter scoop of soil was then taken up in a plastic cup and five milliliters of distilled water was added to it to make a solution. A pH indicator strip was then dipped in the soil solution. The resulting color of the pH strip was compared to the corresponding pH scale and recorded in a data table. This process was completed every meter for ten meters and three transects at each site. Data Analysis: In order to calculate linear regression in Excel, the regression option was accessed from the data analysis tools tab. Age was used for the independent variable and O-Horizon depth/canopy coverage was used as the independent variables. For the graphs that appeared in the hypothesis, the data that was collected from each transect during the initial observations was averaged. The averages were then entered into an Excel spreadsheet with the corresponding age in years of the site from which the data came. The data was then graphed in a scatter plot and trend lines were added. The trend line that was the most accurate based on the R2 and that most logically fit the data as determined by the Excel program was applied. Both a polynomial and a logarithmic curve were applied to the best represent the canopy coverage data. A polynomial curve was applied for two reasons which are that 1) the curve can begin at time zero and 2) it was calculated to be the most accurate (best fitted) according to its corresponding formula and R2 (accuracy) value. However, a polynomial curve is illogical because the canopy cover cannot exceed one hundred percent. A logarithmic curve presents a curve that makes the most logical sense, in that canopy cover appears to increase over time exponentially, eventually leveling off and reaching 100% canopy coverage. A linear regression was used for O-Horizon depth because it fit the data with a 100% R2 value and, in the absence of other disturbances, the accumulation of soil layers logically could occur at a constant rate over time.

ResultsTahoma Creek: Five year old debris flow (2006): Plant life consists of three foot tall, clumped alders. One to three inch tall, clumped, fir seedlings are also present. Dead Douglas Firs predating the debris flow are stripped of bark and branches. Many mosses are also present. There is constant sunlight and thus no shade due to very little canopy cover. Soil composition is mostly sand-sized sediment and there are many large boulders. Microorganisms have fed on the rocks causing oxidation of an orange color on some. There is little organic material and no O-Horizon. Animal life observed includes at least two species of spiders and slugs. The average percent of canopy coverage ranged widely for each transect, at 4.5%, 7.3% and 18% respectively. The average amount of canopy coverage for this site was 9.9%. Due to the lack of an O-Horizon at this site, the average O-Horizon depth for each transect, as well as overall for this site, was 0 cm. The mode height of branches per transect was 5.15 cm, 5.35 cm and 10.6 cm respectively with a mode branch height for the site of 7.03 cm. Soil color was relatively consistent throughout all three transects with individual modes of 3.6, 3.4 and 2.7 for each transect and an overall mode of 3.2. In addition, the pH of the soil was a consistent 5 for every data point collected from this site.

Kautz Creek Trail: Sixty-four year old debris flow (1947)6: Plant life consists of living cedars and hemlocks that are relatively dispersed and a lot of salal. Coniferous trees and alders are of about the same height but densely packed and the ground is very green and covered with moss. There are more fallen logs and there appear to be fewer rocks than what was observed at Tahoma Creek; they are less visible. There is medium canopy coverage so moderate sunlight is able to filter in. Animal life includes small, airborne, winged insects. Canopy coverage ranged widely at this site as well, with 57%, 90% and 68% for each respective transect. The average amount of canopy coverage for this site was 72%. The average O-Horizon depth per transect was relatively close at this site with transect averages of 2.2 cm, 1.6 cm and 1.2 cm and an average overall O-Horizon depth for the site of 1.7 cm. The mode branch height per transect recorded was 56.5 cm, 57.95 cm and 107.75 cm, with a total mode of 74.06 cm. Soil color was fairly consistent throughout all three transects with transect modes of 1.3, 1.9 and 1.3 respectively. The mode was 1.5 for the site overall. Additionally, the soil pH was consistently a 5 for all data points collected from this site.

Twin Firs Trail: Approximately 500 year old disturbance (1512)13: Plant life consists of old growth cedars, hemlocks and Douglas Firs, all

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of which are much more dispersed and there is little clumping. There are vine maples present as well as many diverse bryophytes, ferns primarily. Moss is omnipresent on the trees and ground. No alders seem to exist in this ecosystem. Sunlight is greatly reduced due to the thick canopy cover provided by the old-growth trees. The ground is covered heavily by shed needles from trees and there are few rocks. The average amount of canopy coverage per transect for this site was less stratified, with transect averages of 73%, 90% and 93%. The average amount of canopy coverage was 85%. The O-Horizon depth, however, was not as consistent per transect with measurements of 9.2 cm, 17 cm and 18.2 cm. The average O-Horizon depth for this site was 14.8 cm. The mode branch height per transect, as well as the overall mode of the site was 0 cm; there were no alders present to measure. The mode soil color varied across the three transects with individual modes of 3.2, 1.5 and 2.0 respectively and a total mode of 2.2. In addition, the soil pH was found to be 5 for all data points collected from this site.

West Side Road #1: Estimated twenty-four year old debris flow (1988)6, located 0.9 miles from the Westside Road gate: There is a lot of vegetative undergrowth present which consists of many clumped alders, wetland grass, ferns, stinging nettles, thorn species, and common wetland plants. Also present are sedges, devil’s club and equisetum (horsetails) which are indicators of dampness and suggest that the area may be prone to flooding. There are few Douglas firs present and the majority of fallen trees are alders rather than Douglas firs. The outer rim of the flow area has firs, but within the flow area there are no firs. A manmade levy constructed on one side of the flow area kept the flow from spreading farther and protected part of the ecosystem from destruction. Transects 1 and 2 are sub-perpendicular to a stream which runs through the site and is at 0 meters for transect 2. From 0-4 meters of transect 2 there is a ten degree slope which rises approaching 4 meters. Transect 3 is sub-parallel and at a distance from the aforementioned stream. The affected area is a wetland and there are virtually no rocks present, which normally exist at the top of a debris flow. The O-Horizon depth is determined in this site by the presence of gray sand. This suggests that floods are most likely what affect this site. The percentage of canopy coverage was relatively consistent throughout the site with individual transect averages of 93%, 98% and 97% respectively and a total average for the site of 96%. The depth to the O-Horizon was a little less consistent, but still reasonable with transect averages of 20 cm, 21 cm and 17 cm and a total average for the site of 19.4 cm.

West Side Road #2: Estimated twenty year old debris flow (1992)6, located 1.4 miles from the Westside Road gate: Plant life consists of alders much smaller than those found at West Side Road #1. The firs present are only a couple of inches tall and there are also older firs several feet tall. The trees are more uniformly distributed and there are small boulders present. Transect 2 primarily consisted of .5 centimeters of forest litter. There were a few deviations from the norm at this site, however, for the most part the amount of canopy coverage was consistent throughout the site with individual transect averages of 93%, 87%, 96%. The average percent canopy coverage for the site was 92%. The O-Horizon depth at this site was for the most part very close between the three transects with individual transect averages of 0.85 cm, 0.81 cm and 1.6 cm. The total average for this site was 1.09 cm.

West Side Road #3: Twenty-four year old debris flow (1988)6, located at the trail head 3.2 miles from the Westside Road gate: Plant life consists of standing, dead, Douglas firs, small alders and bryophytes. Many exposed boulders are present. Trees are closely spaced and

Figure 1. Canopy Coverage Model (0-64 years) using the Tahoma Creek Trail, Kautz Creek Trail, and the Twin Firs Trail.

Figure 3. O-Horizon Depth Model (0-500 years) using the Tahoma Creek Trail, Kautz Creek Trail, and the Twin Firs Trail.

Figure 2. Canopy Coverage Model (64-500 years)using the Tahoma Creek Trail, Kautz Creek Trail, and the Twin Firs Trail.

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there is very little underbrush present. The data collected for this site was greatly stratified both within and between transects. Individual transect averages were 65%, 68% and 97% respectively, with a total average for the site of 76%. Despite many obstacles to measuring the depth to the O-Horizon at this site, the transect averages were relatively consistent at 0.75 cm, 0.21 cm and 0.61 cm respectively. The overall average depth to the O-Horizon for this site was 0.52 cm.

The data for the canopy coverage, O-Horizon depth, branch height, soil color, and soil pH, for Tahoma Creek, Kautz Creek, Twin Firs Trail and the three West Side Road study sites are shown in Tables S1 - S15 (Supplementary Data).In order to calculate linear regression in Excel, the regression option was accessed from the data analysis tools tab. Age was used for the independent variable and canopy coverage/O-Horizon depth was used as the independent variables.

The Tahoma Creek, Kautz Creek and Twin Firs Trail sites were selected based on their varying ages and stages of succession. Tahoma Creek was selected because of its recent history of debris flows. Kautz Creek was selected because its last debris flow occurrence is significantly older in comparison to Tahoma Creek. Twin Firs Trail served as our control site due to the fact that it has never experienced any known debris flows and its most recent disturbance was a forest fire estimated to have occurred approximately 500 years ago13. Initially data was collected on the amount of canopy coverage, depth to the O-Horizon, branch height, soil color and soil pH. The data was then analyzed and it was determined that the factors of canopy coverage and depth to the O-Horizon were the most reliable of those studied. Models of succession over time of these two factors were constructed in Excel using the average data points as the framework(Figures 1-3). Predictions were then made for three new sites (Westside Road 1, Westside Road 2 and Westside Road 3) using the equations of the regression curves.

Figures 4 shows the plot from data from the West Side Road sites (24, 20, and 24 years respectively) as well as the data from Tahoma Creek (5 years) & Kautz Creek (64 years) (“validation data). Figure 5 represents changes to the original models after the addition of new data (Westside Road 1, Westside Road 2 and Westside Road 3) that was collected during the second phase of editing (“validation data”).

Figure 4. Canopy Coverage Model (0-64 years) with validation data.

Figure 5. O-Horizon Depth Model (0-500 years) with validation data.

DiscussionThe factors investigated were chosen based on their potential to predict the age of debris flows, which was mostly determined by their relatedness to the occurrence of debris flows. In the initial observations, branch height, soil color and soil pH number were observed in addition to canopy coverage and O-Horizon depth. These factors proved ambiguous, however. Lowest branch height was highly unreliable in that a number of other factors in the ecosystem could affect the livelihood and existence of the lower branches observed and so was deemed inconclusive. Soil color was also difficult to use as a clear indicator of the stage of succession. Usually, soil is darker if it contains more decomposed organic material and lighter if it is not very rich in these materials. In other words, a relatively clear distinction typically exists between stages of succession based on soil coloring. At Mount Rainier, being an active volcanic site, the soil consists primarily of volcanic ash, rock and other matter expelled during volcanic eruptions. This material is typically very dark and although varies subtly from site to site, is still difficult to draw a clear distinction from concerning the stage of succession, no matter what the amount of decomposed organic material that is mixed with it. The pH also proved to be a vague indicator of the stage of succession in that the data, when averaged for each site, came out to be a pH of approximately 5, which is the approximate pH of rainwater. This shows that the pH of soil at Mount Rainier is more dominantly affected by the rainwater that it absorbs than the constituents of the soil itself. Due to these inconsistencies, only canopy cover and the depth of the O-Horizon were targeted for further investigation.

The Westside Road 1 data was excluded from analysis on account of the fact that observations indicate that the site was more likely affected by floods rather than debris flows and is therefore inconsistent with the rest of the data collected that is based on areas affected only by debris flows. Westside Road 1 consists of a wetland terrain, punctuated by various species of plants commonly found in wetlands such as sedges and horsetails. The site also lacks the surface rocks characteristic of a past debris flow occurrence, which is a major indicator that flooding has affected the area following the debris flow that was experienced.

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Table 1. Linear Regression Analysis of Canopy Coverage.

Table 2. Linear Regression of O-Horizon Depth.

Canopy Coverage: As a reliable predictor of the age of a debris flow, the hypothesis concerning canopy coverage was not supported. The canopy coverage increases inconsistently as age increases. This is supported in that canopy coverage has a total of fifteen degrees of freedom (based on the averages of each transect), as determined by the T test, and a T stat of 1.47 (Table 1). A T stat of less than 2.13 has no statistical significance and communicates that there is no significant relationship between the amount of canopy coverage and age based on the data collected. To further support this, the P value of the canopy coverage data is .16, which exceeds the commonly accepted 0.05 or lower that represents a statistically significant relationship. Because both the T stat and P tests were failed, the null hypothesis must be accepted and the hypothesis rejected. Therefore, canopy coverage by itself should not be used as a predictor of age of debris flows.

O-Horizon Depth: As an indicator of age, the hypothesis concerning O-Horizon depth was supported. O-Horizon depth increases as age increases at a rate of approximately three millimeters a year. This is supported in that O-Horizon depth has a total of fourteen degrees of freedom as determined by the T test, and a T stat of 11.1 (Table 2), representing a clear, statistically significant relationship between O-Horizon depth and age based on the data collected. This is further supported by the O-Horizon depth’s P value of 5.29x10-8, which is far below 0.05, punctuating the significant relationship between the depth to the O-Horizon and age of the debris flow. Because both T stat and P tests were passed, the null hypothesis can be rejected and the hypothesis accepted. Therefore, for the areas tested on Mount Rainier, the depth of the O-Horizon is a reliable predictor of age of a debris flow.

One step that would definitely increase the validity of this experiment would be the choice of homogeneous transects in that they need to be selected carefully and methodically with careful regard to how homogeneous they really are. The ability to identify such transects comes with experience, so if this investigation were to be performed again, the data found would most likely be more accurate.

In order to further qualify the conclusions that have been drawn from this data, more data itself needs to be collected in larger sample sizes at more sites at Mount Rainier of varying approximate ages. It may even be helpful to investigate these same factors at similarly affected places such as Mount Saint Helens and other mountains in the Cascade Range. Other abiotic and/or biotic factors may be worth investigating in the future as well.

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References1. National Park Service. “November 2006 Flooding.” National Park Service Website. 6 July 2012.

2. Loehman, Rachel and Greer Anderson. “Understanding the Science of Climate Change: Talking Points – Impacts to Western Mountains and Forests.” U.S. Department of the Interior – National Forest Service Report 2009/090 (February 2009).

3. Crandell, Dwight R. “Postglacial Lahars From Mount Rainier Volcano, Washington.”. Washington U.S. Geological Survey Professional Paper 677 (1971): condensed.

4. Driedger, C.L., J.S. Walder. “Rapid Geomorphic Change Caused by Glacial Outburst Floods and Debris Flows along Tahoma Creek, Mount Rainier, Washington, U.S.A.” Arctic and Alpine Research. Vol. 26. No. 4. (1994): pp. 319-327.

5. Gordon, Susan. Rainier Glacier Melt May Boost Debris Flow Risk. Seattle Post-Intelligencer. Retrieved from the World Wide Web on 2 February 2012.

6. Vallance, James W., et al. “Debris-Flow Hazards Caused by Hydrologic Events at Mount Rainier, Washington.” U.S. Geological Survey Open-File Report 03-368 (2003).

7. Campbell, Neil A., et al. AP Biology Eighth Edition. San Francisco: Pearson Education Inc., 2008.

8. Moral, Roger Del, et al. “Increasing deterministic control of primary succession on Mount St. Helens, Washington.” Journal of Vegetation Science. Wiley Online Library. 8 Sep 2009.

9. Moral, Roger Del, et al. “Primary succession trajectories on a barren plain, Mount St. Helens, Washington.” Journal of Vegetation Science. Wiley Online Library. 20 Apr 2010.

10. Moral, Roger Del, et al. “Spatial factors affecting primary succession on the Muddy River Lahar, Mount St. Helens, Washington.” Springer Link. 2009. Retrieved from the World Wide Web on 26 July 2012.

11. Pierson, Thomas C., “Using Age of Colonizing Douglas-Fir for the Dating of Young Geomorphic Surfaces—A Case Study.” Dating Torrential Processes on Fans and Cone. 2013 (in review).

12. Globe Program, The. The Globe Soil Color Book 2nd Edition. Visual Color Systems, 2005.

13. Pringle, Patrick. Personal interview with Mrs. Thompson June 2010.

AcknowledgementsFunded by the American Association of University Women (AAUW) who provided the grant which paid for all of the project’s expenses. United States Department of the Interior National Park Service scientific research and collection permit #MORA – 2011 – SCI – 0034.

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Supplementary DataAvailable at this link.