Posted by: magmatist | December 18, 2012

MBVRC research grant report- Paul Whelan, soil formation rates in the recently deglaciated Easton forefield

Paul Whelan below the terminus of the Easton Glacier. Click to enlarge any image.

Paul Whelan below the terminus of the Easton Glacier. Click to enlarge any image.

Paul Whelan, a  graduate student in the Geography Department at Western Washington University, was awarded a research grant by MBVRC  in 2012. Paul is working below the Easton Glacier on Mount Baker to  investigate soil formation rates in the recently deglaciated forelands of the Easton Glacier on the south flank of Mt. Baker, between about 4200-5200′. Paul’s provided a progress report, which follows a description of his research project. Our grant to Paul was for $325.11 to cover field expenses: gasoline to get to the trailhead, collection equipment, maps, and a trailhead pass. Grant funding comes from participant fees for MBVRC field trips,the sale of MBVRC T-shirts, calendars and posters, and your generous donations.

The lower limit of Paul’s study corresponds with the approximate terminus of the glacier shown in the 1912 Welsh photo here ( a blow-up showing position of the rubble-covered terminus in 1912 is here.)

Welsh's 1912 photo. The terminus of the Easton is rubble covered, visible  and . Click to enlarge.

Welsh’s 1912 photo. The moraine-covered terminus of the Easton is at the ‘u’ in ‘.edu’ . Click, then click again to fully enlarge.

An Investigation of Pedogenesis in the Forelands of the Easton Glacier, Mount Baker

 

Sample sites in teh Easton forefield, 2012.

Sample sites in the Easton forefield, 2012.

Purpose and background Recently deglaciated valleys expose new surfaces for soil development (pedogenesis), and worldwide glacial recession during the late Holocene is continuing to expose these forelands. Soil characteristics vary across these landscapes as they are contingent upon a host of factors. However, by employing previous studies on the glacial history of Mount Baker, an inference can be made regarding time since exposure (Harper, 1993; Heikkinen, 1984). This hypothesis for the current study is that a quantifiable time sequence of soil development will be found in the  forelands of the Easton Glacier that is consistent with that glacier’s recessional history. This study is meant to further our understanding of how soil genesis occurs within these dynamic environments, especially in the incipient stages. The study employs both quantitative and qualitative measures, as well as using two sampling strategies. This topic is relevant because these landscapes remain poorly understood, especially at mid-latitudes, and also due to their high sensitivity to climatic changes. Within these high-elevation valleys, the threshold separating soil development and unconsolidated till is tenuous. A better understanding of soil processes may inform discussions on climate change and the fate of alpine ecosystems should warming trends continue. As temperatures rise, high-elevation plant and animal communities requiring specific temperature ranges will need to ascend to maintain species composition, and the processes of foreland pedogenesis will be a significant factor in preparing these new surfaces for vegetation colonization. The pedosphere is a highly complex system, and fundamentally our motivation is to contribute to growing body of knowledge. Our intention is to discern a timeline of soil development within these glacial forelands to better understand the relationship between surface age and pedogenesis as well as show what others factors and/or conditions wield significant control over pedogenic processes in these harsh environments.

Small trees have begun to grow several hundred meters below the glacier terminus.

Small trees have begun to grow several hundred meters below the glacier terminus.

Research design  The overall design of this research project is meant to be holistic and employ both qualitative and quantitative data collection using two sampling strategies. By employing a suite of sampling strategies and soil measurements, we hope to more accurately represent these newly-exposed surfaces.

The two methods for sample collection used in the summer of 2012 were a linear, down-valley transect as well as evaluating apparent visible differences in surfaces using air and historic photos. The first strategy samples sites along a transect at measured intervals. At each site, 3 different classification methods are employed: categorical (i.e unconsolidated till, stream, soil, vegetation cover/composition), soil collection for further analysis (carbon/nitrogen concentrations), and if soil accumulation is significant an excavation pit will be dug to observe qualitative measures in situ (i.e. horizonation, depth). The first classification is fairly straight-forward and is meant to break the sampling sites into a nominal dataset. Secondly, at each site a small sample is collected for eventual evaluation of carbon/nitrogen abundance of these two vital nutrients. To complement this quantitative data, records are kept of the typical USDA characteristics (i.e. pH, bulk density) as well as other descriptive measures of visual signs of development such as the Munsell color classification. The intent is to gather as much information about each site as possible so that the dominant influences of glacial foreland pedogenesis can be more readily discernible.

A sample plot.

A sample plot.

The various influences from the host of potentially confounding factors at play in these forelands also warrants consideration in the design of this research. Therefore, readily apparent differences like aspect, slope, annual precipitation and other variations are appropriately incorporated.

Progress Report, December 2012

Current research on pedogenesis following recent (100 years) deglaciation is coming along well, and like any field project in a complex, harsh environment, it has been constantly evolving. The original project was to sample in both the Easton and Coleman Glacier forefields. The scope needed to be more realistic and only the Easton valley was sampled due to difficult access to the Coleman field area. In addition, sampling the Easton valley was more time-consuming than anticipated due to rugged terrain and stream crossings. However, I have assembled a robust dataset of 68 soil samples with 5 quantitative field variables with corresponding qualitative field notes. While the sample size is smaller than originally planned, geomorphic characteristics indicated that the recent lateral glacial extent was less than that estimated based on air photos. Within this more constrained region, alluvial and colluvial influences were avoided to ensure samples were taken on undisturbed glacial till. Site selection and spacing is more dense up-valley and more sparse down-valley as incipient pedogenesis is highly dynamic and heterogeneous while established vegetation communities are slightly more consistent.

"Hmmm. Cross here? Maybe better over there. No, wait, back up there." The upper foot bridge across Rocky Creek was installed very late in 2012, so Paul's work required many stream crossings.

“Hmmm. Cross here? Maybe better over there. No, wait, back up there.” The upper foot bridge across Rocky Creek was installed very late in 2012, so Paul’s work required many stream crossings.

In the lab theses samples have been sieved to separate fine grain (<2mm) and large grain (>2mm) material; the coarse grains were then manually sifted through to separate out large organic material (i.e. moss, roots, twigs) where present. Fine grain and coarse organic
portions will be tested for pH, total organic content (via loss on ignition) and carbon/nitrogen content in Winter, 2013. Clay content may also be assessed as its relationship to pH and organics can provide a coarse estimate of cation-exchange-capacity.
Cementing at some sites produced significant soil crust (0.5 – 3 cm) either as a result of abiotic or biotic processes – such as sulfur-tolerant cyanobacteria. To acquire an additional proxy measure to time since exposure, 11 tree cores were collected from mountain hemlock (Tsuga mertensiana). Establishing a time sequence of glacial retreat and related soil development is fundamental to this study, and initial findings point to changes in vegetative community as the most accurate indicator of surface age; boundaries between and constituents of multiple successional zones were well documented. Statistical analyses for this multivariable dataset are yet to be determined, but may involve principal component analysis or cluster analysis.

Funds provided by MBVRC were used mainly for gas reimbursement to access the
Easton field area ($266.69) as well as additional equipment (sampling shovel, NW Forest Pass, topographic map, Ziploc bags for samples; $58.42) for a total of $325.11.

References:

Harper, J.T., 1993, Glacier terminus fluctuations on Mt. Baker, Washington, USA, 1940-1990, and climatic variations: Arctic and Alpine Research, vol.25, no. 4, p. 332-340.

Heikkinen, O., 1984, Dendrochronological evidence of variations in Coleman Glacier, Mt. Baker, Washington, USA. Arctic and Alpine Research, vol.16, no. 1, p. 53-64.


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