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Krummholz island size, soil inorganic, and organic property data for Saddle, S slope of Niwot Ridge from 1994-6-28 to 1994-7-12

Data set creator(s): Timothy Seastedt

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Engelmann spruce (Picea engelmannii) and subalpine fir (Abies lasiocarpa) tree islands modify the characteristics of surface soils in alpine tundra. Soil C content of the approximate A horizon (top 15 cm) of soil was measured during the summer of 1994 on windward, leeward, upslope and downslope sides, and interiors of tree islands on Niwot Ridge, Colorado, USA. A subset of samples from these sites were also used for CHN analysis and were measured for total phosphorus using persulfate digestions and colorimetric measurements. Results indicate significant (p<.0001) reductions of percent of dry mass represented by C in soil and significant (p<.04) declines in absolute C storage among soils on the windward sides of tree islands as compared to the upslope and downslope controls, and a tendency for reduced C on the leeward sides as well. Surface organic matter (O horizon) accumulations averaging 9.6 +/- 1.02 kg/m^2 are found in the interior of tree islands, but this material, in addition to roots, is not stabilized in the A horizons of soil. The movement of tree islands can therefore be regarded as disturbances to soil building processes in alpine tundra. Timberline forest and adjacent tundra patches of similar aspect and slope were also sampled for comparisons of soil C content.  Results indicated similar C storage beneath trees and tundra at this lower elevation. The wind-induced movement of tree islands across the tundra creates enhanced snowpack within the trees and on their leeward sides. Shading and moisture conditions of the soil are altered, leading to C deposition and decomposition dynamics which differ from that of unimpacted tundra surface soils. However, at timberline, adjacent tundra lacks the ability to exhibit the enhanced C storage of alpine tundra at higher elevations. Snowpack within trees and adjacent tundra at timberline may be relatively constant such that biophysical factors affecting soil characteristics are relatively unchanged by plant life-form.


Study sites were located on a south-facing slope adjacent to the east side of the Niwot Ridge Saddle at an approximate elevation of 3600 m (treeline data), south-facing slopes on Niwot Ridge at an approximate elevation of 2400 m (timberline data), and randomly selected subalpine fir and Engelmann spruce tree islands in dry meadows on Niwot Ridge (tree island data). Contact Tim Seastedt for location of original data.

Date Range:

1994-6-28 to 1994-7-12



length of krummholz tree island, width of krummholz tree island, distance of soil core from leeward side of krummholz tree island, scar length of krummholz tree island, sample depth, organic matter content as a proportion of dry mass, total phosphorus, total nitrogen, total carbon, carbon/nitrogen ratio

Location: Saddle • S slope of Niwot Ridge

At a glance:

Saddle site
Elevation: 3500 m


Location Group: Saddle, S slope of Niwot Ridge

Found within: Niwot Ridge (USFS - UNESCO Biosphere Reserve)
Located in: USFS - UNESCO Biosphere Reserve
(Click to learn more about these locations)

More data from: Saddle, S slope of Niwot Ridge

Core Data Set: No
Discipline: Plant/vegetation ecology, Biogeochemistry

Data Citation

Seastedt, Timothy. 2019. Krummholz island size, soil inorganic, and organic property data for Saddle S slope of Niwot Ridge from 1994-6-28 to 1994-7-12.

CU Boulder

This material is based upon work supported by the National Science Foundation under Cooperative Agreement #DEB-1637686. Any opinions, findings, conclusions, or recommendations expressed in the material are those of the author(s) and do not necesarily reflect the views of the National Science Foundation.

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