Alpine Tundra Ecosystems Research Articles

An integrated geographic information system approach for modeling the suitability of conifer habitat in an alpine environment

Alpine periglacial environments within the forest-alpine tundra ecotone (FATE) may be among the first to reflect changes in habitat characteristics as a consequence of climatic change. Previous FATE studies used Integrated Geographic Information System (IGIS) techniques to collect and model biophysical data but lacked the necessary detail to model the micro-scale patterns and compositions of habitat within alpine periglacial environments. This paper describes several promising data collection, integration, and cartographic modeling techniques used in an IGIS approach to model alpine periglacial environments in Glacier National Park (GNP), Montana, USA. High-resolution (I X I m) multi-spectral remote sensing data and differentially corrected Global Positioning System (DGPS) data were integrated with other biophysical data using a raster-based IGIS approach. Biophysical factors, hypothesized to influence the pattern and composition of the FATE and the alpine tundra ecosystem, were derived from the high-resolution remote sensing data, in-situ GPS data, high-resolution models of digital elevation, and other thematic data using image processing techniques and cartographic modeling. Suitability models of conifer habitat were created using indices generated from the IGIS database. This IGIS approach identified suitable conifer habitat within the FATE and permitted the modeling of micro-scale periglacial features and alpine tundra communities that are absent from traditional approaches of landscape-scale (30 X 30 m) modeling.

Nitric acid, particulate nitrate and ammonium in the continental free troposphere: Nitrogen deposition to an alpine tundra ecosystem

Atmospheric sampling of nitric acid vapor, particulate nitrate and ammonium has been ongoing at a 3540 m a.s.l. alpine tundra site on Niwot Ridge, Colorado, since January, 1993. These nitrogen (N) species data, in conjunction with meteorological data, N data at a 3020 m a.s.l. subalpine site, and back-trajectory information, show that over 90% of the sampling was obtained under free tropospheric but, apparently, N-enriched conditions. Seasonal concentration and estimated N dry deposition trends are presented. Dry plus wet atmospheric N loading is found to provide 2.5–3 kg N ha −1 of new, available N to tundra plants during the growing season (mid-May to mid-September), of which 50%, or more, is dry deposited. During the eight-month, nongrowing season about 5 kg N ha −1 is wet plus dry deposited to the aggrading snowpack or dormant tundra plants. Up to half of this nongrowing season N loading is made available to growing tundra plants during snowmelt. Thus, a total of 3–5 kg N ha − is annually made available to tundra plants by atmospheric deposition of, primarily, anthropogenically derived N. This annual input of new, available N to nutrient N-limited tundra plants may be compared with the dominant pathway for plant N availability at Niwot Ridge—net mineralization of 10–12 kg N ha −1yr −1 recycled through the soil. The ratio of atmospheric N deposition to net N mineralization, presently approaching 0.5, is higher at the Niwot Ridge alpine tundra ecosystem than at most other ecosystems in the continental U.S.

Incorporating topographic and climatic GIS data into satellite image analysis of an alpine tundra ecosystem, front range, Colorado rocky mountains

Abstract A series of digital climate indices have been developed in support of a remote sensing study of complex alpine vegetation patterns at the Niwot Ridge Long‐Term Ecological Research site in the Colorado Front Range, USA. Using an integrated remote sensing‐GIS approach, critical factors which control the distribution of vegetation such as precipitation, temperature, wind, soil moisture and snow accumulation have been derived from a 16 year archive of digital Landsat imagery, geomorphometry from a digital elevation model, and meteorological station data. Five climatic indices were implemented: (i) Orogenic Precipitation Index, (ii) Slope‐Aspect Index, (iii) Snow Probability Index, (iv) Insolation Index, and (v) Growing Degree Days. These indices were tested individually and together with a Landsat TM image and topographic measures from a DEM to assess their significance for increasing the accuracy and precision of maximum likelihood landcover classification with respect to the hierarchical Braun‐Blan...

Extreme Precipitation during 1921 in the Area of the Niwot Ridge Long-Term Ecological Research Site, Front Range, Colorado, U.S.A.

An unusually high amount of precipitation, including a world record 24-h snowfall, was recorded in 1921 at Silver Lake, Colorado, near the Niwot Ridge alpine tundra Long-Term Ecological Research (LTER) site. There was 68.3 in (1735 mm) total annual precipitation which was over five standard deviations above the 1914-1992 mean and the April snowfall produced 76 in (1.93 m) of snow in 24 h. An investigation of these phenomena brings to light the following points. The precipitation at Silver Lake, and presumably the Niwot Ridge LTER site, during 1921 was exceptionally high. The precipitation was highly localized. There are no obvious causes for the high precipitation to be found in the synoptic climatology for the year. However, moisture sources from the west in the winter and spring and from the south in the summer do seem to have been available. Despite well-marked, but temporary, impacts on humans and possibly other higher mammals, there is no evidence of any major or long-lasting impacts to the alpine tundra or subalpine forest ecosystems. Higher temperatures and persistent drought, as might be found with global climatic warming, are proposed as potentially more important disturbance factors to these systems.

The Climate of Niwot Ridge, Front Range, Colorado, U.S.A.

The climate of Niwot Ridge is described using monthly and annual mean temperatures and monthly and annual total precipitation values for the period 1951 to 1985 and comparable precipitation values for the nearby Silver Lake station from 1915. Summary statistics and water budget values are presented. Time series analysis indicates abnormally low temperatures in the early 1980s and an overall downward trend in temperature. Autoregressive moving average forecasting models and spectral analysis hint at some cyclicity in the data series of annual values of both temperature and precipitation. Silver Lake annual precipitation data show only a slight downward trend when the extremely high value for the year of 1921 is excluded. Implications of these changes for the alpine tundra ecosystem are briefly discussed.

Dinitrogen Fixation in Alpine Tundra, Niwot Ridge, Front Range, Colorado, U.S.A.

The process of dinitrogen fixation was studied in the alpine tundra ecosystem at Niwot Ridge, Colorado. In situ fixation activities were measured by the acetylene reduction method in the soils of t...

Effects of human activities on alpine tundra ecosystems in Rocky Mountain National Park, Colorado

The activities of summer visitors to the tundra of Trail Ridge in Rocky Mountain National Park results in the rapid destruction of vegetation in the areas seen by most visitors at close range—especially near parking areas. Ecosystems differ in their reaction to trampling; those with high soil-moisture are most easily damaged. Tall herb ecosystems are next, and then fellfield. Turf types are the most durable. Other activities affecting tundra are rock collecting, littering, crushing by car tyres, and flower picking.