A Geobotanical Analysis Of Circumpolar Arctic Vegetation, Climate, And Substrate

Thesis (Ph.D.) University of Alaska Fairbanks, 2009The objective of the research presented in this dissertation was to better understand the factors controlling the present and potential future distribution of arctic vegetation. The analysis compares the Circumpolar Arctic Vegetation Map (CAVM) with circumpolar data sets of environmental characteristics. Geographical information system (GIS) software was used to overlay the CAVM with a satellite index of vegetation (normalized difference vegetation index, NDVI) and environmental factors that are most important in controlling the distribution of arctic vegetation, including summer temperature, landscape age, precipitation, snow cover, substrate chemistry (pH and salinity), landscape type, elevation, permafrost characteristics, and distance to sea. Boosted regression tree analysis was used to determine the relative importance of different environmental characteristics for different vegetation types and for different regions. Results of this research include maps, charts and tables that summarize and display the spatial characteristics of arctic vegetation. The data for arctic land surface temperature and landscape age are especially important new resources for researchers. These results are available electronically, not only as summary data, but also as GIS data layers with a spatial context (www.arcticatlas.org). The results emphasize the value and reliability of NDVI for studying arctic vegetation. The relationship between NDVI and summer temperatures across the circumpolar arctic was similar to the correlated increases in NDVI and temperature seen over the time period of satellite records. Summaries of arctic biomass based on NDVI match those based on extrapolation from ground samples. The boosted regression tree analysis described ecological niches of arctic vegetation types, demonstrating the importance of summer temperatures and landscape age in controlling the distribution of arctic vegetation. As the world continues to focus on the Arctic as an area undergoing accelerated warming due to global climate change, results presented here from spatially explicit analysis of existing arctic vegetation and environmental characteristics can be used to better understand plant distribution patterns, evaluate change in the vegetation, and calibrate models of arctic vegetation and animal habitat

The Role of Snow Cover in Limiting Surface Disturbance Caused by Winter Seismic Exploration

The relationship between snow cover and the degree of surface disturbance caused by winter seismic vehicles was investigated on the Arctic Coastal Plain of the Arctic National Wildlife Refuge in northeastern Alaska. Ninety study plots were established on seismic lines and camp moves in tussock tundra and moist sedge-shrub tundra. Total snow depth and its components, slab layer and depth hoar, were measured during the winter. Plant cover changes, tussock disturbance, visibility and disturbance levels were determined at the study plots in the summer. Disturbance was found to be generally lower when snow depths were greater. In tussock tundra, plots with snow depths over 25 cm had significantly less disturbance than those with under 25 cm (p <0.05). The relationship between snow cover and disturbance was less clear in moist sedge-shrub tundra, where disturbance appeared to be less at snow depths above 25 cm, but these differences were not statistically significant (p <0.05). Slab depth, which does not include the loose layer of depth hoar, provided a better measure of protective snow cover in most sedge-shrub tundra, as slab depths over 20 cm resulted in significantly less disturbance (p <0.05). Moderate-level disturbance (25-50% decrease in plant cover) did not occur on trails where snow depths were at least 25 cm in tussock tundra and 35 cm in moist sedge-shrub tundra. Low-level disturbances (less than 25% decrease in plant cover) occurred on trails with snow depths as high as 45 cm in tussock tundra and 72 cm in moist sedge-shrub tundra.Key words: surface disturbance, winter seismic exploration, seismic trails, tundra, snow depth, Alaska, Arctic National Wildlife Refuge, Arctic Coastal PlainMots clés: perturbation de surface, exploration sismique d‘hiver, pistes sismiques, toundra, épaisseur de la neige, Alaska, Arctic National Wildlife Refuge, plaine côtière arctiqu

Airphoto Analysis of Winter Seismic Disturbance in Northeastern Alaska

Airphoto interpretation was used to quantify the extent of disturbance caused by seismic exploration on the 60,000 ha coastal plain of the Arctic National Wildlife Refuge during the winters of 1984 and 1985. The relationships of vegetation type, trail location and traffic pattern to the amount of disturbance were investigated. Approximately 20% of the seismic trails were photographed at 1:6000 scale, using color infrared film. Ground data collected at 194 sites were used to develop a photo interpretation key describing the photo signatures of seven vegetation types and four disturbance levels. Vegetation types and disturbance levels were determined for 4914 circles of 3 mm diameter on the aerial photos (18 m ground distance). Fourteen percent of the points were interpreted as having no disturbance (level 0), 57% had level 1 disturbance (low), 27% had level 2 (medium) and 2% had level 3 (high). Wet or partially vegetated areas were the least susceptible to disturbance. Vegetation types with mounds, tussocks, hummocks or high-centered polygons and dryas terraces were more heavily disturbed. Camp move trails and overlapping seismic and camp move trails created in 1984 caused more disturbance than other trail types due to multiple passes of vehicles over narrow trails. U.S. Fish and Wildlife Service monitors were more successful at minimizing disturbance the second year by requesting that vehicle operators avoid multiple passes on the same trail, sensitive vegetation types and areas of low snow cover.Key words: airphoto analysis, winter seismic exploration, seismic trails, vegetation disturbance, traffic patterns, Alaska, Arctic National Wildlife Refuge, arctic coastal plainMots clés: analyse de photographies aériennes, exploration sismique d’hiver, pistes sismiques, perturbations de la végétation, schémas de circulation, Alaska, Arctic National Wildlife Refuge, plaine côtière arctiqu

Conservation of Arctic Flora and Fauna (CAFF) Map No. 1.

The Circumpolar Arctic Vegetation Map shows the types of vegetation that occur across the Arctic, between the ice-covered Arctic Ocean to the north and the northern limit of forests to the south. Environmental and climatic conditions are extreme, with a short growing season and low summer temperatures. As one moves southward (outward from map's center in all directions), the amount of warmth available for plant growth increases considerably

Dynamics of Aboveground Phytomass of the Circumpolar Arctic Tundra During the Past Three Decades

Numerous studies have evaluated the dynamics of Arctic tundra vegetation throughout the past few decades, using remotely sensed proxies of vegetation, such as the normalized difference vegetation index (NDVI). While extremely useful, these coarse-scale satellite-derived measurements give us minimal information with regard to how these changes are being expressed on the ground, in terms of tundra structure and function. In this analysis, we used a strong regression model between NDVI and aboveground tundra phytomass, developed from extensive field-harvested measurements of vegetation biomass, to estimate the biomass dynamics of the circumpolar Arctic tundra over the period of continuous satellite records (1982-2010). We found that the southernmost tundra subzones (C-E) dominate the increases in biomass, ranging from 20 to 26%, although there was a high degree of heterogeneity across regions, floristic provinces, and vegetation types. The estimated increase in carbon of the aboveground live vegetation of 0.40 Pg C over the past three decades is substantial, although quite small relative to anthropogenic C emissions. However, a 19.8% average increase in aboveground biomass has major implications for nearly all aspects of tundra ecosystems including hydrology, active layer depths, permafrost regimes, wildlife and human use of Arctic landscapes. While spatially extensive on-the-ground measurements of tundra biomass were conducted in the development of this analysis, validation is still impossible without more repeated, long-term monitoring of Arctic tundra biomass in the field

The Alaska Arctic Vegetation Archive (AVA-AK)

The Alaska Arctic Vegetation Archive (AVA-AK, GIVD-ID: NA-US-014) is a free, publically available database archive of vegetation-plot data from the Arctic tundra region of northern Alaska. The archive currently contains 24 datasets with 3,026 non-overlapping plots. Of these, 74% have geolocation data with 25-m or better precision. Species cover data and header data are stored in a Turboveg database. A standardized Pan Arctic Species List provides a consistent nomenclature for vascular plants, bryophytes, and lichens in the archive. A web-based online Alaska Arctic Geoecological Atlas (AGA-AK) allows viewing and downloading the species data in a variety of formats, and provides access to a wide variety of ancillary data. We conducted a preliminary cluster analysis of the first 16 datasets (1,613 plots) to examine how the spectrum of derived clusters is related to the suite of datasets, habitat types, and environmental gradients. Here, we present the contents of the archive, assess its strengths and weaknesses, and provide three supplementary files that include the data dictionary, a list of habitat types, an overview of the datasets, and details of the cluster analysis

Biomass offsets little or none of permafrost carbon release from soils, streams, and wildfire : an expert assessment

As the permafrost region warms, its large organic carbon pool will be increasingly vulnerable to decomposition, combustion, and hydrologic export. Models predict that some portion of this release will be offset by increased production of Arctic and boreal biomass; however, the lack of robust estimates of net carbon balance increases the risk of further overshooting international emissions targets. Precise empirical or model-based assessments of the critical factors driving carbon balance are unlikely in the near future, so to address this gap, we present estimates from 98 permafrost-region experts of the response of biomass, wildfire, and hydrologic carbon flux to climate change. Results suggest that contrary to model projections, total permafrost-region biomass could decrease due to water stress and disturbance, factors that are not adequately incorporated in current models. Assessments indicate that end-of-the-century organic carbon release from Arctic rivers and collapsing coastlines could increase by 75% while carbon loss via burning could increase four-fold. Experts identified water balance, shifts in vegetation community, and permafrost degradation as the key sources of uncertainty in predicting future system response. In combination with previous findings, results suggest the permafrost region will become a carbon source to the atmosphere by 2100 regardless of warming scenario but that 65%-85% of permafrost carbon release can still be avoided if human emissions are actively reduced.Peer reviewe