Data file describing the bacterial production and bacterial respiration of water samples collected at various sites near Toolik Lake on the North Slope of Alaska. Sample site descriptors include site, date, time, depth, and category representing severity of thermokarst disturbance. A synthesis of the data presented here is published in Cory et al. 2013, PNAS 110:3429-3434, and in Cory et al. 2014, Science 345:925-928.
Data Set Results
The Changing Seasonality of Arctic Stream Systems (CSASN) was active from 2010 to 2012. The CSASN goal was to quantify the relative influences of through flow, lateral inputs, and hyporheic regeneration on the seasonal fluxes C, N, and P in an arctic river network, and to determine how these influences might shift under seasonal conditions that are likely to be substantially different in the future. Point transects were done throughout the sampling season to determine different substrate and cover types on the stream bottom.
A spectrophotometer was used to scan the canopy vegetation at four sites near Imnavait Creek each year from 2008 - 2010 by Toolik Lake LTER, Alaska. Reflectance spectra from 310-1130 nm are presented here with information relating the date and site of the scan.
Stems were measured, and aged from Ledum palustre and Salix pulchra species on treated plots at Toolik Lake, AK. Stem secondary growth in per cent per year was estimated from the slope of weight per unit length vs. age.
Leave growth of Eriophorum angustifolium and Carex rotundata was measured in a long-term experimental wet sedge tundra site near Toolik Lake, AK. Experimental treatments at each site included factorial NxP, greenhouse and shadehouse and were begun in 1989 (Toolik sites).
Seasonal patterns of leaf exsertion, elongation and senescence for Eriophorum vaginatum and Carex bigelowii was measured in mesic tussock tundra sites near Toolik Lake, AK. In addition, the response of both species to NP fertilizer and to variation in site fertility (after track versus non-track areas) were also assayed and compared. The research was done over two full growing seasons.
Above ground plant and below ground stem biomass was measured in Arctic LTER tussock tundra experimental small mammal exclosures. Treatments included Control, Nitrogen plus Phosphorus with both fenced and unfenced plots. In addition a moist non-acidic tussock tundra site was harvested. Leaf areas were also measured for each quadrat but are in a separate file.
The Anaktuvuk River Fire occurred in 2007 on the North Slope of Alaska. In 2008, three eddy covariance towers were established at sites representing unburned tundra, moderately burned tundra, and severely burned tundra. Eriophorum vaginatum flowers were counted from annual photographs of each site during peak flowering season (6/17-7/20).
Leaf areas were measured on quadrats harvested in Arctic LTER tussock tundra experimental small mammal exclosures. Treatments included Control, Nitrogen plus Phosphorus with both fenced and unfenced plots. In addition a moist non-acidic tussock tundra site was harvested. Biomass was also measured for each quadrat but is in a separate file.
The Anaktuvuk River Fire occurred in 2007 on the North Slope of Alaska. In 2008, three eddy covariance towers were established at sites represent ing unburned tundra, moderately burned tundra, and severely burned tundra. During the 2008-2014 growing seasons, canopy vegetation within the footprint of each of these towers was scanned with a handheld spectrophotometer several times throughout the growing season. Average reflectance spectra per site and collection day are presented here.
A rock-scrubbing technique was used to collect bottom samples at several different stations with three replicates at each station in the Kuparuk River. The stations are measured relative to the 1984 phosphorus dripper. Only July sampling dates are included in this file (ACG). The samples were preserved in ethanol then picked, sorted, counted, and measured in Duluth using a NIKON MICRO-PLAN II digitizing pad.
A Surber sampler (25 X 25 cm frame fitted with a 243 um mesh net) was used to sample invertebrates at several different stations. Two replicates were taken from each station. The same sampling procedure was used for all dates. The stations were measured relative to the site of the dripper ("-" = upstream of the dripper). Samples were preserved in 4% formaldehyde and transported to Orono, Maine, where invertebrates were removed by hand under 15X magnification and then identified and counted. All values are converted to individuals per square meter.
A Surber sampler (25 X 25 cm frame fitted with a 243 um mesh net) was used to sample invertebrates on a single date at each site. Five replicates were taken from at least two riffles at each site. Samples were preserved in 4% formaldehyde and transported to Orono, Maine, where invertebrates were removed by hand under 15X magnification and then identified and counted. All values are the mean of five replicates and have been converted to individuals per square meter.
The data set describes stable carbon and nitrogen isotopes and carbon and nitrogen concentrations from an August 2012 pluck of a fertilization experiment begun in 2006. Fertilization was with nitrogen (N) and phosphorus (P). Fertilization levels included control, F2, F5, and F10, with F2 corresponding to yearly additions of 2 g/m2 N and 1 g/m2 P, F5 corresponding to yearly additions of 5 g/m2 N and 2.5 g/m2 P, and F10 corresponding to yearly additions of 10 g/m2 N and 5 g/m2 P. After harvest, plants were separated by species and then by tissue.
This was an experimental burn conducted in the summer of 2015 to provide sites for an experiment to see whether seeds of Eriophorum vaginatum from different ecotypes could establish in recently burned areas. It consisted of ten 2 meter X 2 meter plots along with a similar number of control plots. There was little seedling establishment but other data have been collected on the plots.
We use a simple model of coupled carbon and nitrogen cycles in terrestrial ecosystems to examine how explicitly representing grazers versus having grazer effects implicitly aggregated in with other biogeochemical processes in the model alters predicted responses to elevated carbon dioxide and warming. The aggregated approach can affect model predictions because grazer-mediated processes can respond differently to changes in climate from the processes with which they are typically aggregated.
Surber sampler (25 X 25 cm frame fitted with a 243 um mesh net) was used to sample invertebrates at on the Kuparuk River in Reference (2001-2012) and Fertilized Reach (2002-2016) reach.
We use a simple model of coupled carbon and nitrogen cycles in terrestrial ecosystems to examine how explicitly representing grazers versus having grazer effects implicitly aggregated in with other biogeochemical processes in the model alters predicted responses to elevated carbon dioxide and warming. The aggregated approach can affect model predictions because grazer-mediated processes can respond differently to changes in climate from the processes with which they are typically aggregated.
This dataset consists of tussock density, mortality rates and causes, and an assesment of rodent-herbivore activity levels in previously burned (2007 Anaktuvuk River fire) and unburned tussock tundra. Eriophourm vaginatum tussocks were counted every meter within a 1 square meter quadrat along three transects. Cause of tussock mortality, as well as level of rodent herbivory was assessed for each tussock, and rodent herbivore activity was assessed for each quadrat.
Small mammals (rodents and shrews) were sampled 7-12 years following the Anaktuvuk River Fire to examine how post-fire ecological changes influence small mammal abundance. Small mammals were snap-trapped in August 2014, 2017-2019 at the site of the 2007 Anaktuvuk River Fire, and a nearby unburned control site. At each site, 120 traps were set in 3 parallel lines spaced 40m apart. Each trap was spaced 10m apart, baited, and set to rodent sign within one meter of the trap station. Traps were checked the following two mornings with all captures collected and sprung traps reset.
This file contains biomass measurements from vole-grazed and ungrazed Eriophorum vaginatum tussocks taken from the 2007 Anaktuvuk River Fire scar in 2019. Rodent-grazed and ungrazed tussocks were harvested to assess the impact voles have on biomass. Eighteen grazed tussocks and seven ungrazed tussocks were harvested and taken back to the lab. Ungrazed tussocks were subsampled to make seperation faster. Eight additional ungrzed tussocks were measured in the field and biomass estimates were made using allometry equations based on diameter.