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.
Data Set Results
Displaying 401 - 412 of 412
Soil temperature data from the 1989 LTER Moist Acidic Tussock (MAT89) Experimental plots. The logging station was installed in 1990 in block 2 of a four block experimental block design. The plots are located on a hillside near Toolik Lake (68 38' N, 149 36'W). Two replicates depth profiles (10, 20 ,40 centimeters) were installed in each block 2 experimental plots. Frost heaving has caused uncertain depths of measurements for many of the profiles. This data set contains only the control profiles from 2008 to 2020.
This dataset consists of Eriophorum vaginatum tussock height and width (diameter) measurements, and was used to evaluate differences in physical strucutre of previously burned tundra (2007 Anaktuvuk River fire) and nearby unburned tundra. At each site, all tussocks that intersected four 100 meter transects were measured from soil surface to tussock top in four cardinal directions, and diameter was measured in two directions.
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.
This file contains leaf area index (LAI) based on biomass measurements from an aboveground pluck in the southern portion of the Anaktuvuk River fire scar, and a nearby unburned site in late July 2017. Vegetation was sampled randomly at 10-m intervals along two 100 meter transects at both the burned and unburned sites. Vegetation was sampled within a 10X40 cm quadrat to the mineral layer, and plant material was sorted into new and old aboveground leaf and woody biomass by species.
This file contains maximum plant heights from point frame measurements made in the southern section of the 2007 Anaktuvuk River fire scar, at a severely burned site and a nearby unburned site. Pin-vegetation contact was recorded using a 0.56 m2 frame with 41 evenly spaced sampling points. Data were collected during peak green in summer 2019.
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.
Tillers from 24 Eriophorum vaginatum individuals were sampled in late July 2019 to examine differences in percent nitrogen between previously burned (Anaktuvuk River Fire) and unburned tussocks at a nearby unburned control site. At the burned site tussocks exhibiting evidence of rodent grazing were also sampled to separate herbivore effects from those of the fire. From each tussock, 3-4 new leaves were sampled (as indicated by lack of brown tips) and dried at 60°C for 24 hours, before being ground and analyzed for percent nitrogen.
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.
This file contains Eriophorum vaginatum rhizome biomass from a 2017 biomass pluck of previously burned tundra (2007 Anaktuvuk River Fire) and nearby unburned tundra. Rhizome biomass from the pluck was combined with rhizome percent nitrogen estimates (2.47% at the Anaktuvuk River Fire, and 1.05% at the nearby unburned site) to estimate grams of nitrogen per meter squared, to evaluate differences in winter forage quality for the rodent herbivore, Microtus oeconomus. Percent nitrogen estimates were derived from pooled rhizome samples collected from the two sites in late 2018.
Climate change is increasing extreme weather events, but effects on high-frequency weather variability and the resultant impacts on ecosystem function are poorly understood. We assessed ecosystem responses of arctic tundra to changes in day-to-day weather variability using a biogeochemical model and stochastic simulations of daily temperature, precipitation, and light. Changes in weather variability altered ecosystem carbon, nitrogen, and phosphorus stocks and cycling rates.
Climate change is increasing extreme weather events, but effects on high-frequency weather variability and the resultant impacts on ecosystem function are poorly understood. We assessed ecosystem responses of arctic tundra to changes in day-to-day weather variability using a biogeochemical model and stochastic simulations of daily temperature, precipitation, and light. Changes in weather variability altered ecosystem carbon, nitrogen, and phosphorus stocks and cycling rates.