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University of Minnesota
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Methods for Experiment 153 -

Plot establishment:

Thirty-two 20 x 20 m plots were established in field B in fall 2000 (see plot map). To reduce edge effects, each plot has a 5 m wide buffer zone along each interior side of the fence/edge. This leaves a central 10 x 10 m area (marked with orange-tipped rebar) in which most sampling takes place.

The experiment design is factorial, with treatments consisting of deer exclosure fences, nitrogen addition, and prescribed burning. Treatments assigned to each plot are found in the treatment table below. Within each plot there is also a 1 sq. m plowed area (located outside of the central 10 x 10 m area). Deer exclosure fences were constructed of 6 ft tall hardware cloth with an opening size of 2 x 4 in.

Aluminum flashing was stapled to the bases of fence posts to protect them from burning. All trees were removed from the 4 m wide area between plots, as well as the out perimeter of the experiment. This buffer provides space for fire vehicles during prescribed burns. Trees within plots that were large enough to pose a fire hazard were removed, as were large trees near fences. This reduced potential damage to the fences, while not disturbing the inner plot where most measurements are made.

Species inventory:

A comprehensive species list was compiled for each plot. Species were listed as common (c), occasional (o), or rare (r). Rare species occurred 1-3 times in the plot, common species were abundant and evenly distributed throughout the plot and occasional species consisted of everything in between. This information was first collected in July 2001, by Heidi Hillhouse, John Haarstad, Jean Knops, Jeffrey Arnold, Steven Metzger, and Sarah Went.

A second species inventory was done September 13-14 in 2005, by Joel Zak, Steph Pimm, Daniel (Todd) Dalton, Kally Worm and David DeVetter. The amount of time spent searching in each plot was limited to 15 minutes. A * following the abundance code indicated that the species was present in the 1 x 1 m tilled area but was either absent or present in a lower abundance category in the rest of the plot.

arce153 - Arthropod sweepnet sampling

Arthropod sweepnet sampling

All 32 plots were sampled for arthropods in 2003-2006 using a 38 cm diameter muslin sweep net to take 50 sweeps per plot. A ?sweep? consisted of a quick, approximately 2-meter-long horizontal swing of the net. Sampling dates were: 15/Aug/03, 19/Aug/04, 16/Jun/05, 12/July/05, 12/Aug/05, 16/Jun/06, 15/Aug/06. Samples were frozen, then sorted under magnification. Arthropods were generally identified to species or genus, but occasionally a morphological descriptive was used when identification was uncertain. Sample collection and sorting was done by John Haarstad.

Arthropod sweepnet sampling: Data Preparation

Data preparation was begun by John Haarstad and Stephanie Pimm Lyon. It was completed by Colleen Satyshur, primarily using the access database that Stephanie prepared for Big Bio and which she used in preparing some of this data, but also using a CODE file J.Haarstad included with his latest data files. *Note about comparing experiments: morphological notes may not indicate the same species/group in different experiments.

bde153 - Soil bulk density

Bulk density

2002: Five 2-in diameter cores taken at the following depths: 0-10, 10-20, and 20-40 cm. Cores were taken at points 1, 3, 5, 7, and 9 (see sampling diagram). Samples were dried and weighed.

2005: One 2-in diameter core taken in the center of each plot (point 5), at the following depths: 0-10, 10-20, 20-40, 40-60, and 60-100 cm. Samples were dried and weighed.

Note on 2005 data: As of August 2007, these data have not been added to the database (they may still need to be entered).

Soil samples

2002: 9 soil samples were taken for C/N analysis (see diagram for sampling locations), at the following depths: 0-10, 10-20, and 20-40 cm.

2005: 9 soil samples were taken for C/N analysis (see diagram for sampling locations), at the following depths: 0-10, 10-20, 20-40, 40-60, 60-100. Samples were sieved and analyzed for carbon and nitrogen content.

Note on data: As of August 2007, we do not have C and N data for soil samples taken in 2002 and 2005.

mse153 - Small mammal abundance

Small mammal trapping:

In the summers of 2003-2005, small mammals were live-trapped in each of the 32 plots. 4 traps were set in each plot, one per side of the inner 10 x 10 m sampling area. The traps were set approximately halfway between each of the corner posts and slightly to the outside of the inner sampling area (see sampling diagram). Traps were labeled according to the side of the plot they were located on (N, S, E, W). Each week, traps were set out on Sunday after 4 PM, and picked up after the Friday evening survey. Traps were checked twice a day, starting at 6 AM and 6 PM (in 2004-5 checked only once a day). Baits were checked every morning, and replaced as necessary. A tight wad of vegetation approx 2? x 3.5? was used when trapping voles.

Any trap not physically capable of capturing animals (not sensitive enough, set off by deer, etc.) was recorded as NTAV (= no trap available) at the time that traps were checked. Captured individuals were recorded as a new capture (N) or a recapture (R). [?P? used for individuals marked in a previous trapping period.] New captures were weighed and tagged. When an individual was recaptured, the numbers on its ear tags were recorded and missing tags were replaced as necessary. Sex (M, F), age (J = Juvenile; usually all gray & small; A = Adult; usually all brown & large; S = Sub-adult; combination of both conditions; U = Unsure), species, and status at release (U = Released unharmed; C = Dead and collected; D = Dead but not collected; H = Hypothermic, treated &released; I = Injured in trap, released; E = Escaped unharmed) were also recorded, along with any unusual or important observations about the captured individual (e.g. deformities, extent of injuries, escapees, notes on burrow use, etc.).

A more detailed protocol can be found in ?smmammlprotocol2003.doc?.

Note on data: As of August 2007, we do not have raw mammal data for the summer of 2003. However, we do have the total number of captures of each species over the season, included in the small mammal data summary table.

pce153 - Plant species percent cover data

Percent cover plots

Ten permanent 0.5 x 1 m percent cover (sub-)plots were established along the interior edge of each 10 x 10 m sampling area. In all cases, the plots are oriented such that the shorter side lay along sampling area edge and the longer side points in towards the plot center. Subplot locations are recorded on the 2001 plot maps. Exact locations of permanent cover plots were partly determined by tree location. Researchers tried to ensure that each cover plot was located least 0.5 m from any tree, though sometimes this was not possible. Within this limitation, plots were distributed as evenly as possible around the edge of the inner plot.

2001: Percent cover of functional groups (C3 grass, C4 grass, forb, legume, woody, litter) was recorded. Plants present by providing insignificant cover were recorded as 0.1 %. Total percent cover did not necessarily equal 100%. Bare ground was not recorded. Sampling was done by Mark Ritchie, Kerry Griffis, Sean Kyle and Karla Hillstrom during the month of July. Subplots were initially labeled 1-10 starting on the northern-most plot of the western side and moving counter-clockwise around the plots. (Note on data: Subplot names were later reassigned to match 2005 methods.)

2004: Percent cover of individual species was recorded. However, there appear to have been problems with species identification. Thus it is probably safer to use the data lumped by functional group, as in 2001. Total percent cover did not necessary equal 100%, though percent bare ground was recorded. Subplots were initially labeled according to their position along the plot edge (NW, WN, etc.), though they were later reassigned to match 2005 methods. Plot 20 labels did not match up with the positions indicated on the plot diagram, though they were relabeled A-J in a clockwise manner regardless.

2005: Percent cover of individual species rooted within a given plot was recorded along with percent cover of litter and bare ground. Species present but providing insignificant coverage were given 0.5 percent cover. Total percent cover always equaled 100%. Where bare ground was the result of a gopher mound, this was noted in the data recorder. If pine needles or downed woody comprised some or all of the litter, the percentage of the subplot covered by that type of litter followed by the word needles or woody was entered as a ?note? in the data recorder. Where the herbaceous ground layer was covered by white pine canopy, an estimate was made as to the percentage of white pine canopy over each subplot. This percentage was included as a ?note? on the data recorder for Pinus strobus with the word canopy behind it. As in the ground layer, canopy percent cover for each subplot was capped at 100. Pinus strobus was always assigned 0 percent for the ground layer because it was never rooted in any subplot. Sampling was done in August by Joel Zak. Subplots labeled A-J starting on the western-most plot of the northern side and moving clockwise around the plots.

ple153 - Plant aboveground biomass data

Aboveground biomass:

2002: 2 clip strips (3 x 0.1 m) were taken within the 10 x 10 m sampling area in each plot. Biomass was sorted into living and dead material (i.e. litter). Locations for the 2002 strips are included on the 2001 plot maps. [Archival sample numbers 049221-049348.]

2005: 2 clip strips (3 x 0.1 m) were taken within each plot. Vegetation was clipped to a height of 1 cm. Living biomass was sorted into the following functional groups: Equisetum laevigatum, Mosses & lichens, Legumes, Non-legume forbs, C3 grasses, C4 grasses, and Sedges. Litter was sorted into three categories: Tree litter?needles and cones, Tree litter?stems (dead white pine stems), and Miscellaneous litter (normal herbaceous litter). The strips were located within the 10 x 10m experimental area whenever possible (see map for approximate placement of clip strips in most plots). However, in some cases trees were too dense in the inner sampling area and strips had to be taken outside it, in areas with representative herbaceous vegetation. On two occasions, clip strips were relocated to avoid gopher mounds.

roote153 - Root biomass data

Root biomass

2002: Three 2-in diameter cores taken within each clip strip and combined for each sample. Cores were taken at the following depths: 0-10, 10-20, 20-40 cm. [Archival sample numbers 049349-049540.]
2005: Three 2-in diameter cores taken in each clip strip (after aboveground harvest) and combined. Cores were taken at the following depths: 0-10, 10-20, 20-40, 40-60, and 60-100 cm. Samples were washed, dried, and weighed separately for each depth and strip.

Soil samples

2002: 9 soil samples were taken for C/N analysis (see diagram for sampling locations), at the following depths: 0-10, 10-20, and 20-40 cm.

2005: 9 soil samples were taken for C/N analysis (see diagram for sampling locations), at the following depths: 0-10, 10-20, 20-40, 40-60, 60-100. Samples were sieved and analyzed for carbon and nitrogen content.

Note on data: As of August 2007, we do not have C and N data for soil samples taken in 2002 and 2005.

skte153 - Skink trapping

Skink trapping

In summer 2004, Eumeces septentrionalis were caught in four pitfall traps each located 2m from a corner of the interior 10 x 10 m vegetation sampling subplot (near where small mammal traps were placed) for the dates indicated in the data. Traps were checked each morning. ID refers to the pattern of toe clipping used to identify individuals. Status indicates the condition of the individual (R=released unharmed, D=Dead, E=Escaped unharmed; only those with status R were measured).

tre153 - Tree data

Trees

During summer 2001, the locations of all trees (dead and alive) in each plot were recorded on a map marked with 1 m intervals. A temporary grid system consisting of ropes knotted at 1 m intervals was used to assist with mapping. Approximate tree canopy sized was diagramed, and each tree was tagged with an identification number.

2001: Height, age, and basal diameter (diameter ground height) of all trees were recorded, as well as any additional notes on an individual?s status. When trees had multiple major trunks branching belowground, only the largest trunk arising from each single base was measured and recorded. Height was measured to the end of the previous years? growth to avoid any bias that might have arisen during the sampling period. Height, species determination, and map location were also recorded for each shrub individual.

2002: Alive/dead recorded for each tagged tree, at two sampling times?presumably, one prior to the spring burn (sampling 1), and one after the spring burn (sampling 2).

2003: Alive/dead recorded for each tagged tree.

2004: Alive/dead recorded for each tagged tree.

2005: Early in the summer, alive/dead was recorded for each tagged tree (sampling 1). Later in the plots were re-sampled (sampling 2). All woody individuals were labeled and/or relabeled (most tags had to be replaced or rehung) and new recruits were added to plot maps. Species determinations for all non-white pine individuals are noted in the data. For all trees and shrubs over 1.5 m, measurements of both DBH (diameter at breast height) and DGH (diameter at ground height) were taken. Measurements of height (highest vertical point), width (shorter horizontal distance), and length (longer horizontal distance) were taken for woody individuals shorter than 1.5 m. Many new aspen seedlings were labeled and mapped in plots 19, 13, and 6.

Note on data: Because trees occasionally must be re-tagged, identification numbers may change over time. The database includes a table which tracks the tag numbers assigned to individual trees, and the most current tag number is included in the full data set.