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Methods for Experiment 133 -

Field Operations: Prescribed Burning

A prescribed burning program was initiated at CCESR in 1964 to restore and maintain oak savanna and woodland vegetation and to test the effectiveness of different prescribed burning treatments. An area of about 210 hectares was divided into 14 management units of 2.4 to 30 hectares each. Each unit was assigned to one of seven burn frequency treatments, ranging from annual burns to complete fire exclusion, which are shown in the following table. Cedar Creek Burn Units - Prescribed Burning Record

Year/BurnUnit101102103104105106107108109(309)110111113115116117201209401409503504506602603703CCNAS1AS2AS3
196204/26/196204/26/1962
196308/30/196305/02/1963
196405/23/196404/23/196404/12/1964
196504/28/196505/07/196504/07/196505/07/196505/07/196504/28/1965
196604/13/196604/12/196604/25/196604/13/196604/25/196604/25/196608/30/196604/13/1966
196704/27/196704/01/196704/14/196705/05/196705/05/196707/31/196709/06/196704/10/196704/27/196704/27/1967
196804/15/196804/26/196804/26/196804/29/196804/29/196804/26/196804/12/1968
196905/12/196905/12/196904/23/196504/23/196905/14/196908/27/1969
197005/04/197005/04/197005/19/197005/04/1970
197104/21/197104/29/197104/29/197105/12/1971
197205/08/197204/17/197205/18/197204/25/197204/25/197204/17/197204/25/197205/08/197205/08/197204/17/1972
197304/26/197304/26/197305/16/197304/26/197305/16/197305/15/197305/16/197305/26/197304/26/1973
197404/16/197404/16/197405/18/197407/19/197404/24/1974
197505/05/197505/05/197505/12/197505/12/197505/12/197505/24/1975
197604/26/197604/26/197604/29/197604/29/197605/06/197604/26/197604/25/197605/01/1976
197704/25/197704/25/197704/26/197704/26/197704/25/197704/25/1977
197805/01/197804/28/197804/28/197805/15/197805/01/197805/10/1978
197904/23/197904/23/197904/23/197905/15/197904/23/197905/15/197905/16/1979
198004/17/198005/14/198005/14/198005/21/1980
198105/12/198105/07/198105/07/198105/20/198105/05/198105/18/198105/12/1981
198204/20/198205/24/198204/26/1982
198305/05/201204/25/201205/05/201205/11/201205/25/201204/11/201204/11/2012
198404/19/201205/10/201205/10/201204/17/201204/19/201204/19/2012
198504/19/201204/29/201204/11/201205/07/201205/05/201205/07/2012
198605/07/201204/10/20125/5?05/07/201205/07/201204/16/201204/16/2012
198705/04/198705/06/198710/06/1987
198805/19/198805/18/198804/11/1988
198904/25/198905/12/198905/12/198904/25/198905/11/1989
199005/03/199005/03/199005/03/199005/03/199005/03/199005/05/1990
199105/14/199105/14/199105/14/199105/14/1991
199205/14/199205/08/199205/08/199205/14/199205/14/199205/08/199205/08/199205/08/199205/14/1992
199305/05/199305/12/199305/12/199305/05/199305/05/1993
199405/05/199404/22/199404/22/199404/20/199405/10/199404/20/199405/12/199404/21/199404/21/1994
199505/03/199501/29/199505/05/199505/12/199505/03/199505/03/1995
199605/07/199605/16/199605/16/199604/29/199604/29/199604/30/199605/07/199605/07/199605/13/199609/20/1996
199705/01/199704/25/199704/21/199704/28/199705/06/199705/06/199704/17/199705/01/199704/29/1997
199804/17/199804/23199804/18/1998
199904/28/199904/26/199904/26/199904/24/199904/24/199904/26/1999
200005/02/200005/24/200004/24/200004/28/200004/26/200005/02/200005/02/200004/26/2000
200010/11/200110/11/200110/11/200110/11/200110/11/200110/11/200110/11/200110/11/2001
2001
200205/14/200204/30/200205/14/200204/26/200204/26/200204/30/2002
200304/24/200304/11/200304/12/200304/12/200304/08/200304/09/200304/25/200304/08/200304/08/200304/23/200304/24/200304/24/200304/09/2003
200404/22/200404/22/200404/22/200404/24/2004
200504/15/200504/14/200504/14/200504/14/200504/14/200504/21/200504/21/200504/21/200504/21/200504/21/200504/15/200504/15/200504/14/2005
200604/27/200604/27/200604/19/200604/24/200604/19/200604/27/2006
200704/20/200704/20/200704/20/200704/20/200704/20/200704/19/200704/19/200704/20/200604/20/200704/20/2007
200805/01/200805/01/200805/01/200805/01/200805/01/200805/01/200805/01/200805/01/200805/01/200805/01/200805/01/200805/01/2008
200904/28/200904/28/200904/28/200905/11/200905/11/200904/22/200904/28/200904/28/200905/05/200905/04/200905/04/200905/04/200905/11/200905/11/200905/11/2009
201004/19/201004/22/201004/18/201004/19/201004/09/201004/09/201004/19/201004/08/201004/09/201004/09/201004/09/201004/09/201004/09/2010
201104/25/201104/25/201104/25/201105/04/201105/04/201104/25/201104/25/201104/25/201105/04/201105/03/201105/04/201104/12/2011
201204/01/201204/17/201203/28/201204/01/201204/01/201204/01/201204/12/201203/28/201204/12/201204/12/201204/01/201204/01/2012
201305/07/201305/07/2013
201405/05/201405/05/201405/05/201405/18/201404/22/201404/22/201405/05/201405/05/201405/18/2014
201505/05/201604/30/201505/05/201505/05/201504/23/201504/27/201504/16/201504/16/201504/16/201504/23/201504/16/201504/16/201504/16/2015
201604/13/201604/12/201604/17/201604/13/201604/13/201604/12/201604/17/201604/17/2016
 

Notes:

DateBurn Unit Comments
-/-/1998503Possibly burned
04/29/2000502Western Half Burned
10/11/2001103Wild Fire
10/11/2001104Wild Fire
10/11/2001105Wild Fire/Southwest 1/3 didn't burn
10/11/2001109(309)Wild Fire/Eastern Edge
10/11/2001201Wild Fire
10/11/2001204Wild Fire
10/11/2001301Wild Fire
10/11/2001401Wild Fire
10/11/2001701Wild Fire/ North of 701 to Hub Street
04/24/2006113Arson/ Northwest of BioCON
04/15/2009113NW across road of 113
 

The first burn was conducted in 1964, and all units not designated for fire protection had been burnt at least once by 1969. Two additional burn units west of East Bethel Blvd. received prescribed burns beginning in 1987 and 1992. Additional burn units have been added to the program in 1996, including 3 units along the west side of East Bethel Blvd., and one unit (409) that is a portion of one of the original "no burn" units. The Nature Conservancy began a similar prescribed burning experiment in 1962 on their 20 hectare Helen Allison Savanna property, which is adjacent to the Cedar Creek burn units. Eight rectangular 1-ha burn units were outlined on the east end of the property in a 4x2 design. The remaining 12 hectares were managed with protection from fire until 1987, when this unit was added to the burning program for conservation purposes. Prescribed fires are generally conducted in the spring using a form of the strip-headfire method. Firebreaks are disked in the spring prior to burning to remove most fuels. In areas where permanent fire breaks do not exist, the grass layer is mowed to produce a 1-2 meter wide fuel break. A backfire is started along the lee side of the burn unit, to widen the firebreak. Flanking fires are then lit along the sides of the units and monitored until a sufficiently wide blackline is produced. Finally, a headfire is started along the windward edge of the unit to complete the burn.

Sampling: Nitrogen cycling

Annual and seasonal nitrogen mineralization rates were estimated on 20 of the permanent plots in 1995. Six of these plots have been designated for long-term monitoring of N mineralization. N mineralization was measured over 5 incubation periods (approx. 30-45 days each) throughout the active growing season (mid-April to mid-October) in 1995. Eight replicates were used in each plot, corresponding to the same eight sample points used in the root core and litter trap samples (points 8-11, 14-17). We used a modified buried bag method to measure N mineralization as developed by Dave Wedin. At each point, a 0.75 inch diameter by 15 cm long soil core was removed from the sample area. This was our "initial" sample. A paired core was placed within 10 cm of the "initial" sample by pounding a sharpened piece of 0.75" diameter PVC pipe into the ground to a depth of 15 cm. The top of the pipe was plugged with a rubber cork to prevent water flow through the pipe. Air holes drilled between the soil surface and the cork facilitated ventilation of the sample during incubation. At the end of the incubation period, the PVC cores were extracted and returned to the laboratory for processing. Samples (both initial and final) were processed using standard Cedar Creek methods and will be described only briefly here. Samples are first homogenized. Soil nitrogen is extracted in 50 ml of 1 molar KCL solution and processed through the Cedar Creek autoanalyzer . Soil moisture content is determined gravimetrically. Additional soil cores were removed in fall of 1995 for purposes of measuring total soil carbon and nitrogen. At each of the 160 sample points used for the N mineralization measurements, four soil cores (0.75" diam. by 30 cm length) were removed from roughly evenly-spaced points along a 0.75 meter strip adjacent to the herbaceous vegetation sampling area. Each of these cores were divided into three depth segments (0-5, 5-15, and 15-30 cm) and pooled by depth. Two cores were extended to a depth of 50 cm and these two subsamples were pooled to produce a fourth depth sample (30-50 cm). Samples were dried and sifted to remove root material. A subsample was homogenized using a coffee mill and stored in a plastic sample bag for carbon and nitrogen analysis. The remainder of the sample was placed in a larger sample bag and archived for future use. Permanent Plot Data Collection - 1995/1996 Field Seasons

Burn Unit Plot No. Tree Tags Tree Survey Sample Points Mapped Trees Mapped Shrub Layer Survey Herb Layer Survey Canopy LAI Readings Tree Cores N Min. Root Core
101 1 Y Y Y Y Y Y Y Y Y Y
101 *21 - - Y - - Y - - - -
102 *22 - - Y - - Y - - - -
103 3 Y Y Y Y Y Y Y Y Y Y
104 4 Y Y Y Y Y Y Y Y Y Y
104 24 Y Y Y Y Y Y Y Y Y -
105 5 Y Y Y Y Y Y Y Y Y Y
106 6 Y Y Y Y Y Y Y Y Y Y
107 7 Y Y Y Y Y Y Y Y Y -
108 8 Y Y Y Y Y Y Y Y Y Y
108 *28 - - Y - - Y Y - - -
109(309) 15 Y Y Y Y Y Y Y Y Y Y
301 18 Y Y Y Y Y Y Y Y Y -
110 10 Y Y Y - Y Y Y - Y Y
111 11 Y Y Y Y Y Y Y - Y -
113 13 Y Y Y Y Y Y Y Y Y Y
115 903 Y Y Y Y Y Y Y Y Y -
115 904 Y Y Y - Y Y Y - Y Y
116 901 Y Y Y - Y Y Y - Y -
116 902 Y Y Y - Y Y Y - Y -
117 905 Y Y Y - Y Y Y - Y -
201 16 Y Y Y Y Y Y Y Y Y -
209 9 Y Y Y - Y Y Y Y Y -
409 17 Y Y Y - - Y Y - - -
409 19 Y Y Y - Y Y Y - - -
CCN 20 Y Y Y - Y Y Y - - -
AS1 101 X Y - - Y Y Y - - -
AS2 102 X Y - - Y Y Y - - -
AS3 103 X Y - - Y Y Y - - -
 

* denotes old field plot. CCN located in an unburned area north of Cedar Bog Lake. AS1, AS2, AS3 all located in Helen Allison Savanna area.

Sampling: Oak seedling survival and demographics

This portion of the study is designed to improve our understanding of the influence of fire frequency and canopy cover on the spatial patterns, growth, and mortality/survival rates of oak seedlings. Belt transects have been established in five burn units representing the complete range of burn frequencies: unit 110 (no burns), 113 (4 burns/32 years), 107 (11/32), 105 (15/32), and 104 (26/32). In burn unit 104, there are four 100-m long transects placed within the macroplot (see E134). In the remaining units, there are three transects of 40 meters each within the permanent plots used for this study. Oak stems, both new germinants and older seedlings/sprouts have been tagged for long-term demographic studies. All oak stems less than 5 cm dbh that lie within 0.5 meter on either side of the transect are tagged with numbered aluminum tags. If an individual has multiple stems, only one stem is tagged. Tag number, location, species, height, and diameter are recorded for each individual at the time it is tagged. The position of each individual relative to the tree canopy is also noted as one of the following: under canopy, canopy edge, or open. Individuals are surveyed annually to assess both mortality and deer browse.

Sampling: Permanent Plots

A series of permanent plots have been established in the burn units to facilitate repeated sampling of tree, shrub, and herbaceous community composition. Plots are sampled every 5-6 years to monitor changes in structure and composition. The first twelve of these were established in CCNHA Fish Lake burn units in 1984 as part of experiment 015. Additional plots were added in 1990 as part of experiment 094, including four additional plots in the Fish Lake burn units, five in the "Davis grid" savanna area west of East Bethel boulevard, and three in the Allison Savanna burn units. Finally, three new plots were added in 1995, two in old fields and one in burn unit 104. Each plot consists of four parallel 50-meter transects placed 25 meters apart, outlining an area 50m x 75m. Points for quadrat sampling of herb and shrub cover are placed at 10 meter intervals along each transect for a total of 24 sample points per plot. (Note: the two old field plots, 22 and 28, were laid out as two 110-meter transects placed 25 meters apart, again producing 24 sample points.) Endpoints of each transect are marked with fenceposts (T-posts). The fencepost on the front end of each transect (points 1, 7, 13 and 19) are labeled with aluminum tags identifying the experiment (E133), plot number, and transect number. Interior sample points on each transect were marked by rebar posts starting in 1995 to facilitate true repeated sampling at each point.

Sampling: Trees

All trees within the 50m x 75m area were tagged in 1995 using numbered round aluminum tags. Tags were nailed to the tree at a height of 1.3-1.7 meters and facing the front of the plot (the long side with labeled fenceposts). Trees on many of the plots were previously tagged as part of experiment 094. These foil tags appear to have been highly susceptible to fire and animal damage, however, and were missing from a large proportion of the trees. Old and new tag numbers were matched up for the vast majority of trees, however, so individual trees can still be followed over time. The aluminum nails from the old tags are valuable, however, because the E094 diameter measurements were made 1 centimeter above this nail. The 1995 measurements were made at "breast height" (about 1.35 meters) as determined by the field crews, so there may be some inconsistencies between 1990 and 1995 measurements. Trees were surveyed in 1995 for species identification, status (alive, dead, snag, fallen), and diameter at breast height (dbh). Previous surveys also recorded approximate tree height and crown vigor (ordinal scale, 1-5) on some plots. On many of the plots, trees were also mapped to the nearest 0.1 meter using the "Topcon Total Station" surveying equipment. Since readings were taken to the edge of the tree, the true accuracy is probably somewhere between 0.1 and 0.4 meters. The mapping process included all tagged trees (>= 5 cm) and the understory vegetation sample points.

aafe133 - Plant traits

Sampling

For leaf trait data, the youngest fully expanded leaves were collected from 4 to 6 individuals of each species
from within or near the experimental plots between June and August 2005.

afle133 - Root tissue carbon and nitrogen

Protocol - Root tissue carbon and nitrogen

In each square that is clipped for aboveground plant sampling, a root core is taken in the center of the plot at the depth of 0-20 cm and then from 20-40 cm. The soil sample from each depth is put into separate labeled plastic T-shirt bags. For washing, each labeled T-shirt bag of soil is placed on the screen. Water is sprayed at a medium speed over the soil (so all of the fine roots don't get blasted through the screen). This removes sand and separates roots from the soil. Oftentimes in the 0-20cm core depth, a dense mat of roots keeps soil and rocks from being washed away by the water stream, this dense mat is ripped apart and broken. The roots are then picked out of the remaining objects that are found on the screen. The person washing the roots has to be able to distinguish the live roots from dead roots and other miscellaneous debris. Live roots are commonly light colored, hard to break, and flexible. Dead roots are commonly flimsy, easily broken, lacking structural integrity, and dark colored. If it is difficult to get all of the dirt/particles out of the sample, we put water in a small tub and float the roots. This allowes the heavier particles, such as sand, to sink to the bottom of the away from the floating roots. After they are washed, the roots are sorted to "fine roots" "coarse roots" and "crowns" in the root washing shed. They're then bagged and sent to the drying room. Samples are dried at 40 degrees C, and then ground with a Wiley Mini-Milll using a 40 mesh screen. Ground samples are analyzed for % carbon and % nitrogen.

Root tissue carbon and nitrogen - Instrumentation

Samples are analyzed using C-N Analyzers, NA1500, Carlo-Erba Instruments or ECS 4010, COSTECH Analytical Technologies Inc., Valencia, CA, USA

agde133 - Soil net N mineralization over five incubation periods

Sampling

Soil net N mineralization rates were measured in 1995 for the 0 to 15 cm depth horizon using in situ incubations for the eight most central subplots within each plot over five incubation periods (30 to 45 days each) from April 10 to October 15. We used a modifided semi- open core method for in situ incubation of samples (Wedin and Tilman 1990). At the beginning of each incubation period, a 2.5-cm diameter by 15 cm long soil core was removed from each sample point and returned to the lab for processing. A paired core was located within 10 cm of the 'initial' sample by pounding a sharpened tube of 2.5 cm diameter PVC pipe into the ground to a depth of 15 cm. The top of the pipe was covered with a rubber cork to prevent water flow through the soil column. Air holes between the soil surface and the cork facilitated ventilation of the sample during incubation. At the end of the incubation period, the PVC cores were extracted and returned to the laboratory for processing. Samples were refrigerated at 4 degrees C for up to 48 h prior to processing. Soil nitrogen was extracted from 20 to 25 g of field-moist soil in 50 mL of 1 mol/L KCl solution and measured colorimetrically on an Alpkem autoanalyzer (Alpkem, College Station, Texas, USA) for N as NO3 and NH4. Nitrication and N mineralization rates were calculated as the difference in NO3 and in total N (NO3 NH4), respectively, between the incubated and initial soil samples. Annual rates per subplot were estimated as the sum of the values for the five incubation periods.

Publications cited in these methods:
Wedin, D.; Tilman, D.; Species effects on nitrogen cycling: a test with perennial grasses. Oecologia 84:433-441. 1990

Results from this data are published in:
Reich, P.; Peterson, D. W.; Wedin, D. A.; Wrage, K.; Fire and vegetation effects on productivity and nitrogen cycling across a forest-grassland continuum. Ecology 82(6):1703-1719. 2001

bde133 - Soil bulk density

Soil measurement

Bulk soil samples were collected during the summer of 2002. Bulk density was determined by carefully extracting soil cores of a known volume and weighing the oven dried soil.

cae133 - Soil Calcium

Soil cation analyses

Bulk soil samples were collected during the summer of 2002. Bulk density was determined by carefully extracting soil cores of a known volume and weighing the oven dried soil. These samples were then composited and 4 subsamples were each analyzed at the Research Analytical Laboratory UMN for exchangeable base cations (Thomas 1992) .

Thomas, G.W. 1982. Exchange cations. In Methods of soil analysis. Part 2. Chemical and microbiological properties, 2nd Ed. Edited by A. L. Page. ASA, SSA, Madison, Wisconsin. pp. 159-165.

herbe133 - Herb Survey

Sampling: Herbaceous vegetation

Herb layer vegetation was sampled at each of the 24 permanent sample points on each plot using a rectangular frame 0.5m x 1.0m. The frame is placed at the sample point with the right front corner touching the permanent marker post, the long sides of the frame lying parallel to the transect, and the short side extending to the left of the point (back and left). This placement is modified for the sample points at the back end of each transect (quadrats 6, 12, 18, and 24), where the frame is placed in front of the marker post (front and left). This modification was apparently used in 1990, so was continued in 1995. Cover classes were estimated for each species in the herb and shrub layers based on the vertical projection of plant parts onto the area of the frame. Plants need not be rooted within the area of the frame to be recorded. This is especially important for some vine and shrub species. We imposed no upper limit on total cover, unlike some other studies within the Cedar Creek LTER program. Cover classes are based on a modified Domin scale (1 = 1%, 2 = 2-5%, 3 = 6-25%, 4 = 26-50%, 5 = 51-75%, and 6 = 76-100%). These classes seemed to work well, though better resolution might have been obtained had category 3 been subdivided into a 6-10% category and an 11-25% category.

Sampling: Plant biomass and productivity

Several methods have been employed to measure the various components of biomass and productivity on the permanent plots, in addition to the herb layer biomass estimates described above. We installed eight litter traps in each of 20 permanent plots to catch leaf, twig, and seed litter dropped from trees and shrubs. The litter traps are mounted on a pair of rebar posts at a height of about 70 cm, and are placed adjacent to sample points 8-11 and 14-17, the interior sample points in each plot. The traps are made of plastic wash basins, with a cross-sectional area of about 0.095 m2. Root cores were taken to a depth of 60 cm at each of the 8 sample points used for litter collection. A 5-cm diameter core was removed from the soil adjacent to the vegetation sample quadrat. The 60 cm core was divided into 3 sections, representing depth ranges of 0-15, 15-30, and 30-60 cm, and each section was placed in a labeled sample bag. Samples were washed over a 1-mm mesh screen to remove sand particles from roots. Roots were then dried and weighed. Increment cores were taken from a subset of trees in several of the plots for the purposes of estimating annual growth increment as a function of tree species and size.

ke133 - Soil potassium

Soil cation analyses

Bulk soil samples were collected during the summer of 2002. Bulk density was determined by carefully extracting soil cores of a known volume and weighing the oven dried soil. These samples were then composited and 4 subsamples were each analyzed at the Research Analytical Laboratory UMN for exchangeable base cations (Thomas 1992) .

Thomas, G.W. 1982. Exchange cations. In Methods of soil analysis. Part 2. Chemical and microbiological properties, 2nd Ed. Edited by A. L. Page. ASA, SSA, Madison, Wisconsin. pp. 159-165.

lite133 - Litter biomass

Sampling: Annual canopy litter biomass

From 1995 to 1999 eight litter traps in each of 20 permanent plots were used to catch leaf, twig, and seed litter dropped from trees and shrubs. The litter traps were mounted on a pair of rebar posts at a height of about 70 cm, and were placed adjacent to sample points 8-11 and 14-17, the interior sample points in each plot. The traps were made of plastic wash basins, with a cross-sectional area of about 0.095 m2.

In 1999 5 gallon plastic buckets were used in some plots, from 2000 onward 5 gallon plastic buckets were used in all plots. They were placed directly on points 3-4, 8-11, 14-17, 21-22 for the entire growing season (the only time the buckets are removed is for burning in the spring). Each pail was held in place by 2 rods of rebar sticking out of the ground (sticking out between 20cm-70cm high) through holes drilled (approx 1 cm dia.) in the bottom of each bucket. All of the buckets also had a couple drainage holes (approx 1cm dia.) drilled in their bottoms.

All plant biomass, except that which came from the plants growing through the holes in the bucket bottom, was collected for each point by taking the leaves, twigs, bark, acorns, etc. and putting it in a point-specific paper bag. All of these bags were then brought back to the lab and the litter inside of them was sorted into 3 categories: oak leaves, acorns, and miscellaneous litter. All species of oaks were put together and miscellaneous litter consisted of twigs, bark, unidentifiable leaf bits, and biomass from species other than oak. The different litter types were all bagged separately and then put into 1 big point specific bag. They were then placed in the drying oven for at least a week, after which they were weighed on a 2 point scale.

lpe133 - Percent light penetration

Sampling: Canopy openness and herb layer biomass

Canopy openness and standing biomass were assessed at each sample point in 1995 (or 1996) using a pair of LICOR LAI-2000 sensors. Eight sensor readings were taken at each sample point using a 270 degree lens cap (90 occluded). Five readings (herb layer) were taken at ground level within the 0.5 m2 quadrat area using a dice pattern. Two readings (shrub layer) were taken above the herbaceous layer, but below the tall shrub layer, if any, usually at a height of 0.5-1.0 meter. The final reading (tree layer) was taken with the sensor above the tall shrub layer. Readings are taken under conditions of uniform, diffuse light (twilight hours, or on cloudy days) and are paired with readings from an "above" sensor operating continuously (one reading every 15 seconds) in a nearby open field. Readings from shrub and tree layers can be used as indirect light measurements, to assess the impact of tree and shrub layer canopy cover on understory species composition. Differences (or ratios) between mean readings for different layers can be used to estimate standing biomass. A calibrated relationship for estimating herb layer biomass from herb and shrub layer LAI-2000 readings was developed from a series of 0.25 m2 plots sampled along transects in several savanna, woodland, and old field sites. LAI-2000 sensor readings were taken at each plot (as described above) after which vegetation was clipped, dried, and weighed. Nonlinear regression was used to develop the relationship between the openness indices and biomass.

mge133 - Soil magnesium

Soil cation analyses

Bulk soil samples were collected during the summer of 2002. Bulk density was determined by carefully extracting soil cores of a known volume and weighing the oven dried soil. These samples were then composited and 4 subsamples were each analyzed at the Research Analytical Laboratory UMN for exchangeable base cations (Thomas 1992) .

Thomas, G.W. 1982. Exchange cations. In Methods of soil analysis. Part 2. Chemical and microbiological properties, 2nd Ed. Edited by A. L. Page. ASA, SSA, Madison, Wisconsin. pp. 159-165.

nae133 - Soil sodium

Soil cation analyses

Bulk soil samples were collected during the summer of 2002. Bulk density was determined by carefully extracting soil cores of a known volume and weighing the oven dried soil. These samples were then composited and 4 subsamples were each analyzed at the Research Analytical Laboratory UMN for exchangeable base cations (Thomas 1992) .

Thomas, G.W. 1982. Exchange cations. In Methods of soil analysis. Part 2. Chemical and microbiological properties, 2nd Ed. Edited by A. L. Page. ASA, SSA, Madison, Wisconsin. pp. 159-165.

ne133 - Soil nitrogen

Soil nitrogen

Soil cores 10 cm deep taken at the center of each of the 24 quadrat were analyzed individually. Total nitrogen was analyzed colorimetrically following persulfate digestion (Tilman 1984). Total nitrogen was determined by using a modification of the alkaline persulfate digestion technique (D'Elia et al. 1977, Solorzano and Sharp 1980). In this modification, 1.0 g of soil was mixed with 100 mL of a reagent containing 27.0 g/L K2S204 (low nitrogen,reagent grade) and 9 g/L NaOH; the mixture was autoclaved at 11 50C for 30 min. This oxidized all organic matter and left all nitrogen as NO3. The digest was then diluted 1:100 with a buffer of pH 8.2, and NO3 was determined by using the cadmium reduction method of Strickland and Parsons (1972).

Methods cited:

Tilman, D.; Plant dominance along an experimental nutrient gradient. Ecology 65(5):1445-1453. 1984

D'Elia, C. F., P. A. Steudler, and N. Corwin. 1977. Determination of total nitrogen in aqueous samples using persulfate digestion. Limnology and Oceanography 22:760-764.

Solorzano, L., and J. H. Sharp. 1980. Determination of total dissolved nitrogen in natural waters. Limnology and Oceanography 25:751-754.

Strickland, J. D., and T. R. Parsons. 1972. A practical manual of seawater analysis. Bulletin of the Fisheries Research Board of Canada, Number 167.

Results from this data are published in:
Tester, J.; Effects of fire frequency on oak savanna in east-central Minnesota. Bulletin of the Torrey Botanical Club 116(2):134-144. 1989

ple133 - Plant aboveground biomass data

Sampling: Plant aboveground biomass

A square 0.5 m x 0.5 m, made of PVC was used as the area that was clipped. The area that was clipped was one meter (meter sticks were used) towards the front of the plot from the point rebar (this refers to the placement of the clipped area with respect to the points in field D (E142) and the fire frequency experiment (E133), the location changes every year). If there was a bucket or a root ingrowth core, or something else we went another half meter to the right. They were measured from the point rebar. We made sure that the area that was clipped was away from the permanent vegetation survey. Everything rooted in the frame was clipped (except for really big trees-exact size cutoff unknown) a centimeter above the soil. The biomass was sorted into herbs and shrubs and put into two separate bags while in the savanna. The bags were then placed in the drying room.

rbe133 - Root biomass data

Sampling and sorting root biomass

Belowground harvest takes place during the week directly following the aboveground harvest. One core is taken in the center of the aboveground clipping square. When there is no aboveground harvest, cores are taken within 2 meters of the point marker. Before the cores are taken, litter or other debris on the soil surface is wiped away by hand. A 2 inch diameter schedule 40 PVC pipe is used to take the cores. Cores can be taken at 1 or 2 different depths, 0 to 20cm and 20 to 40cm. The soil from each single depth are placed in a T-shirt bag. The bags are then taken to the root washing shed.

The soil cores are washed and the roots sorted according to fine roots, coarse roots, and crowns. Fine roots are thin and will usually comprise the bulk of the sample. Coarse roots are defined as having a diameter greater than 1 mm. Calipers are used to determine this width. If part of a root is classified as coarse and part of it is classified as fine, break the root where the difference occurs and place each piece in their own category. Crowns are the points at or below the soil surface where the root joins the stem; they are generally characterized by (a) having several roots radiating out (the radiating roots are cut off and classified as either course or fine, they are not part of the crown) from a small area and/or (b) being connected to aboveground biomass (anything green is removed). Roots are dried at approximately 40 degrees Celsius and weighed.

sape133 - Sapling survey

Sampling: Shrubs, seedlings, and saplings

Shrub and seedling stem densities were sampled within a circular quadrat with 1-meter radius around each of the 24 sample points on the plot. We counted and recorded all woody stems by species at each point. In some cases, species with large local densities (e.g. Parthenocissus vitacea and Rhus radicans) were subsampled within 1 or 2 of the 4 quarters of the quadrat. On many of the plots, an additional 18 quadrats were sampled along 3 temporary 50-meter transect placed midway between each pair of permanent transects to produce a 6x7 grid of sample points. Note: This sampling method is different from the sampling method used in 1984 (point-quarter method, E015) and 1990 (6-10x10 meter subplots) so the data do not necessarily compare well. Saplings were recorded in a circular quadrat with 2-meter radius around each of the sample points (either 24 or 42) in the plot. We define saplings as individuals at least 1.5 meters tall and belonging to a "tree" species. Tree species were defined based on their maximum height and diameter growth potential at Cedar Creek, as determined by the tree surveys. Therefore, Amelanchier was considered a tree species, while chokecherry is classified as a shrub.

shrube133 - Shrub Survey

Sampling: Shrubs, seedlings, and saplings

Shrub and seedling stem densities were sampled within a circular quadrat with 1-meter radius around each of the 24 sample points on the plot. We counted and recorded all woody stems by species at each point. In some cases, species with large local densities (e.g. Parthenocissus vitacea and Rhus radicans) were subsampled within 1 or 2 of the 4 quarters of the quadrat. On many of the plots, an additional 18 quadrats were sampled along 3 temporary 50-meter transect placed midway between each pair of permanent transects to produce a 6x7 grid of sample points. Note: This sampling method is different from the sampling method used in 1984 (point-quarter method, E015) and 1990 (6-10x10 meter subplots) so the data do not necessarily compare well. Saplings were recorded in a circular quadrat with 2-meter radius around each of the sample points (either 24 or 42) in the plot. We define saplings as individuals at least 1.5 meters tall and belonging to a "tree" species. Tree species were defined based on their maximum height and diameter growth potential at Cedar Creek, as determined by the tree surveys. Therefore, Amelanchier was considered a tree species, while chokecherry is classified as a shrub.