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Methods for Experiment 142 -

Field Operations: 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. Field D is in burn unit 106. Each unit was assigned to one of seven burn frequency treatments, ranging from annual burns to complete fire exclusion. E142 is burned approximately two out of every three years. The entire field is burned which includes all plots and points. Dates for field D burnings are show in the table below.

YearMonthDayBurned (1=yes, 0=no)
1966April251
1967July311
19680
1969April231
1970May191
19710
1972April171
1973May151
19740
1975May121
1976April291
19770
1978May11
1979May151
19800
1981May51
1982May241
19830
1984April171
1985April111
19860
19870
1988May181
19890
1990May31
1991May141
1992May141
1993May51
1994April201
19950
1996April291
1997April211
19980
1999April241
2000April281
20010
2002April261
2003April81
20040
2005April211
2006April191
20070
2008May11
2009April221
20100
2011April251
2012March281
20130
2014April221
 

Field Operations: Fertilization

This long-term fertilization experiment began in 1982. Nine plots 20 m wide and 50 m long were placed across the savanna in Field D and randomly assigned to one of two fertilizer treatments or unfertilized control. Unfertilized boundary areas separate adjacent plots. The fertilizer treatments include two levels of nitrogen: 5.4 and 17.0 g N g/m2/year added as NH4NO3 (commercial 34-0-0) slow release pellets. To offset indirect effects of N addition, each fertilization treatment also receives equal background levels of P, K, Ca, Mg, S and citrate-chelated trace metals applied in the following forms and rates: P2O5, 20.0 g/m2/year (as commercial 0-46-0 fertilizer); K2O, 20.0 g/m2/year (commercial 0-0-61); CaCO3, 40.0 g/m2/year (as fine-ground commercial lime); MgSO4, 30.0 g/m2/year (US Pure Epsom salts); CuSO4, 18.0 ??g/m2/year; ZnSO4, 37.7 ??g/m2/year; CoCO2, 15.3 ??g/m2/year; MnCl2,322.0 ??g/m2/year; NaMoO4, 15.1 ??g/m2/year; and H3BO3, 12.0 ??g/m2/year. Control plots remained unfertilized, no nitrogen or micronutrients are added. Fertilization occurs twice annually in early May and in late June.

ExperimentPlotPointMicroplot Fertilizer TreatmentAnnual Nitrgen fertilizer addition (g/m2/year)Annual percent Nitrogen addition (g/m2/year)1996 Canopy cover
14211I00in
14212I00in
14213I00in
14214I00in
14215I00in
14216I00in
14217I00in
14218I00in
14219I00out
142110I00out
142111I00out
142112I00out
142113I00out
142114I00out
142115I00out
142116I00out
14221G5017in
14222G5017in
14223G5017in
14224G5017in
14225G5017in
14226G5017in
14227G5017in
14228G5017in
14229G5017out
142210G5017out
142211G5017out
142212G5017out
142213G5017out
142214G5017out
142215G5017out
142216G5017out
14231E165.44in
14232E165.44in
14233E165.44in
14234E165.44in
14235E165.44in
14236E165.44in
14237E165.44in
14238E165.44in
14239E165.44out
142310E165.44out
142311E165.44out
142312E165.44out
142313E165.44out
142314E165.44out
142315E165.44out
142316E165.44out
14241I00in
14242I00in
14243I00in
14244I00in
14245I00in
14246I00in
14247I00in
14248I00in
14249I00out
142410I00out
142411I00out
142412I00out
142413I00out
142414I00out
142415I00out
142416I00out
14251I00in
14252I00in
14253I00in
14254I00in
14255I00in
14256I00in
14257I00in
14258I00in
14259I00out
142510I00out
142511I00out
142512I00out
142513I00out
142514I00out
142515I00out
142516I00out
14261E165.44in
14262E165.44in
14263E165.44in
14264E165.44in
14265E165.44in
14266E165.44in
14267E165.44in
14268E165.44in
14269E165.44out
142610E165.44out
142611E165.44out
142612E165.44out
142613E165.44out
142614E165.44out
142615E165.44out
142616E165.44out
14271G5017in
14272G5017in
14273G5017in
14274G5017in
14275G5017in
14276G5017in
14277G5017in
14278G5017in
14279G5017out
142710G5017out
142711G5017out
142712G5017out
142713G5017out
142714G5017out
142715G5017out
142716G5017out
14281E165.44in
14282E165.44in
14283E165.44in
14284E165.44in
14285E165.44in
14286E165.44in
14287E165.44in
14288E165.44in
14289E165.44out
142810E165.44out
142811E165.44out
142812E165.44out
142813E165.44out
142814E165.44out
142815E165.44out
142816E165.44out
14291G5017in
14292G5017in
14293G5017in
14294G5017in
14295G5017in
14296G5017in
14297G5017in
14298G5017in
14299G5017out
142910G5017out
142911G5017out
142912G5017out
142913G5017out
142914G5017out
142915G5017out
142916G5017out
 

Layout of plots and point selection

Plots for this experiment are 20 x 50 meters. In 1996, within each of the 9 macroplots, 8 sampling points were randomly placed in areas with oak overstory canopy present and 8 were placed in areas with no overstory canopy cover. Random coordinates were drawn until the 16 points had been located within the proper category of canopy condition. 'IN' plots were underneath the tree canopy cover when selected in 1996, 'OUT' plots were outside the tree canopy cover.

adie142 - Tree survey

Tree survey

Every five years the trees in E133 and E142 are surveyed. We survey each tree within each plot. Each plot is divided into 6 sections so that finding and mapping trees is easier. Once we located and identified the tree number we measured the diameter breast height (DBH) of the tree. The DBH was measured at a point 1.35 m from the ground unless the notes specified otherwise. We measured 1.35 m from the ground on the side of the tree where the tag was located. There could be topography changes around the tree and this gives a consistent measuring point from year to year. Some trees split below 1.35 m. These trees were measured below the crotch. We noted any changes in where the DBH was measured (if there are any).
We also recorded the status of the tagged tree. The tree was classified as alive (L), dead (D), snapped (S), or fallen (X). If a tree had even one leaf left we called it alive. Dead trees were those which were still standing, but not alive. Snapped trees included those whose trunk was snapped and broken off above the tree tag. Some were still attached, while others were on the ground. This was a tall stump. Fallen trees had trunks which had been broken and snapped off below the tag; they are fallen dead trees. We measured all trees in this way. If we were unable to find a tree we made a note of it.
If a tree had not been previously tagged and it was more than 5 cm in diameter we tagged this tree as a new recruit. We gave it a new number and tagged it with that number. See the tree maintenance protocol on where to tag new trees. We measured the DBH, recorded the status, and identified the species of the new trees. We also added any new recruits to the maps we were using.
When entering this data into the computer we double checked all data for entry errors. We re-checked any diameters that were smaller than the last survey. If a tree was still smaller than the last survey we noted that the tree was checked twice. We also re-checked any trees that had a greater than 10 cm DBH growth spurt.

adke142 - Shrub survey

Shrub survey

Shrubs are surveyed in E133, E142, and E133resto in order to examine how plant compositions within plots are changing across time and how shrub compositions differ across a burn or fertility gradient.

E142 plots are sampled approximately once every five years. All points within each plot are sampled. The sampling area is a circular quadrant with a 1-meter radius around each of the sample points in the plot. For each woody species present within the quadrant all stems (dead and alive) of each individual are counted and recorded by plot and point.

Anything that is less than 1.5m tall, no matter how small, of all woody species except Parthenocissus vitacea and Rhus radicans is counted as a shrub. The only exceptions to the 1.5m cutoff are Corylus americana and Rhus glabra because they are always shrubs and never trees.

Past Notes: We noted if a species was a 'grub'. A grub is defined as any well-established (most likely re-sprouting) individual that is bigger than a seedling, but not as large as a sapling, which is defined as being taller than 1.5 m.

adle142 - Plant aboveground biomass

Plant aboveground biomass

Once a year aboveground biomass in E142 was harvested. The harvest area was changed yearly and is away from the permanent vegetation survey. An area of 0.5 m x 0.5 m was clipped using hedge trimmers and the vegetation was sorted to herbs and shrubs. Everything rooted in the frame is clipped, except large trees that cannot be clipped using clippers, a centimeter above the soil. The biomass is sorted into herbs and shrubs and put into two separate bags while in the savanna. The vegetation was then dried at approximately 40 degrees Celsius and weighed.

adme142 - Plant belowground biomass

Plant belowground biomass

We harvest the belowground biomass in the E133 and E142 experiments to examine the effects of fire frequency (E133) and nitrogen addition (E142) on the belowground biomass of the plots.

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. Roots are dried at approximately 40 degrees Celsius and weighed.

adne142 - Herbaceous Vegetation Survey

Herbaceous Vegetation Survey

Once every five years the herbaceous vegetation of E133, E133resto and E142 are surveyed. In E142 all 16 points in each plot (1-9) are sampled. An area of 0.5m x 1.0m is surveyed at each point. Percent cover is estimated for all herb species based on cover classes. The 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%). Percent cover estimates were based on vertical projection of plant parts onto the area of the frame. Plants lower than breast height (1.37m) were considered in the percent cover estimates. Plants did not have to be rooted within the area of the frame to be recorded. We imposed no upper limit on total cover, unlike some other studies within Cedar Creek Ecosystem Science Reserve, so a given point could have over 100% cover if there was significant overlap of leaves. Basically each species was considered independent of all others.

Interns completing herbaceous surveys must calibrate first with one another. The interns estimate the percent cover for the same plots and compare values. This continues until they are within a reasonable percentage (2-4%) of each other for the plots. Once the interns are calibrated to each other they start measuring percent cover on separate plots. Percent cover will be estimated for all herb and shrub species, along with bareground and litter values.

adoe142 - Plant aboveground biomass carbon and nitrogen

Analysis equipment

Samples were analyzed for Carbon Nitrogen with C-N Analyzers (NA1500, Carlo-Erba Instruments or ECS 4010, COSTECH Analytical Technologies Inc., Valencia, CA, USA). Analyses were done at The Ecosystems Analysis Laboratory at the University of Nebraska, Lincoln.

Sample processing for analysis

Once a year aboveground biomass in E142 plots are harvested. The harvested area changes yearly. The biomass collected is sorted to herbs and shrubs and then bagged, dried and weighed. The dried and weighed biomass is then ground and put into individual vials. The ground biomass is then packed and sent to the Ecosystems Analysis Laboratory.

Aggregating samples: Combine all aboveground biomass samples for each plot-canopy combination for each herb and shrub sample. There are a total of 9 plots, each with 8 sampled points (only half of the points in each plot-canopy combination are sampled). Points numbered anywhere from 1 to 8 comprise the IN canopy treatment; and points numbered between 9 to 16 comprise the OUT canopy treatment.

Grinding: Organize and sort samples according to nitrogen treatment and plot number. Grind all the ambient plots (treatment I = plots 1, 4, 5), then low (treatment E = plots 3, 6, 8), and high (treatment G = plots 2, 7, 9) nitrogen plots, wiping the grinder(s) down with ethanol between different nitrogen treatments. We do this to minimize N contamination.

adpe142 - Plant belowground biomass carbon and nitrogen

Analysis equipment

Samples were analyzed for Carbon Nitrogen with C-N Analyzers (NA1500, Carlo-Erba Instruments or ECS 4010, COSTECH Analytical Technologies Inc., Valencia, CA, USA). Analyses were done at The Ecosystems Analysis Laboratory at the University of Nebraska, Lincoln.

Sample processing for analysis

Once a year belowground biomass in E142 plots are harvested. The biomass collected is washed and separated into 0-20 cm roots and 20-40 cm roots, which are then bagged, dried and weighed. The dried and weighed biomass is then ground and put into individual vials. The ground biomass is then packed and sent to the Ecosystems Analysis Laboratory at the University of Nebraska, Lincoln where the samples are analyzed for their CN ratio.

Combine all root samples for each plot-canopy combination for each depth. There are a total of 9 plots, each with 8 sample points. Points numbered anywhere from 1 to 8 comprise the IN canopy treatment; and points numbered between 9 to 16 comprise the OUT canopy treatment. Grinding: Organize and sort samples according to nitrogen treatment and plot number. Grind all the ambient plots (treatment I = plots 1, 4, 5), then low (treatment E = plots 3, 6, 8), and high (treatment G = plots 2, 7, 9) nitrogen plots, wiping the grinder(s) down with ethanol between different nitrogen treatments. We do this to minimize N contamination.

adqe142 - Canopy litter biomass carbon and nitrogen

Analysis equipment

Samples were analyzed for Carbon Nitrogen with C-N Analyzers (NA1500, Carlo-Erba Instruments or ECS 4010, COSTECH Analytical Technologies Inc., Valencia, CA, USA). Analyses were done at The Ecosystems Analysis Laboratory at the University of Nebraska, Lincoln.

Sample processing for analysis

Once a year litter biomass in the E142 plots was collected. The biomass collected is separated into Oak leaves, Acorns, and Miscellaneous litter; which are then bagged, dried and weighed. The dried and weighed Oak leaf litter biomass is then ground and put into individual vials. The ground biomass is then packed and sent to the Ecosystems Analysis Laboratory and the samples are analyzed for their CN ratio.

Combine all Oak leaf litter samples for each plot-canopy combination. There are 9 plots (N1-N9) and two treatments within each plot (points 1-8 = IN the canopy; points 9-16 = OUT of the canopy). You should have 18 composite samples after grinding. Grind samples according to nitrogen treatment and plot number. Grind all the ambient plots (treatment I = plots 1, 4, 5), then low (treatment E = plots 3, 6, 8), and high (treatment G = plots 2, 7, 9) nitrogen plots, wiping the grinder(s) down with ethanol between different nitrogen treatments. We do this to minimize N contamination.

adre142 - Soil carbon flux

Soil CO2 flux

Soil CO2 flux was measured once a month starting in May and continuing through October. All of these samplings were done using a LiCor 6200 on the SCF collar, which is near every intensively sampled savanna point. During the above- and belowground harvests in mid-July, a SCF collar was placed in the center of the freshly clipped area and the flux data was taken there.