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Methods for Experiment 004 -

Burning LTER Plots

All of the burning done within LTER experiments at Cedar Creek Natural History Area are done in late April or early May. Burn permits are issued to Cedar Creek Natural History Area for this time, and the following areas within Cedar Creek, by the Department of Natural Resources (headquarters in Cambridge, MN). In all cases, several people are on hand to help contain the fire. Tools used are "flappers", shovels and hand-pumped, portable water spray-cans. Drip torches containing a mixture of 1/3 gasoline and 2/3 diesel are used to start the fires. A truck carrying a high pressure water sprayer hooked up to a 125 gallon tank of water is always nearby. After the fires are burned out, any remaining hotspots are extinguished or moved to the center of the burned area to insure the prevention of wildfires.

125 gallon water tank and Minnesota Warmer Co. model KW125-7-10 utility sprayer.

Burning Methods

Field D is within burn compartment #6 (106). This field is burned 2 years out of every three. For a description of burning methods, see E015. Starting in 1989, two sections in each macroplot are burned in fields B and C and in 1992, the same was started for field A. These macroplot sections are now considered to be E057. For a description of burning methods, see E057

Field Operations: Burning

Field D is within burn compartment #6 (106). This field is burned 2 years out of every three. Starting in 1989, two sections in each macroplot were burned in fields B and C. Starting in 1992, two sections in each macroplot were burned in field A as well. These sections are now considered experiment E057.

On May 5, 1995, a wildfire burned several parts of B004 macroplots that were not supposed to be burned. Macroplots 1, 2, 6, 7, and 8 were completely burned.

Field Operations: Fertilization

Fertilizer is mixed and spread by hand twice a year, once in early May and once in late June. Each plot gets the fertilizer mixture specified by its fertilizer treatment code. For a list of fertilizer treatments for each plot.

Light Penetration

Light meter readings for E004 were taken in 1982 in the same way as in E001 except gopher mounds were ignored. Light meter readings were taken in the same positions in all plots, regardless of the presence of gopher mounds.

Light Penetration Measurements Methods

From 1982 to 1988, light meter readings were taken using a Li-Cor, Inc. Integrating Quantum/Radiometer/Photometer, model LI-188B. Two people were needed to take light readings with this system. One would hold the control box and record data and the other would hold the light sensor. The batteries would be checked before starting each session. If the batteries were OK, they would proceed to take readings. The sensor was connected to the control box by a relatively short cord, so the two people taking readings were required to stay close together. When taking readings, it was necessary to get a range value for each light value entered. If the integrating time of 1 second was not sufficient, it was increased to 10 seconds. This was also recorded.

In 1989, two new light meters were acquired. These are SF Sunfleck Ceptometers, model SF-40 (40cm probe). They were purchased from Decagon Devices, Inc., P.O. Box 835, Pullman, WA 99163. One person can easily handle a ceptometer alone. This makes is possible for three people to get the readings done more quickly and easily. One person records data while the other two take readings from the plots simultaneously. No range values are needed. To take readings a person needs to select function #1 (PAR readings), position the probe (see below) and press ``A' (read value). More than one reading can be taken and then averaged by pressing a certain sequence of letters (A, A, B, B, A).

Measurements are taken within a 4 hour period, 2 hours on either side of solar noon. (Solar noon is half way between sunrise and sunset; it is not 1200 hours). Solar noon is at 1315 hours, Central Daylight Time. Samples are taken between 1115 hours and 1515 hours. Measurements are not taken when the plot being sampled is shaded. Light readings are done when the sky is clear, whenever possible. If a cloud passes over the plot being sampled, assistants wait for the cloud to pass before taking the readings. If the sky is mostly cloudy, light meter readings are not taken.

Two measurements are taken in each plot. Each measurement consists of one reading above the vegetation and a second reading at ground level. Both values are taken to get the percent of sunlight above the vegetation that reaches ground level. In taking the above vegetation reading, the sensor must be kept level, held high above all vegetation, kept out of the shade (of plants and people) and it must be clean. When taking the below vegetation reading, at ground level, the sensor must be kept level, out of the soil and out of the shade created by people.

In 1991, light meter readings were only taken in E026 and E055. Light profiles were taken using an A-shaped frame made of aluminum. Wires were strung across the frame at 10cm intervals. The frame was placed over the subplot being metered. A reading was taken over the top of the frame, and then at each 10cm level, by placing the light meter across the wires, starting at 90cm above the ground. Readings were taken every 10cm down the frame and again at ground level.
Light Data Transformations:
Light readings are transformed to obtain percent light penetration which represents the percent of light above the vegetation that reaches the ground surface. In cases where the experiment involves shading, another variable is computed to reflect the percent of sun light that reaches above the canopy. This variable is called light available. In the case of absence of artificial shades, the latter is set to 1.

percent light penetration = ( Light below canopy / Light above canopy ).

percent light available = ( Light below shade / Light above shade ).

Microplot Fertilization Treatments

The "microplot" fertilization treatments are used in experiments 1, 2, 4, 8, 9, 11, 23, 25, and 52. Experiments 5, 6, 28, 36,53,97, 98 and 100 are conducted within plots that are fertilized and should be treated as part of the fertilized plot. There are nine treatment levels, assigned a letter A through I. This is also equivalent to the numeric labels 1 to 9. Treatment levels A through H differ in the amount of NH4NO3 added. Treatment I is a true control and receives no nutrients. The nutrients are applied twice a year, once in early May and once in late June. An exception is experiment 25 where time of application is experimentally manipulated. Not all experiments use all possible treatments. Nutrients are given in g/m2 for each fertilization; plot area and treatments used follow the nutrient lists. Treatment A to H receive the following base nutrients:

Rate Volume Element
10 g/m2 150 ml P2O5 (0-46-0)
10 g/m2 150 ml K2O (0-0-61)
20 g/m2 200 ml CaCO3 (lime)
15m2 200 ml MgSO4 (Epsom Salts)
0.0625 ml/m2 trace mineral solution in 1 ml to 10 ml sand
 

The description for making trace mineral sand is at the end of this section. The amount of NH4NO3 fertilizer added at the different treatment levels is:

Treatment Rate Volume
A 0.0 g/m2 0 ml
B 1.5 g/m2 25 ml
C 3.0 g/m2 50 ml
D 5.0 g/m2 90 ml
E 8.0 g/m2 140 ml
F 14.0 g/m2 250 ml
G 25.0 g/m2 445 ml
H 40.0 g/m2 710 ml
I 0.0 g/m2 0 ml
 

These rates are added twice a year. Actual annual N addition is calculated as: 0.34%N * rate (g/m2) * 2 times/year The trace mineral stock solutions are made by adding the following grams of reagent to 1000 ml of water: CuSO4*5H2O 9.8 g ZnSO4*7H2O 22.0 g or ZnCl2 10.5 g CoCl2*6H2O 10.0 g MnCl2*4H2O 180.0 g Na2MoO4*2H2O 6.3 g H3BO3 6.0 g The trace metal solution is made by combining 120ml of each stock solution, adding 67.2g of citric acid dissolved in deionized water and adding deionized water to bring the volume to a total of 2 liters. The working solution is then autoclaved to chelate the trace metals. The size of the plots and treatments used for each experiment are:

Experiment Treatments Plot size (m2)
Experiment 1 except Field D A thru I 16
Experiment 1 Field D A thru I 6
Experiment 2 A thru I 16
Experiment 4 E, G, I 1000
Experiment 8 C, F, H, I 16
Experiment 9 C, F, H, I 16
Experiment 11 E, G, I 16
Experiment 24 E, G, I 16
Experiment 25 E, G, I 5.25
Experiment 52 A, C, F, G 25
 

Microplot Fertilization Treatments

Some changes and/or additions occur from year to year for some experiments. These changes are listed below. Unless specific experiments are mentioned, these differences apply to all experiments in a category.

In 1982, 30ml of each stock solution was combined with 16.8g citric acid, brought to a total volume of 1 liter, and autoclaved to dissolve. 1.5ml of this solution was added to 30ml of silica sand, mixed and dried.

In 1983, 60ml of each stock solution was combined with 25g of EDTA brought to 1 liter, and autoclaved to dissolve. 1ml of this solution was added to 10ml of sand and added to each plot.

In 1984, 60ml of each stock solution was combined with 25g of citric acid and brought to 1 liter.

In 1985, the first fertilization for experiments 1 and 2,
Treatment F received an extra 23 g/m2 of CaCO3
Treatment G received an extra 118.5 g/m2 of CaCO3
Treatment H received an extra 132.5 g/m2 of CaCO3

In 1985, between fertilizations for experiments 1 and 2,
Treatment G received 137.5 g/m2 of CaCO3
Treatment H received 206.25 g/m2 of CaCO3

In 1985, the second fertilization for experiments 1 and 2,
Treatment F received an extra 23.0 g/m2 of CaCO3
Treatment G received an extra 252.7 g/m2 of CaCO3
Treatment H received an extra 441.1 g/m2 of CaCO3

In 1985, the first fertilization for experiment 4,
Treatment E received no CaCO3
Treatment G received an extra 45.5 g/m2 of CaCO3

In 1985, both fertilizations for experiments 8, 9, and 11,
Treatment F received an extra 23 g/m2 of CaCO3
Treatment G received an extra 43.5 g/m2 of CaCO3
Treatment H received an extra 57.5 g/m2 of CaCO3

In the fall of 1989, each plot receiving treatments B, C, D, E, F, G and H in field D of experiment 1, received 1067g of lime to adjust pH.

Sampling D004

All plots in D004 were sampled twice in 1982. In each sampling period, four clip strips were taken from each of the ten plots. Each clip strip was 10cm x 3m. The documentation does not indicate the location of the clip strips within the plots.

Sampling for A004

All plots in A004 were sampled twice in 1982. In each sampling period, four clip strips were taken from each of the ten plots. Each clip strip was 10cm x 3m. The documentation does not indicate the location of the clip strips within the plots.

Sampling for B004

All plots in B004 were sampled twice in 1982. In each sampling period, four clip strips were taken from each of the ten plots. Each clip strip was 10cm x 3m. The documentation does not indicate the location of the clip strips within the plots.

Sampling for C004

All plots in C004 were sampled twice in 1982. In each sampling period, four clip strips were taken from each of the six plots. Each clip strip was 10cm x 3m. The documentation does not indicate the location of the clip strips within the plots.

Treatment layout : trmte04

Layout:

Field IdentificationExperiment NumberPlot NumberTreatmentAmmonium Nitrate (34-0-0) addition(g/m2/yr)
A4190
A42750
A43516
A44750
A4690
A47750
A48516
A4990
A410516
B41516
B4290
B4390
B44750
B4590
B47750
B48516
B49516
B410750
C41516
C42750
C4390
C44750
C4590
C46516
D4190
D42750
D43516
D4490
D4590
D46516
D47750
D48516
D49750
 

Vegetation Sampling Methods

All plots in experiment E004 were sampled twice in 1982 but the documentation does not indicate the location of the clip strips in the plots. Each clip strip was 10cm x 3m. Methods were most likely those described in above ground vegetation sampling methods.