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University of Minnesota
College of Biological Sciences

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Methods for Experiment 053 -

Field Operations: Competition Treatments

No neighbor treatment was imposed by driving a ring of galvanized sheet steel (50cm diameter, 15cm tall) into the ground until its top was at the soil surface, and killing all plants in the enclosed area with Roundup. Any resprouting neighbor biomass was removed by hand. Steel was installed during May 11-13, 1988 and Roundup applied on 13 May 1988. Transplants that were grown with only roots of neighbors had a net that tied back the shoots and leaves of neighbors so that a transplant in the center of the net was not shaded by neighbors but was surrounded by neighbor roots. White plastic garden net (50cm x 50cm; mesh:1cm x 2cm) was fastened at its center to the soil surface using four steel pins, each 8cm long. The center portion (5cm x 5cm) of the net was cut out to allow transplanting. The outer corners of the net were held 10cm above the soil using pins 20cm long. Nets were installed on May 16, 1988.

Field Operations: Fencing

The entire experiment was surrounded by electric fence to discourage entry by white-tailed deer.

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.

Field Operations: Insecticide

Transplants were dusted with an insecticide (Sevin) weekly during June to prevent insect grazing.

Field Operations: Small Mammal Trapping

1400-trap nights in May and June failed to capture any small mammals.

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

Sampling for C053

During May 18-19, the length of each tiller of Agropyron and Poa was measured from its base to the tip of the longest leaf. This information was used to calculate total tiller length, tiller number, and mean tiller length for each individual. Because of difficulty in distinguishing individual tillers of Schizachyrium seedlings, leaf number was recorded for this species. The above and below-ground biomass of 50 seedlings of each species was measured and tested for correlation with size measurements. Tiller number, total tiller length, and flowering stem number of transplants were recorded during September 5-9, 1988. The above-ground parts of transplants were harvested during September 12-16, dried to constant mass, and weighed. Survivorship was determined as the proportion of each species in each competition treatment in each plot that survived from planting to harvest. The proportion of flowering individuals of Schizachyrium was recorded. All above-ground plant material within 15cm of each transplant ("neighbor biomass") was harvested after the transplant had been harvested. Neighbor biomass was harvested during September 12-23, 1988, dried to constant mass and weighed. One sample from each competition treatment in each plot was separated into live standing crop and litter before weighing. The mean proportion of live neighbor biomass in each competition treatment at each nitrogen level was used to estimate live neighbor biomass in each subplot. Root biomass was measured in soil cores taken 10cm from each transplant during September 12-23. Cores were sieved through a 2mm mesh to remove sand and then washed, dried and weighed.

Vegetation Sampling Methods

E053 is in field C. Species composition was measured on August 28, 1988 in those plots not involved in the competition experiments. This was done by centering a 0.5m x 1m quadrat in each plot and recording the cover of each species using Daubenmire's scale (Mueller-Dombois and Ellenberg 1974). Cover values were converted to equivalent percent and the mean cover of each species in each treatment was determined. Documentation on where the strips are located for each year can be found in the clipping maps.