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Methods for Experiment 122 -

1992 Sampling Methods

Since sweep-net samples give excellent estimates of relative abundance within orders, and good estimates of relative abundance between orders, the main method of sampling the insects in the prairies and savannas was sweep-net. Insects were also collected using pitfalls in some of the prairies and savannas. Once during the growing season ants were sampled using scent plates.

Sweep-net sampling occurred within each field using 100 sweeps per sample.

Pitfall traps were placed at the end of 4 permanently marked transects within the sites sampled. Five scent plates were placed evenly from end to end along the transects, thus providing 20 samples per site. The transects were parallel to each other, 25m apart, and in the prairies 40m long and in the savannas 50m long.

Insects were sampled 7 to 9 times throughout the 1992 growing season. All specimens were manually sorted and identified to species (89.8% of specimens) or morphospecies within known genera or families.

Species biovolume, an index of biomass, was calculated as the average product of length (from tip of head to top of abdomen), width (maximum width of body or head) and thickness (maximum thickness of body or head) for 5 specimens in the oldest life stage for each Orthoptera species. Even though body size increases greatly during development, this method seemed justified since most species (84%) only occurred as adults in the samples taken. To minimize counting a species twice, all larvae were examined by outside experts and, if they might have been the same species as an adult insect, they were counted as a single species.

Voucher specimens were deposited in the Cedar Creek insect collection and as of 2012 are mostly in the UMN insect collection on the Saint Paul campus.

Data Preparation

1992 data preparation was done by E. Siemann and J. Haarstad. Data preparation for both old field and savanna samples from 2004 was started by John Haarstad and completed by Colleen Satyshur after his death. Arnett Codes were assigned by John, and Satyshur used the 1998-2004 Code file to expand and clarify taxonomy and morphospecies identification. Satyshur used raw data notes on paper datasheets to verify that data came only from G and Y transects.

Site details

The 1992 study included 38 prairies that had developed from fields which had been abandoned from agriculture at various times in the past and 11 savannas. Twenty-two of the prairies that were associated with experiments E014, E054 and E001. One of the savannas was associated with experiment E001. Some of the prairies were periodically burned. All of the savannas had a burn history. In 2004, sampling included 35 old fields (prairies) that had developed from fields which had been abandoned from agriculture at various times in the past. All but two of these prairies were also sampled in 1992 and all were associated with E014 grasshopper sampling experiment. Savanna sampling in 2004 consisted of 14 savannas, 9 of which were also sample din 1992. Burn histories varied. Listing of Site Details In Last year Cultivated Historical, the years represent the last year of cultivation based on historical documents and interviews of former farmers and/or family members. In Last Year Cultivated Aerial Photographs the years represent estimates of the last year of cultivation based on an historical series of aerial photographs. Pitfall Method and Ant Plate Method columns indicate the sites in which these collection methods were used in 1992. * Helen Allison Savanna is next to, but not within Cedar Creek Natural History Area and is owned by The Nature Conservancy.

Experiment site label (J.Haarstad)Current field number (2013)Alternate namesEcosystemBurn history as of 2004? *consult Cedar Creek for regimeBurn regime in 1992Last year cultivated historicalLast year cultivated aerial photographs1992 sampled with sweepnet method1992 sampled with pitfall method1992 sampled with scentplate method2004 old field sweepnet sampling category2004 savanna sweepnet sampling
Lbs3 prairienonot burnedna1957YesYesYesSupplementalNo
Sv4 prairienonot burned1971post-1960YesYesYesCoreNo
Gv5 prairienonot burned19471951YesYesYesCoreNo
N1011and 10prairienonot burned1997naNoNoNoCoreNo
Bb21 prairienonot burned19571957YesYesYesCoreNo
Blo22E001 Field Bprairieyes-experimental plotsnot burned19571957YesYesNoSupplementalNo
Bgn24 prairienonot burned19681975YesYesYesCoreNo
Bgs26 prairienonot burned19571958YesYesYesCoreNo
Na27 prairienonot burned19471950YesYesYesCoreNo
BLN28 prairienonot burned1991naNoNoNoCoreNo
Alo29E001 Field Aprairieyes-experimental plotsnot burned1968post-1960YesYesNoSupplementalNo
Cnw32 prairienonot burned19411943YesYesYesCoreNo
Csw35 prairienonot burned19411943YesYesYesCoreNo
E39 prairienonot burned19751977YesYesYesCoreNo
Blr40and 514prairienonot burned19721977YesYesYesCoreNo
Bls41 prairienonot burned19821977YesYesYesCoreNo
Bp44 prairienonot burned19611965YesYesYesCoreNo
Ncp45 prairienonot burned19431943YesYesYesCoreNo
Fc47 prairienonot burned19591957YesYesYesCoreNo
Fp53 prairienonot burned19611961YesYesYesCoreNo
Hut58 prairienonot burnedna1950YesYesYesSupplementalNo
Lem61+62 prairienonot burnedna1957YesYesYesSupplementalNo
Pmn67 prairienonot burnednever cultivatednever cultivatedYesNoNonot sampledNo
Clo69E001 Field Cprairieyes-experimental plotsnot burned19341944YesYesNonot sampledNo
Sys70 prairienonot burned19551951YesYesYesCoreNo
Pms71 prairienonot burnedna1957YesYesYesSupplementalNo
Pot72 prairienonot burned1927pre-1938YesYesYesCoreNo
Rc75B101prairieyes1 year in 2na1956YesYesYesSupplementalNo
Sww76 prairienonot burned19521952YesYesYesCoreNo
Swe77 prairienonot burned1952pre-1954YesYesYesCoreNo
Tmg80B108prairieyes1 year in 3na1956YesYesYesSupplementalNo
Mem82B102prairieyes1 year in 3na1945YesYesYesSupplementalNo
Rsw84 prairienonot burnedna1962YesYesYesSupplementalNo
Rse84aB108prairieyes1 year in 3na1945YesYesYesSupplementalNo
ShbF84 savannayes-wildfirewild fire in 1988nanaYesNoNonot sampledNo
Lc85 B108prairieyes1 year in 3na1956YesYesYesSupplementalNo
Dlo94E001 Field D, B10savannayes-experimental plots2 years in 3never cultivatednever cultivatedYesYesNonot sampledNo
Rcb101 savannayes1 year in 2never cultivatednever cultivatedYesYesNonot sampledYes
Nwb103 savannayes9 years in 10never cultivatednever cultivatedYesYesYesnot sampledYes
Seb104 savannayes9 years in 10never cultivatednever cultivatedYesYesYesnot sampledyes two places
Swb105 savannayes1 year in 2never cultivatednever cultivatedYesYesYesnot sampledYes
RCF107 savannayesnanever cultivatednever cultivatedNoNoNonot sampledYes
Tms108 savannayes1 year in 3never cultivatednever cultivatedYesNoNonot sampledYes
EOP110 savannanonanever cultivatednever cultivatedNoNoNonot sampledYes
DSD115 savannayesnanever cultivatednever cultivatedNoNoNonot sampledYes
Mdn115 savannayes1 year in 2never cultivatednever cultivatedYesNoNonot sampledYes
Mds116 savannayes2 years in 10never cultivatednever cultivatedYesNoNonot sampledYes
Oms117 savannayes starting 2000not burnednever cultivatednever cultivatedYesNoNonot sampledYes
SBFL201 savannayesnanever cultivatednever cultivatedNoNoNonot sampledYes
NEM401 savannayesnanever cultivatednever cultivatedNoNoNonot sampledYes
Bps529or B106prairienonot burnedna1956YesNoNonot sampledYes
Gh537 prairienonot burnedna1955YesNoNonot sampledNo
Nc548 prairienonot burnednapre-1938YesYesYesSupplementalNo
Cbl550 prairienonot burnedna1943YesYesYesSupplementalNo
Sts556 prairienonot burnedna1965YesNoNonot sampledNo
HasHelen Allison Savanna* savanna
 

Yes No No not sampled No

 

abye122 - All Insect Savanna Sweepnet Sampling 2004

All Insect Savanna Sweepnet Sampling 2004

In mid-August 2004, sweepnet samples were collected from several savanna burn units at Cedar Creek in such a way as to compliment the sweepnet samples in the Core and Supplemental plots sampled for E122 in the same year. Savannas sampled with 100 sweeps along transects similar to those for E014. All sweeps were taken with a 15-inch muslin sweep net and each sweep consisted of a rapid approximately 2m-long horizontal swing of the net through the vegetation. Sweeps were generally collected between 10am-4pm during a two day period when it had not rained and weather was fair with sunny skies, modest breezes, and temperatures above 70?F. The samples were bagged in 1-gallon plastic bags and frozen until insects could be sorted. The sample was viewed under a dissecting scope, and species and the number of each encountered was tabulated. Identification was generally to species or genus, but occasionally a morphological descriptive is used when identification was uncertain. Collection and identifications were done by primarily by John Haarstad.

Irregularities to note:
1. J.Haarstad designated two separate fields within burn units 104 and 115.

abze122 - Old Field All Arthropod Sweepnet Sampling 2004

Supplemental and Core Old Field All Arthropod Sweepnet Sampling 2004

In 2004, sweepnet samples collected for the E014 old field grasshopper surveys were also sorted for all arthropod species. Sample collection methods for this data are identical to those for the 1989-2006 supplemental and core old field grasshopper datasets in E014 and similar to the 1992 E122 sampling methods. Arthropods were sampled by sweepnet mid-month from June through September of 2004. Sampling dates were: June 14-15, July 14-16, Aug 17-19, Sept 16-17. In the Core old fields, in each sampling period, 50 sweeps were taken along each of four 40m transects (labeled G, R, W, Y) near the center of each plot. Each transect was bagged separately and for this dataset, only the samples from the G and Y transects were sorted resulting in a total of 100 sweeps per plot. In each sampling period, the Supplemental fields received 100 sweeps per plot through a grid 40 x 75 meters in size (which corresponds to size of the transect grid in the core old fields). The total number of sweeps for each field in each sample period was 100. All 100 sweeps/field were stored in the same bag and all samples from supplemental old fields were picked for this data set. All sweeps were taken with a 15-inch muslin sweep net and each sweep consisted of a rapid approximately 2m-long horizontal swing of the net through the vegetation. Sweeps were generally collected between 10am-4pm during a two day period when it had not rained and weather was fair with sunny skies, modest breezes, and temperatures above 70?F. The samples were bagged in 1-gallon plastic bags and frozen until insects could be sorted. The sample was viewed under a dissecting scope, and species and the number of each encountered was tabulated. Identification was generally to species or genus, but occasionally a morphological descriptive is used when identification was uncertain. Collection and identifications were done by primarily by John Haarstad.

Irregularities to note:
1) When aphids were present in large numbers their abundance was generally estimated to the nearest 10.
2) All of the Supplemental field data is sound.
3) When enumerating species counts from Core plots, on very rare occasions John included a few species of non-Orthoptera arthropods that were found in the R and W transects. Any instances in the Aug-Sept data have been corrected so that only the G and Y transects are included in this data set. Notes from July allow 99.9% certainty that this data also only contains G and Y transects (see below). The June data is very likely only G and Y transects, or is minimally biased, but raw data do not allow absolute certainty for this month. June conclusions are based on the following facts:
a. John only added non G-Y arthropods in 3 of 21 plots in September.
b. In 5 of 21 plots in July, he has listed some species in both R-W transects and the G-Y transects. Colleen believes these species were originally found in G-Y transects and are not additions from R-W transects.
c. In the cases above when/if he added non G-Y arthropods, it was only 1-2 species per plot and abundance counts were only 1-2 individuals/species. Total species diversity ranged from ~60-80 species in these plots and abundances ranged from ~100-800 specimens.
d. The ratio of the number of species and individuals between supplemental and core fields are comparable in all months.