flower stem height

PRE02 Reproductive effort of Big Bluestem, Indiangrass and Little Bluestem on selected Konza Prairie LTER watersheds

Abstract: 

This data set focuses on seed production, flowering stem mass, height, and population densities of three dominant prairie grasses: Andropogon gerardii (ANGE), Sorgastrum nutans (SONU), and Schizachyrium scoparium (ANSC) in selected Konza Prairie LTER watersheds. Data set includes measurements of flowering stem height (m), density (no. per sq. m) and production (grams per sq. m) and total seed weight (grams) and production (grams per sq. on 2 soil types (shallow and deep) in watersheds representing different burning-grazing treatment combinations. Specific watersheds sampled have varied over time. Current watersheds include: 001d, R01a, R01b, 002c, 002d, 004a, 004b, 020b, R20a, R20b, 0SpA, 0SpB, 0SuA, 0SuB, 00FA, 00FB, 00WA and 00WB Sampling is done once a year in October/November (end of growing season). (Sampling design slightly altered from PRE01).

Core Areas: 

Data set ID: 

95

Short name: 

PRE02

Purpose: 

To estimate seed reproduction, flowering stem mass, height, and population densities of three dominant prairie grasses: Andropogon gerardii (ANGE), Sorgastrum nutans (SONU), and Schizachyrium scoparium (ANSC) in the Konza Prairie LTER watersheds.

Methods: 

Location of Sampling Stations: Florence and Tully locations of un-grazed watersheds: 001d, R01a, R01b, 002c, 002d, 004a, 004b, 020b, R20a, R20b, 0SpA, 0SpB, 0SuA, 0SuB, 00FA, 00FB, 00WA and 00WB. Sampling is done 2-3 m away from the permanently marked species composition transect (see PVC maps in Appendix M.). Densities are always measured on the opposite side of the species composition transect from where PAB biomass clipping is done.

Frequency of Sampling: Once per year at the time of seed maturation (Oct to Nov).

Variable Measured: 1. Flowering stem heights (in centimeters), 1982-present = PRE021; 2. Weight of inflorescences (g per m2), 1982-1993 = PRE021; 3. Density of flowering stems (No. per m2),1982-present = PRE022; 4. Weight of flowering stems (g per m2),1982-present = PRE022.

Methods: Because these measurements involve destructive sampling, no permanently marked plots were set up. All samples are taken 2-3 m parallel to the permanently marked species composition plots at each LTER site.

Individual flowering stem heights (PRE021):1982 - present. A quasi-random walk is initiated adjacent to the permanent LTER transects during which 25 sampling points per transect (100/LTER treatment) are located at intervals of about 2 m. At each sampling point, the stem height for the nearest (no more than 1m from observer) flowering individual of each of the three species is measured to the nearest cm. Mean flowering stem height is calculated for each species at each site from the 100 values.

Density and weight of flowering stems (PRE022):1982 - present. Along a transect parallel to the permanent LTER plant species composition transects but on the opposite side from where the PAB biomass collections for the year have occurred, six 0.25m2 plots (50cm x 50cm) per transect (x4 transects = 24 per site) are sampled. Each plot is 3 m from the species composition marker and 10 paces from the next plot. Within each of these plots, the number of flowering stems of each species is counted and the stems are clipped at ground level, bagged by species, oven dried at 60oC, and weighed. The density of flowering stems (No. per m2) and the mean biomass of flowering stem (g per m2) are calculated for each species.

Summary of All Changes: PRE021: Prior to 1994, at the first 10 points (or first 10 plants sampled), the inflorescence of each individual was clipped and placed in a separate bag. The seed heads were oven dried at 60oC and weighed. From this data (n=40 plants per species), mean seed weight per plant was calculated for each species at each LTER site.

PRE022: Prior to 1992, following drought years (when reproduction by the three species may be very low) flowering stem density was estimated during the fall by counting flowering stems in the 10m2 circular plots. Flowering stem height and seed weights were measured on those species flowering adjacent to the transects. Using this technique, sample size was variable for flowering stem height and seed weight measurements. Low sample sizes may necessitate pooling replicate LTER treatments.

Grazed Watersheds (exclosures): Measured 1987 - 1992. Height and density of flowering stems: In each grazed LTER watershed there were eight permanent 5 x 5 m grazing exclosures, four located on Tully soil sites and four located on Florence soil sites. Adjacent to each permanent exclosure, another 5 x 5 temporary exclosure was erected and remained in place only during the year during which stem density and biomass data were collected and only from May 1 until the vegetation reached peak biomass. This provided exclosures in pairs, the permanent exclosure half providing an un-grazed treatment and the temporary exclosure half providing a grazed treatment (grazing is only temporarily prevented to allow re-growth biomass and flowering stem measurements).

Watershed

N01A

Site

Florence

Exclosure Nos.

1 – 4

Year started

1988

N01A

Tully

5 – 8

1988

N01B

Florence

1 - 4

1992

N01B

Tully

5 – 8

1992

N04A

Florence

9 – 12

1988

N04A

Tully

13 – 16

1988

N04D

Florence

9 – 12

1992

N04D

Tully

13 – 16

1992

Within both the grazed half and un-grazed half of the paired exclosures, four 50 x 50 cm quadrats were randomly distributed (excluding the edge within 1 m of the exclosure fence) and the number of flowering stems of each of the three grass species were counted and recorded. In addition, four of the flowering stems of each species were randomly selected and their heights were measured to the nearest cm. The density of flowering stems (No. per m2) and mean flowering stem height were calculated for each species at each LTER site.

Brief History of the PRE021-PRE022 Data Set: In 1981, a study was initiated on seed production and flowering culm density of Andropogon gerardii (ANGE), Sorgastrum nutans (SONU), and Schizachyrium scoparium (ANSC). This study measured the flower stalk density, height and seed production for each species. The objective of these measurements was not for population/demographic studies, but rather to provide an additional indicator of patterns of grass production to complement and supplement the long-term ANPP data set.

In 1982, this study underwent slight alterations. The data collected in 1981 was labeled PRE011 while the measurements taken in 1982 and after were designated PRE02.

For additional metadata information see: http://lter.konza.ksu.edu/sites/default/files/DC.pdf

For additional methods information see: http://lter.konza.ksu.edu/sites/default/files/MM.pdf

Data sources: 

Maintenance: 

ongoing

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