We established long-term monocultures and species interaction plots of common grasses, for measuring species traits in a common garden, and testing which traits correlate with competitive ability against two dominant species (blue and black gramma) and abundance in polyculture. The plots are 2 x 2.5 meters to allow the 0.5 meter strip on one side of the plot to be used in invasion future experiments. The purpose of this study is: 1) to measure traits of seven species in a replicated common garden 2) to correlate species traits with the outcome of competition among two species 3) to correlate species traits with the relative abundances of species in polyculture (i.e. all seven species).
There are five monocultures of each of seven grasses (35 plots) for total of 95 plot. There are 55 plots that have two species: Each of the five non-blue and black species will be planted with blue grama and black grama. Blue and black grama will also be planted together, for a total of 11 species interaction treatments, which will also be replicated five times. The plots will be 2 x 2.5 meters to allow the 0.5 meter strip on one side of the plot to be used in invasion future experiments.
In order to maintain the treatments, the plots will be weeded three times a year. The plots are relatively easy to maintain and undergraduate interns with no plant identification experience can easily be trained to weed the plots, since the plots contain only seven species of grass, and these species are relatively well established and conspicuous, and the majority of weeds are forbs. Bouteloua barbata is also a common weed. An effort should be made to remove the roots of weeds, but with minimal disturbance to the planted grasses. Weeding tools are useful for this purpose and can be found in the storage building at the field station (there are four there. they have green handles and white metal parts). The field crew will weed three times per year (March, June and late September). Estimated field time is three people days for the field crew, or one day with one field crew supervisor and three or four undergraduates.
We will sample aboveground and belowground biomass during peak growing season to measure monoculture traits and the outcome of species interactions. The experiment will not be sampled annually, but will instead be sampled selectively depending on establishment and rates of the effects of competition. We will also measure several other plant traits, as time permits, including minimum water potential, stomatal conductance, and specific leaf area.
Aboveground biomass measurement:
Each fall during peak biomass (late September to early Oct.), species richness, count, and cover are visually estimated on each plot. The data are entered onto a palmtop using the data form for ease of entry and transfer to a PC. The procedure is the following: 1. Find the metal tag on the southeast nail and enter the plot code into the palmtop. The canopy cover of the plot is estimated visually. Each plot is 4 m2. 2. A 1-m2 PVC-frame is placed over east, south, west, and north corners that should connete each other quadrat. The plant standing biomass (volume of green foliage) is then recorded for each species inside the quadrat. Each PVC-frame is divided into 100 squares with nylon string. The dimensions of each square are 10cm x 10cm and represent 1 percent of the total area or cover. The cover (area) and height of all separate vegetative units that fall within the one square meter quadrat are measured. To estimate cover, one basically determines how many subunits can fit into the amount of cover for each species. Cover less than 0.1% is T (trace). After cover is estimated for each species,. 3. Height is recorded as a whole number in cms. All heights are vertical heights that are defined as a line parallel to the pull of gravity.
The seven species planted:
Reseeded four species in July 2008. The species planted in each plot can be found in the plot treatment are: Sporobolus cryptandrus, sand_dropseed, Bouteloua gracilis, Blue gramaOryzopsis hymenoides, Indian_ricegrass, Hilaria jamesii, galleta, Aristida purpurea, purple_threeawn, Bouteloua eriopoda, Black gramma, Bouteloua curtipendula, Side oats grama. We reseeded four species in July of 2008.
Additional Information on the Data Collection Period