2012 Annual Report
1a.Objectives (from AD-416):
To investigate (1) the potential for Great Basin native annual forbs to effectively compete with B. tectorum and facilitate the establishment success of native perennial grasses (2) the germination ecology of key Great Basin native annual forbs. The ultimate goal of this work is to determine whether it would be useful to include native annuals in postfire rehabilitation seed mixes.
1b.Approach (from AD-416):
1. Greenhouse competition study: This aspect of the research is being conducted in combination with scientists at UNR. We have completed one greenhouse experiment to look at competition of the two native species with B. tectorum and establishment of E. multisetus with native annual forbs (herbaceous flowering plant), with B. tectorum , and with annual forb-B. tectorum mix. Growing with competitors decreased the size of E. multisetus, however the largest decrease in size was found when grown with B. tectorum and A. tesselata. In contrast, E. multisetus grew best with M. veatchiana. When in competition with B. tectorum, E. multisetus performed best when M. veatchiana was also present. These results support the idea that the presence of certain native annual forbs can enhance the establishment of E. multisetus in B. tectorum invaded rangelands.
2. Buried seed bank experiments for Amsinckia tesselata, Amsinckia intermedia, Blepharipappus scaber, and Mentzelia veatchiana: For each species, I prepared artificial seed bank buried bags. Bags are being retrieved monthly for one year, then in early spring and late summer for up to 5 years or until there is no evidence of seed carryover. For each bag, the number of recently field-germinated seeds, seeds germinable at 2/15°C for 4 weeks are being determined.
3. Field study: Amsincka intermedia and Bromus tectorum demography. I have collected three years of demographic data quantifying plant density and seed output for B. tectorum and Amsinckia intermedia at a field site. We will resample the plots and add seed bank sampling to determine how long-term fluctuations in adult and seed bank densities relate to amount and timing of precipitation for the native and the invasive annual.
4. Field competition study: This experiment also is being conducted in combination with scientists at University of Nevada at Reno at UNR. Last fall, we planted small plots with combinations of native annuals and Bromus tectorum. The experiment looks at the performance of B. tectorum or E. multisetus target plants in annual native forb monocultures, B. tectorum monoculture, or a mixture of annual native forbs and B. tectorum.
This research supports objective 1: Identify and characterize biotic and abiotic conditions and processes that affect plant community factors and ecosystem dynamics on healthy and degraded rangelands to improve the ability to predict how rangelands will respond to changing environmental conditions and alternative management practices. Specifically Sub-objective 1.1: Determine how land management history, the reproductive ecology of invasive annuals, and biotic interactions affect the structure and function of selected Great Basin ecosystems.
Common Garden Experiment
Two parallel experiments were implemented simultaneously to test native seed mix success against (1) cheatgrass or (2) medusahead, according to a completely randomized design. Each seed mix consisted of two forbs (herbaceous flowering plant), two perennial grasses, and one shrub. A novel early seral mix was composed of the following species: Amsinckia tessellata, Mentzelia veatchiana, Elymus elymoides, Poa secunda and Ericameria nauseosa, and these seeds were collected from multiple wild populations. A late seral mix, representative of traditional seeding mixes used in past restoration efforts, was composed of the following species: Penstemon palmeri, Sphaeralcea grossulariifolia, Pseudoroegneria spicata, Achnatherum hymenoides and Artemisia tridentata spp. wyomingensis. These seeds were commercially purchased. A representative clay loam soil (clayey, smectitic, mesic, Lithic Argixeroll) and a representative sandy loam soil (fine-loamy, mixed, superactive, mesic Durinodic Xeric Haplargid) were collected from multiple field locations, homogenized by soil type, and filled into 41-cm deep treepots. The pots were then sunk into the ground at the University of Nevada Agricultural Experiment Station in Reno, Nevada, to allow us to test both soil types using a common garden approach.
In each pot, 10 or 20 seeds were sown (Oct. 2010) into randomized locations using a 20-location fixed grid. We used five species combinations, including (1) exotic species only (10 seeds), (2) early seral native species only (10 seeds, consisting of 2 of each species), (3) late seral native species only (10 seeds, consisting of 2 of each species), (4) exotic and early seral native species together (10+10 seeds), and (5) exotic and late seral native species together (10+10 seeds). All species combinations were crossed with two soil types (i.e. clay loam or sandy loam). Individual seed locations were monitored for seedling emergence and emerged seedlings were monitored biweekly for survival from the date of first emergence in early Novemeber 2010 through summer 2011. Reproductive output was collected as seeds mature for each species. Final survival rates of adult annual and juvenile perennial species were assessed, and peak biomass was collected summer through fall 2011.
Cheatgrass and medusahead plants were grown in all possible pair-wise combinations and in monoculture at the University of Nevada, Reno Greenhouse Facility. Single individuals of each species (i.e. cheatgrass or medusahead) were planted alone or in competition with a single conspecific or heterospecific neighbor. All planting combinations were crossed with soil type. Emergence timing, leaf production rates, and leaf photosynthesis and transpiration rates were measured. Above- and belowground biomass and reproductive output samples were collected. Plant and soil samples will be processed, ground, and analyzed for elemental concentrations of Carbon (C), Nitrogen (N), Phosphorus (P), Potassium (K), Calcium (Ca), Magnesium (Mg), Iron (Fe), Manganese (Mn), Zinc (Zn), and Copper (Cu).