Location: Range and Meadow Forage Management Research
2018 Annual Report
Objectives
The first and primary research goal of this project is to improve our systems approach to restoration for annual grass management in the sagebrush steppe of North America. In 2013, we provided a systems approach that advances ecological restoration beyond conceptual and phenomenological descriptions to quantitative process-based models that can be used to address specific applied questions (James et al. 2013a). Our systems approach uses life histories to identify transitions important to seedling establishment and maturation. It links those transitions to ecological processes directing establishment and management practices that can favorably impact those processes. Our technology transfer goal is to use the research results for developing tools aimed at assisting land managers in selecting seeds based on their quality, guidelines for determining when and what species to broadcast during restoration, and guidelines on assessing and managing defoliation of newly emerged seedlings at risk to herbivory. Specifically, during the next five years we will focus on the following objectives:
Objective 1: Enhance rangeland restoration processes by improving the establishment of seedlings of desirable plant species (such as increasing seed quality and seedling survival), acquiring and implementing basic knowledge to match naturally occurring physical safe-sites with seed traits, identifying and quantifying the effects of herbivory on seedling survivorship, and developing threshold guidelines for mitigation.
Sub-objective 1A: Improve rangeland restoration success by enhancing seed quality and emergence survival of desired restoration species and develop simple seed quality selection criteria.
Sub-objective 1B: Develop the basic knowledge to match naturally occurring physical safesites with seed traits to maximize seedling establishment during restoration.
Sub-objective 1C: Identify and quantify the effects of herbivory on seedling survivorship to develop threshold guidelines for mitigation during restoration.
Objective 2: Integrate research into an ecological systems approach to restoration with current cost/benefit models and link to site-specific best management practices.
Sub-objective 2A: Develop decision-support tools for 1) choosing seeds based on quality characteristics, 2) matching seed size, number, and physical safe-site availability during restoration, and 3) identifying and managing risk to seedlings associated with herbivory.
Sub-objective 2B: Inform and update our systems approach to include important aspects of seed quality, maximizing physical safe-site capture, and minimizing seedlings risk of herbivory and link this model with existing cost/benefit models.
Approach
Rangelands cover nearly one-half of the earths land surface and provide life sustaining goods and services to about one-third of the global population. Low and variable rainfall combined with often infertile soil make the world’s rangelands highly susceptible to degradation, invasion, and global climate change (Millennium Ecosystem Assessment 2005). The inability to establish healthy plant communities is cited by stakeholders as the single largest barrier to implementing restoration and turning the tide against the hundreds of thousands of hectares of sagebrush steppe lost to invasive plants each year. Despite over a century of research, rangeland science lacks a comprehensive understanding of the ecological processes influencing seedling establishment. The goal of this project is to improve restoration for annual grass management in the sagebrush steppe of North America. Using a series of field and laboratory tests, our first study attempts to improve rangeland restoration success by enhancing seed quality and emergence survival of desired restoration species and develop simple seed quality selection criteria. Our second study is aimed at developing the basic knowledge to match naturally occurring physical safe-sites with seed traits to maximize seedling establishment during restoration. Third, we plan to identify and quantify the effects of herbivory on seedling survivorship to develop threshold guidelines for successful restoration. Finally, we will integrate this research into an ecological systems approach to restoration with current cost/benefit models. Strong emphasis will be placed on operationalizing research knowledge and products through our existing outreach program and strengthening outreach through direct support of parallel efforts by Oregon State University. To maximize benefit to a diversity of customers, outreach will target and support numerous regional collaborative management groups.
Progress Report
For Sub-objective 1A and 1B, studies have been initiated to improve rangeland restoration success by enhancing seed quality and emergence survival of desired restoration species, and developing simple seed quality selection criteria. A short-term study assessing how seed mass enhances seedling emergence potential was extended to cover a one-year period to determine seedling survivorship, with results currently drafted into a manuscript. Experiment 3, addressing parental plant performance effects on seed quality, was modified to address effects of defoliation, and to include quantification of parental seed head photosynthesis. Data acquisition for these efforts are currently ongoing. For Sub-objective 1A, a study aimed at understanding how a fire that occurs when maternal plants are dormant effects seed quality (mass) and emergence of bluebunch wheatgrass and bottlebrush squirreltail has been completed. Results from this study are being prepared for publication. Treatments and seeding associated with Sub-objectives 1B and 1C have been completed for both the first and second year of a study matching naturally occurring and modified physical safe-sites with seed traits to maximize seedling establishment on low and high elevations sites. Monitoring of second year survival of the seedlings that established in the first year has been completed. In addition to the planned objectives, the abiotic characteristics of safe sites and non-safe sites (temperature and moisture) were also collected to allow for comparison of safe site environments. Photo documentation to be used in the guidelines for seeding when the land surface is most receptive has occurred and is partially processed. Effects of herbivory on newly established seedlings were monitored on twelve sites in Oregon and Nevada this spring. Mammal activity that might result in herbivory was quantified at each site using a combination of camera traps and surveys that quantified evidence of herbivore presence such as scat, footprints, and burrows. Insect activity was quantified using grasshopper surveys and drench tests to capture soil dwelling insects. Last spring, emerged seedlings from the previous year’s planting received one of five clipping treatments (no defoliation, 30% defoliation once, 30% defoliation twice, 70% defoliation once, 70% defoliation twice). Those seedlings which survived the first year were marked with permanent tags and located this year to determine second year survival. All surviving individuals were clipped to ground level so that total biomass production can be assessed. A paper reporting the results of this experiment is being prepared. This information will be used to create a safe-site ranking system.
Accomplishments
1. Establishment from seeds is central to the survival of predominantly asexual bunchgrasses. Understanding how bunchgrass populations change from initial conditions over long time scales is important for predicting restoration success in sagebrush steppe. A study by ARS researchers in Burns, Oregon, capitalizing on a spatially explicit grazing preference study established in 1998 with eight co-planted bunchgrasses, showed that after 13 years, 90% of the plants occurred in locations outside of their original planting location. This was true regardless of whether a species population increased, decreased, or remained constant over the 13-year period. These findings demonstrate that establishment from seed is the critical process in long-term changes in bunchgrass population dynamics.
2. Restorationists can use Sandberg’s bluegrass and crested wheatgrass for restoring degraded rangeland infested with insect and small rodent herbivores. Scientists in Burns, Oregon, have determined how herbivory affects the establishment of grass seedlings, and that will help improve restoration success by indicting whether or not insect and small-mammal herbivores require control to ensure establishment during restoration. In a somewhat climate controlled hoop house, seedlings of bluebunch wheatgrass, Sandberg’s bluegrass and crested wheatgrass were grown out to the two-leaf stage, then defoliated by removing either 30% or 70% of their leaf area once or twice, or not at all. At the same time, half of seedlings were subjected to low water conditions to simulate frequent dry periods encountered during rangeland restoration. Defoliation did not seem to matter to overall leaf growth, and only the most severe defoliation reduced root mass in crested wheatgrass and Sandberg’s bluegrass. Bluebunch wheatgrass seedlings were negatively affected by nearly all defoliation treatments. However, this species was the most tolerant to droughty conditions during establishment.
Review Publications
Denton, E.M., Smith, B.S., Hamerlynck, E.P., Sheley, R.L. 2018. Seedling defoliation and drought stress: variation in intensity and frequency affect performance and survival. Rangeland Ecology and Management. 71(1):25-34. https://doi.org/10.1016/j.rama.2017.06.014.
Dale, V.H., Denton, E.M. 2018. Plant succession on the Mount St. Helens debris-avalanche deposit and the role of non-native species. In: Crisafulli, C., Dale, V., editors. Ecological Responses at Mount St. Helens: Revisited 35 years after the 1980 Eruption. New York, NY: Springer. p. 149-164.
Griffin-Nolan, R.J., Carroll, C.J., Denton, E.M., Johnston, M.K., Collins, S.L., Smith, M.D., Knapp, A.K. 2018. Legacy effects of a regional drought on aboveground net primary production in six central US grasslands. Plant Ecology. 219(5):505-515. https://doi.org/10.1007/s11258-018-0813-7.
Barron-Gafford, G., Sanchez-Cohen, E., Minor, R., Hyendryz, S., Lee, E., Sutter, L., Tran, N., Parra, E., Colella, T., Murphy, P., Hamerlynck, E.P., Kumar, P., Scott, R.L. 2017. Impacts of hydraulic redistribution on grass-tree competition versus facilitation in a semiarid savanna. New Phytologist. 215(4):1451-1461. https://doi.org/10.1111/nph.14693.
Hardegree, S.P., Moffet, C., Walters, C.T., Sheley, R.L., Flerchinger, G.N. 2017. Hydrothermal germination models: Improving experimental efficiency by limiting data collection to the relevant hydrothermal range. Crop Science. 57(5):2753-2760. doi:10.2135/cropsci2017.02.0133.
Davies, K.W., Boyd, C.S. 2018. Longer-term evaluation of revegetation of medusahead-invaded sagebrush steppe. Rangeland Ecology and Management. 71(3):292-297. https://doi.org/10.1016/j.rama.2018.02.001.
Davies, K.W., Johnson, D.D. 2017. Established perennial vegetation provides high resistance to reinvasion by exotic annual grasses. Rangeland Ecology and Management. 70(6):748-754. https://doi.org/10.1016/j.rama.2017.06.001.
Davies, K.W. 2018. Incorporating seeds in activated carbon pellets limits herbicide effects to seeded bunchgrasses when controlling exotic annuals. Rangeland Ecology and Management. 71(3):323-326. https://doi.org/10.1016/j.rama.2017.12.010.
Boyd, C.S., Davies, K.W., Lemos, J.A. 2017. The influence of soil color on seedbed microclimate and seedling demographics of a perennial bunchgrass. Rangeland Ecology and Management. 70(5):621-624. https://doi.org/10.1016/j.rama.2017.03.004.
