Intensifying drought and increasing plant invasions create substantial challenges for ranchers and land managers to balance profitable cattle production and healthy ecosystems on western grasslands. Producer groups across the southwest note the urgent need for financially and ecologically viable approaches to address this challenge by maintaining stable forage production while restoring multiple essential ecosystem functions. Seeding native and non-native forage species based on traits that confer resilience to drying conditions and are also associated with these positive ecosystem functions may provide utility for allowing producers to achieve multiple management goals in the face of changing environmental conditions.
We identified eight management goals (forage production, invasion resistance, drought resilience, carbon sequestration, soil fertility, erosion control, native biodiversity, and pollinator habitat) that producers noted as priorities, based on recent surveys across California and Arizona. Our proposed study will evaluate how reseeding plants with specific traits can provide ecosystem services to meet those management goals. We will perform this evaluation through on-ranch reseeding experiments in both central California and southern Arizona; regions with extensive productive rangelands that are particularly vulnerable to drought and plant invasion due to the semi-arid climate. Identifying plant trait-ecosystem service relationships will allow ranchers and land managers to select successful reseeding species to meet management goals. We will compare these relationships between two experimental sites to determine whether this reseeding approach can be applied to regions represented by the climate in central California and southern Arizona. In addition to directly engaging producers throughout the experiment, we will translate project outcomes into science-based recommendations via workshops, field days, and a best-practice manual for ranchers and land managers.
Objective 1: Quantify relationships between plant traits and our ability to meet stakeholder-prescribed management goals over three years.
PI Gornish and co-PIs (Fehmi and Barberán) will ensure timely field sample/data collection and sample processing to obtain metrics of plant traits and ecosystem services at the peak biomass. They will also ensure proper statistical analysis to determine relationship between plant traits and ecosystem services achieved in the reseeding experiment. Based on our pilot field trials, we expect that seeding perennials will enhance forage production and quality while simultaneously supporting multiple ecosystem services.
Objective 2: Evaluate whether the reseeding approach can achieve the targeted management goals in both experimental sites that represent the climate in California and Arizona.
These two regions differ in precipitation regimes, with central California grasslands dominated by a spring growing season and Arizona grasslands dominated by a summer growing season. Yet both semi-arid regions consist of extensive, productive rangelands that are vulnerable to drought and plant invasion. PI Gornish will ensure proper selection of plant species suited for each region and proper statistical analysis to compare data acquired from both states over the project period. We expect that management goals can be met in both sites when desirable plant species adapted to the precipitation regime in each region are selected.
Objective 3: Develop stakeholder outreach and extension
PI Gornish and co-PIs Roche and Ruyle will develop products that will translate project findings into science-based recommendations for managers throughout the project period. These products include the deployment of one workshop and one field day per year of the project in each state, presentations, and the development of a best practices manual in year 3, which will highlight the identity of plant traits that provide utility for achieving particular management goals.
Based on our pilot field trials, we expect that seeding perennials will enhance forage production and quality while simultaneously supporting the supply of multiple ecosystem services. In addition, we, expect that seeding of species with functional traits similar to local invasives will be more effective for control, compared to no seeding or reseeding of species with dissimilar functional traits. We also expect that species with high rooting depth and density will have the greatest capacity for soil carbon sequestration and erosion control.
Due to some unexpected personnel changes (e.g. our postdoc quit after two weeks on the job without actually doing any work on the project), we decided to deploy a smaller pre-experiment in year 1. This experiment basically entails assessing which native species do the best (e.g. demonstrate highest germination and establishment) in a restoration context. This work will provide two important pieces of information. First, the project team will understand which of the candidate species will be best for the experiment. Second, this work will be useful in general to restoration practitioners in AZ and CA.
In collaboration with ranchers, we identified 12 native species in California and 18 native species in Arizona to test. The experimental treatments considered of: (1) application type (naked seed, seedballs, none); (2) tilling (absent and present). All treatments were completely crossed with each species in each state in 1meter squared plots, replicated three times. Plots and treatments were deployed in November of 2019. Germination assessments were conducted in February 2020.
We do not yet have the data entered or analyzed. The coronavirus (COVID-19) has sort of halted all work in the labs of the PIs. Based on what we saw in the field, many species are doing very well (high germination and establishment). Seedballs appear to be a better method of delivery for seed than just naked seed in Arizona. Tilling is helpful in both states.
Educational & Outreach Activities
We are still very early on in the project, but we have already deployed several outreach activities. First, we hosted on ranch field tours of the experimental site to local stakeholders just prior to preliminary data collection in February 2020. Both PIs have also presented the plan for study to local rancher groups in both formal and informal settings. We plan to organize several more workshops and field tours this summer for fall deployment and expect several more written outreach materials this year after summer field data collections are complete.