Located on the Sierra Ancha Experimental Forest, this project uses a common garden approach to determine which plant species are best suited for supporting pollinator communities and are most appropriate for restoration activities. Findings from the study will be used to 1) improve pollinator habitat, 2) increase seed stocks of native flowering species for use in restoration, 3) inform U.S. seed zone guidelines and 4) help predict plant-pollinator response to climate change. This carries on a long tradition at the Sierra Ancha Experimental Forest of using common gardens in botanical research. As far back as the 1920s and 30s common gardens were used to study evapotranspiration rates of native herbaceous and shrub species as well as evaluate the potential use of certain species for erosion control. Some of these the same gardens are now being restored nearly a century later for use in this study.
This project will identify appropriate plant species and seed sources for seed production intended to support ecosystem restoration efforts. The project will directly address the critical shortage in locally adapted seed supply for restoration projects. This information can be fed into the emerging restoration economy that will bolster seed production for landscapes, benefitting both agricultural and natural ecological communities. For example, the Southwest Seed Partnership has catalyzed a network of small- and medium-sized farmers to be involved in the development of a seed production economy to address large-scale rehabilitation projects such as those conducted by federal and state agencies. To tackle the combined challenges of supplementing seed supply and increasing pollinator diversity, abundance, and resilience to climate change, this project will leverage these existing cooperative networks and fill critical research gaps directly with multiple partners that include rural farmers.
The project will test fundamental ideas about local adaptation and translate the findings to practical guidelines. For example, the ability of a species to adapt to changing conditions depends on migration rates and newly acquired genetic variation from mutations, both of which are predicted to lag well behind the rate of climatic changes such as a predicted increase of up to 6°C by the end of the 21st century in southern Arizona. Most species are adapted to current conditions. However, species may vary in their sensitivity to the rate of environmental change. This sensitivity will determine the optimal environmental transfer distance during assisted migration. Additionally, a species adapted to a broad climate range would derive less benefit from assisted migration. This project will determine which native plant species are more sensitive to environmental change (i.e., locally adapted) and thus good candidates for assisted migration, in addition to determining which species are less sensitive to environmental change. At the same time, this project will include a detailed examination of the species and functional diversity of pollinators supported by plant species across a range of temperature sensitivities. This will lead to detailed recommendations for the most resilient species to use in restorations during climate change. For example, species with high local adaptation (i.e., more sensitive to environmental change) may need multiple seed sources while non-locally adapted species may only require one seed source, potentially produced at a single site. Large-scale farmers could focus on these later species, while smaller scale farming could focus on the more locally adapted species.
This project consists of two main objectives:
A) a large-scale test of seed zone suitability and local adaptation/maladaptation for 12 pollinator-dependent perennial forb species that are critical for restoration. In this test, the project will quantify pollinator communities interacting with 21 separate plant populations per species at six common gardens, with populations and gardens varying by climate and spatial distance from one another; and
B) a seed lot production test, where the project will focus on development of seed production strategies for promising foundation species (those that support diverse pollinator communities and produce ample seeds that can increase seed supply for large-scale triage-type restoration).
These strategies include examining population-level variation in seed production as impacted by different watering regimes and planting densities. For density treatments, plantings will aim to minimize competition among plant neighbors while maximizing seed production per planted area. For the watering treatment, the plantings will aim to minimize water use while maximizing seed yield. Planting designs will also manipulate pollinator nesting resources alongside different planting strategies to maximize seed set by increasing diversity of pollinator communities.
Plants from 21 populations per species will be planted at common gardens varying in elevation, size, and watering treatments. Plants will be started from seed in the Northern Arizona University greenhouses and then outplanted as seedlings to the experimental common gardens. As seedlings grow and reach reproductive age, the following plant traits will be tracked: aboveground growth rate, survival, number of flowers, petal length, number of seeds, seed mass, seed viability, flower and leaf phenology, specific leaf area, leaf area, leaf thickness, and total plant leaf area. Flower color and chlorophyll will be measured as well. Systematic flower visitation observations will be used to construct pollinator networks for each plant population. These traits will be used to estimate the extent of local adaptation to climate and distance from seed source. Based on local adaptation strength, the foundational status of all plant species and their utility in restoration mixes can be determined.