Revealing climate analogs to restore tomorrow’s ecosystems
Rapid environmental change from abiotic and biotic sources can instigate vegetation transitions that threaten ecological functions and services. Restoration that maintains or improves healthy, productive ecosystems relies on understanding the future trajectory of these plant communities. One critical element of restoration is determining which plant species and genetically adapted populations would be suitable for a designated area under current and future climate conditions. Seed sourcing has been informed by species-specific seed zones which are typically developed from common garden studies that assess the relationships between adaptive traits and climate. Given the vast number of species critical to ecological function that lack this genetic information, the limited research capacity, and the time needed to acquire the data - more than 5 years - a new approach is needed to predict ecological change and guide seed transfer.
We developed a web-tool, the Climate Smart Restoration Tool (CSRT) v2.0, that implements the approach described below. Users enter latitude and longitude coordinates of a reference location and select a 30-year reference period, current (1991–2020), or historic (1961–1990). The reference periods accommodate shorter-live plants such as grasses and forbs that experienced current climates, versus longer-lived plants like trees that have experienced historic climates. Climate analog area and vegetative/biome plots are displayed on a map and provide a seed transfer limit for the specified reference location. Vegetative and biome data are compiled in tables to assess current and potential future species composition based on frequencies of occurrence among the plots. Users can download maps and data tables for further uses in management planning. For example, let's assume a post-fire restoration project for a location southwest of Flagstaff Arizona, as pictured. Land managers can evaluate the current and mid-century seed transfer threshold and potential changes vegetation. At the biome level, there is a decline in plots supporting Montane Conifer Forest and increase in Chaparral plots. Similarly at the species level, declines are predicted for ponderosa pine, while increased prevalence is predicted for juniper species and scrub oak, as seen in the photo inset. Managers may want to increase chaparral species over their current presence, and limit ponderosa pine and other conifer species to microhabitats that would support these species.
Common garden studies have been the foundation for determining adaptive traits and development of seed zones. We use a consensus of common garden results that have shown plant species begin to display differing adaptive traits when seed sources range greater than 300 meters in elevation. This elevation threshold is used to define climatic (dis)similarity based on 20 climate variables. These climate variables are annual and seasonal estimates of temperature, precipitation, and their interactions. Areas found with climate distance below this threshold are consider similar and referred to as climate analogs. We then incorporate national vegetation inventories and a descriptive biome plot database to provide context between climate analogs and associated vegetation. Climate analog plot data is compiled into data tables of species and biomes that include the frequency at which they are found among the climate analog plots for the reference period and mid-century climate. This provides a measure of species occurrence among climate analogs and a prediction of species increase or decline by mid-century.