Repeated Annual Seeding and Higher Seeding Rates Improve Recruitment Outcomes in a Post-Fire Dryland Ecosystem
Loading...
Authors
Genova, Martin
Issue Date
2024
Type
Thesis
Language
en_US
Keywords
Drylands , Fire Ecology , Great Basin , Interannual Climate , Post-Fire Seeding , Sagebrush Steppe
Alternative Title
Abstract
Understanding, predicting, and directing the trajectories of plant communities following disturbances is a major focus of ecological research. Seeding is a widely used approach to influence trajectories with the goal of restoring native plant communities. However, dryland climates are highly variable and ideal conditions for seedling establishment rarely coincide with the time of seeding. One suggestion to overcome this hurdle is higher seeding rates, which can increase the likelihood of successful recruitment against establishment barriers. In addition, repeating seeding over multiple years has been suggested to increase the chance of “hitting” a high precipitation year and reducing water-limiting barriers to seed germination and seedling establishment. By combining seeding rate and repeated seeding over multiple years, we can ask how at how variable annual precipitation interacts with these two treatments. Here, we examined how plant recruitment responds to a low and high seeding rate that were repeated across two years in a fire that occurred in dryland semi-arid Great Basin (USA) sagebrush steppe. Following the 2020 Poeville fire near Reno, Nevada, we seeded a nine-species seed mix of native perennial grasses, forbs, and shrubs at a low (typical land management seeding rate) or high (10 times the low rate) seeding rate at six sites across an elevation gradient. Seeding at each rate was applied in a replicated fully factorial design with three seeding time treatments: the fall of 2021, the fall of 2022, or both years; unseeded plots were included as controls. We hypothesized that applying both repeated seeding across the two years and the high seeding rate would lead to the highest recruit density by increasing the number of possible recruits and by reducing water-limiting barriers to seed germination and seedling establishment. Winter/spring precipitation was below average while temperatures were above average following the first year (2021) seeding in contrast to winter/spring above average precipitation and below average temperatures following the second year (2022) seeding. We measured counts of seeded species recruits in the summer after seeding was applied. Results showed that recruit counts were highest in response to the interactive effect of seeding both before a high precipitation year and at the high seeding rate by matching seeding with a year with favorable precipitation and temperatures. Additionally, recruit counts in response to the high seeding rate was no different to the control during the low precipitation and high temperatures year. These results show strong support for the combined use of repeated annual seeding and higher seeding rates, which together increase the likelihood of “hitting” favorable weather conditions and increasing recruitment success during a high precipitation year.