Matthew A. Keller’s research while affiliated with Bucknell University and other places

Appendix S1 Appendix S1: Table S1. Dates and percentage of the 200-m transect burned by (E) escaped prescribed, (L) lightning, (P) prescribed, or (R) railroad-origin fires that impacted wet prairie and flatwoods stands during the 38-yr. study, 1977-2015. Mean % burned ± sample std. dev. and mean fire-return intervals (yr.) ± std. dev. from the initial documented fire for each transect are compared to Main and Menges' (1997) proposed fire-return intervals. Date of Fire Fire Type Wet Prairie Wet Prairie/ Flatwoods Cutthroat grass Flatwoods Wiregrass Flatwoods Wiregrass Flatwoods WS20 WS21 WS30 WS42 WSP1 % Burned % Burned % Burned % Burned % Burned

Worldwide, humans are altering the fire regimes of fire-prone ecosystems. Efforts to restore fire regimes in natural areas are usually guided by fire-management plans (FMP) using prescribed burning. We assessed an FMP by repeatedly sampling 11 Florida uplands impacted by 2 to 11 fires each during a 38-year period. Stands exhibited ecological resilience with little plant composition change and modest abundance shifts. Resilience was not eroded by repeated FMP-prescribed fires. Species richness and diversity were significantly higher at the end vs. beginning of our study, suggesting that FMP-applied fire regimes are within the range of those with which species evolved.

Worldwide, humans are altering the fire regimes (fire‐return intervals, severity, seasonality) of fire‐prone ecosystems, fragmenting natural landscapes, and altering climates. Efforts to restore fire regimes in natural areas are usually guided by fire management plans (FMP) that rely on prescribed burning. Despite the common use of FMPs, limited efforts have gone to assessing vegetative and faunal responses. While some insights into responses to fire from short‐term studies are available, there is less knowledge about FMP outcomes applied over multiple decades. Peninsular Florida hosts many fire‐prone communities including globally threatened Florida scrub. We repeatedly sampled species composition and abundance during a 38‐yr period (1977–2015) at 11 upland stands including wet prairies, flatwoods, and Florida scrub (i.e., oak scrub, rosemary scrub, hickory scrub). A total of 22 fires impacted the stands with individual stands experiencing as few as 2 and up to 11 fires. There was no invasion of non‐native plants following fires and stands showed remarkable ecological resilience with limited change in species composition and modest abundance shifts due to differential recovery rates. Importantly, ecological resilience was not eroded with repeated fire. Species richness, evenness, and diversity were significantly higher at the end vs. beginning of our study, suggesting that current fire regimes are within the range of those with which species evolved. While resprouting shrubs and trees persevered under a range of fire‐return intervals, an obligate‐seeding shrub was adversely impacted by fires more frequent than FMP‐recommended intervals. Several lessons are apparent from our findings. Best practice should: use the full range of fire‐return variation at evolutionarily appropriate intervals; utilize natural fire seasons to the extent possible; compare outcomes and modify prescriptions as necessary to meet FMP goals; give special consideration to burn units with embedded associations of widely differing fire regimes than principal associations in order to maintain diversity of both associations; and account for climate change in FMPs since fire behavior, frequency, and community responses to fire will likely change in the coming decades. Outcomes of FMPs must be carefully evaluated to ensure prescriptions are evolutionarily appropriate and to ameliorate the impacts of altered climates.

Background/Question/Methods Anthropogenic landscape changes have markedly altered fire-return patterns in many fire-prone ecosystems. Fire-management plans are aimed at restoring fire-return patterns that match those with which the organisms composing the ecosystem have evolved. Despite the common use of fire-management plans, little effort has gone into the assessment of the floral and faunal responses to prescribed treatments. The goal of our study is to assess the successes and shortcomings of fire-management planning using long-term vegetation change data. We used a 31-yr data set (1977-2008) to assess the consequences of the Archbold Biological Station fire-management plan on plant-species composition and cover at 13 permanent, 200-m line transects located in rosemary scrub, scrubby flatwoods, hickory sandhill, flatwoods, seasonal ponds, wet prairie/bayhead associations that have experienced differing fire occurrences. We used nonmetric multidimensional scaling (NMS) ordination to assess vegetative changes over time. Results/Conclusions Vegetation recovery following fires was rapid with associations expressing considerable resiliency. Species responses and NMS-determined community-structure changes confirmed that associations at some sites were stable in response to fire treatments but other associations diverged appreciably from their desired state. Conclusions include the importance of monitoring and fine-tuning of fire-return intervals. Long fire-return-interval associations embedded in shorter return-time matrix associations suffer if matrix fire-return intervals are applied in burn units with multiple vegetation associations. In our study, rosemary scrub with 20-60 yr fire-return intervals is embedded within a scrubby flatwoods matrix, which has a shorter (6-9 yr) fire-return interval. Three fires within 3 decades resulted in rosemary scrub strongly shifting towards scrubby flatwoods. Florida rosemary, the foundation species, declined from 50% cover in 1977 to only 6% by 2008, while oak coverage markedly increased as a consequence of short-interval fire returns. Similarly, frequent fire returns (7 fires during 3 decades) coupled with spring dry-season fires at a wet prairie site (2-5 yr return time) prevented the development and maturation of an embedded bayhead association (60-100 yr return time). Many fire-management plans provide relatively narrow ranges of fire-return intervals and extend prescribed burning beyond the natural fire season. If wrong, narrow intervals and burning outside the natural fire season have the potential to alter species composition and abundance. Our results suggest that best practice should use broad variation in fire-return times, continual comparison of management goals with actual vegetation cover, careful management of embedded associations, and use of the natural fire season for prescription burns.