Because semi-arid ecosystems in the western U.S. are already under pressure from grazing, invasive species, climate change, and water diversion, megafires could cause state changes in terrestrial and aquatic ecosystems that may result in degraded wildlife habitat and watershed resources (Adams 2013; Stephens et al. 2014). For example, megafires could trigger large-scale changes in catchment hydrology, such as decreased groundwater recharge and increased sediment and nutrient loading (Seibert et al. 2010; Smith et al. 2011), which could exacerbate eutrophication and threaten already-stressed surface and subsurface water sources (PSOMAS 2007). Additionally, altered herbivory regimes and plant invasions following megafires may lead to losses of native forest and shrubland habitat (Horn et al. 2012; Rhodes et al. 2018) that strongly affect the carrying capacity of wildlife populations and influence watershed hydrology. As megafires become more common and extreme hydrological events increase, the persistence of native ecosystems and the services they provide to communities in the western U.S. depends largely on ecosystem recovery or succession after disturbance. Understanding the rate and trajectory of terrestrial and aquatic ecosystem succession following megafires is essential to identifying management approaches that support ecosystem resilience in the face of multiple stressors and novel disturbance regimes (St. Clair et al. 2016).

Objective 1) Characterize post-fire ungulate redistribution and forest regeneration across the Pole Creek megafire complex as a function of burn severity and hunting pressure Goal 1: Understand how megafire redistribution of megafauna alters herbivory regimes and characterize how it differentially affects the regeneration and invasibility of different forest types (Pinion-Juniper, Oak-Maple, Aspen-Conifer). Goal 2: Test how increased hunting pressure alters ungulate movement and behavior and whether these changes influence forest regeneration success. Goal 3: Compare habitat quality for wildlife several years post-burn among fenced and open sites. Objective 2) Examine how burn severity and ungulate herbivory impact soil hydrology, nutrient availability, and plant community succession Goal 1: Quantify soil hydrological and nutrient availability in burned vs. unburned and grazed vs. un-grazed plots across ecosystem types. Goal 2: Identify the legacy effects of burn severity and ungulate herbivory on post-fire plant community assembly. Objective 3) Characterize algal, invertebrate, and fish redistribution in burned and unburned stream reaches across the Pole Creek megafire complex Goal 1: Understand how megafire affects recovery of aquatic food webs. Specifically, identify potential thresholds in the relationships among percentage of watershed burned, elevation (ecosystem type), and successional trajectories. Goal 2: Compare how large-scale disturbance to a river network affects native and non-native species recolonization. Objective 4) Quantify riverine fluxes of water, carbon, nutrient, and pollutants immediately after and during recovery from a megafire Goal 1: Quantify terrestrial losses and assess the impact of fire-mobilized material on downstream ecosystems. Goal 2: Understand how megafire affects water available for human use (quantity and quality of runoff and groundwater recharge).

forest regeneration failure, flash flooding, debris flows, lake eutrophication, poor water quality, altered watershed hydrology, plant invasions

Management plans developed

Tracking post-fire ecosystem responses

reductions in water quality and quantity

Collaboration with Manti-Lasal National Forest and Wasatch Cache National Forest

This project will combine information from natural gradients and controlled experiments on the 2018 Pole Creek megafire with results from an ungulate exclosure network installed in 2012 across the Seeley, Box Creek, and Harris Flat fires. The studies will be set up along gradients of burn severity, burn extent, ungulate herbivory, elevation, and vegetation type to examine how megafires affect forest and aquatic habitat recovery and watershed hydrology. Objective 1) Characterize post-fire ungulate redistribution and forest regeneration and recruitment across the Pole Creek megafire complex as a function of burn characteristics and hunting pressure Natural gradient study- Vegetation and burn severity maps will be used to develop a replicated transect network for tracking post-fire forest regeneration across gradients of burn severity and extent, vegetation type (Pinyon-Juniper, Oak-Maple, and Aspen-Conifer), and elevation across the Pole Creek megafire complex. Distribution of elk, deer and cattle will be mapped along the transect network using pellet counts and wildlife cameras (Rhodes et al. 2017) to identify the spatiotemporal redistribution of ungulates. We will take advantage of data from previously collared elk and mule deer to characterize the movement of wild ungulate populations in the study area. Along the same transect network, we will conduct surveys of tree seedling density, growth, and herbivory using standard methods from our lab (Rhodes et al. 2017) to examine how forest regeneration success varies as a function of ungulate distribution, burn severity, vegetation type, elevation, and interannual weather variation. Hunting pressure study- In year 1, after mapping ungulate distributions and browsing patterns across the Pole Creek Fire complex, we will identify 3 landscapes with heavy ungulate browsing pressure. Working with the DWR to control the geographic location of hunting tags, we will divide each landscape unit so one-half experiences higher hunting pressure and the other half receives low or no hunting pressure to experimentally test whether hunting pressure can increase forest recruitment success. Pellet transects and wildlife cameras will be used to quantify the influence of hunting pressure on the distribution of ungulate populations and vegetation transects will be used to monitor seedling regeneration and stand recruitment success. Objective 2) Examine how burn severity and ungulate herbivory impact soil hydrology and nutrient availability and plant community succession Pole Creek Fire Complex - Within the natural gradient and exclosure studies outlined in Objective 1, we propose installing soil moisture sensors and collecting and analyzing soil samples to link the top-down effects of burn severity and ungulate herbivory on post-fire plant community recovery with soil hydrology and nutrient availability. This will allow us to identify mechanisms driving plant and animal community succession and begin connecting these terrestrial dynamics with watershed hydrology, water quality, and aquatic succession. We propose installing a single soil moisture and temperature probe array at each of our transect sites and in each of our wildlife exclosures and unfenced control plots to examine correlations between ungulate distribution, forest regeneration, and soil moisture and nutrient availability. We will collect soil samples annually at the end of each summer for analysis of soil nutrient pools and leachability following protocols developed in our previous work (e.g. Abbott & Jones 2015; Malone et al. 2018). Long-term exclosure network from other fires - In 2012, with funding from the Utah Division of Wildlife Resources, we completed the installation of a four-way exclosure network in the Seeley, Box Creek, and Harris Flat fires to examine aspen regeneration in response to elk, cattle, and deer herbivory. Forest regeneration and ungulate herbivory pressure varied dramatically across the study sites resulting in strong differences in forest succession trajectories. However, we only characterized aspen regeneration and didn't examine the response of the understory plant community, which is a primary forage source for wildlife and livestock. There is also an opportunity to test how forest succession and ungulate herbivory affect soil hydrology and nutrient availability, allowing us to experimentally test how top-down effects from ungulate herbivory and bottom-up effects from vegetation community are likely to impact soil hydrology and nutrient availability, which influence watershed hydrology and water quality. We propose returning to these study sites and installing a soil moisture and temperature sensor array in each plot and conducting soil nutrient analyses to test these relationships. Objective 3) Characterize algal, invertebrate, and fish redistribution in burned and unburned stream reaches across the Pole Creek megafire complex Aquatic community characterization -- We will select 16 sites throughout the Spanish Fork stream network for community sampling based on a spatial analysis of percentage upslope catchment area burned, vegetation type, and stream network position (i.e. network topology and catchment size). Sites will include burned and unburned catchments, allowing comparison and time-series analysis of environmental DNA (eDNA), target metagenomics, quantitative PCR, and traditional invertebrate and benthic primary-productivity sampling to characterize post-burn aquatic communities. By understanding the distribution (identity and density) of aquatic organisms, we will be able to quantify potential successional changes in waters associated with burn severity, and establish the recovery chronology of native and non-native species. Experimentally linking biological community with aquatic nutrient retention -- To assess how disturbed aquatic ecosystems could buffer downstream water bodies from sediment and nutrients mobilized by the megafire, we will implement nutrient injection experiments at a subset of the sites. We will use a recently developed method called tracer additions for spiraling curve characterization (TASCC), which allows quantification of nutrient spiraling dynamics from ambient to saturated conditions with a single slug addition (Covino et al. 2010a, b). This method provides the full spectrum of spiraling metrics (estimates of ecosystem retention capacity) by collecting multiple samples at a single location as a pulse of reactive and conservative tracers pass through the stream reach. Repeat metrics of nutrient dynamics will allow us to test how overall aquatic biomass and community assemblage interact to regulate riverine nutrient transport. Objective 4) Quantify riverine fluxes of water, carbon, nutrient, and pollutants immediately after the fire and during recovery High-frequency monitoring - We will install six high-frequency water chemistry stations (three are already in place) in burned and unburned watersheds, allowing quantification of snowmelt and periodic extreme precipitation event pulses, when the majority of lateral flux occurs (Raymond et al. 2016; Zarnetske et al. 2018). We will analyze the high-frequency data in an ecohydrological framework to assess the impacts of megafire on runoff and groundwater recharge. These methods will include hydrograph characterization (runoff ratios, surface/subsurface flowpaths, total water storage) and environmental tracer analysis of weathering products (Abbott et al. 2016a). Synoptic sampling across burn gradients -- To identify specific locations of lateral sediment and nutrient transport from terrestrial ecosystems, we will continue occasional "synoptic" sampling of ~250 sites within and around the burn. We have periodically sampled these sites since 2017 as a part of a large citizen science project. In combination with long-term monitoring sites where water chemistry data is available from the Utah Department of Water Quality, these data allow direct pre-post comparison of the nature and magnitude of wildfire effects on stream chemistry across broad geologic and ecosystem-type gradients. Assessing bioavailability of burn-mobilized material - To assess the potential impact of fire-mobilized sediment and organic matter on the eutrophication state of Utah Lake (the main receiving water body), we will quantify bioavailability of organic matter and nutrients with incubations and optical characterization of dissolved and particulate fractions (Abbott et al. 2014).

Monitoring of plants, wildlife, soils and streams, rivers and lakes

BYU and DNR

Project deliverables 1. Two M.S. theses and a Ph.D dissertation 2. Annual reports will be produced during the funded period with more frequent updates available when needed. 3. Conference presentations at The Wildlife Society, the Ecological Society of America or American Geophysical Union meetings. 4. At least 10 published papers in the peer-reviewed scientific literature are anticipated. 5. Ungulate herbivory maps that link landscape heterogeneity and burn severity in the Pole Creek megafire to variation in herbivory risk and forest regeneration failure so that ungulate management can be targeted to specific times and places to reduce cost 6. Hunting pressure recommendation report 7. Aquatic biodiversity maps that show rate of redistribution of native and non-native algae, invertebrates, and fish through the stream network 8. Invasion maps to identify how post-fire conditions and ungulate management may facilitate or limit distribution of invasive aquatic and terrestrial species 9. Estimates of sediment and nutrient loads to vulnerable water bodies following wildfire 10. Public outreach to affected communities through presentations and fact sheets

assessment included in reports