The effects of vegetative type, edges, fire history, rainfall, and management in fire‐maintained habitat

Abstract

The combined effects of fire history, climate, and landscape features (e.g., edges) on habitat specialists need greater focus in fire ecology studies, which usually only emphasize characteristics of the most recent fire. Florida scrub‐jays are an imperiled, territorial species that prefer medium (1.2–1.7 m) shrub heights, which are dynamic because of frequent fires. We measured short, medium, and tall habitat quality states annually within 10‐ha grid cells (that represented potential territories) because fires and vegetative recovery cause annual variation in habitat quality. We used multistate models and model selection to test competing hypotheses about how transition probabilities vary between states as functions of environmental covariates. Covariates included vegetative type, edges (e.g., roads and forests), precipitation, openings (gaps between shrubs), mechanical cutting, and fire characteristics. Fire characteristics not only included an annual presence/absence of fire covariate, but also fire history covariates: time since the previous fire, the longest fire‐free interval, and the number of repeated fires. Statistical models with support included many covariates for each transition probability, often including fire history, interactions, and nonlinear relationships. Tall territories resulted from 28 yr of fire suppression and habitat fragmentation that reduced the spread of fires across landscapes. Despite 35 yr of habitat restoration and prescribed fires, half the territories remained tall, suggesting a regime shift to a less desirable habitat condition. Edges reduced the effectiveness of fires in setting degraded scrub and flatwoods into earlier successional states, making mechanical cutting an important tool to compliment frequent prescribed fires.

Integrated hierarchical models to inform management of transitional habitat and the recovery of a habitat specialist

“…Although the model accounts for some aspects of spatial dependencies (e.g., a neighborhood effect on occupancy), our habitat dynamics analysis did not consider explicit spatial variability or correlated effects. Such conditions could result from shared levels of precipitation or drought, as well as edge effects, fire history, below‐ground vegetation biomass, and other biophysical processes (Breininger et al 2018). Adding spatially dependent or other complex variables to these models could be considered if managers decide that additional realism is likely to improve decision making.…”

“…Evaluating changes in a composite metric of variance over time suggests the rate of learning may have reached an asymptote after approximately four to five years of observations. This finding does not suggest, however, that continued monitoring and model updating are without value, as state‐dependent decisions will require annual observations on habitat state and FSJ status, and some model parameters (e.g., transitions induced by less‐frequent actions) may require many years of observation to reduce uncertainty (Breininger et al 2018). In addition, concerns about system non‐stationarity (i.e., due to climate change) argue for continued parameter estimation.…”

“…2, column 1). With no management, tall‐mixed (TM) oak and flatwood scrub have a low probability (~0.15) of reverting to earlier states (OpO, OpC) as a result of wildfire (Breininger et al 2018). Managers predicted that burning alone would increase the likelihood of habitat transitioning to an earlier successional state, but with little confidence in this resulting state.…”

Interpreting Smoke Signals: Fire Ecology and Land Management for Four Federally Listed Birds

“…While research has yielded state-of-the-art habitat models and management guidelines (Breininger et al, 2009(Breininger et al, , 2010Florida Fish and Wildlife Conservation Commission [FFWCC], 2018), the process of maintaining and restoring suitable conditions with fire is complicated by geographic differences in the dominant shrubs and trees present and the response vegetation has when burned (Breininger et al, 2018). Suitable habitat conditions in areas dominated by sand pine (Pinus clausa) were maintained historically by high-intensity crown fires that are difficult to control and mimic using prescribed fires.…”

“…In addition, much of the plant biomass found in scrub lies underground and is used to store the nutrients plants need to recover after a burn. As a result, growth of scrub vegetation post-fire varies greatly based on pre-burn conditions, species composition, nutrient availability, and depth to water table (Breininger et al, 2010(Breininger et al, , 2018. Scrub that has not been burned for long periods grows back faster post-burn than scrub subjected to shorter fire-return intervals.…”