Fuels, Vegetation, and Avifauna
Piñon pine and juniper woodlands are widespread, variable, and incompletely understood forests of the western United States. These woodlands represent the third largest vegetation type in the continental U.S., occupying 40 million ha (Laylock 1999), and the most widespread forest type in Colorado, covering 9 million ha. Piñon-juniper ecosystems support remarkably diverse and unique bird communities— these habitats contain the largest species list of nesting birds of any upland habitat type in the western U.S (Colorado Partners in Flight 2000), 20% of these species are piñon-juniper obligates (Paulin et al. 1999), and many are species of conservation concern (Colorado Partners in Flight 2000; USFWS 2008). Unfortunately, many piñon-juniper ecosystems have been considerably degraded by human practices over the last century (Floyd and Romme 2012). However, in spite of their ubiquity and ecological importance, piñon-juniper management and restoration is often hindered by both conflicting management aims and inadequate scientific understanding (Romme et al. 2002, 2009).
Land managers frequently face trade-offs between wildand fire hazard reduction objectives and ecological goals (Lehmkuhl et al. 2007; Romme et al. 2002). Unfortunately, an understanding of the nature and degree of these trade-offs in piñon-juniper woodlands remains limited by sparse quantitative research. Across the western U.S., piñon-juniper woodlands make up a large proportion of the wildland-urban interface (WUI); consequentially many stands are high priority for fuels treatments to reduce wildland fire hazard (e.g., NFP 2000). Ideally such treatments would mimic natural, historic patterns of vegetation composition, structure, and patchiness (Landres et al. 1999). However, data on pre-settlement piñon-juniper forest structure and fire regimes is sparse (Baker & Shinneman 2004). Land managers are further confronted with a wide range of local conditions and variation in stand dynamics (Romme et al. 2009; Floyd and Romme 2012). In some cases, restoring pre-settlement stand structure may not even be feasible (e.g., where droughts have altered stand structure at landscape- or regional- scales; Breshears et al. 2006). Furthermore, restoration of historic conditions may not always be desirable given current and future management demands (Coop and Schoettle 2011) including promoting ecosystem resilience in the face of future environmental change.
The purpose of our research is to assess the relationships between piñon-juniper fuels treatments and ecological values, and to develop strategies to integrate fuels treatments with ecological restoration in piñon-juniper woodlands. To what extent do piñon-juniper fuels treatments achieve ecological objectives, where are they in conflict, and how might future fuels treatments be altered to reduce undesirable ecological impacts? Our study focuses on the piñon-juniper landscapes of the Arkansas River valley in south-central Colorado (Fig. 1), lands managed by the BLM Royal Gorge Field Office (BLM-RGFO). Nearly 17,000 acres of this landscape have been treated in over 300 fuels treatments between 1998 and 2009. In addition to reducing wildand fire hazard, secondary ecological objectives of treatments include the creation of patches of open canopy in otherwise closed-canopy woodlands and the removal of trees encroaching into grassy meadows. However, the effectiveness of these treatments in meeting these goals is not adequately understood, nor their effects on other important ecological features, including bird populations of concern. Our research was initiated in 2011 to fill these information gaps. A pilot study—examining effects of eight hydroaxe treatments on avifauna communities in contrast with eight controls—was completed on the RGFO during summer 2012. Treatments exerted significant influences on bird communities, including substantial decreases of a piñon-juniper obligate species (Fig. 2). During 2014-2015 we will build on this work to 1) eludicate relationships between piñon-juniper avian communities, vegetation composition and structure, landscape attributes, and fuels, 2) develop metrics of the ecological effects of fuels treatments based on these relationships, and 3) model fire behavior, fuels, and vegetation dynamics in treated and untreated stands.
Figure 1. Fuels treatments (1998-2009) in lands managed by the BLM Royal Gorge Field Office, Colorado.
In addition to assessing relationships between fuels, vegetation structure, composition, and dynamics, and modeled fire behavior, our research incorporates a novel means to gauge fuels treatments effects via avian community composition. Effects of fuels treatments on piñon-juniper birds in the BLM-RGFO are unknown; in fact, very little is known about avian responses to piñon-juniper treatments in general. Additionally, bird species occupancies are likely to serve as particularly useful metrics of piñon-juniper ecosystem condition in ways not served by fuels or vegetation measures. This is because bird habitat selection integrates both stand-level attributes (e.g., vegetation structure; MacArthur & MacArthur 1961) and landscape-scale variation (e.g., fragmentation; Coppedge et al. 2001), with different species’ responding divergently to factors that span a hierarchy of spatial scales (Hagan & Meehan 2002). As such, avian community composition can provide insight into ecological conditions not easily captured by other metrics. Bird community composition is also relatively easy and inexpensive to sample using widely accepted, standardized protocols, and presents unique opportunities for citizen-science to generate very large, comparative datasets and long term monitoring (e.g., the North American Breeding Bird Survey).