Effects of Fire on Riparian Forests Along a Free-Flowing Dryland River

Abstract

Riparian fire studies in the American Southwest have focused on flow-regulated rivers and typically show increase in introduced Tamarix, a species with high resprout capacity, and declines in Populus. Effects of fire, however, can vary with environmental setting. We examined riparian fire along the free-flowing Upper San Pedro River (Arizona) by making temporal comparisons supplemented by spatial contrasts between burned and unburned sites. Pre-fire, Populus fremontii and Salix gooddingii were dominant species, with Tamarix sparse in the understory. Species differed in mortality and resprout rates, producing post-fire vegetation change. Mortality was highest for Tamarix, intermediate for Salix, and lowest for Populus, and also varied among size classes. Resprout rate was low for Populus, high for Salix, and also high for the few surviving Tamarix. The net effect was changes in population size structure (relative shifts towards larger Populus but smaller individuals of other species) and forest composition (decreased abundance of Tamarix relative to Populus and Salix), and in spatial distribution of stems. Tamarix's low ability to survive fire resulted from competitive suppression by Populus and Salix, with their dominance a product of the site's flow regime. Results indicate that post-fire outcomes within the riparian Southwest are variable and context-dependent.

Climate change, forests, fire, water, and fish: Building resilient landscapes, streams, and managers

“…Fire has also influenced the species composition, structure, and environmental conditions of the riparian and aquatic communities associated with stream networks that drain these landscapes (Gom and Rood 1999;Everett and others 2003;Skinner 2003;Reeves and others 2006;Petitt and Naiman 2007;Stromberg and Rychener 2010). Research on riparian fire frequency and severity has primarily been conducted in forests of the Pacific Northwest (see text box on fire histories in riparian areas).…”

Fire created habitat partitioning and isolation between hybridizing warblers

“…Based on our results, reduction of willow cover and promotion of grassland cover by fire are the most likely candidates. We found both habitat covariates useful for modeling whether a habitat patch would be mixed (both GWWA and BWWA) or pure GWWA and both willow cover (negatively) (Lee et al 2005, Stromberg andRychener 2010) and grassland cover (positively) (Higgins et al 1989, Telfer 2000 are affected by fire. Our results are consistent with Klaus and Buehler (2001) and Confer et al (2003) who demonstrated a negative relationship between canopy cover and GWWA nest site selection and fledging success respectively.…”

Mapping Annual Riparian Water Use Based on the Single-Satellite-Scene Approach

“…In the short-term, riparian water use could increase by the abundance of sprouting shoots [8]. In the long-term, however, changes in forest composition by shifts in tree-age structure may reduce the forest leaf area compared to a pre-fire condition, ultimately decreasing the ET rates [72]. …”