Linking stream flow and groundwater to avian habitat in a desert riparian system

Abstract

Increasing human populations have resulted in aggressive water development in arid regions. This development typically results in altered stream flow regimes, reduced annual flow volumes, changes in fluvial disturbance regimes, changes in groundwater levels, and subsequent shifts in ecological patterns and processes. Balancing human demands for water with environmental requirements to maintain functioning ecosystems requires quantitative linkages between water in streams and ecosystem attributes. Streams in the Sonoran Desert provide important habitat for vertebrate species, including resident and migratory birds. Habitat structure, food, and nest‐building materials, which are concentrated in riparian areas, are provided directly or indirectly by vegetation. We measured riparian vegetation, groundwater and surface water, habitat structure, and bird occurrence along Cherry Creek, a perennial tributary of the Salt River in central Arizona, USA. The purpose of this work was to develop an integrated model of groundwater–vegetation–habitat structure and bird occurrence by: (1) characterizing structural and provisioning attributes of riparian vegetation through developing a bird habitat index (BHI), (2) validating the utility of our BHI through relating it to measured bird community composition, (3) determining the riparian plant species that best explain the variability in BHI, (4) developing predictive models that link important riparian species to fluvial disturbance and groundwater availability along an arid‐land stream, and (5) simulating the effects of changes in flow regime and groundwater levels and determining their consequences for riparian bird communities. Riparian forest and shrubland vegetation cover types were correctly classified in 83% of observations as a function of fluvial disturbance and depth to water table. Groundwater decline and decreased magnitude of fluvial disturbance caused significant shifts in riparian cover types from riparian forest to shrublands. Variability in the BHI was best explained by the cover of deciduous riparian tree species, primarily Populus fremontii, Platanus wrightii, and Salix gooddingii. The distributions of these plant species were well explained by the depth to groundwater and magnitude of fluvial disturbance along the stream. Bird species diversity and richness were significantly higher in sites with higher habitat indices. This quantitative linkage between surface and groundwater, plant species composition, habitat complexity, and bird communities has implications for water management and in determining environmental flows.

Changes in Community-Level Riparian Plant Traits over Inundation Gradients, Colorado River, Grand Canyon

“…Vegetation encroachment, streamward expansion of xeric communities (terrestrialization), and reduced recruitment of some species commonly occur in riparian ecosystems of southwestern North America following changes to flow regimes (Turner and Karpiscak 1980;Shafroth et al 2002;Merritt and Bateman 2012;Sankey et al 2015). These changes strongly suggest that flooding and water stress influence riparian community-level traits (Kyle and Leishman 2009;Hough-Snee et al 2015).…”

Integrated STEM: Focus on Informal Education and Community Collaboration through Engineering

“…Guided by mentors using research scientists' work [29,30] the scouts were taught that macro-invertebrate diversity and presence can be used to determine water quality. Second, vegetation height was recorded, as it affects both aquatic and on-shore species that rely on riparian vegetation [31]. Third, the scouts recorded the canopy cover, as a greater canopy equals cooler water and more macro-invertebrates [32].…”

Seasonality of Groundwater Recharge in the Basin and Range Province, Western North America

“…Riparian trees such as cottonwood, willow, sycamore, and netleaf hackberry provide habitat preferred by migrating bird species (Powell and Steidl, 2002;Stromberg and Tellman, 2009). The quality and distribution of habitat for migrating birds is dependent upon the distribution of deciduous riparian tree species, which in turn depends upon depth to groundwater and surface flow regime (Merritt and Bateman, 2012). Deciduous tree species sustain riparian food webs by making groundwater available to insects and animals via greenfall (Sabo et al, 2008).…”