Sycamore Creek is a unique treasure in mountainous central Arizona, being a verdant and dynamic stream–riparian ecosystem close to the sprawling Phoenix metropolis. The stream originates in the Mazatzal Mountains, where higher rainfall and some snow provide enough water so that Sycamore Creek— in places—has perennial flow.  During its passage from mountain headwaters to its junction with the Verde River, the stream passes through spruce, fir, and pine forest in the mountains, through pinyon–juniper woodland and impenetrable chaparral, to upper and lower Sonoran desert shrublands. The desert portions of the watershed represent ~65% of its area, and are of particular scientific and public interest because perennial, undammed streams are so rare in the desert Southwest.  These habitats, and their riparian zones (the wetter woodlands that border the stream, featuring cottonwood, willow, sycamore, and ash trees and more distant mesquite forest), are threatened in the Southwest by river impoundment (e.g., Salt River), groundwater pumping (e.g., Santa Cruz River, San Pedro River), invasive species like saltcedar (e.g., Gila River, Verde River), and climate change.  Thus Sycamore Creek, an undammed stream whose watershed is almost entirely within National Forest land, experiences few of these assaults and has a relatively intact riparian forest that is home to many species of plants, bird,s bats, insects, and other life. Native desert fishes (longfin dace, Gila mountain sucker) are abundant in the stream.

The focus of nearly 30 years of ecological research, Sycamore Creek is known worldwide in scientific circles as the quintessential desert stream. ASU researchers focused on the desert portion of the watershed because so little was previously known about this type of stream: how its extreme swings of flow (from a mere trickle to large flash floods (see photos on left). Not only within a year, but also among years, the flow of the stream and its dynamic changes in form, plant and animal populations, and chemistry vary tremendously. Ecological studies have shown how climatic differences among years (i.e., more or less rainfall), changes in resources for plants, algae, and animals, and even human intervention have shaped the character of this beautiful place. Early research in the stream focused on how the ecosystem changes following individual flash floods, which scour the stream bottom, remove animals and algae, and initiate regrowth and reestablishment of these populations upon recession of floodwaters. Owing to notably high productivity, post-flood changes in Sycamore Creek are rapid, and peak abundance of algae and stream animals can be reached within as little as 20 days. Rates of ecosystem change vary with the size and seasonal timing of floods can be enhanced when the nutrient nitrogen is plentiful. A central hypothesis of the research is that nitrogen controls many aspects of stream ecosystem structure and function. Nitrogen availability, in turn, is influenced by many processes at different scales, including connections with the upland desert system during rainstorms that produce flash floods. Therefore, many pioneering studies on nitrogen biogeochemistry in streams have been conducted in Sycamore Creek. In total, ~$4M in funding from the National Science Foundation and >120 scholarly publications have resulted from the research on Sycamore Creek. Most recently, Sycamore Creek is included as a potential monitoring and experimental site for the National Ecological Observatory Network (NEON).

During wet winters, the mainstem of Sycamore Creek and several of its major tributaries are fully connected. The mainstem has five perennial sections that arise during the low-flow season at distinct springs and flow for tens to hundreds of meters, separated by vast stretches of dry streambed; however, the perennial sections are connected under the sand by flowing shallow groundwater. Dos S Ranch is located at the upstream end of one of the perennial sections with the longest run of chemical and biological data (e.g., 1978–2008).  Below the ranch property, canyon walls constrict and the stream meanders across a sandy channel, then abruptly drops over boulder cascades. For ~3 km the stream is inaccessible except by foot, and features steep canyon walls, beautiful pools, healthy riparian trees, interesting backwater wetlands, and tributary junctions. The reach below Dos S ranch is amenable to both long term monitoring and long term, large scale experiments such as the activities proposed by STREON.

Central Arizona - Phoenix Long-Term Ecological Research
Global Institute of Sustainability | Arizona State University
PO Box 873211 | Tempe AZ 85287-3211
(480) 965-2975 | FAX (480) 965-8087

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