Dynamics of Fremont cottonwood (Populus fremontii) and saltcedar (Tamarix chinensis) populations along the San Pedro River, Arizona

摘要: Abstract Woodlands of the exotic saltcedar (Tamarix chinensis) have replaced forests native Fremont cottonwood (Populus fremontii) and willow (Salixspp.) along many rivers American South-west. In middle basin San Pedro River, dominates only at drier sites where surface ground-water conditions no longer support cottonwood–willow forests. At with perennial (or near-perennial) stream flow, is co-dominant cottonwood. However, has been declining in importance these sites, perhaps due to recent occurrence that favour establishment (frequent winter flooding, high rates flow during spring, exclusion livestock). This shift provides evidence capacity for self-repair degraded Sonoran riparian ecosystems. upper basin, contrast, increased relative abundance show decline, signaling a need vigilance river management. Saltcedar generally sparse probably combination cool temperatures persistence or near-perennial flows most areas. Throughout both influenced by changing flood patterns. Expansion populations initial colonization correlate post-1960 increases fall frequency decreases summer size.