Three Pronged Analysis of Water Stressed Populus angustifolia Riparian Forest Along Dolores River, In Southwestern United States

Abstract

The arid Southwestern United States’ highly productive riparian ecosystems are in decline due to damming for irrigation purposes, which is in high demand due to prolonged drought conditions. Riparian forests are highly depended upon for their water quality, physical dynamic, biodiversity, and wildlife habitat. This water shortage has greatly affected vegetation in these areas, like Populus angustifolia, which have responded by altering their physiology. In an effort to understand the effects of damming on cottonwoods below McPhee Dam this three-pronged study focused on cottonwood canopy cover, xylem pressure, and a re-survey along a long-term transect to assess cottonwood survival over time along the Dolores River. Canopy cover was measured along three 100-meter transects at sites above and below the dam. Xylem pressure was gathered along the second transect at predawn and late afternoon once per month. Long-term data, along a permanent transect at site 3, tracked the fate of individual trees. Canopy cover, directly linked to discharge, was about 50% lower below the dam. Insignificant xylem pressure variation between sites suggested drought adaptation, or increased precipitation due to El Niño. These results demonstrate on-going effects of hydraulic modifications and the eventual loss of habitat during this time of increased drought.