Academic Affiliation: Lawrence University
Breanna was born on the Navajo reservation in Gallup, New Mexico and grew up in Salt Lake City, Utah. She is currently finishing her undergraduate degree at Lawrence University in Appleton, Wisconsin. Her interest in geology was kindled after meddling in environmental science during high school. After taking a geology class from an inspiring professor, she decided to pursue geology. When Breanna isn’t studying, she enjoys being with friends and watching sappy romantic comedies.
Transpiration source water and geomorphological potential of root growth in the Boulder Creek CZO, Colorado
The influence of vegetation on the hydrological cycle and the possible effect of roots in geomorphological processes are poorly understood. Gordon Gulch watershed in the Front Range of the Rocky Mountains, Colorado, is a montane climate ecosystem in the Boulder Creek Critical Zone Observatory (CZO) whose study adds to the understanding of ecohydrology in different climates. This work sought to identify the sources of water used by different tree species and to determine how trees growing in rock outcrops may contribute to the fracturing and weathering of rock. Stable isotopes (18O and 2H) were analyzed from water extracted from soil and xylem samples from trees.We found that Pinus ponderosa trees on the south-facing slope consume water from deeper depths during dry periods and use water from soils saturated by rainfall events. Pinus contorta trees on the north-facing slope show a similar, expected response in water consumption, before and after rain.
Two trees (Pinus ponderosa) growing within rock outcrops demonstrate water use from cracks replenished by new rains. An underexplored question in geomorphology is whether tree roots growing in rock outcrops contribute to long-term geomorphological processes by physically deteriorating the bedrock. The dominant roots of measured trees contributed approximately 30 – 80% of total water use, seen especially after rainfall events. Preliminary analysis of root growth rings indicates that root growth is capable of expanding rock outcrop fractures at an approximate rate of 0.6 –1.0 mm per year. These results demonstrate that tree roots play a significant role in a tree’s physiological processes and in bedrock fracturing.