How does the leaf out of deep rooting phreatophyte, Populus deltoides, respond to variations in groundwater levels?
Kyle Skoda1, Theresa Crimmins1,2, Martha Whitaker3
1 School of Natural Resources and the Environment
2 USA National Phenology Network, School of Natural Resources and the Environment
3 Department of Hydrology & Atmospheric Sciences
Groundwater resources are decreasing throughout the American southwest and becoming more variable. The seasonal timing of annual vegetation behavior like leaf out, is captured in phenology, reflecting plants’ responses to their environment. For plants relying on access to groundwater, like eastern cottonwood and other deep rooting phreatophytes, available water is important to ecosystem function. A simple linear regression analysis was used to identify a relationship between groundwater levels measured by USGS Well 350301106383601 and timing of eastern cottonwood (Populus deltoides) taken from multiple sites in urban Albuquerque, New Mexico. Leaf out of eastern cottonwood is inversely correlated with depth to groundwater, and as the groundwater levels have risen, leaf out timing has occurred later in the year. Later leaf out in eastern cottonwood during the study period may be better explained by the rate of groundwater drawdown and recharge. Whether eastern cottonwood leaf-out is impacted temporally by variations in groundwater annual averages is not explored in the literature. Managing phreatophyte vegetation in the semi-arid southwest for ecosystem services like leaf out, flowering, and fruiting can be informed by the depth to groundwater measured at nearby wells. In future drought conditions, with greater groundwater level variability, the onset of leaves by eastern cottonwood could continue to progress later in the year.