Ecological vs. hydrological drought in changing seasons: Learning from full gradient monitoring in the Great Basin
Abstract
In snow-dominated, semi-arid mountainous regions like the Great Basin, USA, hydrological drought is directly associated with declining snowpacks and shifts in precipitation phase and timing. Perennial surface flows and seasonal mountain-block recharge are the mechanisms that fill reservoirs, nurture riparian zones, and replenish aquifers across the region. In spite of this, monitoring of inputs and snowmelt across elevation zones is extremely sparse, creating uncertainty in assessing hydrological shifts in the Great Basin. Additionally, impacts of "snow drought" on ecology in the Great Basin is yet a very open question, as primary vegetation zones distributed across the elevation gradient are historically under-studied. Our study presents in this context high-resolution in-situ observational data from a representative elevation gradient observatory in the Great Basin. We combine atmospheric conditions, soil water, precipitation amount and phase, snowpack, phenology imaging, water well, and sap flow measurements to understand snow timing and input interaction with ecology and hydrology during significant drought periods between 2012-2018 across several sites ranging from 1750-3360 m elevation. We observed that during this period, which was generally associated with snowpack reduction and elevated temperatures, variable summer precipitation had a significant impact on sap flow activity and drought stress in trees, with response closely associated with root-zone plant-available water. Years with significant snow drought did not always experience significant ecological drought due to these seasonal events. During times of extreme ecological drought stress, we also observed differences in species resiliency, including contrasts between limber pine (Pinus flexilis) and bristlecone pine (Pinus longaeva). We also observed during this period that primary contribution of groundwater recharge comes from upper-elevation zones above the pinyon-juniper conifer band. These results bring up critical questions regarding the variability of snow drought in the Great Basin, how ecological and hydrological drought are differentiated from a management perspective, and impacts/importance of other seasonal mechanisms like summertime "monsoon" events.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.H13H..08S
- Keywords:
-
- 0740 Snowmelt;
- CRYOSPHERE;
- 1621 Cryospheric change;
- GLOBAL CHANGE;
- 1813 Eco-hydrology;
- HYDROLOGY;
- 1817 Extreme events;
- HYDROLOGY