When
SPEAKER: Susan Moran, USDA-ARS, Southwest Watershed Research Center, Tucson, AZ
DATE: Wednesday, February 18, 2015
TIME: 3:00-4:00 PM
LOCATION: Marley Building, Room 230
ABSTRACT:
Grasslands across the United States play a key role in regional livelihood and national food security. Yet, it is still unclear how this important resource will respond to the regional drying and warming predicted with climate change. The early 21st century drought in the southwestern U.S. resulted in hydroclimatic conditions that have been recognized as similar to those expected with climate change.
The first part of this presentation will focus on the impact of the early 21st century drought on six grasslands across the southwestern United States. There is evidence of an exceptional decrease in grassland growth, and the replacement of native grasses with less-nutritious and more-fire-prone invasive grasses.
This led to the question: What is the temporal threshold of soil moisture deficit that results in a change in grassland function? After only 10 consecutive months of below average soil moisture, water-limited grasslands experienced mortality and changes in species composition, and some light-limited grasslands underwent a striking shift from light- to water-limitation.
These compelling results in a natural setting offer an insight into ecosystem response to climate variability, and encourage the use of satellite observations to further understand ecosystem response on a regional scale.