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Science HAPPENINGS June 2019

Recovering from Drought: Monitoring Plant Health in the National Parks
by Dana Witwicki
Monitoring blackbrush in Canyonlands National Park,
April 2018. Photo NPS/Amy Washuta.

Due to a long, intense drought, 2018 was a tough year for plants in Southeast Utah. Some of the worst conditions were at Natural Bridges National Monument, where precipitation was below long-term averages for 16 consecutive months. Further north, rare showers punctuated intensely dry conditions near Arches and Canyonlands national parks, but the landscape remained parched.

Drought can have major effects on the plant communities that anchor park ecosystems. From an office in Moab, a group of National Park Service (NPS) scientists helps park managers know what kinds of changes are happening. Each spring for the past 10 years, they have collected data that reveal the health of grasslands, blackbrush shrublands, and pinyon-juniper woodlands at Arches and Canyonlands. By looking at changes in the number and cover of live plants, we can assess whether they are thriving or declining. Compiling a long-term, place-based record helps us understand how plant communities respond to climatic events (like the recent drought), and which species, locations, and soils are most vulnerable or resilient. Park managers use this information to make decisions about which species to restore, and which exotic-plant populations to target for removal.

Dying junipers in southeast Utah, April 2019. Photo NPS/Dana Witwicki.
Rain finally came in October 2018, and the winter and spring of 2019 have been much wetter than the long-term averages. Data from this spring’s field visits are still rolling in, so it’s too early to fully assess the effects of the drought, but we do know a few things. Perennial bunchgrasses were hit the hardest. Most grasses barely greened up during the 2018 growing season, and have been slow to green up for the 2019 growing season. Unlike cacti or woody plants, grasses don’t have any way to store water. To survive a drought, they let some of their shoots die back. Although there’s been above average precipitation over the past eight months based on the past 30 years, these grasses don’t have the live shoots and roots to respond as well after the drought. It’s difficult to tell which grasses perished in the drought and which ones have just been slow to start growing again during this cool, moist spring.

Monitoring grasslands in Arches National Park, April 2018. Photo NPS.
Our pinyon-juniper woodlands also struggled during the drought. Many pinyon pines died throughout the region. Junipers were yellowing at an alarming pace, especially in the drier, southernmost part of the state. On many junipers, most of the canopy died. But some show tiny signs of life—a few green branches near the base. Scientists are watching to see if they will ultimately survive.

Many shrub species, with their deep roots and woody stems, fared better. They’re greening back up after the wet winter and spring. If you look closely, you’ll see tiny shrub seedlings that have germinated all over the desert.

Scientists will continue to observe the recovery of these plants and learn more about regional drought effects. Along with dryland plant communities, the NPS Northern Colorado Plateau Network also monitors the health of soils, riparian plants, rivers, streams, and springs on the Colorado Plateau. For more information on our work, or to download species lists for parks in the area, visit https://www.nps.gov/im/ncpn/.
 
 
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