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Farrell HL, Munson SM, Butterfield BJ, Duniway MC, Faist AM, Gornish ES, Havrilla CA, Larios L, Reed SC, Rowe HI, Laushman KM, McCormick ML. Soil surface treatments and precipitation timing determine seedling development across southwestern US restoration sites. ECOLOGICAL APPLICATIONS : A PUBLICATION OF THE ECOLOGICAL SOCIETY OF AMERICA 2023; 33:e2834. [PMID: 36864737 DOI: 10.1002/eap.2834] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2022] [Revised: 11/04/2022] [Accepted: 02/01/2023] [Indexed: 06/02/2023]
Abstract
Restoration in dryland ecosystems often has poor success due to low and variable water availability, degraded soil conditions, and slow plant community recovery rates. Restoration treatments can mitigate these constraints but, because treatments and subsequent monitoring are typically limited in space and time, our understanding of their applicability across broader environmental gradients remains limited. To address this limitation, we implemented and monitored a standardized set of seeding and soil surface treatments (pits, mulch, and ConMod artificial nurse plants) designed to enhance soil moisture and seedling establishment across RestoreNet, a growing network of 21 diverse dryland restoration sites in the southwestern USA over 3 years. Generally, we found that the timing of precipitation relative to seeding and the use of soil surface treatments were more important in determining seeded species emergence, survival, and growth than site-specific characteristics. Using soil surface treatments in tandem with seeding promoted up to 3× greater seedling emergence densities compared with seeding alone. The positive effect of soil surface treatments became more prominent with increased cumulative precipitation since seeding. The seed mix type with species currently found within or near a site and adapted to the historical climate promoted greater seedling emergence densities compared with the seed mix type with species from warmer, drier conditions expected to perform well under climate change. Seed mix and soil surface treatments had a diminishing effect as plants developed beyond the first season of establishment. However, we found strong effects of the initial period seeded and of the precipitation leading up to each monitoring date on seedling survival over time, especially for annual and perennial forbs. The presence of exotic species exerted a negative influence on seedling survival and growth, but not initial emergence. Our findings suggest that seeded species recruitment across drylands can generally be promoted, regardless of location, by (1) incorporation of soil surface treatments, (2) employment of near-term seasonal climate forecasts, (3) suppression of exotic species, and (4) seeding at multiple times. Taken together, these results point to a multifaceted approach to ameliorate harsh environmental conditions for improved seeding success in drylands, both now and under expected aridification.
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Affiliation(s)
- Hannah L Farrell
- U.S. Geological Survey, Southwest Biological Science Center, Flagstaff, Arizona, USA
| | - Seth M Munson
- U.S. Geological Survey, Southwest Biological Science Center, Flagstaff, Arizona, USA
| | - Bradley J Butterfield
- Department of Biological Sciences, Northern Arizona University, Flagstaff, Arizona, USA
| | - Michael C Duniway
- U.S. Geological Survey, Southwest Biological Science Center, Moab, Utah, USA
| | - Akasha M Faist
- College of Forestry and Conservation, University of Montana, Missoula, Montana, USA
| | - Elise S Gornish
- School of Natural Resources and the Environment, University of Arizona, Tucson, Arizona, USA
| | - Caroline A Havrilla
- Department of Forest and Rangeland Stewardship, Colorado State University, Fort Collins, Colorado, USA
| | - Loralee Larios
- Department of Botany and Plant Sciences, University of California, Riverside, California, USA
| | - Sasha C Reed
- U.S. Geological Survey, Southwest Biological Science Center, Moab, Utah, USA
| | - Helen I Rowe
- School of Earth and Sustainability, Northern Arizona University, Flagstaff, Arizona, USA
- McDowell Sonoran Conservancy, Scottsdale, Arizona, USA
| | | | - Molly L McCormick
- Southwest Fire Science Consortium and School of Forestry, Northern Arizona University, Flagstaff, Arizona, USA
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Christensen EM, James D, Randall RM, Bestelmeyer B. Abrupt transitions in a southwest U.S. desert grassland related to the Pacific Decadal Oscillation. Ecology 2023:e4065. [PMID: 37186307 DOI: 10.1002/ecy.4065] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/27/2022] [Revised: 03/31/2023] [Accepted: 04/10/2023] [Indexed: 05/17/2023]
Abstract
Prediction of abrupt ecosystem transitions resulting from climatic change will be an essential element of adaptation strategies in the coming decades. In the arid southwest United States, the collapse and recovery of long-lived perennial grasses have important effects on ecosystem services, but the causes of these variations have been poorly understood. Here we use a quality-controlled vegetation monitoring dataset initiated in 1915 to show that grass cover dynamics during the 20th century were closely correlated to the Pacific Decadal Oscillation (PDO) index. The relationship out-performed models correlating grasses to yearly precipitation and drought indices, suggesting that ecosystem transitions attributed only to local disturbances were instead influenced by climate teleconnections. Shifts in PDO phase over time were associated with the persistent loss of core grass species and recovery of transient species, so recovery of grasses in aggregate concealed significant changes in species composition. However, the relationship between PDO and grass cover broke down after 1995; grass cover is consistently lower than PDO would predict. The decoupling of grass cover from the PDO suggests that a threshold had been crossed in which warming or land degradation overwhelmed the ability of any grass species to recover during favorable periods. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Erica M Christensen
- USDA-ARS-Jornada Experimental Range, New Mexico State University, Las Cruces, NM, USA
| | - Darren James
- USDA-ARS-Jornada Experimental Range, New Mexico State University, Las Cruces, NM, USA
| | - Robb M Randall
- DEVCOM Army Research Laboratory, White Sands Missile Range, NM, USA
| | - Brandon Bestelmeyer
- USDA-ARS-Jornada Experimental Range, New Mexico State University, Las Cruces, NM, USA
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Osborne BB, Bestelmeyer BT, Currier CM, Homyak PM, Throop HL, Young K, Reed SC. The consequences of climate change for dryland biogeochemistry. THE NEW PHYTOLOGIST 2022; 236:15-20. [PMID: 35706381 DOI: 10.1111/nph.18312] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/22/2022] [Accepted: 06/05/2022] [Indexed: 06/15/2023]
Abstract
Drylands, which cover > 40% of Earth's terrestrial surface, are dominant drivers of global biogeochemical cycling and home to more than one third of the global human population. Climate projections predict warming, drought frequency and severity, and evaporative demand will increase in drylands at faster rates than global means. As a consequence of extreme temperatures and high biological dependency on limited water availability, drylands are predicted to be exceptionally sensitive to climate change and, indeed, significant climate impacts are already being observed. However, our understanding and ability to forecast climate change effects on dryland biogeochemistry and ecosystem functions lag behind many mesic systems. To improve our capacity to forecast ecosystem change, we propose focusing on the controls and consequences of two key characteristics affecting dryland biogeochemistry: (1) high spatial and temporal heterogeneity in environmental conditions and (2) generalized resource scarcity. In addition to climate change, drylands are experiencing accelerating land-use change. Building our understanding of dryland biogeochemistry in both intact and disturbed systems will better equip us to address the interacting effects of climate change and landscape degradation. Responding to these challenges will require a diverse, globally distributed and interdisciplinary community of dryland experts united towards better understanding these vast and important ecosystems.
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Affiliation(s)
- Brooke B Osborne
- Southwest Biological Science Center, US Geological Survey, Moab, UT, 84532, USA
| | - Brandon T Bestelmeyer
- Jornada Experimental Range, US Department of Agriculture, Las Cruces, NM, 88003, USA
| | - Courtney M Currier
- School of Life Sciences, Arizona State University, Tempe, AZ, 85287, USA
| | - Peter M Homyak
- Department of Environmental Sciences, University of California, Riverside, CA, 92521, USA
| | - Heather L Throop
- School of Life Sciences, Arizona State University, Tempe, AZ, 85287, USA
- School of Earth and Space Exploration, Arizona State University, Tempe, AZ, 85287, USA
| | - Kristina Young
- Department of Extension Agriculture and Natural Resources, Utah State University, Moab, UT, 84532, USA
| | - Sasha C Reed
- Southwest Biological Science Center, US Geological Survey, Moab, UT, 84532, USA
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