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Abstract Changes in climate and land management over the last half‐century have favoured woody plants native to grasslands and led to the rapid expansion of woody species. Despite this being a global phenomenon, it is unclear why some woody species have rapidly expanded while others have not. We assessed whether the most abundant woody encroaching species in tallgrass prairie have common growth forms and physiology or unique traits that differentiate their resource‐use strategies.We characterized the abundance, above‐ground carbon allocation, and leaf‐level physiological and structural traits of seven woody encroaching species in tallgrass prairie that span an order of magnitude in abundance. To identify species‐specific increases in abundance, we used a 34‐year species composition dataset at Konza Prairie Biological Station (Central Great Plains, USA). We then compared biomass allocation and leaf‐level traits to determine differences in carbon and water use strategies among species.While all focal species increased in abundance over time, encroachment in this system is primarily driven by three species:Cornus drummondii,Prunus americanaandRhus glabra. The most dominant species,Cornus drummondii, had the most extreme values for several traits, including the lowest leaf:stem mass ratios, lowest photosynthetic capacity and highest turgor loss point.Two of the most abundant species,Cornus drummondiiandRhus glabra, had opposing growth forms and resource‐use strategies. These species had significantly different above‐ground carbon allocation, leaf‐level drought tolerance and photosynthetic capacity. There were surprisingly few interspecific differences in specific leaf area and leaf dry matter content, suggesting these traits were poor predictors of species‐level encroachment.Synthesis. Woody encroaching species in tallgrass prairie encompass a spectrum of growth forms and leaf physiology. Two of the most abundant woody species fell at opposite ends of this spectrum. Our results suggest niche differences among a community of woody species facilitate the rapid encroachment by a few species. This study shows that woody encroaching species do not conform to a ‘one‐size‐fits‐all’ strategy, and a diversity of growth forms and physiological strategies may make it more challenging to reach management goals that aim to conserve or restore grassland communities.
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Elevated CO2 counteracts effects of water stress on woody rangeland-encroaching species
Abstract The ubiquity of woody plant expansion across many rangelands globally has led to the hypothesis that the global rise in atmospheric carbon dioxide concentration ([CO2]) is a global driver facilitating C3 woody plant expansion. Increasing [CO2] also influences precipitation patterns seasonally and across the landscape, which often results in the prevalence of drought in rangelands. To test the potential for [CO2] to facilitate woody plant growth, we conducted a greenhouse study for 150 days to measure CO2 effects on juveniles from four woody species (Cornus drummondii C.A. Mey., Rhus glabra L., Gleditsia triacanthos L., Juniperus osteosperma Torr.) that are actively expanding into rangelands of North America. We assessed chronic water-stress (nested within CO2 treatments) and its interaction with elevated [CO2] (800 p.p.m.) on plant growth physiology for 84 days. We measured leaf-level gas exchange, tissue-specific starch concentrations and biomass. We found that elevated [CO2] increased photosynthetic rates, intrinsic water-use efficiencies and leaf starch concentrations in all woody species but at different rates and concentrations. Elevated [CO2] increased leaf starch levels for C. drummondii, G. triacanthos, J. osteosperma and R. glabra by 90, 39, 68 and 41%, respectively. We also observed that elevated [CO2] ameliorated the physiological effects of chronic water stress for all our juvenile woody species within this study. Elevated [CO2] diminished the impact of water stress on the juvenile plants, potentially alleviating an abiotic limitation to woody plant establishment in rangelands, thus facilitating the expansion of woody plants in the future.
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- Award ID(s):
- 2025849
- PAR ID:
- 10468287
- Editor(s):
- Adams, Henry
- Publisher / Repository:
- Tree Physiology
- Date Published:
- Journal Name:
- Tree Physiology
- ISSN:
- 1758-4469
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1093/treephys/tpac150
