Abstract
Rainfall timing, frequency, and quantity is rapidly changing in dryland regions, altering dryland plant communities. Understanding dryland plant responses to future rainfall scenarios is crucial for implementing proactive management strategies, particularly in light of land cover changes concurrent with climate change. One such change is woody plant encroachment, an increasing abundance of woody plants in areas formerly dominated by grasslands or savannas. Continued woody plant encroachment will depend, in part, on seedling capacity to establish and thrive under future climate conditions. Seedling performance is primarily impacted by soil moisture conditions governed by precipitation amount (quantity) and frequency. We hypothesized that (H1) seedling performance would be enhanced by both greater soil moisture and pulse frequency, such that seedlings with similar mean soil moisture would perform best under high pulse frequency. Alternatively, (H2) mean soil moisture would have greater influence than pulse frequency, such that a given pulse frequency would have little influence on seedling performance. The hypotheses were tested with Prosopis velutina, a shrub native to the United States that has encroached throughout its range and is invasive in other continents. Seedlings were grown in a greenhouse under two soil moisture treatments, each which was maintained by two pulse frequency treatments. Contrary to H1, mean soil moisture had greater impact than pulse frequency on seedling growth, photosynthetic gas exchange, leaf chemistry, and biomass allocation. These results indicate that P. velutina seedlings may be more responsive to rainfall amount than frequency, at least within the conditions seedlings experienced in this experimental manipulation.
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Availability of data and materials
Data are available in the Dryad repository: https://doi.org/10.5061/dryad.tht76hf0d.
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R code used for this work are standard statistical analyses; no novel code was developed. Code is available upon request from the corresponding author.
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Acknowledgements
We thank the Arizona State University School of Life Sciences for use of the greenhouse and the Desert Botanical Garden for the soil. We thank N. Hornslein, M. Farrell, A. Hayes, B. Monus, F. Kangombe, J. Hunter, K. Amari, and D. Koepke for laboratory and greenhouse assistance. We appreciate constructive comments from three anonymous reviewers on a prior version of this manuscript.
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No grant funds supported this work. Supplies and space were provided by Arizona State University and the Desert Botanical Garden.
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Communicated by Louis Stephen Santiago.
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Davis, A.R., Hultine, K.R., Sala, O.E. et al. Seedling responses to soil moisture amount versus pulse frequency in a successfully encroaching semi-arid shrub. Oecologia 199, 441–451 (2022). https://doi.org/10.1007/s00442-022-05193-w
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DOI: https://doi.org/10.1007/s00442-022-05193-w