Predicting the impact of invasive trees from different measures of abundance

J. Moyano* (Corresponding Author), L.B. Zamora Nasca, P. Caplat, Pablo Garcia Diaz, B. Langdon, Xavier Lambin, Lia Montti, Aníbal Pauchard, M.A. Núñez

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)

Abstract

Biological invasions produce negative impacts worldwide, causing massive economic costs and ecological impacts. Knowing the relationship between invasive species abundance and the magnitude of their impacts (abundance-impact curves) is critical to designing prevention and management strategies that effectively tackle these impacts. However, different measures of abundance may produce different abundance-impact curves. Woody plants are among the most transformative invaders, especially in grassland ecosystems because of the introduction of hitherto absent life forms. In this study, our first goal was to assess the impact of a woody invader, Pinus contorta (hereafter pine), on native grassland productivity and livestock grazing in Patagonia (Argentina), building abundance-impact curves. Our second goal, was to compare different measure of pine abundance (density, basal area and canopy cover) as predictors of pine's impact on grassland productivity. Our third goal, was to compare abundance-impact curves among the mentioned measures of pine abundance and among different measures of impact: total grassland productivity, palatable productivity and sheep stocking rate (the number of sheep that the grassland can sustainably support). Pine canopy cover, closely followed by basal area, was the measure of abundance that best explained the impact on grassland productivity, but the shape of abundance impact curves differed between measures of abundance. While increases in pine density and basal area always reduced grassland productivity, pine canopy cover below 30% slightly increased grassland productivity and higher values caused an exponential decline. This increase in grassland productivity with low levels of pine canopy cover could be explained by the amelioration of stressful abiotic conditions for grassland species. Different measures of impact, namely total productivity, palatable productivity and sheep stocking rate, drew very similar results. Our abundance-impact curves are key to guide the management of invasive pines because a proper assessment of how many invasive individuals (per surface unit) are unacceptable, according to environmental or economic impact thresholds, is fundamental to define when to start management actions.
Original languageEnglish
Article number116480
Number of pages11
JournalJournal of Environmental Management
Volume325
Issue numberPart B
Early online date25 Oct 2022
DOIs
Publication statusPublished - 1 Jan 2023

Bibliographical note

Acknowledgements
We are very grateful with Martin Reto, who provided key help with the filed work of this study. We thank the owners of the private lands where we carried out our field work for giving us permission to work there. We also thank Nadia Rojas, who helped with sample processing. This research project was funded under the Latin American Biodiversity Programmme as part of the Newton Fund (NE/s011641/1), with contributions from NERC and the Argentine National Scientific & Technical Research Council (CONICET, -2019-74-APN-DIR#CONICET). AP and BL were funded by ANID/BASAL FB10006.

Data Availability Statement

The data are freely available from Environmental Information Data Centre (EIDC) (http://eidc.ceh.ac.uk/) for non-commercial use under Open Government Licence terms and conditions. https://doi.org/10.5285/54fe47f3-778e-4e0b-b2fda2473b7f.

Supplementary data to this article can be found online at https://doi.
org/10.1016/j.jenvman.2022.116480.

Keywords

  • Impact-based management
  • Grasslands
  • Livestock grazing
  • Pinus
  • Primary productivity
  • Woody invasions

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