Floristic patterns in the Andes of northern Patagonia’s forests, Argentina: towards integrating ecological responses with expert-based and unsupervised classification methods

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Prepared by Natalia Zoe Joelson, Alois Simon, Friedemann von Lampe, Gabriel Ángel Loguercio, Stefan Zerbe, Christoph Leuschner, and Helge Walentowski

Different communities found in northern Patagonia, Argentina. Images show typical examples of: A) Broadleaved montane forest: Humid, evergreen forests found in wetter western areas, with dense tree coverage of Nothofagus dombeyi, B) Mixed montane forest: Mid-elevation evergreen forests adapted to moderate rainfall with a mix of broadleaved N. dombeyi and the conifer Austrocedrus chilensis, C) Coniferous montane forest: Drier forests dominated by A. chilensis, the type most impacted by human activities and invasive plant species, D) Herbaceous subandean forest: Higher-elevation forests dominated by the summer-green Nothofagus pumilio with many grasses and herbs beneath the trees, E) Woody subalpine forest: High-elevation forests near the tree line, dominated by dominated by N. pumilio and hardy, cold-tolerant trees and shrubs, F) Shrubland: open areas with bushes and small trees, usually colonizing after fire. Photo credit: Natalia Joelson

Patagonia’s Andean forests represent one of Earth’s unique biodiversity hotspots, shaped by steep gradients in climate, soil chemistry, and disturbance influence. Yet, traditional studies and classifications used in this region have often surveyed only wetter or drier areas or have not used numerical methods nor systematic sampling.

To fill this knowledge gap, we conducted an extensive survey of 141 forest sites in the Río Puelo watershed, spanning diverse conditions from lush montane wet forests to dry forests and post-fire shrublands. We used numerical tools that grouped similar sites based on the plant species found in them and showed how plant communities change across the different environmental conditions in the landscape.

What we found?

  • Six plant communities, which are distinct in their floristic composition, made up of 241 plant species.
  • Elevation (as an indirect measure of temperature) is the most important factor shaping plant communities, followed by rainfall and soil chemistry (particularly acidity and nitrogen availability).
  • Wet and cold forests have fewer species, mostly native ones that are well-adapted to shady conditions. In contrast, warmer, drier forests have more species, including many that were introduced by people.
  • Human disturbances like cattle grazing also have a strong impact on plant composition, increasing the numbers of non-native species and promoting open, disturbed habitats.
  • Traditional classifications (mainly developed in wet Chilean areas) match well in humid regions, but fail to adequately represent transitional and disturbed communities. This shows that we need updated classification approaches to better reflect the variation in composition.

Why it matters?

This is the first study on the Argentine side of the Andes to link climate, soil, and human impact to plant communities using both traditional expert knowledge and modern numerical analysis methods. Understanding these patterns helps us to have better frameworks to protect native forests, prepare for climate change impact, and make better decisions about land use in the future.

This is a plain language summary of the paper by Joelson et al. published in the Vegetation Classification and Survey (https://doi.org/10.3897/VCS.134621). This post was prepared by Natalia Zoe Joelson and Stefan Zerbe