Environment and anthropogenic impacts as main drivers of plant assemblages in forest mountain landscapes of Southern Patagonia.

HUERTAS HERRERA, A; CELLINI, JM; BARRERA, MD; LENCINAS, MV; MARTINEZ PASTUR, G

FOREST ECOLOGY AND MANAGEMENT

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2018 vol. 430 p. 380 - 393

0378-1127

Management of natural areas generated multiple trade-offs (e.g., land-sharing and land-sparing), and exotic species occurrence was identified as one of the most harmful ones. In this context, understanding the drivers of exotic plant occurrences is critically important for biodiversity conservation and land planning. The aim of this work was to evaluate the relationships between environmental gradients in mountain landscapes and anthropogenic impacts related to economic uses (cattle grazing and harvesting) as drivers for the plant assemblages in South Patagonian forests. The study was located in the Andorra Valley basin (12934 ha) in the southern Tierra del Fuego Island (Argentina), where mountain landscape units (land-cover and land-use) were identified according to their vegetation types (forests and open-lands), elevational effects (400 m.a.s.l.) and anthropogenic impacts derived from economic activities (harvesting and cattle grazing). Classification was based on Landsat 8 OLI images with fieldwork samplings, relevating 101 landscape units. In each unit, forest structure and floristic surveys (dicots, monocots, pteridophytas and bryophytes) were conducted. Data were evaluated using ANOVAs and multivariate analyses (cluster, detrended and canonical correspondence analysis). A total of 104 plant species were surveyed (88% natives and 12% exotics), where managed deciduous forests (Nothofagus pumilio) had the highest values of exotic species occurrence frequency (20%). The multivariate analyses showed that environmental gradients and anthropogenic impacts highly affected the distribution of exotic plant species. Native species had higher cover values at upper elevations, while exotic plants had a higher cover at lower elevations, where the N-S aspect was strongly correlated with species preferences due to shaded/lighted aspects. The presence of exotic species can be specifically related to harvesting and cattle grazing (e.g., Agrostis stolonifera and Rumex acetosella with cattle grazing, Poa nemoralis, Ranunculus repens and Stellaria media with harvested forests) but one of them (P. trivialis) was related with unharvested forests. We conclude that environmental gradients and anthropogenic impacts define the plant assemblages at a landscape level, and they also influence the distribution of exotic species, where the main driver was the harvesting. We propose that land-sharing in mountain landscapes could be a better approach towards sustainability ensuring the preservation of the land-cover and the land-use at the low and upper elevations.