High Andean ecosystems: emerging trends in vegetation dynamics in a context of climate change

CARILLA, JULIETA; GRAU, ALFREDO; CUELLO, SOLEDAD; HALLOY, STEPHAN

Obergurgl

Workshop; Long-term research in Mountain Regions; 2017

ABSTRACT We established a long term monitoring site to assess alpine vegetation dynamics in response to climate change in Cumbres Calchaquíes, Argentina. We hypothesize that temperature as driven by elevation and summit orientation are the main environmental filters of plant community distribution in these high Andean summits. We assessed short-term dynamics of vegetation on an elevation gradient of 700m, 4040 to 4740 m asl, during a five-yr period (2007-2012). We recorded 147 plant species in 21,851 m2, with a maximum concentration of 22 species per m2, particularly in E and N warmer slopes, with several endemisms. For both censuses, Asteraceae and Poaceae were the most diverse families and Pycnophyllum convexum, Festuca orthophylla and Deyeuxia colorata the dominant species, corresponding to the primarily life forms, cushion plants and tussock grasses. Soil temperature strongly decreased with elevation, as well as vegetation cover, richness and diversity at both sampling scale, with stronger negative pattern in re-measurement. Change ratio of vegetation cover and richness was higher in the upper and lower extremes of the gradient with 22 new species appearing, mostly in the lower summit, and 15 species missing in the highest summit. Changes in community composition are reflected in a high turnover rate at summit and plot scale; with 32% and 94% in the highest summit (summit and plot scale respectively), evidencing a negative trend between temperature (associated to elevation) and community turnover. Longer term temperature records suggest an incipient warming trend. Emerging patterns in vegetation dynamics might reflect long-term trends in plant species diversity, plant life forms, green index and soil temperature related to ecosystem dynamics and associated to climate change. Keywords: climate change, elevation gradient, GLORIA initiative, plant diversity and turnover.