SOTTILE Gonzalo David
congresos y reuniones científicas
Exploring vegetation resilience of the Subantarctic Patagonian communities by ecological modelling and the analysis of Holocene records
Congreso; 20th INQUA Congress; 2019
Subantarctic Patagonian ecosystems might experiment important changes under future climate warming. The precipitation and temperature gradient at the southernmost Andes determines a clear zonation of High Andean dwarf shrubs communities, mid-altitude Nothofagus forests and shrub-grass communities in the lowlands. In this research we show how ecological and paleoecological methods provide interesting results to study Subantarctic Patagonian vegetation long-term ecological resilience. We focus on the analysis of modern and paleo vegetation arrangements and diversity patterns variability. First we explore modern patterns of vascular plant taxonomic and functional diversity through generalized linear models. Second we evaluate modern vegetation diversity representation by pollen diversity collected at moss polster samples. Third we interpret past vascular plants diversity patterns and past vegetation changes during the last 12.000 cal yrs BP through the analysis of pollen, charcoal and macro-remains of a peat bog at Parque Nacional Los Glaciares, Santa Cruz, Argentina (50.26°S; 72.85°W). We identified 4 different vegetation arranges during the Holocene: High Andean grass-dwarf shrubland, dwarf shrubland, forest and grassland. We evaluated past vegetation and diversity changes related to past disturbance regime (fire occurrence and tephra deposition) and climate variability (mean annual precipitation and temperature). The analysis of the proxy record and the comparisons with past climate reconstructions suggest that High Andean grass-dwarf shrublands are more resilient to fire regime changes than forest communities. Also we detected that the replacement of High Andean grass-dwarf shrublands by forests since ca 8000 cal yrs BP which produced a high decrease in plant diversity has never been reverted. Since the last 7000 cal yrs forests communities have been quite stable despite to climate variability except during the Little Ice Age (LIA) where there was a sharp replacement of forest by grasslands. Forest recovery after LIA took a hundred years to recover to values similar to those recorded at 400 cal yrs BP. Modern rates of forest recovery after human induced fires during the early 20s century are much slower than those registered by the proxy record after LIA. The decrease in forest recovery rate may be related to the introduction of cattle and the European hare since European settlement in the area ca 1880s. The long term perspective warns us about possible vegetation displacements in the future. The continuous reduction of the high Andean communities during the last 12.000 cal yrs alert us about possible local or regional extinctions of different vascular plants adapted to these cold Patagonian environments and its consequences to other insects, mammals or birds that depends on these unique flora.