Dinámica de la coexistencia a largo plazo de pastos de la estepa patagónica: sucesión y transiciones de Markov.

COUSO, LUCIANA; MARCOS TEXEIRA; MARTIN AGUIAR; ROBERTO FERNANDEZ

Puerto Varas

Congreso; VI Reunión Binacional (Arg.-Chile) de Ecología; 2013

SOCECOL-ASAE

In semiarid grasslands, morpho-functional differences among coexistent grasses are associated with their distribution at microsite scale and with temporal dynamics. Studying spatial changes along time would allow us to analyze changes in community structure and thus, simulate grass dynamics in the long term. Objective: evaluate changes in community structure of semiarid Patagonian grassland in ecological time through a spatially explicit Markovian model. We drew vegetation maps in a 600 m2 exclosure at the Rio Mayo INTA experimental station in 2001 and 2008 (7-year time resolution: iterations). We digitized them and evaluated distribution and abundance. We simulated long term dynamics based on projections of our 7-year resolution (stationary structure resulted from 140-year projection). Change in point identity (categories: 5 biotic-species- and 2 abiotic) was called "transition". Results showed that 70% of points changed between 2001-2008 (attributable to disturbance or replacement), 35% of the points occupied by a given species in 2001 were occupied by some others in 2008. The most abundant species, in 2001 and 2008, were Poa ligularis, followed by Pappostipa speciosa. In turn, Pappostipa humilis and Bromus pictus, showed the lowest abundance. Stationary structure resulted similar to 2001 and 2008 structure and was reached in less than one iteration. It was dominated by P. ligularis and P. speciosa. This Patagonian steppe grass community is highly complex (all the transitions between categories were possible) and entropic (all the transitions presented comparable values). Thus, the prediction of the fate of any point along time was a task almost impossible.