State-and-Transition Models: Process-based modelling of a system's capacity to generate ecosystem services

RUSCH, GRACIELA; RUSCH, VERÓNICA; GOIJMAN, ANDREA; LÓPEZ, DARDO R.; CAVALLERO, LAURA; CLAPS, LEONARDO.; PERI, PABLO; CARDOZO, ANDREA; VARELA, SANTIAGO; GROSFELD, JAVIER

Lisboa

Congreso; World Congress Silvo-pastoral Systems 2016; 2016

Universidade Évora

Silvopastoralism is the main land use of native Nothofagus antarctica (Ñire) forest in Argentinian Patagonia. However, grazing and fuelwood extraction may lead the system into an unsustainable pathway and threaten the long-term multiple benefits provided by these semi-natural systems, i.e. the ecosystem services (ES) they generate. We propose a methodology to model the dynamics of Ñire forest as a response of levels of critical natural and management processes, and that explicitly links these processes to the condition of the silvopastoral system and its capacity to provide important ES. We developed a State-and-Transition model (STM) for Ñire forests in northern Patagonia that helped gather the existing ecological knowledge of the system, using multiple sources, including historical maps and essays, vegetation surveys and field data. We adjusted the model in a workshop of experts and subsequent field andliterature checks. Seven states and 13 negative transitions were described, as well the factors that trigger transitions and their associated levels of grazing and fuel-wood extraction. Most transitions are irreversible, which means that there is a need of specific interventions to revert ecological degradation. States were characterized by state variables indicating structural and functional features such as cover of dominant plant species, vegetationcover and tree recruitment, which were in turn linked to ecological processes and structures underpinning the provision of services such as herbaceous primary productivity, stand basal area, habitat quality, soil erosion control, and recreation opportunities. The model was implemented as a Bayesian Belief Network (BBNs) which provides a graphical and easily accessible representation of the model, at the same time that it incorporates uncertainty. We propose STMs implemented as BBNs as a robust tool to inform policy and management ofsilvopastoral systems based on the best available ecological knowledge of the system, and modelling its capacity to generate ES.and its capacity to provide important ES.