A dynamic graph automata approach to modeling landscape change in the Andes and the Amazon

Authored by Sahotra Sarkar, Kelley A. Crews-Meyer, Kenneth R. Young, Christopher D. Kelley, Alexander Moffett

Date Published: 2009-03

DOI: 10.1068/b33146

Sponsors: No sponsors listed

Platforms: C++

Model Documentation: Other Narrative

Model Code URLs: Model code not found

Abstract

A generalization of cellular automata was developed that allows flexible, dynamic updating of variable neighborhood relationships, which in turn allows the integration of interactions at widely disparate spatial and temporal scales. Cells in the landscapes were modeled as vertices of dynamic graph automata that allow temporally variable causal connectivity between spatially nonadjacent cells. A trial was carried out to represent changes in an Amazonian and a tropical Andean landscape modeled as dynamic graph automata with input from a Landsat TM-derived Level 1 classification with the following classes: for the Amazon-forest, nonforest vegetation, water, and urban or bare (soil); for the Andes-forest, scrub (shrub or grassland), agriculture, and bare or exposed ground. Explicit automata transition rules were used to simulate temporal land-cover change. These rules were derived independently from fieldwork in each area, including vegetation plots or transects and informal interviews. Such a generalization of cellular automata was useful for modeling land-use-land-cover change (LULCC), although it potentially increases the computational complexity of an already data intensive process (involving 5-8 million cells, in 1000 stochastic simulations, with each simulation encompassing 15 annual time steps). The interannual predicted LULCC, while more nuanced in the Andean site, poses a serious threat to compositional and configurational stability in both the Andes and the Amazon, with implications for landscape heterogeneity and habitat fragmentation.

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