Spatial patterns in mesic savannas: the local facilitation limit and the role of demographic stochasticity

We propose a model equation for the dynamics of tree density in mesic savannas. It considers long-range competition among trees and the effect of fire acting as a local facilitation mechanism. Despite short-range facilitation is taken to the local-range limit, the standard full spectrum of spatial structures obtained in general vegetation models is recovered. Long-range competition is thus the key ingredient for the development of patterns. The long time coexistence between trees and grass, and how fires affect the survival of trees as well as the maintenance of the patterns is studied. The influence of demographic noise is analyzed. The stochastic system, under the parameter constraints typical of mesic savannas, shows irregular patterns characteristics of realistic situations. The coexistence of trees and grass still remains at reasonable noise intensities.Comment: 12 pages, 7 figure

Allelomimesis as universal clustering mechanism for complex adaptive systems

Animal and human clusters are complex adaptive systems and many are organized in cluster sizes $s$ that obey the frequency-distribution $D(s)\propto s^{-\tau}$. Exponent $\tau$ describes the relative abundance of the cluster sizes in a given system. Data analyses have revealed that real-world clusters exhibit a broad spectrum of $\tau$-values, $0.7\textrm{(tuna fish schools)}\leq\tau\leq 2.95\textrm{(galaxies)}$. We show that allelomimesis is a fundamental mechanism for adaptation that accurately explains why a broad spectrum of $\tau$-values is observed in animate, human and inanimate cluster systems. Previous mathematical models could not account for the phenomenon. They are hampered by details and apply only to specific systems such as cities, business firms or gene family sizes. Allelomimesis is the tendency of an individual to imitate the actions of its neighbors and two cluster systems yield different $\tau$ values if their component agents display different allelomimetic tendencies. We demonstrate that allelomimetic adaptation are of three general types: blind copying, information-use copying, and non-copying. Allelomimetic adaptation also points to the existence of a stable cluster size consisting of three interacting individuals.Comment: 8 pages, 5 figures, 2 table

Ecosystem-Oriented Distributed Evolutionary Computing

We create a novel optimisation technique inspired by natural ecosystems, where the optimisation works at two levels: a first optimisation, migration of genes which are distributed in a peer-to-peer network, operating continuously in time; this process feeds a second optimisation based on evolutionary computing that operates locally on single peers and is aimed at finding solutions to satisfy locally relevant constraints. We consider from the domain of computer science distributed evolutionary computing, with the relevant theory from the domain of theoretical biology, including the fields of evolutionary and ecological theory, the topological structure of ecosystems, and evolutionary processes within distributed environments. We then define ecosystem- oriented distributed evolutionary computing, imbibed with the properties of self-organisation, scalability and sustainability from natural ecosystems, including a novel form of distributed evolu- tionary computing. Finally, we conclude with a discussion of the apparent compromises resulting from the hybrid model created, such as the network topology.Comment: 8 pages, 5 figures. arXiv admin note: text overlap with arXiv:1112.0204, arXiv:0712.4159, arXiv:0712.4153, arXiv:0712.4102, arXiv:0910.067

Modelling global pyrogeography using data derived from satellite imagery

Doutoramento em Engenharia Florestal e dos Recursos Naturais - Instituto Superior de Agronomia - ULVegetation burning has an important impact on the global atmosphere and vegetated land surface. Deforestation fires, peatland fires, and ecosystems with shortening fire return interval contribute substantially to the build-up of atmospheric greenhouse gases affecting environmental quality and the climate system at local and regional scales. Recognition of the role of fire in the Earth system led to its designation as an Essential Climate Variable (ECV), a physical, chemical, or biological variable that has a crucial contribution towards characterization of Earth’s climate. The central task of this thesis was the development of a new global classification and map of fire regimes, using multiple correspondence analysis and hierarchical clustering, and relying on active fire data from the Moderate Resolution Imaging Spectroradiometer (MODIS) MCD14ML product. That work was preceded by study dedicated to a thorough screening and exploratory spatial analysis of the dataset, and led to the development of an improved algorithm for identifying individual active fire clusters, and to global analysis of size inequality in their statistical distributions. In addition to this core research, other continental-global pyrogeography studies were developed, and are presented, dealing with: the time lag between the timing of optimal fire weather conditions and peak fire season dates as a diagnostic of anthropogenic vegetation burning; the spatial non-stationarity in the parameters of the relationship between population density and area burned; and the modulation of weekly cycles of vegetation burning in African croplands by regionally dominant religious affiliation. We hope that this set of studies may constitute a useful contribution to the burgeoning topic of global pyrogeograph