%0 Journal Article
%T Exergetic Model of Secondary Successions for Plant Communities in Arid Chaco (Argentina)
%A Marcos Karlin
%A Rodrigo Gal¨¢n
%A Ana Contreras
%A Ricardo Zapata
%A Rub¨¦n Coirini
%A Eduardo Ruiz Posse
%J ISRN Biodiversity
%D 2013
%R 10.1155/2013/945190
%X Ecosystems are open systems where energy fluxes produce modifications over plant communities. According to the state and transition model, plant formations are defined by changes in natural conditions and disturbs. Based on these changes, it is possible to define vectors that show the tendencies of the communities towards other states. Within the subregion of Arid Chaco, mature communities of Aspidosperma quebracho blanco represent the quasistable equilibrium communities or ¡°climax,¡± similar to that observed in the Chancan¨ª Natural Reserve (C¨®rdoba, Argentina). Biodiversity values and Lyapunov coefficients were calculated based on plant abundance and cover data. Lyapunov coefficients were calculated as the Euclidean distance of each site with respect to reference condition (community of Aspidosperma quebracho blanco), representing for each state the necessary exergy to reach the reference condition. When Lyapunov coefficients decrease in time, it is expected for the system to drive towards a quasistationary state; otherwise, the equilibrium is unstable and becomes less resilient. The diversity of species has a significant effect over the resistance to perturbations but equivocal for the recovery rate. Lyapunov coefficients may be more precise succession indicators than biodiversity indexes, representing the amount of exergy needed for a vegetation state to reach the reference condition. 1. Introduction Ecosystems are open systems that exchange energy with the surrounding environment, modifying among other components the plant frequencies. Based on these changes it is possible to define vectors that show the tendencies of the succession to reach mature or quasistationary states and their modifications by natural or anthropic disturbances [1]. Concepts of succession are based on the observation and the analysis of the system¡¯s states over space and time. The search for a successional theory that can be empirically verified is still ongoing. From the successional theories of Clements [2], Gleason [3], and Tansley [4], there is no reconciliation between multiple aspects of such theories. The first is based fundamentally on a deterministic mechanism where, starting from an initial vegetation state, succession moves by an autoorganization process through distinguishable phases (communities) reaching a ¡°monoclimax¡± situation. For Gleason, the main defect of this theory is precisely the change of phases from community to community. This author claims for a succession given by the substitution species by species [5]. Tansley developed similar concepts as those
%U http://www.hindawi.com/journals/isrn.biodiversity/2013/945190/