Thermodynamic analysis of an ecologically restored plant community:Number of species

Abstract

Conducting a thermodynamic analysis of a plant community can be an approach to macro-ecology that emphasizes not only the diversity and abundances of plant species but also the exchange of matter and energy among species within the community and that with its physical and biological environment. The experimental data used for the test were obtained from an ecological restoration project implemented at a manganese tailing site. The relations derived from the maximal discrete entropy theorem show that the maximum entropy will increase with increase in the total number of species N, suggesting that N has an upper limit Nm at a habitat subject to its heterogeneity in physical conditions and species resource in its surrounding areas. As an important macroscopic property of an ecosystem, N is the number of species that are present at a habitat while its upper limit Nm is the potential number of species that have been or can be adapted to the physical conditions of the habitat, and can thus possibly be present at the habitat. As a function of the maximum entropy, ln(N) is applied as a biodiversity index. As an upper limit of ln(N), ln(Nm) can be regarded as a biodiversity potential index as it takes into account the available number of species distributed in the surrounding areas of the habitat, showing the potential limit for further increase in its biodiversity. Following the thermodynamic laws, given that there is no further change in system enthalpy H, ∆H = 0, the equilibrium number of species Neq can be found at the point ∆N = 0 and Nm can be determined by Nm = Neq2. The restoration of the investigated plant community was shown to be an irreversible process characterized by spontaneous increases in its total biomass and total number of plant species associated with increases in its enthalpy, Gibbs free energy and entropy. The analytical results gave support to the argument that the internal energy factors of a plant community are functions of its productivity and biodiversity and the difference between ln(N) and ln(Nm) determines its internal energy distribution.