Thermodynamic analysis of an ecologically restored plant
community:Process and diversity
Abstract
The experimental data used for testing the applicability of the
thermodynamic equations presented in the theoretical section were
obtained from an ecological restoration project implemented at a
manganese tailing site. Restoration of the plant community was shown to
be an irreversible process characterized by spontaneous increases in its
total biomass CT and total number of plant species N associated with
increases in its enthalpy H, Gibbs free energy G and entropy S. Species
enrichment was the cause for the decease in mass ratio xi (biomass of a
species Ci divided by CT) and biomass growth potential μi (the partial
derivative of Gi with respect to Ci). The increase in s/CT (s denoting
the ratio of S to gas constant R) associated with decrease in f/CT (f
denoting the ratio of G to RT) with increasing N confirmed that the
restored plant community possessed natural trends towards increase in
its species richness and evenness. The observed trends gave support to
use of the thermodynamic functions for describing the
productivity-biodiversity relationship. The present analysis did not
fully prove the use of the Shannon form of information entropy as a
biodiversity index for the investigated plant communities. Because of
the presence of significant differences in individuals among species,
the biodiversity of the plant community could not be uniquely determined
by its individual numbers. In comparison, the entropy factor s was shown
to be a suitable biodiversity index. The fact that N is the key factor
that determines the changes in s/CT and f/CT makes △N > 0 a
useful index for determining the direction of spontaneous changes for
all open systems with continuous input of matter and energy. As a
measure of disorder, s can be generally applied as a diversity index for
all systems involving transformations of matter and energy.