Introduction
The objective of this study is to examine the applicability of the
thermodynamic equations presented in the theoretical section
(Theoretical basis) for description of a plant community ecologically
restored at a manganese tailing site. Remediation of a damaged ecosystem
should be a manipulated process well-designed with proper measures and
explicit targets (Baldera et al., 2018; Laughlin, 2014; Zhao et al.,
2016; Haapalehto et al., 2017; Tongkoom et al., 2018) that can maximize
the benefits and minimize the damages that are currently existed and
that can possibly be brought into the site due to use of improper
methods (González et al., 2014; Wallace et al., 2017; Garrouj et al.,
2019). Performing a thermodynamic analysis focusing on changes in
individual, population and community traits in the restoration process
can provide useful information not only for assessment of the
remediation effect but also for development of relevant knowledge and
technology (Hesse et al., 2018; Kollmann & Mahy, 2018; Fiedler et al.,
2018).
Biomass quantity C , individual number m and species numberN are the three basic parameters that can be directly used as
indicators for, respectively, productivity, species abundance and
species richness. Other parameters developed for describing a specific
state of an ecosystem, such as the Shannon-Wiener and Simpson indexes
(Ricklefs & Relyea, 2014), exergy (Jørgensen, 2010; Jørgensen et al.,
2016) and entropy-based indicators (Laner et al., 2017; Ludovisi &
Scharler, 2017), etc., are all presented as functions of C ,m or N , or a combination of them. Accounted for by their
additive nature, C , m and N are extensive
properties of an ecosystem. Thus, as primary state variables of an
ecosystem, C , m and N all have fixed values at a
given state and their changes can be uniquely determined by their
difference between states regardless of the process history. It follows
that all indexes presented as functions of either C , m orN are also state variables with defined meanings in
thermodynamics. The conventional indexes are useful and sufficient if
one is only interested in assessing the remediation effect. They are
not, however, sufficient enough if one is also interested in revealing
their related mechanisms and apprehending their significances in
ecology. The difference, for an example, in mathematical expressions
between the Shannon-Wiener index (or the Shannon form of information
entropy) as a function of m and N (Harte & Newman, 2014;
Newman et al., 2014) and entropy S as a function of C andN will lead to differences in advantages and disadvantages of
their applications. Analysis of their difference using the obtained
experimental data can offer a better understanding of the restoration
process reflected by the changes in C , m and N .
Two fast-growing tree species P. fortunei andK. bipinnata were used as dominant species in the
implemented restoration project. Analysis of their thermodynamic
behaviors and the changes in their contribution rates with increase in
species richness and abundance should be a meaningful approach to
determine the causes that lead to the changes in the internal energy
state of the restored plant community. Due to limited scope, the present
analysis will be focused on identification of the key thermodynamic
factors related to spontaneous changes and biodiversity of the restored
plant community.