全 文 ：第 19卷第 6期
1999年 11月
生 态 学 报
ACTA ECOLOGICA SINICA
Vo1．1 9．No 6
Nov．，1999
湖泊水库结构生态动态模型
张永泽 ，王 一垣 Q t 7 j i
(1 中国环境科学研究院科技处．北京．100012f 2 北京师范大学环科所．北京 ．100875)
摘要 ：综述了湖泊水库结构生态动态模型的研究进展厦其在朝怕水库环境生志模拟 中的应用。结果表 明．热力学理论为
获取湖泊水库生态系统特性提供了一条整体性的途径，热力学概念 烟 可将生态学理论(进尔文理论)和热力学理论(最
大堋原理)租好地联系起来 。 I^ 堋后 ．许多重要模型参数的 目标函数可根据最大烟原理获得 ，迭尔文 适者生存”理论可
被定量为一十生态约束条件用于开发湖泊水库结构生意动志模型，从而使得提出的模型在生志上更合理．在应用上更灵
活 为了更好地将堋用于朝泊水库的生态模拟和环境管理中．还需进一步对烟的检验和优化进行讨论和研究。
关蕾调 ；拥|生态撰
Structural
库
fo／"lakes and reservoirs
ZHANG Yong—Ze ，W ANG Xuan (1，Departm~t ofSct~n⋯ nd Tech~olog),，(hinese Research Academy of
E⋯ m Sci~ces，Beijing 100012，Cfiina*2．Institute ofEnvironmental Smence．BeijingNormalUniv~sity．B~jing
100875 Chi )
Abstract：This paper reviews the researches on the structural ecodynamic models for lakes and reservoirs
and their applications in ecological modelling of lake and reservoir environment．The results follow that the
thermodynamic theories provide a holistic approach for capturing the properties of Lake and reservoir
ecosystem ．the thermodynamic concept“exergy links wel the ec ological theory(Darwin’s theory)with
thermodynamic theory(the maximum exergy principle)．By the application of exergy，a goal function of
some important model parameters is obtained according to the maximum exergy principle，and Darwin’s
theory survival of the fittest"can be quantified as an ecological constraint to develop the structural ec ody
namic model for lakes and reservoirs，which makes the proposed model ecologically more reasonable and
practically more flexible．However，in order to use effectively exergy in ecological modeL Ling and environ-
mental management of lakes and reservoirs，the camination and optimization of exergy are stil needed to
discuss and study further．
Key words：exe gy|ec0l0gical modelling；structural ecodynamic model
文●绷号 t1000—0933(1999)06 0902-o6 中田舟类号 ：X17 文献标讯码 tA
l Introdactton
W ith the development of computer technology，many models were developed to USE in ec ological mod—
elling of lake and reservoir environment．the field covers a wide range of models，from population dynamics
to oxygen balances in streams and 1akes．and from eutrophication models to models of toxic substances in
fresh water ecosystems．Jorgensen[口divided the development of ecological modeling in limnology into five
generations of models tthe first generation were mod els of oxygen balance in a stream (the Street—Phelps
mode1)and of the prey predator re[ationship (the Lotka Volterra mode1)developed in the early 1920s．The
population dynamic models took place in the l 950s and 1960s and more complex river models developed in
1960s could be named the second generation of models The third generation started around l970 with the
development of eutrophication models used in environmental management．The mod els from the late 1970s
Reoeived date{1997 10 08
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g期 ZHANG Yong—Ze．et al：Structural ecnd ynamicmode[forlakes and reservoirs
to the middle 1980s could be calted the fourth generation of models．Since the middle 1980s mod elers have
proposed the fifth generation of models，which attempt to account for structural changes．
In this paper，the fifth generation of mod els—— structural ecodynamic mod els for lakes and reservoire
are reviewed and their applications in environmental management and ecological research are analyzed．
Based up6n the reviews and analyses，it is pointed out that with the use of the thermodynamic concept ex—
ergy in ecological models。Darwin’s theory of“surviva[of the fittest’*can be quantified as an ecological con
straint of ecological modets to develop the structural ecodynamic models for lakes and reservoirs，and the
changes in ecological structure and species composition of ecosystem can be reflected by the changing．mod —
el parameters and the changing exergy values
2 Structural ecodynam ie model for lakes and r~ rvoirs
The development of the structural dynam c models has recently been developed as a research direction
within the traditional established discipline of ecological modelling ．The term structural dynamic refers
to the ability of the models to perform changes in species composition and trophic structure of the ecosys
tern modeled．The development of this type of models was started in the area of aquatic ecosystem mod els—
especially lake ecosystems，where the models through some years have reached a state to certain degree，
they are abte to give acceptable prognosis of the quantitative development of ecosystem as a consequence of
changes in external factors influencing the system．
2-1 Excrgy in ecosystem s
The concept of exergy，through its definition by Evans based on thermodynamic in formation·de—
fined as deviation in entropy state of a system ．finds its roots back in the classical thermod ynamics and the
earliest lormulations of the second law by Carnot and Clausius．The entropy as a macroscopic property of
a system was then defined as a function of m Jcrostates via the statistical thermodyn amics founded by Boltz—
man and further developed by Gibbs．An important step since it is their formulations which makes it possi—
ble to calculate exergy[ ．
Exergy．Ex，is defined by the following equation ：
Ex一 7 D(S S) C1j
whereTn，S arethe temperature and entropy ofthe system respectively，S Pisthe e~xtropy ofthe same
system at thermodynamic equilibrium ．
For an open system with inorganic net inflow and passive organic outflow ，self-organization will affect
the concentration of component chemical species and，therefore．the chemical contribution to exergy COil—
tent．Assuming that temperature and pressure of the system (了1 and P)are the same as those of the envi—
ronment(Tn and P。)，exergy from Eq．(1)becomes：
一 盯塞[ 一cG )]
in which C．and C are the concentration of the ith component in the far from equilibrium state and in
thermodynamic equilibrium state respectively，C0 is the concentration of the component in the inorganic
matter．R the gas constant and T the absolute temperature By 11(~ans of the above equation·Jorgensen
derived a formula to evaluate the exergy of ecosystems：
Ex／RT=( ． )ZC ／RT一∑G1nP (3)
In Eq．(3)。 1 represents the chemicat potentiat of detritus organic matter and P is the probability to
obtain a given component during the evolution by organizing organic matter according to information in
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904 生 态 学 报 19卷
Table 1 Approximate number of genes in organisms and
exergy CORVeI~QR factors
genes Aminoacids in living organisms are 20 and
each gene determines a sequence of 700
a noacids，thus：
P． = 20 (4l
(r— number of genes in the organism)．
Therefore—the exergy can be calculated on the
basis of existing studies on the evolution of DNA
and genes in living organisms．Table．1 gives some
average results for different organisms
Considering an aquatic environment，Eq．(3)
and Table l yield a simple formula to calculate the
global exergy of the system ：
Ex 一 (1．79× 1O )，J+ (104．9× 10 ) +
(2．52× 10。)F + (7．34× 10 )
(D + P + Z + F)(g／L) (5)
in which P—Z，F and D are respectively the c0ncentr蛐 0n(g／L)of phytoplankton，zooplankton，fishes and
detritus organic matter If the right hand of Eq．(5)is divided by the detritus exergy coefficient(7，34×
l0 )一the same result expressed in grams of detritus equivalent can be obtained：
Ex = (1)D + (3．4)P + (144)Z + (344)F(g detritus equivalent／L) (6)
Numbers in parentheses are conversion factors that give an approximate measure of the larger exergy
contribution in P·Z and F，in comparison with detritus exergy D．Conversion factors account for the in．
formation embodied in the organism ．in addition to the exergy of the biomass itself．
It can be concluded that the higher the exergy of the system ，the higher the distance of the system
from thermod ynamic equilibrium as well as the contribution that can be obtained from it when appropriate．
1y used[ ，and different organizational levels could be measured by using their specific exergy content
．
2．2 The application of exergy in the development of structural ecodynamic mod el
In general，the model constraints should include the conservation principles，the chemical composition
and the law of thermodynamics，however，only a few mod els can include the ecological constraints due to
under-consideration of the properties of ecosystem．The thermodynamic concept exergy”has the follow-
ing advantages compared with other thermodynamic concepts：~It is an energy term which is easily inter—
preted}②Exergy is easily computed in the model；@It is directly related to Darwin’s theory and the appli—
cation of exergy has therefore an ecological interpretation；8nd④It is dependent on the environment，and is
not a state variable as entropy，which makes it be tter fitted to be used in ecology．
According to Darwin’s theory，all the species in an ecosystem have the properties (【e．the set of pa．
rameters)tha t are be st fitted for survival Under the prevailing conditioins．The property of ‘suivival can
be tested on the system level by use of exergy_2’’ it]-so the set of parameters that gtves the best survivors
can be found．Jorgensen ⋯ proposed a parameter combination modelling procedure based on the maximum
exergy principle and Darwin’s theory (see table 2)．
By application of exergy，the ma ximum exergy principle and Darwin’s theory can be used to construct
the above parameter combination modeling procedure，which alows a continuous development of the es．
senfial parameters of the model during simulation in accordance with the optimized function．
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6期 ZHANG Yong Ze，“ al：Structural ecodynamic model for lakes and reservoirs 905
Table 2 The parameter combination modeling procedure
《
3 Applications of structural ecodynamic m odel
for lakes and reserv0jJ
Using the structural ecodynamlc model pro—
posed in this paper，the changes in ecosystems can
be accounted for and the changes in ecological
structure and species composition can be reflected
by the changing model parameters and the chang
ing exergy values[ ．
In the study of Lake Dianchi[⋯ ．the eco]og
ical model proposed by Jorgensen[is3was selected 0s
the basic model，exergy was introduced into the e—
cological model as a goal function of the maximum
growth rate，settling rate of phvtop ankton，the
maximum growth rate of zooplankton to develop a
structuraI ecodyr~mic modeI for Lake Dianchi．and
parameter combinations were carried out by using
the above modeling procedure． In Lake Dianchi．
phosphorus is the main Limiting factor of nutri—
e／1is，s。only the contribution to exergy from the
phosphorus cycle ,~vas considered． in the study．
exergy was computed using Eq． (2)，the state
variables included the concentrations of phospho—
rus in a Lgal cells，soluble phosphorus，phosphorus
in detritus and phosphorus in zooplankton． The results folowed that this model can account for the
changes in the ecological structure and species composition of lake ecosystem ，and the changes in Lake
ecosystem can be reflected by the changing model parameters and the changing exergy values．
A structural dynamic model had been developed by Nielsen。in order to describe the shifts in compo—
sition of the phytoplankton society and tropic structures in a Danish shalow lake(Lake Vang)as response
to changes in loading or biomanipulation．In this model，phosphorus was taken as the only limiting nutri—
ent：the development of the phytoplankton society was chosen to be governed by a combination of the fol
lowing factors：growth processes．Loss processes，higher tropic levels，biological compartments(9 types
of algae were included in the model：microc ystis，aphanizomenon，stephanodlscus，asterionella，pedias
trum，scenedesmus，dinobryon，peridinum and eryptomonas)，the growth and the development of the
phytoplankton society were governed by the grazing on phytoplankton and described as an ordinary Monod
kinetic relationship and Loss rate were included as an assimilation coefficient and excretion；the biological
model was combined with a simple flow—ratio based hydrologieaL mode1．chosen to be sufficient to simulate
the hydrodynamics in this lake．The results indicated that exergy may play an important role in gove rning
the development of the phytoplankton society．
Species composition often tels more about the condition of a lake or reservoir than water quality．The
presence of blue green algae or toxic algae is much greater environmental problem than a low transparency
or a high nutrient concentration．In Jorgensen and Nielsen s study，a two classes phytoplankton model
(diatoms and green algae)had been developed to try to predict the shifts in species composition between
the dry and the rainy seasons．In this model，two nutrients were considered}phosphorus and silica．The
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生 态 学 报 19卷
settling rate for the diatoms was set to 0．5 m／d，but with a relation between the precipitation and the set—
tling which wil reduce the settling rate to 0．15m／d at the most rainy days．For green algae the settling
rate was 0．2 m／d in the dry season with a reduction to 0．1 m／d in the rainy season．The resulta had
shown that dominance of diatoms gave the highest exergy in the rainy season under the given
(temperature，solar radiation，the stirring up effect of the rain and the retention time)．M eanwhile，the
distribution between the two classes of algae in the dry period gave the highest exergy．
In the study of Lake Glumso．exergy was used by Salomonsen and Jensen as a measure of build—up
of biological structure．Data from Lake Glumso for the period 1981—1984 were chosen for the study，in
tha t period，the lake underwent a cha nge in phytoplankton species composition．The study had shown that
the two phytoplankton groups(ehlorophytes and diatoms)did perform a larger build—up of exergy than if
only one of the groups had been presented，and that the calibrated gr owth parameters for the chlorophytes
represented the highest build-up of exergy while the results for the diatoms were less univocal-
In the study of Da nish estuary．Roskilde Fjord，Nielsen㈨ developed a structural mod el to simulate
the structural dynamics of the macrophyte societies．The results have shown tha t it was possible to simu-
late the competition between the spe cies and alow spatial coexistence through time in a very simple mod el
based on growth capacity．1ight and tempe rature characteristics alone．
All the above studies have followed tha t exergy can be used as a goal function to develop the strue—
turn1 ecod yna mic models for lakes and reservoirs to describe the shifts in the species composition and the
changes ecological structure of ecosystem ．and used widely in the ecological modelling of take environ-
m ent．
● Conelu~lons
The thermodynamic theories provide a holistie approach for capturing the properties of lake eeosys—
tem ．the thermod ynamic concept exergy”links well the ecological theory (Darwin’theory)wi th thermo—
dyn amic theory (the maximum exergy principle)．By the application of exergy，a goal function of some
important model parameters is obtained according to the maximum exergy principle，and Darwin’s theory
“sⅡrv al 0f the fittest can be quantifled as an ecological constraint to develop the structural ecod yna mic
mod el for lakes and reservoirs．which ma kes the proposed model ecologically more reasonable and practi—
tally more flexible．However，it is of course still open question whether the proced ure can be applied more
generally and whether the development of this type of models requires tha t other factors are considered ．
The exarmnation and optimization of exergy are still needed to discuss and study further．
Referenees
[1]
[2]
[3]
[4]
[5]
[5]
7]
[8]
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Nielsen SN．Appllca~ion m m exergyin strgct~raldynamicmodel~．Ph．D．Thes~．Denmark,National Envi—
roRi2le：n~2．1 Research Institute and DFH ，1992．
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6期 ZHANG Yong—Ze，et ：Structural ecodynamic model for lakes and reservoirs 907
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州 三I 脚 加 Ⅲ 蜘 旧 脚 州
r L _ l llL u L l I l ； [ [
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