Part five
Ecosystem Ecology
Contents of Part Five
一、Ecosystem energetics
二、Decomposition and Nutrient Cycling
三、Biogeochemical Cycles
Outlines of this part
1.The Laws of Thermodynamics Govern Energy Flow
2. Energy fixed in the process of photosynthesis is primary production
3. Factors influencing Primary Production
4. Primary production varies with time
5. Primary productivity limits secondary production
6. Consumers vary in efficiency of production
7. Ecosystem have two major food chains
8. Energy flow through tropic levels can be quantified
9. Consumption efficiency determines the pathway of energy flow
through the ecosystem
10. Energy decreases in each successive trophic level
1.The Laws of Thermodynamics Govern Energy
Flow
The first law of thermodynamics states that
Energy is neither created nor destroyed.
The second law of thermodynamics states
that when energy is transferred or transformed,
part of the energy assumes a form that cannot
pass on any further. Entropy increases.
Energy flow of ecosystem
• Energy flow is a one-directional process.
•
• sun---> heat (longer wavelengths)
FIRST LAW of THERMODYNAMICS:
Energy can be converted from one form to another, but
cannot be created or destroyed.
SECOND LAW of
THERMODYNAMICS
• Transformations of energy always result in some loss or
dissipation of energy能量转化过程中一定伴随着损失
• or
• In energy exchanges in a closed system, the potential energy of
the final state will be less than that of the initial state封闭系统中
最终稳定状态下的能量必低于初始水平
• or
• Entropy tends to increase (entropy = amount of unavailable
energy in a system)熵值增加
• or
• Systems will tend to go from ordered states to disordered states
(to maintain order, energy must be added to the system, to
compensate for the loss of energy)系统总是趋向于无序化（如
果要维持有序，系统则需要消耗能量补偿能量损失）
Internal
combustion
engines in cars
are 25% efficient
in converting
chemical energy
to kinetic energy;
the rest is not
used or is lost as
heat.
2. Energy fixed in the process of
photosynthesis is primary production
Gross primary
productivity (GPP):
Total rate of
photosynthesis
Net primary
productivity (NPP):
rate of energy as
storage as organic
matter after respiration
NPP=GPP-R
• Primary production is the production of
organic compounds from atmospheric or
aquatic carbon dioxide, principally through
the process of photosynthesis, with
chemosynthesis being much less
important. All life on earth is directly or
indirectly reliant on primary production.
• The organisms responsible for primary
production are known as primary
producers
Photosynthesis
Energy change
Chloroplast ultra structure
Plant cells with visible chloroplasts
Leaf in light
2，地球上初级生产力的分布
Standing crop biomass: amount of accumulated
organic matter in an area at a given time
Biomass is expressed as g organic matter per
square meter (g m-2)
Productivity is the rate at which organic matter
is created by photosynthesis (g m-2 yr-1)
How to measure?
Terrestrial ecosystem:
Change in standing crop
biomass over a given
time interval
(see Hui & Jackson 2006 for
grasslands)
Aquatic ecosystem:
黑白瓶测氧法
一、测定原理
Bottle
Light Bottle
Dark bottle
将几只注满水样的白瓶和黑瓶悬挂在采水深度处，曝光24
小时，黑瓶中的浮游植物由于得不到光照只能进行呼吸作用，
因此黑瓶中的溶解氧就会减少；
而白瓶完全曝露在光下，瓶中的浮游植物可进行光合作用，
因此白瓶中的溶解氧量一般会增加。因此，通过黑白瓶间溶
解氧量的变化，就可估算出水体的生产力。
黑白瓶测氧法
二、测定方法和步骤
1. 采水与挂瓶
2. 溶解氧的固定与分析
曝光结束，立即取出黑瓶和白瓶，加入MnSO4和碱性碘化
钾进行固定，充分摇匀后，测定溶氧量。
黑白瓶测氧法
三、计算方法
各挂瓶水层日生产量（mgO2/L）的计算
GPP＝白瓶溶解氧一黑瓶溶解氧
NPP=白瓶溶解氧一原始瓶溶解氧
R＝原始瓶溶解氧一黑瓶溶解氧
毫克/升·日（mg/L·d）
3. Factors
influencing Primary Production
Net primary productivity for a variety
of terrestrial ecosystem as a function
of mean annul precipitation (MAP) and
mean annual temperature (MAT) as
well as length of growing season
N
P
P
Deciduous forest in N. America
Warm temperature and
adequate water supply
for transpiration that
gives the highest
primary productivity.
(Remember that
photosynthesis and
transpiration are
coupled processes)
Global map of primary productivity
Patterns of productivity reflect global patterns of temperature
and precipitation. High NPP in equatorial zone and coastal
region.
Primary production varies with
nutrient availability
Different forest ecosystems
RO, red oak; RP, red pine; SM,
sugar maple, Hem, hemlock; WP,
white pine
20 oak savanna in
Minnesota
in aquatic ecosystems
Changes in available
light, respiration, NPP
with water depth
Compensation depth:
Depth that available
light is equal to the
light compensation
point (NPP=0 or
GPP=R)
Geographic variation in primary
productivity of world’s oceans
1.Great
transport of
nutrient from
bottom to top
2.Nutrient from
terrestrial
ecosystems
High productivity is along coastal regions
4. Primary
production varies
with time
Park Grass,
Rothamsted
Experimental
Station in England
Climatic variation
Disturbance
Stand aging
5. Primary productivity limits secondary production
Net primary production is the energy available to the
heterotrophic component of the ecosystem
Secondary production: net energy of production of
secondary consumers
•Consumed( waste products)
•assimilated (respiration)
•Reminder is available for maintenance – capturing or
harvesting food etc, and lost as heat
•Energy left over from maintenance and respiration goes
into production, including growth of new tissues and
production of young
Secondary productivity: secondary production per unit of
time
Secondary production
depends on primary
production for energy
69 studies for terrestrial
ecosystems (from Arctic
tundra to tropical forests)
Sam McNaughton,1989
Similar
relationship
in lake
ecosystems
43
lakes+12
reservoirs
Tropic to
Arctic
Bottom-up
and topdown
control
TROPHIC STRUCTURE
• Trophic structure is the pattern of movement
of energy and matter through an ecosystem.
• It is the result of compressing a community
food web into a series of trophic levels.
green and brown food webs
Green food web
Brown food web
TROPHIC STRUCTURE
2O &
HIGHER LEVEL
CONSUMERS
1O
CONSUMERS
PRODUCERS
• The result of combining all
producers and consumers
in Hubbard Brook would
be a biomass pyramid.
• Since consumers can be
at several trophic levels,
the fraction of the food
they consume at each
trophic level is determined
and proportioned among
levels.
TROPHIC STRUCTURE
2O & HIGHER LEVEL
CONSUMERS
DECOMPOSERS
1O
CONSUMERS
PRODUCERS
Detritivores (species
that feed on the dead
remains of organisms)
are also known as
decomposers. These
include bacteria, fungi
and invertebrate
animals of numerous
species.
Lindeman's efficiency
• The ratio of energy assimilated at one
trophic level to that assimilated at the
preceding trophic level; the ratio of energy
intake at successive trophic levels. It is
one of the earliest and most widely applied
measures of ecological efficiency.
10%?
Less than 6O
Ecological efficiency
• the efficiency with which energy is
transferred from one trophic level to the
next. It is determined by a combination of
efficiencies relating to organismic resource
acquisition and assimilation in an
ecosystem.
6. Consumers vary in efficiency of
production P426
P
A
I
R
W
Parameters
•
Ingestion 摄食量（I）：
•
Assimilation 同化量（A）：
•
Respiration 呼吸量（R）：
•
Production 生产量（P）：P = A - R。
assimilation efficiency 同化效率
Ae = A n / I n
production efficiency 生产效率
Pe = P n / A n
Energy Loss –
Energy flow ,not
Energy cycling
Energy lost as heat
consumption efficiency (Pg 177) 消费效率
Ce=In+1/Pn
Lindemans efficiency 林德曼效率
是指n+1营养级所获得的能量占n营养级获得能量之比，
相当于同化效率、生长效率与消费效率的乘积。
Le = An/In×Pn/An×In+1/Pn = In+1/In= An+1 / An
Law of 1/10
1915—1942
Cedar Bog Lake
Assimilation efficiency
• Vary widely among animal groups
• Endotherms(内温动物） are much more
efficient than ectotherms（外温动物）
• Carnivorous animals (肉食动物） (even
ectothermic ones) have high assimilation
efficiency than herbivores (草食动物） (meat
vs veg)
Production
efficiency
varies mainly
according to
taxonomic
class
7. Ecosystem have two major food chains
捕食食物链
碎屑食物链
Within any
ecosystem,
there are two
major food
chains
Difference
1. Source of
energy for
herbivores
2. Energy flow
direction
3.
interconnected
8. Energy flow through tropic levels can
be quantified
Energy flow
within a single
trophic
compartment
Consumption
efficiency:
In/Pn-1
9. Consumption efficiency
determines the pathway of
energy flow through the
ecosystem
In terrestrial ecosystems and shallow
water ecosystems, with their high
standing biomass and relative low
harvest of primary production by
herbivores, the detrital food chain is
dominate.
In deep water aquatic ecosystem, with
low biomass, rapid turnover and high
rate of harvest, grazing chain may be
dominate.
P434
10. Energy decreases in each successive
trophic level
• Trophic efficiency (TE) is the ratio of
productivity in a given trophic level (pn) to the
trophic level it feeds on (Pn-1): TE=Pn/Pn-1
• Ecological pyramids
are graphical representations of the
trophic structure of a given ecosystems
A universal diagram of energy flow
A universal diagram of energy flow
P.E.Odum,1968
Characteristics of Energy
flow:
One-way flow
Descent by trophic levels
Summary
1.The Laws of Thermodynamics Govern Energy Flow
2. characteristics of energy flow are one-way flow and descent by trophic
levels
3. Factors including temperature, precipitation and growing seaon,
controlling Primary Production
4. Primary productivity can be measured by the method of light and dark
bottle in aquatic ecosystem, and by calculating change standing crop
biomass over a given time interval in terrestrial ecosystem.
5. Primary productivity limits secondary production
6. Consumption efficiency determines the pathway of energy flow
through the ecosystem——Grazing food chain and Detrial food chain
Question
• Please expound the relationship between
primary production and secondary
production.