Climax communities
Transcript of Climax communities
Climax communities
Guido Chelazzi
Climax communities Main climatic determinants of biomes
Guido Chelazzi
Climax communities Main ecological determinants of biomes
Guido Chelazzi
0.00
0.01
0.10
1.00
rank
Log
rela
tive
abun
danc
e
1 yr
40 yr
25 yr 15 yr
4 yr
logarithmic
lognormal
Brocken-stick
Community structure change during succession Years after farmland abandonment
Guido Chelazzi
N o
f spe
cies
time
P1 P2 p3
P1 P2 P3 P4
m1 m2 P4
m1 m2 m3 m4 c2 c3
c4 c1 c2 c3
c4 c1
pioneers pioneer-intermediate climax
Biodiversity change during succession
Max diversity
r K
Guido Chelazzi
Biodiversity change during succession D
iver
sity
Frequency of disturbance
Low
Medium
High
Guido Chelazzi
Biodiversity change during succession
Intermedium disturb
Frequency of disturbance
Div
ersi
ty
high medium high
Guido Chelazzi
smaller medium larger
Bebbles-stones dimension
0 1
2
3
4
5
N a
lgal
spe
cies
Bebble-stony beach
Biodiversity change during succession
Intermedium disturb (Sousa experiment)
Guido Chelazzi
Biodiversity change during succession
Frequency of wildfires
Guido Chelazzi
Biodiversity change during succession
Intensity of grazing
Guido Chelazzi
Climate-Fire-Grazing interactions
climate
enhances depress Fire
Herbivores Vegetation
affects
Guido Chelazzi
Human impact
climate
enhances depress Fire
Humans
Herbivores Vegetation
affects
Climate-Fire-Grazing interactions
Guido Chelazzi
However formed, communities must have an internal, functional consistency to persist within an ecosystem, or to develop coherently Each species must find its own functional, ecological space to be a stable member of a given community Species are “packaged” within communities according to their ecological prophyle (e.g. trophic prophyle, sustainable interactions with other species in terms of predation, competition, mutualism etc.)
Community as a functional system
Guido Chelazzi
A description of the trophic relationship within the community
Trophic web
Guido Chelazzi
Primary producers
Herbivores
Carnivores
Top predators
Trophic levels
Vertical stratification of the community (Food chain)
Mat
ter/E
nerg
y tra
nsfe
r
Guido Chelazzi
Assessment of the “vertical position” of each species along the trophic chain
A) Ethological assessment: direct observations of the foraging behaviour of the single species B) Dietary assessment: analysis of gut content, faeces content, discarded items etc. C) Isotopic assessment: sorting of different stable isotopes of N and C
Guido Chelazzi
Predatory birds’ pellet analysis Dietary assessment of the position along the trophic chain
Guido Chelazzi
Trophic position (N isotopes)
Guido Chelazzi
Trophic position (C isotopes)
Guido Chelazzi
C = Consumed
A = Assimilated
S = Discarded
U = Utilized
Es = Escreted
P = Allocated into “production” (Growth + Reproduction)
M = Spent for Metabolism biosyntesis concentration mobility
Se = Secreted
E = Energy available (per unit space and time)
Not intercepted
P / A = Net coefficient of production
Biomass/Energy transfer at each step of the food chain
Guido Chelazzi
Bottom PP
C1 Herbivores
C2 Carnivores
Top Predators-Parasites
Trop
hic
Leve
ls
1
2
3
4
Taxa
Reduction of the total biomass/energy with increasing level of the food web
Guido Chelazzi
1
.15
.02
.003
Phytoplancton
Carnivore zooplancton
Anchovetas
Herbivore zooplancton
Relative biomass per habitat unit
Oceanic trophic chain (off Peru coast)
Guido Chelazzi
1 10
100 1000
10000
1 10
100 1000
0
BN
PP
AN
PP
Mammals Birds Insect
Artrhropods Nematodes
BPC
APC
BSC
ASC
kcal·m
-2·y
-1
Above- and below-ground energy allocation in mixed (savannah like) ecosystem
Guido Chelazzi
A B C D E
A 0 0 0 1 0
B 1 0 1 1 1
C 1 0 0 1 0
D 0 0 0 0 0
E 1 0 1 1 0
A consumes E
B is consumed by D
A does not consume D
Consumer
Con
sum
ed
D is not consumed by D
Consumption matrix
Ø Direct observation in field or in the laboratory Ø Indirect assessment (gut content, faeces etc.)
Guido Chelazzi
Consumption matrix
Sp1 Sp2 Sp3 Sp4 Sp5 Sp1 0 1 1 1 1 Sp2 0 0 1 1 1 Sp3 0 0 0 1 1 Sp4 0 0 0 0 1 Sp5 0 0 0 0 0
Trophic Cascade
Consumer
Con
sum
ed
Sp1 Sp2 Sp3 Sp4 Sp5 Sp1 1 1 1 1 1 Sp2 0 0 1 1 1 Sp3 1 0 0 1 1 Sp4 0 0 0 1 1 Sp5 0 0 0 0 1
Cannibalism + Circularity
Consumer
Con
sum
ed
Guido Chelazzi
Biodiversity within trophic webs
Horizontal biodiversity (Taxa within each level)
Verti
cal b
iodi
vers
ity
(Num
ber o
f lev
els)
Guido Chelazzi
Biodiversity within trophic webs
Ø Horizontal diversity
is controlled by demographic interactions between species of the same trophic level (competition, mutualism) Ø Vertical diversity
is controlled by prey-predators interactions (energy flow, structural and behavioural characteristics of both)
Guido Chelazzi
11
−⋅= nn EE η
( ) ( )( )ηLog
ELogELogn 1min1 −+=
Energy available at nth level
Energy available at the basal level
Energy conversion coefficient
Minimun energy to sustain a level
Number of permitted levels
Energetic control of vertical biodiversity
Guido Chelazzi
Biomass/Energy
Primary production control of vertical biodiversity
Higher Primary production
Biomass/Energy
Lower Primary production
This is not a general effect because:
ü Increased mass production can impair the functionality of organisms at higher levels of the trophic chain (e.g. hypoxia)
ü Vertical packaging depends also on morpho-functional & behavioural hierarchy
Low
er v
ertic
al d
iver
sity
Hig
her v
ertic
al d
iver
sity
Guido Chelazzi
Competition links Lc
Predation links Lp
Taxa
Connectedness: Lc+Lp Connectance: Connectedness/Possible links
Community connectedness (connectance)
Guido Chelazzi
0 10 20 30 40 50 60 Number of species (S)
0
0.2
0.4
0.6
0.8
1.0 Co
nnec
tanc
e (C
)
S·C=2
( )1−⋅=
SSLC
Connectance in real (benthonic) communities
Guido Chelazzi
0
0.20
0.40
0.60
0.80
1.00
0 0.2 0.4 0.6 0.8 1 Connectance
Sta
bilit
y
S = 4
S = 7
S = 10
Stability vs connectance in simulated communities
S = number of species
Guido Chelazzi
Propagation of demographic disturbance
Top-down (predation)
Bottom-up (production)
increase
decrease
increase
increase
Guido Chelazzi
Propagation of demographic disturbance
Ø Top-down progagation prevails in communities where classic predator-prey relationships are dominant
Ø Bottom-up prevails where donor-controlled relationships
are common (e.g. in scavenger dominated communities)
Predator
Prey
Consumer
Producer
Consumed stuff (e.g. dead organic matter)
Guido Chelazzi
Bottom-up biomagnification of POP Top-down propagation of demographic disturbance
Biomagnification Demographic disturbance
Guido Chelazzi
DDD treatment of Clear Lake (California) to eliminate the non biting dipteran Chaoborus astiptocus Diclorodifenildicloroetano
Grebe disappearence
0.02 ppm
5 ppm
10 ppm
1500 ppm
1600 ppm
1949-51
1954
Biomagnification of persistent pollutants and community disruption
Flint & van der Bosch, 1981 in Begon et alii, 1990
Guido Chelazzi
Propagation of demographic disturbance
Top-down
Taxonomic horizontal diversity is a buffer for top-down demographic disturbance propagation Reducing horizontal diversity reduces the community resilience to demographic fluctuations
Guido Chelazzi
Non-trophic relationships within communities
Members of a community (different species) may establish relationships different from predation and competition: Mutualism/Commensalism – Reciprocal or directional trophic exchange between species Facilitation – Non-trophic reciprocal or directional benefits (e.g. modification of abiotic components of the environment which “facilitate” the presence of another species) Ecological engineering - When one species modifies the abiotic/biotic structure of an ecosystem in such a way that this reshape the environment and makes it suitable for survival-reproduction of other species Niche construction – When protracted and profound niche construction leads to selection of new traits (genetic-phenotipic) in the constructor species and in other species which became “entrapped” into the constructed niche (one extreme case is domestication)
Guido Chelazzi
PP DOM
H S Dc
TP
C
Energy transfer Matter transfer Heat loss
PP primary production DOM dead organic matter H herbivores S scavengers Dc decomposers C carnivores TP top predators
Schemes of energy/matter circulation in communities
Guido Chelazzi
PP DOM
P Dv
B)
PP DOM
P Dv
C)
I
PP DOM
P Dv
A)
E
Schemes of energy/matter circulation in communities
PP primary production DOM dead organic matter P predators Dv detritivores Energy transfer Matter transfer Heat loss
Guido Chelazzi
Sagittaria & other macrophytes periphyton
Crostaceans Chironomids Tricoptera Gastropods Herb. fish
Celenterati Macroinvertebrates Carn. Fish
Top predator fish
Bacteria Crustaceans
Biomass (100 gps·m-2)
Stream community (USA) Standing biomass
Guido Chelazzi
Stranded seaweeds and macroalgae
Phyt
opla
ncto
n
Stra
nded
ani
mal
res
idua
ls
Isopods Coleopters
Birds
Moll. scs Coleopt Diptera
larvae
Amphipods
6·103
10·103 141·103 584·103
2146·103
1198·103
1903·103
356·103
4·103
3·103 16·103
Releaseed to the sea and interstitial system
Fluxes: Kj · m-2 · y-1
Sandy beach community Energy flows
Guido Chelazzi
Source-sink coupled ecosystems
Rocky shores
Sea currents
Seagrass beds
Sandy beach
Stranded organic materials
Rivers
Guido Chelazzi