Download Definitions

Does biodiversity play a
significant role in ecosystem
function?
ASB Sustainable Land Use Mosaic
(SLUM) Working Group
Symposium
12-15 November 2001
Chiang Mai, Thailand
CBM
Definitions
Biodiversity
Conceptual: The variety of life on earth expressed in
terms of gene, species and ecosystem. (cf. Heywood & Baste,
1996)
Operational: The quantity and composition of species
and functional types recordable in any area. (Gillison, 2001).
Functional types: (FTs) are sets of organisms showing
similar responses to environmental conditions and having
similar effects on the dominant ecosystem processes.
(Diaz, 1998).
ASB SLUM Mtg Chiang Mai 11 Nov 01
Diversity
…The number of different items and their
relative frequency. For biological diversity these
items are organized at many levels …. Thus the
term biodiversity encompasses different
ecosystems, species, genes and their relative
abundance. (US Congress, Office of Technology
Assessment, 1987).
ASB SLUM Mtg Chiang Mai 11 Nov 01
Indicators and surrogates
The vast number of biota that influence
ecosystem function are mainly small organisms
that are very difficult to measure. For most
practical purposes their diversity and that of
other larger, difficult-to-measure organisms, is
assumed to be indicated by more readily
observable units such as plant species and
functional types.
(This tends to be an act of faith commonly
applied in private and denied in public).
ASB SLUM Mtg Chiang Mai 11 Nov 01
Ecosystem
1. A community of interdependent organisms together
with the environment which they inhabit and with
which they interact. (Allaby, 1977).
2. A functional system which includes the organisms of
a natural community together with their environment.
(Lapedes, 1976)
3. … the sum total of vegetation, animal, and physical
environment in whatever size segment of the world is
chosen for study. (Fosberg, 1967)
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The ecosystem concept is used widely
but ambiguously. It can:
a) contain only a functional meaning,
b) have a spatial connotation which includes any
level of scale or
c) the spatial aspect can be included, but
additionally, relative homogeneity must
characterize the system
(Johnson and French, 1981, quoted by Godron & Forman, 1983)
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Differences between ecosystem
and landscape:
Ecosystems: are relatively homogeneous
Landscapes: are relatively heterogeneous.
A landscape is “…a kilometers wide area where a
cluster of interacting stands or ecosystems is
repeated in similar form” (Godron & Forman, 1983)
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‘Ecosystem’ conversion to ‘landscape’
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Landscape
assemblages
In NW Mato
Grosso,
Western Amazon
basin
Brazil
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Species
Elevation (m)
500 700 900 1100 1300 1500 1700 1900 2100 2300 2500
Plants
Dipterocarpus tuberculatus
Shorea obtusa
Castanopsis sp.
Chromolaena odorata
Imperata cylindrica
Smilax sp.
Melastoma malabathrica
Arisaema sp.
Birds
Collared Falconet
Sooty-headed Bulbul
Red Jungle Fowl
Scarlet Minivet
Striped Tit-babbler
Grey-throated Babbler
Arctic Warbler
Range (elevational) distributions of some key
taxa across different landscapes – Mae Chaem,
Northern Thailand
ASB SLUM Mtg Chiang Mai 11 Nov 01
Differing views of species role
in ecosystems
1. Systematists and population biologists:
– No two species can exist in exactly the same
habitat
– Every species has a unique resource
requirement and hence use pattern
ASB SLUM Mtg Chiang Mai 11 Nov 01
2. Ecologists:
– More than one species can occupy a functional
type or resource niche (e.g. mesophyte, xerophyte,
producer, consumer, life form, C3, C4 path, nitrogen
fixer, PFT…)
– More than one functional type can occur within
a species.
Approaches to species, biodiversity and
ecosystem function:
Traditional: Community ecology: Species
diversity is a dependent variable controlled
by abiotic conditions and ecosystem
constraints. Ecosystem ecology: Dominant
species control ecosystem properties.
Recent: Now consider role of biodiversity as a
potential modulator of ecosystem processes.
ASB SLUM Mtg Chiang Mai 11 Nov 01
Some general assertions
• Ecosystem stability and primary
productivity vary directly with diversity in
species and functional type
• Species properties expressed as functional
types exert a greater degree of control on
ecosystem function than species diversity
(richness)
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(After Springett, 1976)
See also Swift & Anderson (1993)
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Biodiversity and ecosystem function:
Recent consensus*
• Some minimum number of species is essential for
maintaining ecosystem function under constant
conditions
• A larger number of species is probably required
for maintaining ecosystems in changing
environments
• Determining which species have significant
impact on which processes in which ecosystem
remains an open emiprical question
*Loreau et al. (2001)
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Cont..
• Increased primary production via higher plant
diversity can be expected to stimulate secondary
productivity.
• Changes in one trophic level may lead to a variety
of potential responses for processes at higher
trophic levels.
• Mechanisms for generating primary productivity
may range from systems with a few dominant
species or functional types (low diversity) to
systems with high diversity, low level dominance
and high complementarity (synergy).
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Hypothetical
mechanisms
involved in
biodiversity
experiments
using synthetic
communities
Loreau et al.
(26 October, 2001)
Science: 294:804-808
Dual hypothetical mechanisms for species, FT
diversity and ecosystem productivity
Diversity of
Spp and FTs
Dominance
Complementarity
Low
High
(few groups)
low
High
Low
(many ‘ rare’ )
High
Primary
productivity
Local, regional, random
processes. Within and
between landscape
heterogeneity high
ASB SLUM Mtg Chiang Mai 11 Nov 01
?
Local, deterministic processes.
Niche diff’n high . Within
landscape heterogeneity low
Ecosystem functions and processes related to the transfer of
energy, nutrients, water and genetic information
Function/ Process
Nutrient capture
Decomposition and soil formation
Mycorrhizal activity
Photosynthesis
Herbivory
Pollination
Species interactions (mutualisms,
symbiosis, predation, parasitism,
competition)
Water uptake and loss
Source: Hobbs (1992)
See also Giller et al. ( 1997 ) for below-ground
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Action
Nutrient cycling
Nutrient cycling
Enhanced nutrient uptake
Energy capture and productivity
Energy and nutrient capture
Genetic information transfer
Energy, water and nutrient
transfer
Water transfer
Plants as basal ecosystem units
• Most terrestrial (mobile, heterotrophic)
biota ultimately depend on plants for
survival
• Plants as mostly sessile, autotrophic units
are readily observable in nature
• Variation in plant form and function is
measureable along key environmental
gradients
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Water
Light (energy)
High
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Medium
Low
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Plant Functional Types*
• Photosynthetic envelope (leaf size, inclination,
chlorotype, morphotype)
• Physical support system or life form based on
position of perennating buds
• Above-ground rooting system
• Minimum set of attributes
• ‘Coherent’ functional model
* after Gillison (1981)
ASB SLUM Mtg Chiang Mai 11 Nov 01
VegClass, Windows-based, user-friendly software for
data entry and meta-analysis; integrated with field
proforma to support rapid vegetation survey
Plant Functional Types: leaf + stem
photosynthesis, incl. parasites, carnivores
ASB SLUM Mtg Chiang Mai 11 Nov 01
Ecosystem functions and processes related to the transfer of
energy, nutrients, water and genetic information*
Function/ Process
Nutrient capture
Decomposition and soil formation
Mycorrhizal activity
Photosynthesis
Herbivory
Pollination
Species interactions (mutualisms,
symbiosis, predation, parasitism,
competition)
Water uptake and loss
* PFT relevance highlighted in red
ASB SLUM Mtg Chiang Mai 11 Nov 01
Action
Nutrient cycling
Nutrient cycling
Enhanced nutrient uptake
Energy capture and productivity
Energy and nutrient capture
Genetic information transfer
Energy, water and nutrient
transfer
Water transfer
Patterns of richness in plant species and functional
types under different land use types
Indonesia : Jambi - Lampung
Legend
Cassava
Imperata
Mono. Plantation
Natural Forest
Logged Forest
Agroforestry
160
140
120
Species
100
80
60
40
20
0
0
10
20
30
40
50
Modi
Plant FunctionalTypes
(modi)
ASB SLUM Mtg Chiang Mai 11 Nov 01
60
Regression plot of termite abundance & basal area
of woody plants [r2=0.985]
over 7 land use systems: Jambi BS Nov. 97
100
Primary Forest
Termite Abundance
90
Jungle Rubber
80
70
Secondary
Forest
60
Rubber Plantation
50
40
30
Paraserianthes
Plantation
20
10
Imperata
0
Cassava
0
2
4
6
8
10 12 14 16 18 20 22 24
Basal Area m2 ha-1
ASB SLUM Mtg Chiang Mai 11 Nov 01
Ratio of plant species richness to plant functional types as
an indicator of Termites species richness [R-Sq = 0.97]
over 7 land use systems : Jambi BS Nov. 97
4
0
Termite species richness
Primary Forest
3
0
Secondary
Forest
Jungle Rubber
2
0
Paraserianthes
1
0 Plantation
Rubber Plantation
Imperata
0
Cassava
1
.
0
1
.
2
1
.
4
1
.
6
1
.
8
2
.
0
2
.
2
2
.
4
2
.
6
2
.
8
3
.
0
Ratio of plant species to plant functional types (modi)
ASB SLUM Mtg Chiang Mai 11 Nov 01
Correlations between key plant variables,
fauna and above-ground Carbon
Jambi Baseline survey
Attribute
Species
Modi
Spp/Modi
Ground-dwelling
Termite abundance
0.872
0.766
0.946
Termite species
0.849
0.698
0.976
Lep/ground
0.834
0.790
0.920
Canopy:
Unident. insects
0.771
0.418
0.839
Collembola
0.643
0.089
0.882
Ant-total
0.633
0.729
0.393
Total insects
0.593
0.487
0.526
Orthoptera
0.545
0.378
0.528
Thysanoptera
0.470
0.756
0.138
Isoptera (canopy)
0.417
0.140
0.496
Psocoptera
0.398
0.148
0.457
Coleoptera
0.312
0.458
0.127
Hymenoptera
0.302
0.446
0.129
Formicidae
0.274
0.370
0.142
Acari
0.190
-0.232
0.443
Spiders
0.186
0.307
0.050
Blattodea
0.124
-0.014
0.204
Hemiptera
0.098
0.229
-0.026
Diptera
0.038
0.404
-0.197
0.599
0.347
0.704
Bird total spp.
0.796
0.558
0.909
Above-ground
carbon
# Shaded areas with r = >0.500. Bold type = high indicator value.
ASB SLUM Mtg Chiang Mai 11 Nov 01
Above-ground carbon and species: PFTs along
a gradient of Land Use Types, Jambi [r2 = 0.814]
60
(Y=13.56  23.52X + 11.30 X**2)
1
50
AG-carbon
2
5
40
30
4
20
9
6
10
12
8
7
14
15
13
0
3
16
1.0
1.2
1.4
1.6
1.8
2.0
2.2
Species : PFTs
ASB SLUM Mtg Chiang Mai 11 Nov 01
10
11
2.4
2.6
2.8
3.0
Aboveground Carbon and Species:PFTs
All ASB benchmark sites
Plant Spp:PFT ratio
3.00
Primary
Forest
2.50
2.00
Managed
Forest
Fallow
1.50
Tree-based
1.00
0.50
Crop
Pasture
0
50
100
150
200
250
Aboveground - C t/ha
300
350
400
Correlations between soil and vegetation variables*
Variable
pH-H2O pH-KCl C%
N% C/N%
Na
Al3
H+
PFT
-0.448
0.028
-0.459
0.024
0.586
0.003
0.592
0.002
0.497
0.013
0.568
0.004
0.465
0.022
0.503
0.012
Species
-0.424
0.039
-0.427
0.037
0.529
0.008
0.585
0.003
0.435
0.033
0.503
0.012
0.458
0.024
0.441
0.031
Mean Height
-0.358
0.086
-0.331
0.114
0.559
0.005
0.530
0.008
0.477
0.019
0.457
0.025
0.379
0.068
0.480
0.018
Basal Area
-0.331
0.114
-0.260
0.219
0.482
0.017
0.572
0.003
0.383
0.064
0.375
0.071
0.400
0.053
0.402
0.052
V-Index
-0.433
0.034
-0.432
0.035
0.550
0.005
0.622
0.001
0.448
0.028
0.495
0.014
0.486
0.016
0.457
0.025
Tree wt1
-0.588
0.002
-0.586
0.003
0.777
0.000
0.566
0.004
0.722
0.000
0.700
0.000
0.570
0.004
0.755
0.000
Tree wt2
-0.576
0.003
-0.568
0.004
0.753
0.000
0.557
0.005
0.697
0.000
0.668
0.000
0.558
0.005
0.735
0.000
Plot Age
-0.421
0.041
-0.410
0.046
0.613
0.001
0.566
0.004
0.528
0.008
0.569
0.004
0.390
0.060
0.546
0.006
* Upper line = ‘r’ value; lower line = ‘P’ value; shaded areas with P <0.020
Tree wt1 = Quirine data; Tree wt2 = Brown data; only variables with highest
correlations listed.(Source: Gillison, 2001; Hairiah and van Noordwijk, 2001)
Conclusions
• Specific knowledge of functional types may be
essential to predict ecosystem responses under
different global scenarios or where management
seeks to manipulate species composition directly
as in complex agroecosystems.
• Hypotheses and models must be tested in a wider
array of ecosystem types e.g. tropical forests.
• To predict and understand changes in biodiversity
and ecosystem function we need to move beyond
simple causality and address multiple feedbacks.
• Relationships between local, landscape and
regional scales require critical attention.
ASB SLUM Mtg Chiang Mai 11 Nov 01