does biodiversity play a significant role in ecosystem function? asb sustainable land use mosaic...
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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
DefinitionsBiodiversityConceptual: 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).
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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 assemblagesIn 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
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Differing views of species role in ecosystems
1. Systematists and population biologists: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. Ecologists2. 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.
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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)
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See also Swift & Anderson (1993)
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
Primaryproductivity
Diversity of Spp and FTs
Low
High
High(few groups)
Low (many ‘ rare’ )
Complementarity
low
High
Local, regional, random processes. Within and between landscape heterogeneity high
Local, deterministic processes. Niche diff’n high . Within landscape heterogeneity low
?
Dominance
Dual hypothetical mechanisms for species, FT diversity and ecosystem productivity
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Function/ Process ActionNutrient capture
Decomposition and soil formation
Mycorrhizal activity
Photosynthesis
Herbivory
Pollination
Species interactions (mutualisms, symbiosis, predation, parasitism, competition)
Water uptake and lossSource: Hobbs (1992)
See also Giller et al. ( 1997 ) for below-ground
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
Ecosystem functions and processes related to the transfer of energy, nutrients, water and genetic information
ASB SLUM Mtg Chiang Mai 11 Nov 01
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
High Medium LowL
igh
t (e
ner
gy)
L
ow
M
ediu
m
Hig
h
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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)
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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
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Function/ Process ActionNutrient 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
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
Ecosystem functions and processes related to the transfer of energy, nutrients, water and genetic information*
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0 10 20 30 40 50 60
Modi
0
20
40
60
80
100
120
140
160
Spe
cies
Patterns of richness in plant species and functional types under different land use types
Indonesia : Jambi - Lampung
Legend CassavaImperataMono. Plantation
AgroforestryLogged ForestNatural Forest
Plant FunctionalTypes (modi)
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0 2 4 6 8 10 12 14 16 18 20 22 24
Basal Area m2 ha-1
0
10
20
30
40
50
60
70
80
90
100
Ter
mit
e A
bu
nd
ance
Regression plot of termite abundance & basal area of woody plants [r2=0.985]
over 7 land use systems: Jambi BS Nov. 97
Primary Forest
SecondaryForest
Imperata
Cassava
Rubber Plantation
Jungle Rubber
ParaserianthesPlantation
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1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0
0
10
20
30
40T
erm
ite
sp
ecie
s r
ich
nes
s
Primary Forest
SecondaryForest
Imperata
Cassava
Rubber Plantation
Jungle Rubber
ParaserianthesPlantation
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
Ratio of plant species to plant functional types (modi)
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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 Bird total spp. 0.599 0.347 0.704 Above-ground carbon
0.796 0.558 0.909
# 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]
1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0
0
10
20
30
40
50
60
1
2 5
4
101139
86
7
151316
1412
AG
-car
bo
n
Species : PFTs
(Y=13.56 23.52X + 11.30 X**2)
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0.50
1.00
1.50
2.00
2.50
3.00
0 50 100 150 200 250 300 350 400
Aboveground Carbon and Species:PFTsAll ASB benchmark sites
Pla
nt
Sp
p:P
FT
ra
tio
Aboveground - C t/ha
Primary Forest
Managed Forest
Tree-based
Fallow
CropPasture
Correlations between soil and vegetation variables* Variable pH-H2O pH-KCl C% N% C/N% Na Al3 H+
PFT -0.448 -0.459 0.586 0.592 0.497 0.568 0.465 0.503 0.028 0.024 0.003 0.002 0.013 0.004 0.022 0.012
Species -0.424 -0.427 0.529 0.585 0.435 0.503 0.458 0.441 0.039 0.037 0.008 0.003 0.033 0.012 0.024 0.031
Mean Height -0.358 -0.331 0.559 0.530 0.477 0.457 0.379 0.480
0.086 0.114 0.005 0.008 0.019 0.025 0.068 0.018
Basal Area -0.331 -0.260 0.482 0.572 0.383 0.375 0.400 0.402 0.114 0.219 0.017 0.003 0.064 0.071 0.053 0.052
V-Index -0.433 -0.432 0.550 0.622 0.448 0.495 0.486 0.457 0.034 0.035 0.005 0.001 0.028 0.014 0.016 0.025
Tree wt1 -0.588 -0.586 0.777 0.566 0.722 0.700 0.570 0.755 0.002 0.003 0.000 0.004 0.000 0.000 0.004 0.000
Tree wt2 -0.576 -0.568 0.753 0.557 0.697 0.668 0.558 0.735 0.003 0.004 0.000 0.005 0.000 0.000 0.005 0.000
Plot Age -0.421 -0.410 0.613 0.566 0.528 0.569 0.390 0.546 0.041 0.046 0.001 0.004 0.008 0.004 0.060 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
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