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This is an author-deposited version published in : http://oatao.univ-toulouse.fr/
Eprints ID : 16374
To cite this version : Alignier, Audrey and Deconchat, Marc Forest
edge responses present a variety of patterns in southwestern France.
(2009) In: 9th Annual Meeting of the British Ecological Society - BES 2009, 7 September 2009 - 10 September 2009 (Hertfordshire, United Kingdom). (Unpublished)
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F
OREST
E
DGE
R
ESPONSES PRESENT
A VARIETY OF PATTERNS IN
S
OUTHWESTERN
F
RANCE
Audrey Alignier & Marc Deconchat
Spatial dynamics of landscape
modified by human activities:
Fragmentation/ Defragmentation
- Loss of habitat (e.g. by forest cutting) - Isolation of patches
F
OREST
E
DGES IN
L
ANDSCAPE
:
A CRITICAL
ROLE FOR
V
EGETATION
B
IODIVERSITY
- Isolation of patches
Increase of discontinuity proportion in landscape
Ex. Progressive fragmentation of a woodlot since 1750, in southwestern France (Arrignon, 2003)
F
OREST
E
DGES IN
L
ANDSCAPE
:
A CRITICAL
ROLE FOR
V
EGETATION
B
IODIVERSITY
Edge = zone, in the forest, under
discontinuity influence
(Murcia, 1995)Discontinuities influence
environmental conditions to which vegetation respond (richness,
Forman (1995)
Theoretical pattern of response to discontinuity, widely accepted.
Distance from border
V a ri a b le v a lu e
Field Forest edge Forest interior
vegetation respond (richness, abundance, composition).
O
UR
Q
UESTIONS
How do forest vegetation (richness, abundance and
composition) and abiotic variables respond to edge
effect ?
Comparing vegetation response curves to forest edges between
several transects
Method
several transects
Can we characterize a common pattern of response to
edges ?
Attributing a statistical model to responses of vegetation and
abiotic variables
S
TUDY
S
ITE
Nord
1km
Site LTER « Vallées et coteaux de Gascogne »
Subatlantic climate with mediterranean influence
(average annual T°C = 11°C; average annual rainfall = 800mm) Woodlots managed by private owners ; coppice with standards Dominant species: oaks (Quercus robur, Q.pubescens, Q.petreae), hornbeam (Carpinus betulus), wild cherry (Prunus avium)
S
AMPLING
D
ESIGN
28 transects, extended fromthe border to 40m into the forest interior
Border =line formed by the first tree trunks (Murcia,1995)
40m away from clearcut or
40m Border Forest interior Adjacent land cover
2m
Crop or meadow One transect:
Localisation map of 28 transects studied (in red)
40m away from clearcut or
D
ATA
A
NALYSIS
: M
ODEL
A
PPLICATION
PER
T
RANSECT
Vegetation data:
Total species richness
Total abundance (cover percent) Composition
(Scores on Axis 1 of centered PCA on presence/absence matrix)
In relation to distance from border
Response curves
Models adjustment and
1 Comparison Environmental data: Soil temperature Soil moisture (RH) Soil pH Soil penetrability Canopy openess (%)
2 Models adjustment and
best model selection
(Ewers & Didham, 2006)
Characterization of edge reponses by adjusted models Comparison of models
* 28 transects
Alignier – Response patterns to forest edge
D
ATA
A
NALYSIS
: B
EST MODEL
S
ELECTION
Distance from border
V a ri a b le v a lu e NULL
Distance from border
V a ri a b le v a lu e EXPONENTIAL v = tested variable d = distance from border
βx= constant
Selection on AIC
ε
+ =v v v=β0exp(β1*d)+ε LINEARDistance from border
V a ri a b le v a lu e
Distance from border
V a ri a b le v a lu e LOGISTIC Widely accepted theoretical model « Simple » models - Complexity +
Selection on AIC
criterion
ε β β + + = d v 0 1* ( ) ( ) (β β β ) ε β β + − + − + = 3 * 2 exp 1 0 1 0 d vR
ESULTS
: V
EGETATION
123 species from 42 families ; 75 herbaceous
perennials, 42 woody species and 6 annual species
2 0 0 3 0 0 4 0 0 5 0 0 b u n d a n c e Hedera helix Rubus fructicosus gr. Tamus communis Lonicera per. H. helix R. fructicosus L.peryclimenum T.communis 1 5 2 0 ri c h n e s s Max = 15 Min = 6 Mean = 10.7
High variation in species richness between transects (similar results for abundance).
0 20 40 60 80 100 120 0 1 0 0 2 0 0 Species rank A b u n d a n c e 80% of species have an occurrence frequency <10%. 1 3 5 7 9 11 13 15 17 19 21 23 25 27 5 1 0 1 5 Transect T o ta l s p e c ie s ri c h n e s s
R
ESULTS
: A
BIOTIC
V
ARIABLES
High variation of soil temperature between transects:
variation between transect (up to 4°C) > variation within a transect (max 1.3°C)
pH was stable with distance from
border except for 7 transects with a slight decrease in forest interior as in Marchand & Houle (2006).
General decrease of % canopy
Soil moisture was stable with General decrease of % canopy
openess with distance from border.
High variation of abiotic variables between transects,
often > variation within transect.
Results consistent with previous studies.
Soil moisture was stable with
distance from border, except for 6 transects which present an increase of soil moisture in forest interior.
R
ESULTS
: V
EGETATION
R
ESPONSE
M
ODELS
8 1 0 6 0 8 0 1 0 0 0 .0 0 .5 1 .0 1 .5Species richness Percent cover Composition
Example for transect n°19:
Different models between vegetation descriptors
0 10 20 30 40
4
6
Distance from border (m)
0 10 20 30 40
2
0
4
0
Distance from border (m)
0 10 20 30 40 -1 .5 -1 .0 -0 .5
Distance from border (m)
EXPONENTIAL NULL LINEAR
R
ESULTS
: A
BIOTIC
R
ESPONSE
M
ODELS
1 6 .8 1 7 .0 1 7 .2 1 7 .4 5 .8 6 .0 6 .2 1 5 1 6 1 7Soil temperature pH Soil moisture
( Penetrability) (Canopy openess) Example for transect n°19:
Different models between abiotic descriptors
0 10 20 30 40 1 6 .2 1 6 .4 1 6 .6
Distance from border (m)
0 10 20 30 40 5 .2 5 .4 5 .6
Distance from border (m)
0 10 20 30 40 1 2 1 3 1 4
Distance from border (m)
R
ESULTS
: F
REQUENCY OF
M
ODELS FOR
ALL
TESTED VARIABLES
Model complexity 25 30 35 40 45 F r e q u e n c y (% )
No discernible
edge effect
0 5 10 15 20 1 2 3 4 F r e q u e n c y Adjusted modelsNull Linear Exponential Logisitic
Model « null » dominant
BUT
Edge effects in the majority of cases
R
ESULTS
: M
ODELS
A
DJUSTMENT
10 15 20 25 30 N u m b e r o f tr a n se c ts Logistic PowerAbiotic variables Biotic variables
Complexity +
Logistic model
dominant
Simple models are dominant for the majority of variables.
0 5 10 N u m b e r o f tr a n se c ts Linear Null Complexity
D
ISCUSSION
How forest vegetation (richness, abundance and composition)
respond to edge effect ? And abiotic variables ?
No unique (general) model but different models between vegetation descriptors and abiotic variables.
D
ISCUSSION
V a ri a b le v a lu eField Forest edge Forest interior
Border
NULL
NO EDGE EFFECT
Distance from border Distance from border
EXPONENTIAL
LINEAR
D
ISCUSSION
How forest vegetation (richness, abundance and composition)
respond to edge effect ? And abiotic variables ?
No unique (general) model but different models between vegetation descriptors and abiotic variables.
Can we characterize a common response pattern to edges ?
High variability of edge responses between transects: - Different adjusted models according to tested variables
- Null model predominant for overall transects NO EDGE EFFECT - Selection among 4 models not always the best adjustment to data
D
ISCUSSION
How to explain the absence of edge effects ?
Small woodlots (from <0.05 to 5ha)
Human management
Frequent perturbation over years Frequent perturbation over years Management by private owners
Perspectives :
To integrate forest management (cuttings) and forest continuity as explicative variables in data analysis
This work was granted by the French Ministry of Research and Education. Thanks to:
L.Burnel, M.Fakorellis, J.Willm for their field assistance
A.Cabanettes, M.Goulard for their helpful comments on statistical analysis Private woodland farmers and owners
SEVAB for financial support in participation of this meeting
Thanks for your attention
Thanks for your attention
Hemispherical photography Hedera helix Rubus fructicosus Tamus communis Lonicera periclymenum 0 20 40 60 80 100 120 0 10 20 30 40 50 60 70 80 90 S p e c ie s n u m b e r Fréquence (%)
3 5 0 4 0 0 4 5 0 P e n e tr a b il it y 1 4 1 6 1 8 2 0 2 2 % C a n o p y o p e n e s s 0 10 20 30 40 3 0 0
Distance from border (m)
0 10 20 30 40
1
2
1
4
R
ESULTS
: M
ODELS
A
DJUSTMENT
For all transects:
Simple Complex 30 40 50 60 70 80 90 100 Composition Percent cover Species richness % Cnpy Openess pH Penetrability O c c u r r e n c e f r e q u e n c y
Null Linear Power Logisitic
Models complexity 0 10 20 30 1 2 3 4 Penetrability Soil moisture Soil T°C O c c u r r e n c e