Long-term vegetation monitoring, an update.

Pierre Hiernaux, Eric Mougin, Josiane Seghieri, François Lavenu, Nogmana Soumaguel, Lassine Diarra

Post-drought dynamics on sandy and clayed soils

19

1985

21

1985

19

1988

21

1988

19

2005

21

2005

An asset to study long term vegetation dynamics in the sahel

• Asset:12 years of vegetation monitoring over 24 rangeland sites sampled in a South_North transect across the Gourma from 1984 to 1995.

• The monitoring developed to assess the seasonal and interannual changes in rangeland ressource, on sites sampled to be representative of the range climates, soils and intensity of grazing pressure in the Gourma.

• Measured initiated in 1984, matching with the peak of the worse drought that stroke the Sahel, and kept active till 1993 with a few measures in 1994 and 1995. Then, observations resumed by AMMA in 1998 and sites are monitored till now.

• From the onset, the sampling methods on the field were designed to match with a remote sensing approach (NOAA-AVHRR in collaboration with NASA, Agrhymet, Institut de Geographie, CESBIO…). The minimum size of the field sites are 1x1km, when possible located within a larger area with similar ecology. Landscape pattern and vegetation heterogeneity considered through enbedded stratified sampling, and distinct methods for the annual herbaceous community, and woody plants and in a few cases perennial herbaceous.

Vegetation monitoring in 2005

Data set organisation: data entry, checking, standardisation, systematic statistical analysis

2006 plans

Vegetation patterns: the facies, the stratas

Vegetation sampling design

Fixed central axis of 1000 x 1 m for herb layer non-destructive stratification

12 1x1 m plots (per facies) for destructive mass sampling location at random a few meters off the axis

Measures every 15 d during the wet seasonMeasures every 60 d during the dry season

facies 2

facies 1 facies 1 facies 1

facies 2

facies 2

Observations, measures and indicators on annual herbaceous

Visual estimate of herb cover (%) (green/dead, standing/litter, grass/dicots)

Desctuctive measure of herb mass (g/m²) (green/dead, standing/litter, grass/dicots)

List of species with visual estimate of cover (%)

Observed/measured on 1x1 m plots

Observed/measured on 0.2x0.2 m sub-plots

Direct measure of leaf area (cm²) Indirect with hemispherical photo

Root masses by layers of 10 cm (g/m²)

Soil seed stock by 2cm layers extracted and counted, in and ex-situ germination

mean, varianceby strata

weighted mean,random resampled mean

by facies, site

Field data

cover, mass means and variances

LAI, root mass weighted means

and variances

cover, mass weighted means

and variances

Leaf area, root mass means

and variances

Species weighted contribution

to cover

Species weighted contribution to seed stock

Calendar of measures on the herbaceous layer in Gourma sites in 2005-06

2005 2006 Sites Juin Juillet Aout Septembre Décembre Mars

1 4/08 26/09 16/03/06 2 26/09 16/03/06 4 21-06 25/09 16/03/06 5 21-06 31/07 25/09 16/03/06 6 25/09 8 24/09 9 22-06 2/07;24/07 24/09 17/03/06

10 2/07;24/07 24/09 17/03/06 12 22-06 8/07;23/07 21/08 23/09 6/12 11/03/06 14 23/07 21/08 23/09 6/12 18/03/06 15 - 18/03/06 16 8/07 17/08;28/08 22/09 5/12 09/03/06

17EW 17/06; 26/06 4/07;17/07;27/07

4/08;14/08;23/08

16/09;28/09 18/03/06 17NS 28/09 19/03/06

18 9/07;19/07 19/08 19/09 18/03/06 19 16-juin 8/07;18/07 22/08 19/09 1/12 20/03/06 20 18/09 21/03/06 21 27-juin 9/07;22/07 30/08 17/09;29/09 2/12 22/03/06 22 28-juin 20/09 22/03/06 25 28-juin 21/09 5/12 22/03/06 28 18-juin 28/07 30/09 22/03/06 30 28/07 21/09 20/03/06 31 27-juin 18/07 19/08 20/09 2/12 10/03/06 32 25-juin 24/03/06 37 24-juin - 7/12 23/03/06 38 16-juin - 18/03/06 40 8/07;25/07 17/08 18/09 4/12

Weighted means of standing herbaceous cover (%) dry mass –kg/ha) and plant density (#/m²),site 17 in 2005

site 17, EW

2005

0,0

5,0

10,0

15,0

20,0

25,0

30,0

35,0

40,0

45,0

1-juin 1-juil 1-août 1-sept 1-oct

0,0

500,0

1000,0

1500,0

2000,0

2500,0

3000,0

mrecs

mdens

mbios

Species contribution to cover at site 17 the 26/06/05 and during the 2005 rainy season

0,00

2,00

4,00

6,00

8,00

10,00

12,00

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18,00

17/06/2005 26/06/2005 04/07/2005 17/07/2005 27/07/2005 14/08/2005 23/08/2005 02/09/2005 16/09/2005 28/09/2005

ALYSOVAL

ARISMUTA

BORRRADI

BRACXANT

CENCBIFL

CHLOPRIE

DACTAEGY

DIGICILI

ERAGTREM

FIMBHISP

GISEPHAR

INDIASPE

SCHOGRAC

STRIHERM

TRAGBERT

TRIAPILO

TRIBTERR

ZORNGLOC

Déposer champs de page Ici

Max of mrspsit

DATE

ESP

couvert site 17 26/06/05 CENCBIFL

ZORNGLOC

TRAGBERT

BRACXANT

TRIBTERR

ALYSOVAL

FIMBHISP

GISEPHAR

ARISMUTA

HELISTRI

DACTAEGY

DIPCTACC

CHLOPILO

Contribution of taxonomic or functionnal species groups to herbaceous vegetation cover in the Gourma sites in 2005

0,00

20,00

40,00

60,00

80,00

100,00

1 5 9 10 12 16 17 17 18 19 21 21 28 31 38 40

sites

gra

sses

an

d l

egu

mes

%

ctgr ctlg

Calendar of vegetation and soil observations in the IER sites in Bamba district.

Herbacées annuelles Herbacées pérennes Peuplements

ligneux

Site N°

Nom du site Dates de

mesure Stratification,

(1000 m2)

Couvert, composition floristique et

masse (8 x 1m²)

Densité (PCQ)

Echantillons (mensurations

et masse)

Densité et couvert (PCQ)

Topographie et états de surface des

sols

B8 Bamba 03.10/05 - - - - - 13/03.06 X X

A3 Adjarara 03.10/05 X X X X X A2 In Amankor 03.10/05 X X X X B6 In Amankor 03.10/05 X X X X X R9 Tamayort 03.10/05 X X X X R8 Tamayort 03.10/05 - - - - B5 Tamayort 03.10/05 - - - - R7 Tin Tates 03.10/05 - - - - R6 Tin Tates 03.10/05 X X X X R5 Tin Tates 03.10/05 X X X X R8 Tamayort 13/03.06 X X X

R3 In Adeskane 13/03.06 X X X

R7 Tamayort 13/03.06 X X X

B5 Tamayort 13/03.06 X X X

A1 In Adeskane 13/03.06 - - X

B11 In Adeskane 13/03.06 - - X

B13 In Adeskane 13/03.06 - - X

R11 Sobori 13/03.06 X X X

R2 Sobori 13/03.06 X X R10 Maha 13/03.06 - -

Comparing cover and masses of annuals, perennial

grasses and woody plants

foliage in the Haoussa

sites

Masse des pérennes et annelles kg/ha

0,0

1000,0

2000,0

3000,0

4000,0

R5 A2 R6 B6 A3 R9

her

bac

ées

(A e

t P

0,0

200,0

400,0

600,0

800,0

1000,0

lig

neu

ses

(feu

ille

s)

bioper mbios biotl

Masse des pérennes et annelles kg/ha

0,0

1000,0

2000,0

3000,0

4000,0

R5 A2 R6 B6 A3 R9

her

bac

ées

(A e

t P

0,0

200,0

400,0

600,0

800,0

1000,0

lig

neu

ses

(feu

ille

s)

bioper mbios biotl

Observations, measures and indicators on perennial and woody plants

Record of individuals in circular plots (per category or per species)

Record the four closest individuals and measure distance from random points

Record individuals which crown interceptthe 1000m site axis, measure interception

Observed/measured populations

Observed/measured on individuals

Measure crown heighth, length and width (m)

Measure basal circonference of stems or basal crown (cm)

Record species name of all individuals

density and Crown coverassessment weighted mean,

of foliage and wood masses using

allometry relationspre-established for

each species

Field data

density mean and variance by category

Foliage, wood, masses

weighted means and variances

crown cover mean and

variance by category

Species weighted contribution

to cover, masses..

crown cover estimate

Sampling woody plant populations (trees and shrubs) in circular plots, which area is fitted to the population density

Lineartransect

A B

LargeCircularPlot used torecord low density Tree: ~ 10/ha

Small circularPlot used to record Densely populated shrubs: ~100/ha

Assessing plant population densities and structure by measuring the distance of closest plant to random points

Perpendicular to the transect line

d1, d2, d3 and d4 the distances from A to

four closest millets hills

d1

Transect d4 A (200m)

d3 d2

density D = 10000/ d2 ;

with d2 = [( d1+d2+d3+d4)/4]2

Source:Josiane Seghieri

Root system Acacia raddiana, Agoufou (site 17), 2005

Vegetation monitoring in 2005

Data set organisation: data entry, checking, standardisation, systematic statistical analysis

Upscaling: mapping vegetation, soil, water balance and landuse

2006 plans

Flow chart of the data files and program codes for the statistical analysis of the data on herbaceous layers

stratosXX mesvegXX compflorXXRow fieldData files

Stratification Mass, cover… Species composition

stratosXX

SAS code files

Standardized data files

msvegXX ctspXX

herb_str_XX herb_fac_XXHerb_sit_XX

alpltXX alfacXXalsitXX

resucla_XX

Interannual data base

Herbfac Herbsit Ctsp Resucla

biomassXX

spcompXX

Standardized statistics and indicator files

Weighted means of standing herbaceous at Agoufou (site 17) from 1990 to 2005

Site 17 - 1990-2005

0,0

500,0

1000,0

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2000,0

2500,0

3000,0

juil-

90

jan

v-9

1

juil-

91

jan

v-9

2

juil-

92

jan

v-9

3

juil-

93

jan

v-9

4

juil-

94

jan

v-9

5

juil-

95

jan

v-9

6

juil-

96

jan

v-9

7

juil-

97

jan

v-9

8

juil-

98

jan

v-9

9

juil-

99

jan

v-0

0

juil-

00

jan

v-0

1

juil-

01

jan

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2

juil-

02

jan

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3

juil-

03

jan

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4

juil-

04

jan

v-0

5

juil-

05

sta

nd

ing

ma

ss

(k

g/h

a)

No observations

Flow chart of the data files and program codes for the statistical analysis of the data on woody populations

circgoXX pcqgoXX intlingoXXRow fieldData files

Circular plots Distance Crown linear intercept

circXX

SAS code files

Standardized data files

pcqXX intlinXX

circdnXX circmfXXcircboiXX

pcqdnXX pcqmfXXpcqboiXX

Interannual data base

linrc

circXX intlinXX

Standardized statistics and indicator files

linrcXX

pcqXX

Circdn/mf/boi Pcqdn/mf/boi

Changes in woody plants canopy cover and species composition from 1988 to 2005, sites 14 and 21

21 1988

0,79

0,76

0,48

0,05

0,00

0,00

0,29

0,11

0,13

49,71

Acacia seyal Balanites aegyptiaca

Anogeissus leiocarpus Acacia nilotica

Dichrostachys glomerata Acacia seyal

Acacia nilotica Acacia raddiana

Acacia laeta

21 2005

65,56

3,47

2,00

1,31

0,05

Acacia seyal Balanites aegyptiaca

Acacia laeta Acacia raddiana

Grew ia tenax

14 1988

6,41

0,10

0,39

0,01

0,27

0,01

Acacia raddiana Combretum aculeatum

Acacia raddiana Acacia senegal

Balanites aegyptiaca

ligneux morts

14 2005

7,75

5,15

0,43

Acacia raddiana Leptadenia pyrotechnica

Balanites aegyptiaca

Seasonal and internnual changes in leaf mass, Acacia senegal, 1984-92

Acacia senegal, Agoufou (17)

0,05,0

10,015,020,025,030,035,040,0

27/0

6/19

84

27/1

2/19

84

27/0

6/19

85

27/1

2/19

85

27/0

6/19

86

27/1

2/19

86

27/0

6/19

87

27/1

2/19

87

27/0

6/19

88

27/1

2/19

88

27/0

6/19

89

27/1

2/19

89

27/0

6/19

90

27/1

2/19

90

27/0

6/19

91

27/1

2/19

91

27/0

6/19

92

masse de feuille (g)

Vegetation monitoring in 2005

Data set organisation: data entry, checking, standardisation, systematic statistical analysis

Upscaling: mapping vegetation, soil, water balance and landuse

2006 plans

Monitoring of herbaceous annuals

Frequency and type of measures will be adapted to season and site priority:• Five ranks in priority:

– Agoufou (17) – Other flux station sites (21, 40, A3)– Other super-site sites (18, 19, 20, 22, 31)– Other Gourma sites (1,2,4,5,6,8,9,10,12,14,16,25,28,30,32,37,38)– Other Bamba sites (A1, A2, B5, B6, B8, B13, R3, R5, R6, R7, R8, R9, R10, R11)

• Two seasons:– Wet season (from June to October): every 10d, 15d, month– Dry season (from November to May): every 2 months (11, 01, 03, 05)

• Nature of observation or measure: – Stratification, cover and mass– species composition (once at the end of the wet season except in 17 ?– Leaf area ?– Root mass ?– Germination-soil seed stock ?

Monitoring perennial grasses and woody plants

Frequency of observations and measures depends on the type of observation and the component:

• Population studies (CIRC or PCQ): – Woody plants: every 5 years thus next in 2010 – Perennial plants (sites 32 and twelve of the Bamba sites): every year ?

• Quantitative phenololy (standard branchlets; sampled tussocks):– Wet season (from June to October): every month– Dry season (from November to May): every two months (11/01/03/05)– List of species populations and sites to monitor for leaf/flower/frut pheno– List of species populations and sites to monitor LAI– List of species populations and sites to monitor root masses