1. Introduction

AgroParisTech - Formations GEEFT et BioGET 2015-2016

Some features of tree ecosystems in the dry tropics

Raphael Manlay

AgroParisTech GEEFT, Montpellier, France UMR Eco&Sol, Montpellier, France 14.12.2015 2

1. Introduction . Some terminology

Some features of tree ecosystems in the dry tropics - R. Manlay AgroParisTech - Formations GEEFT et BioGET 2015-2016

Bioclimatic approach

 Holdridge (1967, cited by House and Hall, 2001): extension area of tropical and subtropical dry forests and woodlands =  No freezing  Mean annual temperature > 17°C  Mean annual rainfall (MAR): 250-2000 mm  PET/MAR > 1

PET: potential evapotranspiration 4

Physiognomic approach of the Forest Resource Assessment (FAO, 2010)

 A forest  area> 0.5 ha  recovery of the canopy> 10%  Height of mature population> 5m  Other woodland = cover of the stratum  by trees able to reach 5 m high: 5-10% or  by all trees: > 10%

Some features of tree ecosystems in the dry tropics - R. Manlay AgroParisTech - Formations GEEFT et BioGET 2015-2016

Physiognomic approach

 A savanna (Frost et al. 1986, in House and Hall, 2001)  tropical ecosystem  with a more or less continuous grass cover  a variable and discontinuous shrub or tree cover  A tropical dry forest (Mooney et al., 1995, in Milne et al. 2006)  Strong rainfall seasonality  Several month-long annual drought 6

Physiognomic approach: a typology for Africa (Mayaux et al., 2004)

Structural category Grass cover Shrub Tree Canopy (%) cover cover height (%) (%) (m) Grasslands sparse 1-5 none none open 5-15 none none open with sparse shrubs 15-40 <20 none closed > 40 <20 none Deciduous woodlands and shrublands shrublands > 15 1-5 shrublands with sparse trees > 15 5-15 1-5 open woodlands 15-40 > 40 1-5 Closed deciduous woodland 15-40 > 40 > 5

Some features of tree ecosystems in the dry tropics - R. Manlay AgroParisTech - Formations GEEFT et BioGET 2015-2016

For more information:

 House J.I., D.O. Hall, 2001. Productivity of tropical savannas and grasslands. In: J. Roy, B. Saugier, H.A. Mooney (Eds.), Terrestrial Global Productivity, Academic Press, London, p. 363-400.  Bourliere F. (Ed.), 1983. Tropical Savannas, Ecosystems of the World, Vol. 13. Elsevier Scientific Publishing Co., Amsterdam, 730 p.  And many more ...

2. Global approach . Where are savannas and dry forests located in the world ?

Some features of tree ecosystems in the dry tropics - R. Manlay AgroParisTech - Formations GEEFT et BioGET 2015-2016

Potential range expansion

Distribution of biomes with trees under tropical dry climate : biogeographical zoning of Olson et al. (2001)

Tropical and subtropical moist broadleaf forests Tropical and subtropical dry broadleaf forests Tropical and subtropical savannas 10

Difference with potential Case of tropical dry forests: consideration of the state of vegetation cover by Miles et al. (2006) Olson et al., 2001 + MODIS 2000-2001

Olson et al. 2001

Some features of tree ecosystems in the dry tropics - R. Manlay AgroParisTech - Formations GEEFT et BioGET 2015-2016

Distribution of dry vegetation in sub-Saharan Africa

Legend

Grasslands with shrubs open closed

Deciduous woodlands and shrublands shrublands shrublands with sparse trees

open woodlands

Closed deciduous woodland (Miombo)

Croplands (> 50%)

Croplands with open vegetation

(Adapted from Mayaux et al., 2004) 12

Two + one regional case studies

Legend

Grasslands with shrubs open closed

Deciduous woodlands and shrublands shrublands shrublands with sparse trees open woodlands

Closed deciduous woodland (Miombo)

Croplands (> 50%)

Croplands with open vegetation

(Adapted from Mayaux et al., 2004) 13

Some features of tree ecosystems in the dry tropics - R. Manlay AgroParisTech - Formations GEEFT et BioGET 2015-2016

Example 1: regional determinism of vegetation in West Africa

0-200

200-400 400-600 600-800 800-1000 1000-1200 1200-1400

Open grassy savanna with low shrub Croplands (> 50%) Croplands with open vegetation Shrublands with/without sparse trees Open woodlands (Adapted from Isohyets for the period 1969-1998 Mayaux et al., 2004; (Average annual rainfall in mm) Ardoin-Bardin, 2004) 14

Seasonal oscillations of the Intertropical Convergence Zone (ITCZ)

June–August, Equinoxes November–February, sun over Tropic of Capricorn sun over Tropic of Cancer

 : winds converging at ITCZ

(Shorrocks, 2007) 16

Some features of tree ecosystems in the dry tropics - R. Manlay AgroParisTech - Formations GEEFT et BioGET 2015-2016

Sahel - Dahra, Ferlo, Senegal (credit: J-M Harmand) 15

Tiger bush - Burkina Faso 16

Some features of tree ecosystems in the dry tropics - R. Manlay AgroParisTech - Formations GEEFT et BioGET 2015-2016

Sudano-sahelian region - Mali, road to Sikasso 17

Sudanian zone – Mandingue Monts region, Mali 18

Some features of tree ecosystems in the dry tropics - R. Manlay AgroParisTech - Formations GEEFT et BioGET 2015-2016

Sudano-guinean zone - Lamto station, Ivory Coast (credit J. Gignoux, CNRS) 19

Example 2: local determinism of vegetation in Northern Madagascar

~ 15 km

(Mayaux et al., 2004)

Some features of tree ecosystems in the dry tropics - R. Manlay AgroParisTech - Formations GEEFT et BioGET 2015-2016

Forest diversity in northern Madagascar

10 km Montagne d’Ambre Ankarana

Montagne des Français

11.6 km 21

Local climatic determinism of vegetation in Northern Madagascar Sea trade wind

Ankarana NP Montagne d’Ambre NP

Montagne des Français

11.6 km 22

Some features of tree ecosystems in the dry tropics - R. Manlay AgroParisTech - Formations GEEFT et BioGET 2015-2016

What drives tree cover density?

Africa Australia

South America Pantropical (Hirota et

Tree cover (%) cover Tree al., 2011)

Annual rainfall (mm) 23

Example 3: local determinism of vegetation in the Rincon de la Vieja Volcano NP, Costa Rica

Some features of tree ecosystems in the dry tropics - R. Manlay AgroParisTech - Formations GEEFT et BioGET 2015-2016

Example 3: local determinism of vegetation in Costa Rica

Rincon de la Vieja NP, Costa Rica. The forest zone

Some features of tree ecosystems in the dry tropics - R. Manlay AgroParisTech - Formations GEEFT et BioGET 2015-2016

Rincon de la Vieja NP, Costa Rica. The savanna zone, onset of rainy season

Some features of tree ecosystems in the dry tropics - R. Manlay AgroParisTech - Formations GEEFT et BioGET 2015-2016

Example 3: local determinism of vegetation in Costa Rica

Sea trade wind

(Credit: OVSICORI - Geoffroy Avrad 2014)

Some features of tree ecosystems in the dry tropics - R. Manlay AgroParisTech - Formations GEEFT et BioGET 2015-2016

2. Ecosystem Approach . Some traits of highly stressed ecosystems

A spectacular soil constraint in Mali

Some features of tree ecosystems in the dry tropics - R. Manlay AgroParisTech - Formations GEEFT et BioGET 2015-2016

Another soil constraint in Burkina Faso

Which functional common features explain structural common features ?

Regrowth of perennial Gapped bush grass after fire in Lamto in Niger (photo X. Leroux) (Lefever et al, 2004)27

Some features of tree ecosystems in the dry tropics - R. Manlay AgroParisTech - Formations GEEFT et BioGET 2015-2016

Functional interactions

Tree

Grass

Environment

Role of the tree in the ecosystem

"The tree of life", Tsavo East National Park, Kenya (Photo Y. Arthus-Bertrand)29

Some features of tree ecosystems in the dry tropics - R. Manlay AgroParisTech - Formations GEEFT et BioGET 2015-2016

Impact of the environment on the tree

Tree

Grass

Environment

Spatial structuration of vegetation by the physical environment  Example 1: Ankarana massif, Madagascar

Aerial view, February 2009. Source CNES / Spot Images/ Google Earth

3600 m 31

Some features of tree ecosystems in the dry tropics - R. Manlay AgroParisTech - Formations GEEFT et BioGET 2015-2016

Example 1: Ankarana Massif, Madagascar

Aerial view, February 2010. Source CNES / Spot Images / Google Earth

786 m 32

Ankarana massif, Madagascar. Ground view.

Facies 

Facies 

Facies 

Some features of tree ecosystems in the dry tropics - R. Manlay AgroParisTech - Formations GEEFT et BioGET 2015-2016

Facies : Calcimorphic soil on karst (Tsingy)

Facies : Lateritic soil on basalt

The tiger bush: oblique view in Niger

Slope

100 m

Credit: Valentin, in Lefever et al, 2004 36

Some features of tree ecosystems in the dry tropics - R. Manlay AgroParisTech - Formations GEEFT et BioGET 2015-2016

 Tiger bush near Batama-Beri, Niger

Credit: Vincent Deblauwe

Tiger bush - Burkina Faso 38

Some features of tree ecosystems in the dry tropics - R. Manlay AgroParisTech - Formations GEEFT et BioGET 2015-2016

Herbaceous and Thicket of Senescent shrub mature trees vegetation vegetation

(William et al. 2001) 39

Isotopic C13/ C14 signature of soil organic matter of a tiger bush

Herbaceous (Guillaume et al., 2001) and shrub vegetation Bare soil Signature of of Signature C4 plants

Soil depth

Senescent Thicket of vegetation mature trees Signature of of Signature C3 plants 40

Some features of tree ecosystems in the dry tropics - R. Manlay AgroParisTech - Formations GEEFT et BioGET 2015-2016

When the slope disappears, the tiger bush becomes ...

… gapped bush (ex: Niger, in Barbier et al, 2006)

Impact of environment on the tree: water

Deciduous forest near Chamela, Mexico. Dry season (Bullock et al., 1995) 43

Some features of tree ecosystems in the dry tropics - R. Manlay AgroParisTech - Formations GEEFT et BioGET 2015-2016

Impact of environment on the tree: water

Deciduous forest near Chamela, Jalisco, Mexico (Bullock et al., 1995)

Dry season Rainy season

Deciduousness in the Santa Josa national park, Costa Rica

Source: The Dry Forest Laboratory & youtube.com 56

Some features of tree ecosystems in the dry tropics - R. Manlay AgroParisTech - Formations GEEFT et BioGET 2015-2016

Responses of tree water stress

 Evergreen to deciduous vegetation  Drivers of the balance between the two phenological types  Regional: site aridity * deciduousness: correlation +  Local: site fertility * evergreenness: correlation +

Phenological diversity in the dry forest: Ankarana massif in the late dry season, Madagascar

Responses of tree water stress

 Xerophytic traits to  limit water loss  store water  improve water intake succulence, microphyllie, coriaceous leaves

Caudex ofAdenia epigea H. Perrier, Ankarana, Madagascar. 46

Some features of tree ecosystems in the dry tropics - R. Manlay AgroParisTech - Formations GEEFT et BioGET 2015-2016

Responses of tree water stress

 Xerophytic traits to  limit water loss  store water  improve water intake succulence, microphyllie, coriaceous leaves

Caudex of Phylostemma sp., Montagne des Français, Madagascar 47

Responses of tree water stress

 Xerophytic traits to  limit water loss  store water  improve water intake succulence, microphyllie, coriaceous leaves

Euphorbia sp. (corraliforme), Montagne des Français, Madagascar. 48

Some features of tree ecosystems in the dry tropics - R. Manlay AgroParisTech - Formations GEEFT et BioGET 2015-2016

Tree response to water stress

 Determinants of leaf senescence:  global (air humidity, photoperiod)  local (state of the overstory)

Jacquinia pungens A. Gray : A remarkable inverse phenology. Costa Rica, Barra Honda National Park, dry season 2011. 49

Faidherbia albida (Del.) A. Chev: another remarkable inverse phenology. Ouahigouya district, Burkina Faso, dry season 2006. 62

Some features of tree ecosystems in the dry tropics - R. Manlay AgroParisTech - Formations GEEFT et BioGET 2015-2016

Response of tree water stress

 carbon allocation to the rooting system  Static: high (sometimes> 1) root:shoot (R:S) ratio , shallow systems  Dynamic: one of highest shares of net primary production allocated to roots in the world

Young stump ofTerminalia macroptera 0 Guill and Perr., High Casamance, Senegal

0.5

Depth (m) 1 50

15 years-old stump of Combretum glutinosum Perr. ex DC., High Casamance, Senegal 51

Some features of tree ecosystems in the dry tropics - R. Manlay AgroParisTech - Formations GEEFT et BioGET 2015-2016

Response of tree water stress  carbon allocation to the rooting system Illustration of a mapping system: Parkia biglobosa (Jacq.) G.Don in Burkina Faso (Tomlinson et al. 1998)

The mineral constraint

 The constraint  Low stock and/or availability of nutrients  Limiting factor varies depending on rainfall: N in dry tropics, P in humid tropics  The facts  High efficiency of the use of mineral elements. Example: phosphorus in the forest litter  Conservation mechanisms  translocation of nutrients before senescence  developing lateral rooting systems  other mechanisms based on the herbaceous layer: see the Grass section

Some features of tree ecosystems in the dry tropics - R. Manlay AgroParisTech - Formations GEEFT et BioGET 2015-2016

The mineral constraint

 Conservation mechanisms  controlled cycling of carbon and nutrients in the dry season. Ex: loss of root biomass in Senegal (subhumid climate)

rainy season

Soil fauna effect

(Manlay et al, 2004) 54

Branch fragmentation by termites Ouahigouya, Burkina Faso 55

Some features of tree ecosystems in the dry tropics - R. Manlay AgroParisTech - Formations GEEFT et BioGET 2015-2016

Impact of the environment on the tree: reproduction

 Vegetative reproduction: dry zone> wetland

 Modes: stump resprouting, suckering, layering

Stump Seedling Sexual and resprouting vegetative propagation of a Combretacea at Lamto, Côte d’Ivoire

Adult

(Abbadie et al, 2006) Young adult Mature adult 56

Stump resprouting in Ouahigouya, Burkina Faso 57

Some features of tree ecosystems in the dry tropics - R. Manlay AgroParisTech - Formations GEEFT et BioGET 2015-2016

Suckering of Combretum glutinosum Perr. ex DC (Dieng, 2006) 58

Suckering of Faidherbia albida (Del.) A.Chev. (Dieng, 2006) 59

Some features of tree ecosystems in the dry tropics - R. Manlay AgroParisTech - Formations GEEFT et BioGET 2015-2016

Impact of environment on tree: reproduction

 Consequences of importance of vegetative reproduction:  Resilience  Structuring in patches  vulnerability

 Flowering and fruiting often (but not always) before foliation

Impact of fire on stand

Number of individuals ha-1

Savanna  Variable depending on species  climates  tree age (role of height and bark thickness)  the trigger period  Ex: effect of fire suppression at Lamto, Côte d’Ivoire (Bourliere, 1983)

Forest on the density of species individuals

Duration of protection (years) 61

Some features of tree ecosystems in the dry tropics - R. Manlay AgroParisTech - Formations GEEFT et BioGET 2015-2016

Impact of fire on stand

 Ex: effect of fire suppression at Lamto, Ivory Coast (Bourliere, 1983) on species diversity

No. of species ha-1

Forest species

Savanna species

Duration of Protection (years) 62

Impact of the tree on the environment

Tree

Grass

Environment

Some features of tree ecosystems in the dry tropics - R. Manlay AgroParisTech - Formations GEEFT et BioGET 2015-2016

Impact of the tree on the environment

 Tree impact on soil C and nutrients depends on tree species and functional traits C (mg g-1 soil) Prosopis juliflora Zizyphus Joazeiro Spondias tuberosa Swartz D. C. Mart Arruda Cam.

 Effect of tree crown of three N (mg g-1 soil) woody species on the soil (0-15 cm) CNP contents, -1 Pt (Mg g soil) Brazil, semi-arid climate (Tiessen et al. 2003)

Impact of the tree on the environment: soil

 Positive interpretation of evolutions  Water conservation  Conservation of C and nutrients ... but to the extent of what?

Some features of tree ecosystems in the dry tropics - R. Manlay AgroParisTech - Formations GEEFT et BioGET 2015-2016

Impact of the tree on other trees

Tree

Grass

Environment

Impact of the tree on other trees

 Two distinct areas of influence  under the canopy: effects on soil + protection from heat and herbs> competition for light  canopy off: competition for water and nutrients  The tension between these two zones set up a heterogeneous structure without human intervention (Lefever et al., 2004)

Field potential for C. micranthum G. Don. (Lefever et al., 2004)

Some features of tree ecosystems in the dry tropics - R. Manlay AgroParisTech - Formations GEEFT et BioGET 2015-2016

Impact of the tree on other trees

 At least two explanations for the results of Hirota et al. (2011)  The influence of a tree on its neighbours depends on rainfall:  rainfall =  exclusion zone  extreme events control tree mortality in dry areas

Africa Australia

South America Pantropical Woody cover (%) cover Woody

Annual rainfall (mm) 68

Impact of the tree on the grass

Tree

Grass

Environment

Some features of tree ecosystems in the dry tropics - R. Manlay AgroParisTech - Formations GEEFT et BioGET 2015-2016

Impact of the tree on the grass

Exclusion of the herbaceous layer by thickets in a savanna in Mali

Impact of the tree on the grass

The impact of the tree on the herbaceous biomass is positive in arid conditions.  Case of Northern Senegal Herbaceous biomass (gDM m-2) Below crown

Outside crown rainy season

Date (d/m) (Grouzis and Akpo, 1997)

Some features of tree ecosystems in the dry tropics - R. Manlay AgroParisTech - Formations GEEFT et BioGET 2015-2016

Impact of the tree on the grass Tree impact on herbaceous production depends on rainfall: a north-south transect in West Africa (NPP: net primary productivity)

Ratio Below-crown grass NPP Outside-crown grass NPP (%) Effect + Effect -

Annual rainfall (mm)

(Abbadie et al, 2006) 72

Impact of the tree on the grass

The impact of the tree on the productivity herbaceous depends on the soil and grazing pressure

a. Fertile site or b. Weakly fertile site or limited herbivory strong herbivory

Herbaceous Herbaceous cover cover

Tree cover Tree cover 73

Some features of tree ecosystems in the dry tropics - R. Manlay AgroParisTech - Formations GEEFT et BioGET 2015-2016

Role of grass in the ecosystem

Tree

Grass

Environment

Role of grass in the ecosystem

Regrowth in perennial grass tuft after fire at Lamto (Photo Xavier Leroux)75

Some features of tree ecosystems in the dry tropics - R. Manlay AgroParisTech - Formations GEEFT et BioGET 2015-2016

Control of grass by the environment

Tree

Grass

Environment

Control of  Perennial or the grass layer annual? by water and fire  Dry climate: annual species  Subhumid zone: perennial species  But the link to disturbances is not so simple  Adaptation to fire: seedling or resprouting depending on biological type

 Coexistence of annual and perennial grasses in the Sudanian zone - Manding Monts, Mali 77

Some features of tree ecosystems in the dry tropics - R. Manlay AgroParisTech - Formations GEEFT et BioGET 2015-2016

Impact of environment on grass: soil

Structure of tufted perennial grasses after fire in Lamto (Credit: Xavier Leroux) 78

Impact of environment on the grass: soil

 Soil features: secrets of the paradox of an African savanna – Specificities of the nitrogen cycle in the savanna: closure, blockage of nitrification (Abbadie et al., 2000)

biological N2 N2O fixation Living plants Dead humification and plants μorganisms R-NH2 R-NH2 ammoni fication Humus + NH4 R-NH2 assimilation nitrifica tion denitri- NO - cation Soil 3

leaching  Conclusion: the key role of the rooting system for ecosystem integrity (Pieri, 1992) 79

Some features of tree ecosystems in the dry tropics - R. Manlay AgroParisTech - Formations GEEFT et BioGET 2015-2016

Control of the environment and the tree by the grass

Tree

Grass

Environment

Control by the herbaceous layer

 Soil  Limited control but...  Tree  Competition – At settlement – After fire occurence

Some features of tree ecosystems in the dry tropics - R. Manlay AgroParisTech - Formations GEEFT et BioGET 2015-2016

The tree-grass relationship A variety of arrangements

Loudetia savanna, Andropogonacea savanna, Lamto, Côte d'Ivoire Lamto, Côte d'Ivoire (Credit X Leroux) (Credit X Leroux) 82

The tree-grass relationship Tree Dead Grass A variety of arrangements tree

Facilitation Competition Competition Forest Topographical Edaphic transgression anisotropy anisotropy and facilitation

Some features of tree ecosystems in the dry tropics - R. Manlay AgroParisTech - Formations GEEFT et BioGET 2015-2016

The tree-grass relationship

 A complex relationship  dynamics on short to long terms  natural and anthropic factors asymmetric competition between grass and tree leading to structural instability.  Long-term control of the balance  Global climate change  edaphic factors: expressed under both wet and dry climates  anthropogenic factors: the habit of fire  Short-term control of the balance  grazing  the extension of agriculture  fire: different coexistence modes depending on the climate (exclusion vs. coexistence)

The tree-grass relationship

 Conclusion: stable vs. unstable savanna

Tree cover (%) Weak (mm) seasonality rainfall Rainfall Rainfall Annual Strong Low High 7 months Fire frequency dry season Mayer & Khalyani, 2011 85

Some features of tree ecosystems in the dry tropics - R. Manlay AgroParisTech - Formations GEEFT et BioGET 2015-2016

Ecosystem productivity

Measuring productivity: how difficult?

 Dry forest, Niokolo-Koba national park (NP), Senegal

1984 1994 (Tappan et al., 2004) 87

Some features of tree ecosystems in the dry tropics - R. Manlay AgroParisTech - Formations GEEFT et BioGET 2015-2016

Scientific follow-up of CIRAD - Mali, road to Sikasso 88

Net primary productivity (simulated): average and heterogeneous

gC m-2 year-1

(Cramer et al., 1999) 89

Some features of tree ecosystems in the dry tropics - R. Manlay AgroParisTech - Formations GEEFT et BioGET 2015-2016

A low net (measured) primary productivity, but ...  savannas: 3.8 t DM* ha-1 year-1 (House and Hall, 2001)  Dry forests: 8-21 t DM* ha-1 year-1 (Murphy and Lugo, 1986)

Aboveground NPP Belowground NPP (t DM ha-1 year-1) (t DM ha-1 year-1)

* DM: dry matter (Saugier et al., 2001) 90

4. Human ecology of tropical dry forests and savannas

Some features of tree ecosystems in the dry tropics - R. Manlay AgroParisTech - Formations GEEFT et BioGET 2015-2016

A traditional area of settlement: the case of Central America

Population density per bioclimatic zone in Central America in the 60s (Murphy and Lugo, 1986) 92

A traditional area of settlement: the case of West Africa

≥ 300

0 500 1000 km 0 Population density (inhab km-2) in West Africa in 2005 (UNEP, 2008)

Some features of tree ecosystems in the dry tropics - R. Manlay AgroParisTech - Formations GEEFT et BioGET 2015-2016

Why live in the savannas and dry forests ...

 favourable conditions for the birth of agriculture  pastoral value  timber value  environmental value

Anthropisation of the environment in Northern Madagascar

Agriculture and livestock around Ankarana NP 95

Some features of tree ecosystems in the dry tropics - R. Manlay AgroParisTech - Formations GEEFT et BioGET 2015-2016

Anthropisation of the environment in Northern Madagascar

Coal production and forest degradation around Ankarana NP 96

Anthropisation of the environment in Northern Madagascar

Towards new tree landscapes ... 97

Some features of tree ecosystems in the dry tropics - R. Manlay AgroParisTech - Formations GEEFT et BioGET 2015-2016

Importance of ecosystem mimicking for the development of sustainable land use systems: two examples

111

A remarkable forest in Burkina Faso ...

100

Some features of tree ecosystems in the dry tropics - R. Manlay AgroParisTech - Formations GEEFT et BioGET 2015-2016

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101

Some features of tree ecosystems in the dry tropics - R. Manlay AgroParisTech - Formations GEEFT et BioGET 2015-2016

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103

Some features of tree ecosystems in the dry tropics - R. Manlay AgroParisTech - Formations GEEFT et BioGET 2015-2016

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An example of successful reconstitution of a forest ecosystem: forest zaï in Ouahigouya, Burkina Faso 105

Some features of tree ecosystems in the dry tropics - R. Manlay AgroParisTech - Formations GEEFT et BioGET 2015-2016

Zaï forest (right) created on a zipélé (left) by Yacouba Sawadogo in Ouahigouya, Burkina Faso 106

Slow restoration in Northern Madagascar ...

Regeneration of baobab (Adansonia suarezensis H. Perrier) at the Parc des Mille Baobabs (Montagne des Français, Antsiranana)

8-year old planted specimen Spontaneous adult specimen

107

Some features of tree ecosystems in the dry tropics - R. Manlay AgroParisTech - Formations GEEFT et BioGET 2015-2016

… (not) as an alternative to Eucalyptus?

Industrial Eucalyptus sp. coppice for charcoal production (south of Antsiranana)

108

5. Conclusions

Some features of tree ecosystems in the dry tropics - R. Manlay AgroParisTech - Formations GEEFT et BioGET 2015-2016

Resource economy: the main feature of dryland ecosystems?

 Water conservation  Nutrient economy  Carbon economy  Importance of soil biology

The future of tropical dry ecosystems

 Tropical dry ecosystems are threatened today...

(Miles et al., 2006)

... but still poorly understood 109

Some features of tree ecosystems in the dry tropics - R. Manlay AgroParisTech - Formations GEEFT et BioGET 2015-2016

Expansion of drylands in a warmer world…

corrected CMIP5-EM from RCP8.5 projections

corrected CMIP5-EM from RCP4.5 projections CPC observations CMIP5-EM from RCP8.5 projections CMIP5-EM from RCP4.5 projections

(Huang & al., 2015) 125

How will climate change impact those ecosystems?

 [atm CO2]  =  trees cover?

Simulated tree cover a: 2000 as a function of mean [CO2] level annual precipitation (MAP) • Red and black dots/curbs: simulation with two kind of b: 2100 initialization [CO2] level • Blue dots: observed data (IPCC SRES from Sankaran et al. (2005) A2B scenario)

(Moncrieff et al., 2014) 126

Some features of tree ecosystems in the dry tropics - R. Manlay AgroParisTech - Formations GEEFT et BioGET 2015-2016

Web resources

 Dry Forests (reasearch at CIFOR)  Global dry forests (Special Issue of International Forestry Review)  Tropi-Dry (collaborative research network)

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References

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