Potential natural vegetation maps for western and central Kenya Presently underutilized tools for the selection of indigenous tree species and their seed sources Roeland Kindt (ICRAF / VVOB [Flanders, Belgium]) Jens-Peter B Lillesø (ICRAF / FaL [Denmark]) Paulo van Breugel (ecologist, formerly IPGRI)
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Potential natural vegetation mapsfor western and central Kenya
Presently underutilized tools for the selection of indigenous tree species and
their seed sources
Roeland Kindt (ICRAF / VVOB [Flanders, Belgium])Jens-Peter B Lillesø (ICRAF / FaL [Denmark])Paulo van Breugel (ecologist, formerly IPGRI)
Overview• Which species to plant in a certain area for a
certain purpose: use of potential natural vegetation maps to indicate ecological suitability and databases/books to select potential functions– How were the maps and species lists developed?– Do potential natural vegetation maps provide an
adequate picture of climatic/edaphic variation in Kenyan highlands?
– Do potential natural vegetation maps delineate assemblages of indigenous tree species?
– What are the options for agroecosystem diversification?
Map of potential natural vegetation of south-western Kenya
• High resolution maps available for south-western Kenya (Trapnell and co-workers)– Four 1: 250,000 maps with vegetation boundaries for 1960
based on aerial photographs (1:30,000 and 1:50,000) and dense traverses (< 1 mile apart where accessible roads)
– Photographs mainly 1945-63 and fieldwork mainly 1945-1963– Vegetation classified in 18 groups, 23 subgroups, 55 classes
and 217 subclasses– Interpretation of climax vegetation types and eco-climatic
conditions through remnants of climax types and pioneer (secondary) vegetation types
– Unfortunately limited documentation of criteria for vegetation types
– Publication of maps took long time (1966-1986)– Maps have not been used in the realm of agroforestry
1966
1969
1976
1986
17 potential natural vegetation types
• Potential natural vegetation = the vegetation structure that would become established if all successional processes were completed under the present or future climatic and edaphic conditions
• Determined from names of original vegetation types and eco-climatic maps• Main classification scheme is physiognomic (based on structure such as
percentage aerial cover and height) (similar in other schemes)• Secondary classification scheme is floristic (based on dominant or typical
species)• Other differences between types are interpretation of climatic conditions, but
not determined from rainfall or altitude criteria (eg dry montane forest)
• Four sheets produced (1:300,000; A3 format)• Excel sheet with uses and vegetation types compiled for 362 tree species
that are indigenous to Kenya (types from legend map, other paper by Trapnell on forests, other literature, herbarium vouchers; uses from AgroforesTree Database + Useful trees book by RELMA)
• Herbarium locations obtained for 110 species (but > 20 for only 2 species)• Detailed documentation of map interpretation and vegetation-specific lists
almost finalized (want to avoid problem with original map!)
Physiognomic vegetation typesForest
touching and interlocking crowns≥ 8 (10) m talllianas
Woodland≥ (40) 50% cover, open≥ 8 m tall
Wooded grassland (savanna)10 – (40) 50% cover≥ 6 m tall
Bushland and thicket (impenetrable)≥ (40) 50% cover3 - 7 m tall
Bushed grassland10 – (40) 50% cover< 6 m tall
Special types: swamp, bamboo, afro-alpine, moorland
Upland Acacia woodland, savanna and bushland Lowland Acacia woodland, bushland and thicket
Lowland Acacia woodland, bushland and thicket
Evergreen and semi-evergreen bushland
Bushland and thicket vegetation types (3)
Semi-evergreen thickets
Evergreen and semi-evergreen bushlandSemi-evergreen thickets
Lowland Acacia woodland, bushland and thicket
Acacia and allied vegetation on soils with impeded drainage
Swamp and Papyrus
Vegetation types on soils with impeded drainage (3)
Open grassland areas on soils with impeded drainage
Open grassland areas on soils with impeded drainage
Swamp and Papyrus
Acacia and allied vegetation on soils with impeded drainage
Distribution of vegetation types, climate and species
• Both vegetation and species distribution can be explained by the same explanatory variables (biotic, abiotic, landscape configuration, evolutionary time)
• Literature on vegetation types lists typical species for each type
• Flora, databases, books and herbarium records list vegetation types (habitat) for each species
• Present and historical climatic conditions can be determined from pollen composition
• Vegetation map of Africa (White) turned out to be map of plant endemism (phytochoria) and was later used as biogeographical map for African terrestrial ecoregions
• Sophisticated statistical models perform better when vegetation (landuse) is one of the explanatory variables
Biome 4 model (Kaplan et al. 2003)Equilibrium distribution of 28 major potential natural vegetation types (biomes) from latitude (photosynthetically active solar radiation), atmospheric CO2 concentration, mean monthly climate (mean monthly precipitation, temperature, and percent sunshine) and soil physical properties (water holding capacity and percolation rate)
Check of relevance of maps
• Vegetation boundaries vs. patterns in climatic/soil differences
• Vegetation boundaries and original species composition vs. current species composition
Interpolated surface layers
Data layer Resolution
Annual precipitation 5 km (grid)
Annual potential evapotranspiration 5 km (grid)
Mean minimum temperature of the coldest month
5 km (grid)
Number of dry months 5 km (grid)
Rootable depth 1:1 000 000 (vector)
Cation exchange capacity 1:1 000 000 (vector)
Soil water pH 1:1 000 000 (vector)
Percentage of clay 1:1 000 000 (vector)
Percentage of sand 1:1 000 000 (vector)
Altitude (DEM) 92 m (grid)
Slope 92 m (grid)
Topographic wetness index 92 m (grid)
• Investigation how well potential vegetation types correspond to climate, soil and DEM information
1000 2000 3000 4000
600
800
1000
1200
1400
1600
1800
Altitude
Pre
cipi
tatio
n
ALP
BAM
DCO
DIF
DMFEB
IAC
LAC
MCOMIF
MIX
MMFMSM
OGRSET
SWA
UAC
Interpolated surface layersAfro-alpine
Montane scrublandand moorland
Bamboo
Crosses indicate 10%-25%-75%-90% quantilesand are centred on mean
Limitations of vegetation maps to map species distribution
• Changes in climatic or soil conditions from those associated with the map– Need for successional processes (pioneer, climax)– Ecosystem restoration: first abiotic, then biotic filters? – Changes in ecological/dispersal/habitat pools? (landuse, climate
change, invasive species)• Mapped vegetation types are often mosaics with some
small vegetation types that differ from the main type• Vegetation types have ecotones where each species
reaches another environmental limit (fuzzy boundaries between vegetation types), whereas maps show hard boundaries (indicate ecotone width by LDA?)
• Species consist of different populations (provenances) that differ in adaptation to local conditions (precautionary principle!)
Seed sources of Calliandra calothyrsus identified during seed source survey (2004)
21
4
11
4126
3530
23
19
2018
6
12
33
15
31
3628
22897 29
24
34
2
5
13
32
4325
27
381716
55
54
5049
4445
4846
47
5352
51
57
56
1
3
424014
39937
Poor seed sources
Good seed sources
Correspondence to other vegetation classification schemes
11a
11a
44
42
4242
42
45
19a19a
45
45
19a
65
45
54
White. 1983.1:5,000,000
Good correspondence for high mountain vegetation(65), montane forest (19a), evergreen and semi-evergreen bushland (45),moist Combretum savanna (11a), lowlandAcacia bushland (42) and semi-evergreenthickets (45)
Correspondence to other vegetation classification schemes
AT1005
AT0108AT0108
AT0108
AT0108
AT0721
AT0711
AT0711
AT0711
AT0716
AT1313
Olson et al. 2001.
1:5,000,000From White
11a
11a
44
42
4242
42
45
19a19a
45
45
19a
65
45
54
What happened with evergreen and semi-evergreen bushland, semi-evergreenthickets and in the western part of the map?
Boundary between lowland Acacia types?
Conclusions• Bad news: good models and detailed maps for species
distribution or suitability require good presence-only or presence-absence data, and detailed input maps for large range of explanatory variables, whereas neither are commonly available for most components of biodiversity (including tree populations!)
• Good news: potential natural vegetation maps can provide a reasonable summary of climate and the potential distribution of indigenous tree species, they are available for most places on earth and information is available on their species assemblages
• Best news: we already compiled information for a couple of hundred species for a detailed map for central and western Kenya + confirmed some of climatic/floristic information + have information for their uses for many
• Way forward: combine existing potential natural vegetation maps with more extensive set of presence-data and GIS layers to build better species suitability maps
A (some) word of thanks
• Meshack• Sammy, Jonathan, Sally-Anne, Walter• Trees and markets (Tony)• Our donors• Everybody in the audience today
Topics for discussion?• How confident should users
be when using the maps or we when we advise?
• Further testing of maps• Expansion of maps to
White/WWF ecoregions, Eastern Africa, …
• Sharing of information (printed maps, website, documentation)