Development and Use of vegetation maps to infer Environment No. 6 • 2007 on the ecological suitability of species using central and western Kenya as an example Part I: Description of potential natural vegetation types for central and western Kenya Roeland Kindt, Paulo van Breugel and Jens-Peter Barnekow Lillesø 1 2 Use of vegetation maps to infer on the ecological suitability of species using central and western Kenya as an example Part 1: Description of potential natural vegetation types for central and western Kenya Roeland Kindt, Paulo van Breugel and Jens-Peter B Lillesø Titel Use of vegetation maps to infer on the ecological suitability of species using central and western Kenya as an example Part 1: Description of potential natural vegetation types for central and western Kenya Authors Roeland Kindt1, Paulo van Breugel1 and Jens-Peter Barnekow Lillesø2 Collaborating Partners World Agroforestry Center1, Nairobi, Kenya Publisher Forest & Landscape Denmark University of Copenhagen2 Hørsholm Kongevej 11 DK-2970 Hørsholm Press Prinfo DK-9100 Aalborg Series - title and no. Development and Environment No. 6-2007 ISBN ISBN 978-87-7903-306-1 (Print) ISBN 978-87-7903-307-8 (Internet) Number printed 500 DTP Melita Jørgensen Front page image The digitized vegetation map of Southwest Kenya superimposed on the Kenya map (thick lines). The vague lines show the outlines of the vegetation types of White's (1983) vegetation map of Africa. Citation Kindt R, van Breugel P, Lillesø JPB. 2007. Use of vegetation maps to infer on the ecological suitability of species using central and western Kenya as an example. Part 1: Description of potential natural vegeta- tion types for central and western Kenya. Development and Environ- ment No. 6-2007. Forest & Landscape Denmark and World Agrofor- estry Centre, Kenya. Citation allowed with clear source indication Written permission is required if you wish to use Forest & Landscape Denmark's name and/or any part of this report for sales and advertis- ing purposes. The report is available electronically from www.SL.life.ku.dk or may be requested from [email protected] Acknowledgements We thank Meshack Nyabenge for hs help n checkng and correctng the dgtsed maps. We very much apprecate the encouragement gven by Tony Smons, Prncpal Tree Scentst at ICRAF and Lars Graudal, Head of De- partment for genetc resources of woody plants, at Forest and Landscape, Denmark. We are grateful to VVOB and DANIDA for supportng the se- condment of Roeland Kndt and Jens-Peter Barnekow Lllesø to the World Agroforestry Centre (ICRAF). Acronyms ALP Alpne BAM Bamboo woodland and thcket CEC Caton Exchange Capacty DCO Dry Combretum savanna DEM Dgtal Elevaton Model DIF Dry Intermedate forest DM Number of Dry Months DMF Dry Montane forest EB Evergreen and sem-evergreen bushland IAC Acacia and alled vegetaton on sols wth mpeded dranage LAC Lowland Acacia-Commiphora woodland, bushland and thcket MCO Most Combretum-Terminalia savanna MIF Most Intermedate forest MIX Broad-leaved savanna-evergreen bushland mxtures MMF Most Montane forest MSM Mountan scrubland and moorland OGR Open grassland areas on clay plans P Annual Precptaton PET Annual Potental Evapotranspraton PNV Potental Natural Vegetaton RD Rootable depth SET Sem-evergreen thcket SWA Papyrus and swamp Tmn Mean mnmum Temperature of the coldest month TWI Topographc Wetness Index UAC Upland Acacia woodland, savanna and bushland Contents Acknowledgements i Acronyms i Contents iii 1. ������������Introduction 1 2. Methods 3 2.1 Determination of potential natural vegetation types 3 2.2 Description of potential natural vegetation types with information from literature 6 3. Results 9 3.1 Description of potential natural vegetation types from literature information 9 3.2 Description of potential natural vegetation types with information from spatial datasets 16 4. Discussion 28 4.1 Characterization of potential natural vegetation types 28 4.2 The use of vegetation maps 31 4.3 Limitations of vegetation maps 33 5. Conclusion/Recommendations 34 6. R���������eferences 36 7. ����������Appendices 41 Appendix I. Correspondence between potential natural vegetation types and original vegetation types (groups, subgroups and classes) 41 Appendix II. Correspondence between vegetation classes and subclasses of the original map. The code for the vegetation class corresponds to Appendix I. 45 Appendix III. Small-scale distribution maps for the 17 potential natural vegetation maps 49 v 1. Introduction Vegetation maps show classifications of plant communities based on differ- ences in floristics (composition and relative abundances of species), physio- gnomc structure (such as growth form, heght, ground cover, type of leaves) and seasonal actvty patterns (van der Maarel 2005, Box and Fujwara 2005). Potential natural vegetation (PNV) has been defined as the vegetation struc- ture that would become establshed f all successonal sequences were com- pleted wthout nterference by man under the present clmatc and edaphc (sol) condtons, ncludng those created by man (Tüxen 956, Mueller-Dom- bois and Ellenberg 1974, Box and Fujiwara 2005). This definition makes it clear that PNV s not necessarly the orgnal vegetaton as the ste condtons may have changed after the orgnal vegetaton was removed. Maps of the PNV of large regons have been produced, ncludng global maps and maps for Afrca, tropcal Asa, South Amerca and the manland USA (Box and Fujwara 2005). These maps have been used n land use plan- nng (e.g., Froude 999, Wells et al. 2004, Global Forest Watch 2006), for the desgn of conservaton strateges (e.g., Olson et al. 200), for studes of spe- ces dstrbuton (e.g. Pearce et al. 200, Pearce and Ferrer 200, Peterson et al. 200, Frankln 2002, Kndt et al. 2007) and for the determnaton of seed, provenance, tree plantng, or genecologcal zones (Graudal et al., 997; Lllesø et al, 200). PNV maps are a promsng tool for brngng ndgenous tree speces nto use wthn anthropogenc landscapes, but such maps have unfor- tunately been gnored largely by the agroforestry world. The purpose of our studes of PNV of eastern Afrca s therefore to document how the utlty of PNV maps can be ncreased. As a documentaton of the approach, we used a detaled PNV map that was developed for the hghlands of Kenya and the adjacent areas. Trapnell and hs co-workers (Trapnell et al. 966, 969, 976, 986; Trapnell and Brunt 987) produced four sheets of a vegetaton map for south-west- ern Kenya on a scale of :250 000 that mapped vegetaton as t was n 960 (hereafter called the ‘orgnal map’). We beleve that the orgnal map s stll useful today as, despite the fact that the main aerial and field surveys were completed n the early 960s, the map allowed to determne the PNV of the mapped area. Gven that the dstrbuton of speces can be lnked wth the dstrbuton of PNV, the new PNV map that we developed can assst n selectng speces for partcular locatons wthn the map. Such selectons can be linked conceptually to the ecological definition of agroforestry in ‘mim- ckng natural ecosystems’, whch we nterpret here to the detal of estab- lshng smlar tree speces assemblages as those that were occurrng under natural condtons. Although Trapnell and hs co-authors were aware of possble lmtatons of ther approach as they acknowledged that vegetaton s changng, they dd see the purpose of ther maps as a tool for landuse plannng: »The use of ecologcal zones for agrcultural development plannng rested on the concept that clmax vegetaton communtes develop n response to local lmtatons of clmate and sol. In the absence of detaled sol survey and a complete network of clmatc statons, mappng clmax vegetaton s therefore an ndrect means of establshng the lmts of dfferent eco-cl- matic zones, each suitable for a specific range of crops« (Trapnell and Brunt 987, p. ). »Vegetation (…) is constantly changing under the several influences of fire, grazng, cultvaton and tmber extracton. Ths apples partcularly to the clmax forest areas (…). Ths fact, however, n no way nvaldates the con- cept of using vegetation as an index of land potential« (Trapnell and Brunt 987, p. 4). Although Trapnell and hs co-workers produced a detaled map, the docu- mentaton of the used methodology (.e., Trapnell and Brunt 987) n df- ferentatng between dfferent vegetaton types lacks detal, especally snce they dd not provde the exact crtera that were used to dfferentate be- tween the varous types. As we are convnced that the detal of the orgnal vegetation maps was justified given the amount of survey work and the -in formaton provded wthn the lmted documentaton, the man attempt of ths document s to provde a more comprehensve descrpton of the PNV types for whch the maps show detaled patterns of dstrbuton. We used two man sources for these addtonal descrptons for PNV types: () nformaton avalable from lterature on vegetaton types that cover the area of the orgnal map; and () nformaton avalable from spatal datasets that cover the area of the orgnal map. The correspondence between PNV types provded n the new map and those descrbed n other lterature sources also enabled us to expand vegeta- tion-specific species lists (Kindtet al. 2007). Even f nformaton from spa- tal datasets do not provde clear thresholds between dfferent PNV types, the map could smply be used as a summary of the man clmatc and sol condtons wthn the mapped boundares gven the objectves of maps to provde abstractons of spatal patterns. 2 2. Methods 2.1 Determination of potential natural vegetation types It s unfortunate that the orgnal vegetaton maps and ther documenta- ton provde lttle nformaton on the crtera that were used to dstngush between the dfferent vegetaton types. Although the boundares between the vegetaton types are provded on the map on a scale of :250 000, no nformaton was provded on the actual crtera that were used to dstngush between the types on aerial photographs and during fieldwork.