Plant Ecology

, Volume 216, Issue 10, pp 1441–1456 | Cite as

Patterns of CO2 exchange and productivity of the herbaceous vegetation and trees in a humid savanna in western Kenya

  • Dennis OtienoEmail author
  • Joseph Ondier
  • Sebastian Arnhold
  • Daniel Okach
  • Marianne Ruidisch
  • Bora Lee
  • Andreas Kolb
  • John Onyango
  • Bernd Huwe


Factors governing the dynamics between woody and herbaceous vegetation in the savanna are of ecological interest since they determine ecosystem productivity and stability. Field measurements were conducted in a humid savanna in the Lambwe valley, western Kenya, to compare CO2 exchange of the herbaceous vegetation and trees and its regulation. Soil characteristics and root distribution patterns under tree canopies and in the open locations dominated by the herbaceous vegetation were profiled in 1-m-deep soil layers. Soil water content (SWC) was measured at 30 cm depth both in the herbaceous vegetation and also under the tree canopies. The mean maximum monthly gross primary production (GPPmax) in the herbaceous vegetation was determined from chamber measurements, while daily GPP (GPPday) in both the grass and tree canopies was simulated using the PIXGRO model. The highest mean GPPmax in the herbaceous vegetation was 26.2 ± 3.7 μmol m-2 s-1 during April. Seasonal fluctuations of GPP in the herbaceous vegetation were explained by soil water availability (R 2 = 0.78) within the upper 30-cm soil profile. Seasonal GPPday fluctuations were larger (between 1 gC m-2 d-1 and 10 gC m-2 d-1) in the herbaceous vegetation compared to the trees, which fluctuated around 4.3 ± 0.3 gC m-2 d-1 throughout most of the measurement period. Daily tree canopy transpiration (Ec), canopy conductance (Gc), and GPPday were decoupled from SWC in the top 30-cm soil profile. On average, ecosystem GPPday (mean of tree and herbaceous vegetation) was 14.3 ± 1.2 gC m-2 d-1 during the wet period and 6.1 ± 0.9 gC m-2 d-1 during drought. Differences between the herbaceous and tree canopy responses were attributed to soil moisture availability.


Canopy conductance Canopy transpiration Gross primary production Hydraulic lift Humid savanna Soil water availability 



We thank the Kenya National Youth Service (NYS) Lambwe unit for allowing us to conduct the experiments on their land, for working tirelessly to secure the equipment, and for supporting with data collection. We thank Mrs. Margarete Wartinger for her support with sample analyses. We are grateful to the British Ecological Society (BES) for providing funds for field work under Grant Number: BES 1430 - 4399.

Compliance with ethical standards

Conflict of Interest

The authors declare that they have no conflict of interest.

Supplementary material

11258_2015_523_MOESM1_ESM.docx (38 kb)
Supplementary material 1 (DOCX 37 kb)
11258_2015_523_MOESM2_ESM.doc (26 kb)
Supplementary material 2 (DOC 25 kb)


  1. Adiku S, Reichstein M, Lohila A, Dinh NQ, Aurela M, Laurila T, Lueers J, Tenhunen JD (2006) PIXGRO: a model for simulating the ecosystem CO2 exchange and growth of spring barley. Ecol Models 190:260–276CrossRefGoogle Scholar
  2. Ahlström A, Xia J, Arneth A, Luo Y, Smith B (2015) Importance of vegetation dynamics for future terrestrial carbon cycling. Environ Res Lett 10:054019. doi: 10.1088/1748-9326/10/5/054019 CrossRefGoogle Scholar
  3. Allsopp R, Baldry DAT (1972) A general description of the Lambwe Valley area of South Nyanza District, Kenya. Bull World Health Organ 47:691–697PubMedCentralPubMedGoogle Scholar
  4. Archer S, Boutton-Thomas W, Hibbard KA (2000) Trees in grasslands: biogeochemical consequences of woody plant expansion. In: Schulze E-D, Harrison SP, Heimann M, Holland EA, Lloyd J, Prentice IC, Schimel D (eds) Global biogeochemical cycles in the climate system. Academic Press, San DiegoGoogle Scholar
  5. Ardö J, Mölder M, El-Tahir BA, Elkhidir HAM (2008) Seasonal variation of carbon fluxes in a sparse savanna in semi arid Sudan. Carbon Balance Manag 3:7. doi: 10.1186/1750-0680-3-7 PubMedCentralCrossRefPubMedGoogle Scholar
  6. Arnhold S, Otieno D, Onyango J, Koellner T, Huwe B, Tenhunen J (2015) Soil properties along a gradient from hill slopes to the savanna plains in the Lambwe Valley, Kenya. Soil Tillage Res 154:75–83CrossRefGoogle Scholar
  7. Barron-Gafford GA, Scott RL, Jenerette GD, Hamerlynck E, Huxman TE (2012) Temperature and precipitation controls over leaf- and ecosystem-level CO2 flux along a woody plant encroachment gradient. Glob Change Biol 18:1389–1400CrossRefGoogle Scholar
  8. Baudena M, D’Andrea F, Provenzale A (2010) An idealized model for tree–grass coexistence in savannas: the role of life stage, structure and fire disturbances. J Ecol 98:74–80CrossRefGoogle Scholar
  9. Belsky AJ (1994) Influences of trees on savanna productivity: tests of shade, nutrients, and tree-grass competition. Ecology 75:922–932CrossRefGoogle Scholar
  10. Belsky AJ, Amundson RG, Duxbury JM, Riha SJ, Ali AR, Mwonga SM (1989) The effect of trees on their physical, chemical, and biological environments in a semi-arid savanna in Kenya. J Appl Ecol 6:1005–1024CrossRefGoogle Scholar
  11. Belsky AJ, Mwonga SM, Duxbury JM (1993) Effects of widely spaced trees and livestock grazing on understory environments in tropical savannas. Agrofor Syst 24:1–20CrossRefGoogle Scholar
  12. Bhark EW, Small EE (2003) Association between plant canopies and the spatial patterns of infiltration in shrubland and grassland of the Chihuahuan Desert, New Mexico. Ecosystems 6:185–196CrossRefGoogle Scholar
  13. Casper BB, Schenk HJ, Jackson RB (2003) Defining a plant’s belowground zone of influence. Ecology 84:2113–2321CrossRefGoogle Scholar
  14. Caylor KK, Shugart HH, Rodriguez-Iturbe I (2005) Tree canopy effects on simulated water stress in Southern African savannas. Ecosystems 8:17–32. doi: 10.1007/s10021-004-0027-9 CrossRefGoogle Scholar
  15. Cook KH, Vizy EK (2013) Projected changes in East African rainy seasons. J Clim. doi: 10.1175/JCLI-D-12-00455.1 Google Scholar
  16. Cook PG, Hatton TJ, Pidsley D, Herczeg AL, Held A, O’Grady A, Eamus D (1998) Water balance of a tropical woodland ecosystem, Northern Australia: a combination of micro-meteorological, soil physical and groundwater chemical approaches. J Hydrol 210:61–177CrossRefGoogle Scholar
  17. Cowan I (2002) Fit, fitter, fittest; where does optimisation fit in? Silva Fenn 36:745CrossRefGoogle Scholar
  18. Cowan I, Farquhar G (1977) Stomatal function in relation to leaf metabolism and environment. Symp Soc Exp Biol 31:471–505PubMedGoogle Scholar
  19. Dai A (2011) Drought under global warming: a review. WIREs Clim Change 2:45–65CrossRefGoogle Scholar
  20. David TS, Henriques MO, Kurz-Besson C, Nunes J, Valente J, Vaz M, Pereira JS, Siegwolf R, Chaves MM, Gazarini C, David JS (2007) Water-use strategies in two co-occurring Mediterranean evergreen oaks: surviving the summer drought. Tree Physiol 27:793–803CrossRefPubMedGoogle Scholar
  21. Devitt DA, Smith SD (2002) Root-channel macropores enhance downward movement of water in the Mojave Desert ecosystem. J Arid Environ 50:99–108CrossRefGoogle Scholar
  22. D’Odorico P, Caylor K, Okin GS, Scanlon TM (2007) On soil moisture-vegetation feedbacks and their possible effects on the dynamics of dryland ecosystems. J Geophys Res 112:G04010. doi: 10.1029/2006JG000379 Google Scholar
  23. Eamus D, Hutley LB, O’Grady AP (2001) Daily and seasonal patterns of carbon and water fluxes above a north Australian savanna. Tree Physiol 21:977–988CrossRefPubMedGoogle Scholar
  24. Ewers BE, Mackay DS, Gower ST, Ahl DE, Burrows SN, Samanta SS (2002) Tree species effects on stand transpiration in northern Wisconsin. Water Resour Res 38(7):1103. doi: 10.1029/2001WR000830 Google Scholar
  25. Farquhar GD, Caemmerer S (1982) Modelling of photosynthetic response to environmental conditions. In: Lange OL, Nobel PS, Osmond CB, Ziegler H (eds) Physiological Plant Ecology II, 12/B. Springer, Berlin, pp 549–587CrossRefGoogle Scholar
  26. Frost P, Medina E, Menaut J-C, Solbrig O, Swift M, Walker B (1986) Responses of savannas to stress and disturbance. Biology International (I.U.B.S.). NTIS, 10, ParisGoogle Scholar
  27. Gibbens RP, Lenz JM (2001) Root systems of some Chihuahuan Desert plants. J Arid Environ 49:221–263CrossRefGoogle Scholar
  28. Granier A (1987) Evaluation of transpiration in a Douglas-fir stand by means of sap flow measurements. Tree Physiol 3:309–320CrossRefPubMedGoogle Scholar
  29. Hamerlynck EP, Scott RL, Moran MS, Schwander AM, Connor E, Huxman TE (2011) Inter- and under-canopy soil water, leaf-level and whole-plant gas exchange dynamics of a semi-arid perennial C4 grass. Oecologia 165:17–29CrossRefPubMedGoogle Scholar
  30. Harley PC, Tenhunen JD (1991) Modeling the photosynthetic response of C3 leaves to environmental factors. In: Boote KJ, Loomis RS (eds) Modeling crop photosynthesis- from biochemistry to canopy. Crop Science Society of America, Anaheim, pp 17–39Google Scholar
  31. Hudak T, Wessman CA (1998) Textural analysis of historical aerial photography to characterize woody plant encroachment in South African Savanna. Remote Sns Environ 66:317–330CrossRefGoogle Scholar
  32. Hutley LB, O’Grady AP, Eamus D (2000) Evapotranspiration from Eucalypt open-forest savanna of tropical Northern Australia. Funct Ecol 14:183–194CrossRefGoogle Scholar
  33. Huxman TE, Cable JM, Ignace DD, Eilts JA, English NB, Weltzin J, Williams DG (2004) Response of net ecosystem gas exchange to a simulated precipitation pulse in a semi-arid grassland: the role of native versus non-native grasses and soil texture. Oecologia 141:295–305CrossRefPubMedGoogle Scholar
  34. Jenerette GD, Scott RL, Huxman TE (2008) Whole ecosystem metabolic pulses following precipitation events. Funct Ecol 22:924–930CrossRefGoogle Scholar
  35. K’Otuto GO, Otieno DO, Seo B, Ogindo HO, Onyango JC (2013) Carbon dioxide exchange and biomass productivity of the herbaceous vegetation of a managed tropical humid savanna ecosystem in western Kenya. J Plant Ecol 6:286–297CrossRefGoogle Scholar
  36. Kutsch WL, Hanan N, Scholes RJ, McHugh I, Kubheka W, Eckhardt H, Williams C (2008) Response of carbon fluxes to water relations in a savanna ecosystem in South Africa. Biogeosciences 5:2197–2235CrossRefGoogle Scholar
  37. Le Roux X, Bariac T, Mariotti A (1995) Spatial partitioning of the soil water resource between grass and shrub components in a West African humid savanna. Oecologia 104:147–155CrossRefGoogle Scholar
  38. Maitima JM, Olson JM, Mugatha SM, Mugisha S, Mutie IT (2010) Land use changes, impacts and options for sustaining productivity and livelihoods in the basin of lake Victoria. J Sustain Dev Afr 12:189–206Google Scholar
  39. Merbold L, Ardo J, Arneth A, Scholes RJ et al (2009) Precipitation as driver of carbon fluxes in 11 African ecosystems. Biogeosciences 6:1027–1041CrossRefGoogle Scholar
  40. Midgley GF, Thuiller W (2010) Potential responses of terrestrial biodiversity in Southern Africa to anthropogenic climate change. Reg Environ Change 11:127–135CrossRefGoogle Scholar
  41. Miranda AC, Miranda HS, Lloyd J et al (1997) Fluxes of carbon, water and energy over Brazilian cerrado, an analysis using eddy covariance and stable isotopes. Plant Cell Environ 20:315–328CrossRefGoogle Scholar
  42. Mordelet R, Abbadie L, Menaut J-C (1993) Effects of tree clumps on soil characteristics in a humid savanna of West Africa (Lamto, C6te d’Ivoire). Plant Soil 153:103–111CrossRefGoogle Scholar
  43. Myers BA, Duff GA, Eamus D, Fordyce IR, O’Grady A, Williams RJ (1997) Seasonal variation in water relations of trees of differing leaf phenology in a wet–dry tropical savanna near Darwin, northern, Australia. Aust J Bot 45:225–240CrossRefGoogle Scholar
  44. Noy-Meir I (1982) Stability of plant-herbivore models and possible applications to savanna. In: Huntley BJ, Walker BH (eds) Ecology of tropical savannas. Springer, Berlin, pp 591–609CrossRefGoogle Scholar
  45. O’Grady AP, Eamus D, Hutley LB (1999) Transpiration increases during the dry season: patterns of tree water use in eucalypt open-forests of northern Australia. Tree Physiol 19:591–597CrossRefPubMedGoogle Scholar
  46. Otieno DO, Schmidt MWT, Kurz-Besson C, Lobo Do Vale R, Pereira JS, Tenhunen JD (2007) Regulation of transpirational water loss in Quercus suber trees in a Mediterranean-type ecosystem. Tree Physiol 27:1179–1187CrossRefPubMedGoogle Scholar
  47. Otieno DO, Wartinger M, Nishiwaki A, Hussain MZ, Muhr J, Borken W, Lischeid G (2009) Responses of CO2 exchange and primary production of the ecosystem components to environmental changes in a mountain peatland. Ecosystems 12:590–603CrossRefGoogle Scholar
  48. Otieno DO, Li Y-L, Oua Y-X, Chenga J, Liua S, Tanga X, Zhanga Q, Jung E, Zhanga D, Tenhunen J (2014) Stand characteristics and water use at two elevations in a sub-tropical evergreen forest in southern China. Agric For Meteorol 194:155–166CrossRefGoogle Scholar
  49. Owen K, Tenhunen J, Reischtein M, Wang Q, Falge E, Gayer R et al (2007) Comparison of seasonal changes in CO2 exchange capacity of ecosystems distributed along a north-south European transect under non water stressed conditions. Glob Change Biol 13:734–760CrossRefGoogle Scholar
  50. Roques KG, Oconnor TG, Watkinson AT (2001) Dynamics of shrub encroachment in an African savanna: relative influences of fire, herbivory, rainfall and density dependence. J Appl Ecol 19:268–280CrossRefGoogle Scholar
  51. Ruidisch M, Nguyen TT, Li YL, Geyer R, Tenhunen J (2015) Estimation of annual spatial variations in forest production and crop yields at landscape scale in temperate climate regions. Special issue: long-term and interdisciplinary research on forest ecosystem functions: Challenges at Takayama site since 1993. Ecol Res 30:279–292CrossRefGoogle Scholar
  52. Sankaran M, Ratnam J, Hanan NP (2004) Tree–grass coexistence in savannas revisited—insights from an examination of assumptions and mechanisms invoked in existing models. Ecol Lett 7:480–490CrossRefGoogle Scholar
  53. Schaap MG, Leij FJ, van Genuchten MT (2001) ROSETTA: a computer program for estimating soil hydraulic parameters with hierarchical pedotransfer functions. J Hydrol 251:163–176CrossRefGoogle Scholar
  54. Scholes RJ, Archer SR (1997) Tree–grass interactions in savannas. Ann Rev Ecol Syst 28:517–544CrossRefGoogle Scholar
  55. Scholes RJ, Walker BH (1993) The African savanna. Synthesis of the Nylsvley study. Cambridge University Press, CambridgeCrossRefGoogle Scholar
  56. Scott RL, Huxman TE, Williams DG, Goodrich DC (2006) Ecohydrological impacts of woody plant encroachment: seasonal patterns of water and carbon exchange within a semi-riparian environment. Glob Change Biol 12:311–324CrossRefGoogle Scholar
  57. Scott RL, Huxman TE, Barron-Gafford GA, Jenerette DG, Young JM, Hamerlynck EP (2014) When vegetation change alters ecosystem water availability. Glob Change Biol 20:2198–2210CrossRefGoogle Scholar
  58. Sillmann J, Kharin VV, Zwiers FW, Zhang X, Bronaugh D (2013) Climate extreme indices in the CMIP5 multi-model ensemble. Part 2: future climate projections. J Geophys Res Atmos 118:2473–2493CrossRefGoogle Scholar
  59. van Genuchten MT (1980) A closed-form equation for predicting the hydraulic conductivity of unsaturated soils. Soil Sci Soc Am J 44:892–898CrossRefGoogle Scholar
  60. Veenendaal EM, Kolle O, Lloyd J (2004) Seasonal variation in energy fluxes and carbon dioxide exchange for a broad-leaved semi-arid savanna (mopane woodland) in southern Africa. Glob Change Biol 10:318–328CrossRefGoogle Scholar
  61. Walker BH, Noy-Meir I (1982) Aspects of the stability and resilience of savanna ecosystems. In: Huntley BJ, Walker BH (eds) Ecology of tropical savannas. Springer, Berlin, pp 556–590CrossRefGoogle Scholar
  62. Walter H (1971) In: Burnett JH (ed) Ecology of tropical and subtropical vegetation. Oliver & Boyd, EdinburghGoogle Scholar
  63. Wang L, D’Odorico P, Ringrose S, Coetzee S, Macko SA (2007) Biogeochemistry of Kalahari sands. J Arid Environ 71:259–279CrossRefGoogle Scholar
  64. Weltzin JF, Coughenour MB (1990) Savanna tree influence on understory vegetation and soil nutrients in northwestern Kenya. J Veg Sci 1:325–334CrossRefGoogle Scholar
  65. Williams CA, Albertson JD (2004) Soil moisture controls on canopy-scale water and carbon fluxes in an African savanna. Water Resour Res 40:W09302. doi: 10.1029/2004WR003208 Google Scholar
  66. Williams CA, Hanan NP, Neff JC, Scholes RJ, Berry JA, Denning AS, Baker DF (2007) Africa and the global carbon cycle. Carbon Balance Manag 2:3. doi: 10.1186/1750-0680-2-3 PubMedCentralCrossRefPubMedGoogle Scholar
  67. Williams CA, Hanan N, Scholes RJ, Kutsch W (2009) Complexity in water and carbon dioxide fluxes following rain pulses in an African savanna. Oecologia 161:469–480PubMedCentralCrossRefPubMedGoogle Scholar
  68. Wong SC, Cowan IR, Farquhar GD (1979) Stomatal conductance correlates with photosynthetic capacity. Nature 282:424–426CrossRefGoogle Scholar
  69. Xu L, Baldocchi DD (2003) Seasonal trends in photosynthetic parameters and stomatal conductance of blue oak (Quercus douglasii) under prolonged summer drought and high temperature. Tree Physiol 23:865–877CrossRefPubMedGoogle Scholar

Copyright information

© Springer Science+Business Media Dordrecht 2015

Authors and Affiliations

  • Dennis Otieno
    • 1
    Email author
  • Joseph Ondier
    • 2
  • Sebastian Arnhold
    • 3
    • 4
  • Daniel Okach
    • 1
  • Marianne Ruidisch
    • 1
  • Bora Lee
    • 1
  • Andreas Kolb
    • 3
  • John Onyango
    • 2
  • Bernd Huwe
    • 3
  1. 1.Department of Plant EcologyUniversity of BayreuthBayreuthGermany
  2. 2.Department of BotanyMaseno UniversityMasenoKenya
  3. 3.Department of Soil PhysicsUniversity of BayreuthBayreuthGermany
  4. 4.Professorship of Ecological ServicesUniversity of BayreuthBayreuthGermany

Personalised recommendations