Influence of Thinning Regime on Woody Species Density and Abundance in Kimondi Forest, Nandi County, Kenya
Keywords:
Silvicultural Regimes, Thinning Regime, Woody Species Abundance, Woody Species Density
Abstract
A silvicultural regime refers to the planned sequence of treatments applied to a forest stand, which mainly includes pruning and thinning regimes. The latter is a silvicultural practice that is important for the management of forest growth, composition, structure, and health. Despite the ecological and silvicultural importance of thinning, its limited application in plantation forests has constrained the effective management of woody species density and abundance. Thus, the aim of this research was to assess the influence of the thinning regime on woody species density and abundance. This study focused on Eucalyptus saligna, Cupressus lusitanica and Pinus patula as the woody species that are harvested for timber in the Kimondi forest. The study applied a cross-sectional descriptive study design. Systematic sampling was used in collecting primary data. Data were analysed using box plots, Analysis of Variance and Duncan multiple range test. The box plots showed Eucalyptus saligna having the highest median density and the widest interquartile range, indicating both a greater abundance and variability across sampling sites. Cupressus lusitanica and Pinus patula had a moderate median density with a narrower distribution, indicating lower variability. Analysis of variance revealed a highly significant difference in tree abundance and density across the thinning regime (p = 0.000), with an effect size (Eta² = 0.7519), indicating that 75.19% of the variation of woody species density and abundance can be explained by the thinning regime. Duncan’s Multiple Range Test confirmed that mean abundance varied significantly across the thinning regime. The study concluded that a thinning regime can improve the density and abundance of woody species, Eucalyptus saligna, Cupressus lusitanica, and Pinus patula. We recommend that forest managers in plantation forests adopt thinning regimes to improve woody species density and abundance.
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References
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Pfister, O. (2009). Influence of spacing and thinning on tree and wood characteristics in planted Norway spruce in southern Sweden. Doctoral thesis No:61. Faculty of Forest Science, Swedish University of Agricultural Sciences, Alnarp. 54 pp.
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Richard M. (2024), A Model for Spatially Explicit Landscape Configuration and Ecosystem Service Performance, ESMAX: Model Description and Explanation; Sustainability 16(2):876 DOI:10.3390/su16020876.
Rossman A. K., Halpern C. B., Harrod R. J., Urgenson L. S., Peterson D. W., Bakker J. D. (2018). Benefits of thinning and burning for understory diversity vary with spatial scale and time since treatment. For. Ecol. Manage. 419 58–78. 10.1016/j.foreco.2018.03.006 .
Royo AA, Pinchot CC, Stanovick JS, Stout SL (2019) Timing is not everything: assessing the efficacy of pre- versus post-harvest herbicide applications in mitigating the burgeoning birch phenomenon in regenerating hardwood stands. Forests 10:324. https://doi.org/10.3390/f10040324
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SIS-Swedish Institute for Standards (2020).Tree Care — Processes and Methods for Tree Pruning — Part 2: Requirements for Providers Swedish Institute for Standard, pp. SS 990001–SS 990002.
Smith, L. L., Cox, J. A., Conner, L. M., McCleery, R. A., and Schlimm, E. M. (2018). Management and restoration of wildlife. Pages 233-251 in L. K. Kirkman, and S.B. Jack (eds.). Ecological Restoration and Management of Longleaf Pinus patula Forests. CRC Press, Boca Raton, Florida.
Stimm, K.; Heym, M.; Uhl, E.; Tretter, S.; Pretzsch, H.(2021). Height growth-related competitiveness of oak (Quercus petraea (Matt.) Liebl. and Quercus robur L.) under climate change in Central Europe. Is silvicultural assistance still required in mixed-species stands? For. Ecol. Manag. 482, 118780.
Swaim J.T, Dey D.C, Saunders M.R, Weigel D.R, Thornton C.D, Kabrick J.M, Jenkins M.A (2018) Overstory species response to clearcut harvest across environmental gradients in hardwood forests. Forest Ecology and Management 428:66–80. 8.
Syampungani, S., Geldenhuys, C. J., and Chirwa, P. W. (2016). Regeneration dynamics of miombo woodland in response to different anthropogenic disturbances: forest characterisation for sustainable management. Agroforest. Syst. 90, 563–576. doi: 10.1007/s10457-015-9841-7.
Terefe A.and Gure A.(2019), “Effect of exclosure on woody species abundance and population structure in comparison with adjacent open grazing land: the case of Jabi Tehnan district north western Ethiopia,” Ecosystem Health and Sustainability, vol. 5, no. 1, pp. 98–109.
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Ulvcrona, K.A. (2011). Effects of silvicultural treatments in young Scots Pinus patula-dominated stands on the potential for early biofuel harvest. Doctoral thesis No. 79. Faculty of Forest Science, Swedish University of Agricultural Sciences, Umeå. 64 pp.
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Wahungu, G., Chira, R., & Kirui, P. (2024). Influence of thinning intensities on woody species regeneration in East African savannas. Frontiers in Ecology and Evolution, 12, 1461573. https://doi.org/10.3389/fevo.2024.1461573
Wang, Y., Wang, A.D. delCampo, X. Wei, R. Winkler, W. Liu, Q. (2020). LiResponses of forest carbon and water coupling to thinning treatments from leaf to stand scales in a young montane Pinus patula forest Carbon Balance Manag., 15 (1), p. 24, 10.1186/s13021-020-00159-y.
Wang, J. et al., (2021). Impacts of juniper woody plant encroachment into grasslands on local climate. Agric. For. Meteorol. 307, 108508.
Wanjira, E.O & Muriuki, J. (2020). Review of the Status of Agroforestry Practices in Kenya. Background study for preparation of Kenya National Agroforestry Strategy (2020 – 2030). World Agroforestry, Nairobi.
Wekesa, C., Maranga, E.K., Kirui, B.K., Muturi, G.M., Gathara, M. (2018). Interactions between native tree species and environmental variables along forest edge-interior gradient in fragmented forest patches of Taita Hills, Kenya. For. Ecol. Manage. 409, 789–798.
Zhou J.Y, Li R, Zhang W.H, He J.F (2012) Effects of thinning intensity on structure characteristics and spatial distribution of Quercus wutaishanica populations. Sci Silv Sin 48(4):149–155.
Anna L., Johan Ö. And Björn W. (2023), Pruning revisited – effect of pruning season on wood discoloration and occlusion in four temperate broadleaved tree species Forestry: An International Journal of Forest Research, Volume 96, Issue 4, October 2023, Pages 605–617,
Anyango, E. (2020). Effects of forest fragmentation on tree species richness in Kakamega Forest, Kenya. Maseno University.https://edocs.maseno.ac.ke/handle/123456789/3999
Assèdé, E. S. P., Azihou, F. A., Biaou, S. S. H., Mariki, S. B., Geldenhuys, C. J., Sinsin, B. (2021). Managing woodland development stages in Sudanian dry woodlands to meet local demand in fuelwood. Ener. Sustain. Dev. 61, 129–138. doi: 10.1016/j.esd.2021.01.006
Binglin P., Zhenyu W., Mei Y., Shinan L. (2020). Effects of thinning on tree growth and soil chemical properties of Betula luminifera plantation. J. Beihua Univ. (Nat. Sci.) 21 398–404. 10.11713/j.issn.1009-4822.2020.03.024
Brancalion, P.H.S et al., (2019). Global restoration opportunities in tropical rainforest landscapes. Sci. Adv.5, essav 3223.
D’Amato AW and Palik B.J. (2020). Building on the last “new” thing: exploring the compatibility of ecological and adaptation silviculture. Canadian Journal of Forest Research 51:172–180. https://doi.org/10.1139/cjfr--0306
Felix L. Mogambi M. and Zipporah L. (2022). The Role of Forest Resource and Resource Users’ Boundaries in Improving the Livelihoods of Communities Adjacent to Arabuko-Sokoke Forest Reserve, Kenya. International Journal of Natural Resource Ecology and Management. Vol. 7, No. 1, 2022, pp. 54-58. doi: 10.11648/j.ijnrem,0701.17
Geldenhuys, C. J., Prinsloo, A. J., and Antão, L. V. T. (2018). Monitoring the impact of selective thinning and pruning on recovery of condition, biodiversity and productivity in Miombo woodland development stages: Report 2: Wood harvested through different harvesting intensities, Vila Ulongwe and Nkantha areas, Tete Province, Mozambique. Report FW-07/18. Pretoria: Forest wood cc.
Horáček, P., Fajstavr, M., Stojanović, M., 2017: The variability of wood density and compression strength of Norway spruce (Picea abies /L./ Karst.) within the stem. Beskydy 10(1,2): 17–26
Kariuki, M., Wekesa, C., & Omondi, S. (2023). Tree species identity and biomass dynamics in the Taita Hills forests. Forests, 14(3), 642. https://doi.org/10.3390/f14030642
Kenya Forest Service (2020) Economic Potential of Popular Commercial Tree Species in Kenya. pp. 2-3. http://www.kenyaforestservice.org/documents/Brochure commercial forestry.
Kinyanjui, M. J., Langat, D., & Njenga, M. (2023). Silvicultural practices and forest recovery in Kenya’s highland plantations. Forest Ecology and Management, 531, 120785. https://doi.org/10.1016/j.foreco.2023.120785
Koivula M., I.and Vanha-Majamaa (2020), Experimental evidence on biodiversity impacts of variable retention forestry, prescribed burning, and deadwood manipulation in Fennoscandia, Ecological Processes, 9, 11.
Magnus P. (2022). Evaluating thinning practices and assessment methods for improved management in coniferous production forests in southern Sweden, Department of Department of Forestry and Wood Technology, Linnaeus University, Växjö, ISBN: 978-91-89709-54-6 (print), 978-91-89709-55-3.
Mwanzia, R. K., Gitonga, D. K., & Wekesa, J. (2021). Monitoring biodiversity changes in Nandi Forest ecosystems. African Journal of Ecology, 59(3), 349–358. https://doi.org/10.1111/aje.12798
Mutiso, D., Kamondo, B., & Wambugu, C. (2024). Woody species composition and regeneration in Londiani Forest, Kenya. Forests, 15(4), 653. https://doi.org/10.3390/f15040653
Otuoma, J., Anyango, B., Ouma, G., Okeyo, D., Muturi, G.M., Oindo, B. (2016). Determinants of above-ground carbon offset additionality in plantation forests in a moist tropical forest in Western Kenya. For. Ecol. Manage. 365, 61–68.
Pachas A.N.A, Sakanphet S, Soukkhy O, Lao M, Savathvong S, Newby JC, Souliyasack B, Keoboualapha B, Dieters M.J. (2019). Initial spacing of teak (Tectona grandis) in northern Lao PDR: impacts on the growth of teak and companion crops. Forest Ecology and Management. 435:77–88.
Pfister, O. (2009). Influence of spacing and thinning on tree and wood characteristics in planted Norway spruce in southern Sweden. Doctoral thesis No:61. Faculty of Forest Science, Swedish University of Agricultural Sciences, Alnarp. 54 pp.
Resende C.L, Scarano F.R, Assad E.D, Joly C.A, Metzger J.P, Strassburg B.B.N, (2018).From hotspot to hopespot: An opportunity for the Brazilian Atlantic Forest. Perspect Ecol Conserv. 16, 208–214.
Richard M. (2024), A Model for Spatially Explicit Landscape Configuration and Ecosystem Service Performance, ESMAX: Model Description and Explanation; Sustainability 16(2):876 DOI:10.3390/su16020876.
Rossman A. K., Halpern C. B., Harrod R. J., Urgenson L. S., Peterson D. W., Bakker J. D. (2018). Benefits of thinning and burning for understory diversity vary with spatial scale and time since treatment. For. Ecol. Manage. 419 58–78. 10.1016/j.foreco.2018.03.006 .
Royo AA, Pinchot CC, Stanovick JS, Stout SL (2019) Timing is not everything: assessing the efficacy of pre- versus post-harvest herbicide applications in mitigating the burgeoning birch phenomenon in regenerating hardwood stands. Forests 10:324. https://doi.org/10.3390/f10040324
Sadono R. (2017). Temporary site index for two-invented teak clones with generative regeneration in the state forestland in East Java, Indonesia. Advances in Environmental Biology. 11:6‒ 12.
SIS-Swedish Institute for Standards (2020).Tree Care — Processes and Methods for Tree Pruning — Part 2: Requirements for Providers Swedish Institute for Standard, pp. SS 990001–SS 990002.
Smith, L. L., Cox, J. A., Conner, L. M., McCleery, R. A., and Schlimm, E. M. (2018). Management and restoration of wildlife. Pages 233-251 in L. K. Kirkman, and S.B. Jack (eds.). Ecological Restoration and Management of Longleaf Pinus patula Forests. CRC Press, Boca Raton, Florida.
Stimm, K.; Heym, M.; Uhl, E.; Tretter, S.; Pretzsch, H.(2021). Height growth-related competitiveness of oak (Quercus petraea (Matt.) Liebl. and Quercus robur L.) under climate change in Central Europe. Is silvicultural assistance still required in mixed-species stands? For. Ecol. Manag. 482, 118780.
Swaim J.T, Dey D.C, Saunders M.R, Weigel D.R, Thornton C.D, Kabrick J.M, Jenkins M.A (2018) Overstory species response to clearcut harvest across environmental gradients in hardwood forests. Forest Ecology and Management 428:66–80. 8.
Syampungani, S., Geldenhuys, C. J., and Chirwa, P. W. (2016). Regeneration dynamics of miombo woodland in response to different anthropogenic disturbances: forest characterisation for sustainable management. Agroforest. Syst. 90, 563–576. doi: 10.1007/s10457-015-9841-7.
Terefe A.and Gure A.(2019), “Effect of exclosure on woody species abundance and population structure in comparison with adjacent open grazing land: the case of Jabi Tehnan district north western Ethiopia,” Ecosystem Health and Sustainability, vol. 5, no. 1, pp. 98–109.
Tsai H.C, Chiang J.M, McEwan R.W, Lin T.C (2018) Decadal effects of thinning on understory light environments and plant community structure in a subtropical forest. Ecosphere 9:e02464. https://doi.org/10.1002/ecs2.2464.
Ulvcrona, K.A. (2011). Effects of silvicultural treatments in young Scots Pinus patula-dominated stands on the potential for early biofuel harvest. Doctoral thesis No. 79. Faculty of Forest Science, Swedish University of Agricultural Sciences, Umeå. 64 pp.
Velamazán M, San Miguel A, Escribano R, Perea R (2017) Threatened woody flora as an ecological indicator of large herbivore introductions. Biodivers Conserv 26:917–930.
Wahungu, G., Chira, R., & Kirui, P. (2024). Influence of thinning intensities on woody species regeneration in East African savannas. Frontiers in Ecology and Evolution, 12, 1461573. https://doi.org/10.3389/fevo.2024.1461573
Wang, Y., Wang, A.D. delCampo, X. Wei, R. Winkler, W. Liu, Q. (2020). LiResponses of forest carbon and water coupling to thinning treatments from leaf to stand scales in a young montane Pinus patula forest Carbon Balance Manag., 15 (1), p. 24, 10.1186/s13021-020-00159-y.
Wang, J. et al., (2021). Impacts of juniper woody plant encroachment into grasslands on local climate. Agric. For. Meteorol. 307, 108508.
Wanjira, E.O & Muriuki, J. (2020). Review of the Status of Agroforestry Practices in Kenya. Background study for preparation of Kenya National Agroforestry Strategy (2020 – 2030). World Agroforestry, Nairobi.
Wekesa, C., Maranga, E.K., Kirui, B.K., Muturi, G.M., Gathara, M. (2018). Interactions between native tree species and environmental variables along forest edge-interior gradient in fragmented forest patches of Taita Hills, Kenya. For. Ecol. Manage. 409, 789–798.
Zhou J.Y, Li R, Zhang W.H, He J.F (2012) Effects of thinning intensity on structure characteristics and spatial distribution of Quercus wutaishanica populations. Sci Silv Sin 48(4):149–155.
Published
16 July, 2025
How to Cite
Anyango, E., Obuoyo, J., & Oindo, B. (2025). Influence of Thinning Regime on Woody Species Density and Abundance in Kimondi Forest, Nandi County, Kenya. East African Journal of Forestry and Agroforestry, 8(1), 324-335. https://doi.org/10.37284/eajfa.8.1.3330
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Copyright (c) 2025 Emma Anyango, Joyce A. Obuoyo, PhD, Boniface O. Oindo, PhD
This work is licensed under a Creative Commons Attribution 4.0 International License.
