Ecological Models Reveal a Weakened Population Structure, and Distribution Drivers of Osyris lanceolata (Santalaceae) in the Karamoja Sub-Region, Uganda
Osyris lanceolata is heavily and illegally exploited in East Africa for its essential oils, yet little is known about its population status and ecological requirements. This study examined its population structure and environmental factors influencing its distribution in the semi-arid Karamoja sub-region, Uganda. We surveyed 388 plots (5 m radius) at different altitudes, recording life stages, stem diameters, and regeneration patterns, and analyzed soil samples. Multivariate analyses, including Canonical Correspondence Analysis (CCA), Detrended Correspondence Analysis (DCA), Non-metric Multidimensional Scaling (NMDS), and Multiple Regression Modeling (MRM), identified key environmental factors affecting its distribution. Findings show that O. lanceolata populations in Moroto, Nakapiripirit, and Amudat districts are severely degraded due to overexploitation. The species is primarily regenerating through coppicing rather than seedlings, with an exploitation intensity of 56.6%. Population densities are low, distribution is irregular, and sustainable harvesting is not viable. Soil properties, particularly Ca2+, N, P, K+, Na+, and organic matter, significantly influence its abundance. Conservation efforts should focus on identifying suitable provenances for genetic preservation and plantation establishment. Areas with at least 9 trees per hectare in Moroto, Nakapiripirit, and Amudat could serve as potential sites for ex-situ plantations. Further research should explore how biotic interactions, genetic diversity, and morphology affect oil yield and quality to support restoration, breeding, and domestication initiatives.
References
[1]
Gitehi, G., Bernard, M.K., Jane, W.N., Simon, M., Nathan, K. and Celestine, I. (2023) Rooting African Sandalwood Stem Cuttings Using Low-Cost Technology Employed in the Commercial Propagation of Camellia Sinensis in Kenya. Journal of Horticulture and Forestry, 15, 1-11. https://doi.org/10.5897/jhf2022.0703
[2]
Kamondo, B. (2007) Domestication of Osyris lanceolata in Kenya: Propagation, Conservation, Management and Commercialization. Muguga Regional Research Center Annual Report.
[3]
Shyaula, S. (2012) A Review on Genusosyris: Phytochemical Constituents and Traditional Uses. Journal of Natural Pharmaceuticals, 3, 61-70. https://doi.org/10.4103/2229-5119.102747
[4]
Mugula, B.B., Kiboi, S.K., Kanya, J.I., Egeru, A., Okullo, P., Curto, M., et al. (2021) Knowledge Gaps in Taxonomy, Ecology, Population Distribution Drivers and Genetic Diversity of African Sandalwood (Osyris lanceolata Hochst. & Steud.): A Scoping Review for Conservation. Plants, 10, Article 1780. https://doi.org/10.3390/plants10091780
[5]
Gachambi Mwangi, J., Haggar, J., Mohammed, S., Santika, T. and Mustapha Umar, K. (2023) The Ecology, Distribution, and Anthropogenic Threats of Multipurpose Hemi-Parasitic Plant Osyris lanceolata. Journal for Nature Conservation, 76, Article ID: 126478. https://doi.org/10.1016/j.jnc.2023.126478
[6]
Mumbu, D.M. (2020) Assessing the Utilization and Socio-Economic Impacts of Osyris lanceolata (Hochst & Steud) and Associated Environmental Degradation in Kitui County. Master’s Thesis, South Eastern Kenya University (SEKU).
[7]
Liu, X., Gao, Y., Khan, S., Duan, G., Chen, A., Ling, L., et al. (2008) Accumulation of Pb, Cu, and Zn in Native Plants Growing on Contaminated Sites and Their Potential Accumulation Capacity in Heqing, Yunnan. Journal of Environmental Sciences, 20, 1469-1474. https://doi.org/10.1016/s1001-0742(08)62551-6
[8]
Chavan, S.B., Uthappa, A.R., Chichaghare, A.R., Ramanan, S.S., Kumar, R., Keerthika, A., et al. (2024) Past, Present and Future of Indian Sandalwood (Santalum album) Cultivation and Commercial Prospects. Discover Applied Sciences, 6, Article No. 627. https://doi.org/10.1007/s42452-024-06337-8
[9]
Mbuya, L.P., Msanga, H.P., Ruffo, C.K., Birnie, A. and Tengnas, B.O. (1994) Useful Trees and Shrubs for Tanzania. SIDA (Swedish International Development Authority, 542.
[10]
Page, T., Hannington, T., Bunt, C., Potrawiak, A. and Berry, A. (2012) Opportunities for the Smallholder Sandalwood Industry in Vanuatu. ACIAR Technical Reports No. 79; Australian Centre for International Agricultural Research.
[11]
CITES (2013) Consideration of Proposals for Amendment of Appendices I and II. 1-10.
[12]
Otieno, J.O., Omondi, S.F., Perry, A., Odee, D.W., Makatiani, E.T., Kiplagat, O., et al. (2016) Development and Characterization of Microsatellite Markers for Osyris lanceolata Hochst. & Steud., an Endangered African Sandalwood Tree Species. Tropical Plant Research, 3, 701-703. https://doi.org/10.22271/tpr.2016.v3.i3.092
[13]
Bunei, E.K. (2017) The Hunt for the Precious Wood. Society and Business Review, 12, 63-76. https://doi.org/10.1108/sbr-04-2016-0025
[14]
Kokwaro, J. (2009) Osyris lanceolata. In: Kokwaro, J.O., Ed., Medicinal Plants of East Africa, University of Nairobi Press, 534 p.
[15]
Mwang’ingo, P.L., Teklehaimanot, Z., Hall, J.B. and Lulandala, L.L.L. (2003) African Sandalwood (Osyris lanceolata): Resource Assessment and Quality Variation among Populations in Tanzania. The Southern African Forestry Journal, 199, 77-88. https://doi.org/10.1080/20702620.2003.10431751
[16]
Mwang’ingo, P.L., Teklehaimanot, Z., Lulandala, L.L. and Mwihomeke, S.T. (2005) Host Plants of Osyris lanceolata (African Sandalwood) and Their Influence on Its Early Growth Performance in Tanzania. The Southern African Forestry Journal, 203, 55-65. https://doi.org/10.2989/10295920509505219
[17]
Teixeira da Silva, J.A. (2016) Sandalwood Spike Disease: A Brief Synthesis. Environmental and Experimental Biology, 14, 199-204. https://doi.org/10.22364/eeb.14.26
[18]
Mugula, B.B. (2024) Population Structure, Parasitic Associations, Distribution Drivers, and Genetic Diversity of Osyris lanceolata (Hochst. & Steud.) in Uganda and Kenya. PhD Thesis, University of Nairobi (UoN).
[19]
Gathara, M., Makenzi, P., Kimondo, J. and Muturi, G. (2014) Prediction of Osyris lanceolata (Hochst. & Steud.) Site Suitability Using Indicator Plant Species and Edaphic Factors in Humid Highland and Dry Lowland Forests in Kenya. Journal of Horticulture and Forestry, 6, 99-106.
[20]
Watson, D.M. (2009) Determinants of Parasitic Plant Distribution: The Role of Host Quality. Botany, 87, 16-21. https://doi.org/10.1139/b08-105
[21]
Watson, D.M., Roshier, D.A. and Wiegand, T. (2007) Spatial Ecology of a Root Parasite—From Pattern to Process. Austral Ecology, 32, 359-369. https://doi.org/10.1111/j.1442-9993.2007.01701.x
[22]
Jiang, F., Jeschke, W.D., Hartung, W. and Cameron, D.D. (2008) Does Legume Nitrogen Fixation Underpin Host Quality for the Hemiparasitic Plant Rhinanthus minor? Journal of Experimental Botany, 59, 917-925. https://doi.org/10.1093/jxb/ern015
[23]
Jiang, R. and Zhang, G. (2021) Distribution Patterns and Influencing Factors of Different Parasitic Angiosperm Types in China. Global Ecology and Conservation, 27, e01533. https://doi.org/10.1016/j.gecco.2021.e01533
[24]
Irving, L.J. and Cameron, D.D. (2009) Chapter 3 You Are What You Eat: Interactions between Root Parasitic Plants and Their Hosts. Advances in Botanical Research, 50, 87-138. https://doi.org/10.1016/s0065-2296(08)00803-3
[25]
Těšitel, J., Plavcová, L. and Cameron, D.D. (2010) Interactions between Hemiparasitic Plants and Their Hosts: The Importance of Organic Carbon Transfer. Plant Signaling & Behavior, 5, 1072-1076. https://doi.org/10.4161/psb.5.9.12563
[26]
Scalon, M.C. and Wright, I.J. (2015) A Global Analysis of Water and Nitrogen Relationships between Mistletoes and Their Hosts: Broad‐scale Tests of Old and Enduring Hypotheses. Functional Ecology, 29, 1114-1124. https://doi.org/10.1111/1365-2435.12418
[27]
Dueholm, B., Bruce, D., Weinstein, P., Semple, S., Møller, B.L. and Weiner, J. (2016) Spatial Analysis of Root Hemiparasitic Shrubs and Their Hosts: A Search for Spatial Signatures of Above-and Below-Ground Interactions. Plant Ecology, 218, 185-196. https://doi.org/10.1007/s11258-016-0676-8
[28]
Dean, W.R.J., Midgley, J.J. and Stock, W.D. (1994) The Distribution of Mistletoes in South Africa: Patterns of Species Richness and Host Choice. Journal of Biogeography, 21, 503-510. https://doi.org/10.2307/2845654
[29]
Pfenninger, M., Salinger, M., Haun, T. and Feldmeyer, B. (2011) Factors and Processes Shaping the Population Structure and Distribution of Genetic Variation across the Species Range of the Freshwater Snail Radix balthica (Pulmonata, Basommatophora). BMC Evolutionary Biology, 11, Article No. 135. https://doi.org/10.1186/1471-2148-11-135
[30]
Chen, Y., Yang, X., Yang, Q., Li, D., Long, W. and Luo, W. (2014) Factors Affecting the Distribution Pattern of Wild Plants with Extremely Small Populations in Hainan Island, China. PLOS ONE, 9, e97751. https://doi.org/10.1371/journal.pone.0097751
[31]
Cirimwami, L., Doumenge, C., Kahindo, J. and Amani, C. (2019) The Effect of Elevation on Species Richness in Tropical Forests Depends on the Considered Lifeform: Results from an East African Mountain Forest. Tropical Ecology, 60, 473-484. https://doi.org/10.1007/s42965-019-00050-z
[32]
Anic, V., Hinojosa, L.F., Díaz-Forester, J., Bustamante, E., de la Fuente, L.M., Casale, J.F., et al. (2010) Influence of Soil Chemical Variables and Altitude on the Distribution of High-Alpine Plants: The Case of the Andes of Central Chile. Arctic, Antarctic, and Alpine Research, 42, 152-163. https://doi.org/10.1657/1938-4246-42.2.152
[33]
Cousins, S.R., Witkowski, E.T.F. and Pfab, M.F. (2014) Elucidating Patterns in the Population Size Structure and Density of Aloe Plicatilis, a Tree Aloe Endemic to the Cape Fynbos, South Africa. South African Journal of Botany, 90, 20-36. https://doi.org/10.1016/j.sajb.2013.09.012
[34]
Rodrigues, P.M.S., Silva, J.O. and Schaefer, C.E.G.R. (2019) Edaphic Properties as Key Drivers for Woody Species Distributions in Tropical Savannic and Forest Habitats. Australian Journal of Botany, 67, 70-80. https://doi.org/10.1071/bt17241
[35]
Amundrud, S.L. (2020) Abiotic and Biotic Processes Shape Species Distributions and Ecological Communities across Spatial Scales. Ph.D. Thesis, University of British Columbia.
[36]
Zhang, X., Yang, X., Li, Y., He, X., Lv, G. and Yang, J. (2017) Influence of Edaphic Factors on Plant Distribution and Diversity in the Arid Area of Xinjiang, Northwest China. Arid Land Research and Management, 32, 38-56. https://doi.org/10.1080/15324982.2017.1376004
[37]
Lomolino, M.V. (2001) Elevation Gradients of Species-Density: Historical and Prospective Views. Global Ecology and Biogeography, 10, 3-13. https://doi.org/10.1046/j.1466-822x.2001.00229.x
[38]
Weatherby, J.M. (1988) The Secret Spirit Cult of the Sor in Karamoja. Africa, 58, 210-229. https://doi.org/10.2307/1160662
[39]
Egeru, A., Osaliya, R., MacOpiyo, L., Mburu, J., Wasonga, O., Barasa, B., et al. (2014) Assessing the Spatio-Temporal Climate Variability in Semi-Arid Karamoja Sub-Region in North-Eastern Uganda. International Journal of Environmental Studies, 71, 490-509. https://doi.org/10.1080/00207233.2014.919729
[40]
Wanyama, J., Nakawuka, P., Bwambale, E., Kiraga, S., Kiggundu, N., Barasa, B., et al. (2024) Evaluation of Land Suitability for Surface Irrigation under Changing Climate in a Tropical Setting of Uganda, East Africa. Agricultural Systems, 217, Article ID: 103937. https://doi.org/10.1016/j.agsy.2024.103937
[41]
Terradas, J., Peñuelas, J. and Lloret, F. (2009) The Fluctuation Niche in Plants. International Journal of Ecology, 2009, Article ID: 959702. https://doi.org/10.1155/2009/959702
[42]
Jensen, A. and Meilby, H. (2012) Assessing the Population Status of a Tree Species Using Distance Sampling: Aquilaria crassna (Thymelaeaceae) in Northern Laos. International Journal of Forestry Research, 2012, Article ID: 265831. https://doi.org/10.1155/2012/265831
[43]
Tabuti, J.R.S. and Mugula, B.B. (2007) The Ethnobotany and Ecological Status of Albizia coriaria Welw. ex Oliv. in Budondo Sub‐County, Eastern Uganda. African Journal of Ecology, 45, 126-129. https://doi.org/10.1111/j.1365-2028.2007.00869.x
[44]
Mohammed, E.M.I., Hammed, A.M.E., Minnick, T.J., Ndakidemi, P.A. and Treydte, A.C. (2021) Livestock Browsing Threatens the Survival of Balanites Aegyptiaca Seedlings and Saplings in Dinder Biosphere Reserve, Sudan. Journal of Sustainable Forestry, 41, 1046-1063. https://doi.org/10.1080/10549811.2021.1935279
[45]
Kikoti, I.A. and Mligo, C. (2015) Impacts of Livestock Grazing on Plant Species Composition in Montane Forests on the Northern Slope of Mount Kilimanjaro, Tanzania. International Journal of Biodiversity Science, Ecosystem Services & Management, 11, 114-127. https://doi.org/10.1080/21513732.2015.1031179
[46]
Osman, E.M.H. and Idris, E.Z.A. (2012) Species Dynamics and Potential Disturbances in El Nour Natural Forest Reserve. Journal of Forest Products & Industries, 1, 10-20.
[47]
Olsen, S.R., et al. (1982) Methods of Soil Analysis. ASA and SSSA.
[48]
Okalebo, J.R., et al. (2002) Laboratory Methods of SOIL and plant Analysis. 2nd Edition, Sacred Africa.
[49]
Nieder, R. and Benbi, D. (2024) Handbook of Processes and Modeling in the Soil-Plant System. CRC Press.
[50]
Chenu, C., Rumpel, C., Védère, C. and Barré, P. (2024) Methods for Studying Soil Organic Matter: Nature, Dynamics, Spatial Accessibility, and Interactions with Minerals. In: Paul, E.A. and Frey, S.D., Eds., Soil Microbiology, Ecology and Biochemistry, Elsevier, 369-406. https://doi.org/10.1016/b978-0-12-822941-5.00013-2
[51]
Lykke, A.M. (1998) Assessment of Species Composition Change in Savanna Vegetation by Means of Woody Plants’ Size Class Distributions and Local Information. Biodiversity and Conservation, 7, 1261-1275.
[52]
Obiri, J., Lawes, M. and Mukolwe, M. (2002) The Dynamics and Sustainable Use of High-Value Tree Species of the Coastal Pondoland Forests of the Eastern Cape Province, South Africa. Forest Ecology and Management, 166, 131-148. https://doi.org/10.1016/s0378-1127(01)00665-x
[53]
Maua, J.O., Mugatsia Tsingalia, H., Cheboiwo, J. and Odee, D. (2020) Population Structure and Regeneration Status of Woody Species in a Remnant Tropical Forest: A Case Study of South Nandi Forest, Kenya. Global Ecology and Conservation, 21, e00820. https://doi.org/10.1016/j.gecco.2019.e00820
[54]
Ter Braak, C.J.F. and Verdonschot, P.F.M. (1995) Canonical Correspondence Analysis and Related Multivariate Methods in Aquatic Ecology. Aquatic Sciences, 57, 255-289. https://doi.org/10.1007/bf00877430
[55]
Rao, P., Barik, S.K., Pandey, H.N. and Tripathi, R.S. (1990) Community Composition and Tree Population Structure in a Sub-Tropical Broad-Leaved Forest along a Disturbance Gradient. Vegetatio, 88, 151-162. https://doi.org/10.1007/bf00044832
[56]
Anderson, M.J. and Willis, T.J. (2003) Canonical Analysis of Principal Coordinates: A Useful Method of Constrained Ordination for Ecology. Ecology, 84, 511-525. https://doi.org/10.1890/0012-9658(2003)084[0511:caopca]2.0.co;2
[57]
Tajuba, P. (2015) How Oil Firm Is Burning Up Karamoja Valuable Trees. Daily Monitor.
[58]
Forest Sector Support Department (FSSD) (2021) Production, Trade, Processing, Monitoring and Control of the East African Sandalwood, Osyris lanceolata in Uganda. Ministry of Water and Environment.
[59]
Sexton, J.P., Hufford, M.B., C.Bateman, A., Lowry, D.B., Meimberg, H., Strauss, S.Y., et al. (2016) Climate Structures Genetic Variation across a Species’ Elevation Range: A Test of Range Limits Hypotheses. Molecular Ecology, 25, 911-928. https://doi.org/10.1111/mec.13528
[60]
Bin, Y., Ye, W., Muller-Landau, H.C., Wu, L., Lian, J. and Cao, H. (2012) Unimodal Tree Size Distributions Possibly Result from Relatively Strong Conservatism in Intermediate Size Classes. PLOS ONE, 7, e52596. https://doi.org/10.1371/journal.pone.0052596
[61]
Deb, P. and Sundriyal, R.C. (2008) Tree Regeneration and Seedling Survival Patterns in Old-Growth Lowland Tropical Rainforest in Namdapha National Park, North-East India. Forest Ecology and Management, 255, 3995-4006. https://doi.org/10.1016/j.foreco.2008.03.046
[62]
Kohira, M. and Ninomiya, I. (2003) Detecting Tree Populations at Risk for Forest Conservation Management: Using Single-Year Vs. Long-Term Inventory Data. Forest Ecology and Management, 174, 423-435. https://doi.org/10.1016/s0378-1127(02)00076-2
[63]
Mehes, M., Nkongolo, K.K. and Michael, P. (2009) Assessing Genetic Diversity and Structure of Fragmented Populations of Eastern White Pine (Pinus strobus) and Western White Pine (P. monticola) for Conservation Management. Journal of Plant Ecology, 2, 143-151. https://doi.org/10.1093/jpe/rtp016
[64]
Cueva-Agila, A.Y., Manchego, C., Bastidas, C. and Curto, M. (2021) Development and Characterization of Microsatellite Markers for Two Subspecies of Handroanthuschrysanthus. Rodriguésia, 72, e00722020. https://doi.org/10.1590/2175-7860202172088
[65]
de Groot, M. and Vrezec, A. (2019) Contrasting Effects of Altitude on Species Groups with Different Traits in a Non-Fragmented Montane Temperate Forest. Nature Conservation, 37, 99-121. https://doi.org/10.3897/natureconservation.37.37145
[66]
Nepali, B.R., Skartveit, J. and Baniya, C.B. (2021) Impacts of Slope Aspects on Altitudinal Species Richness and Species Composition of Narapani-Masina Landscape, Arghakhanchi, West Nepal. Journal of Asia-Pacific Biodiversity, 14, 415-424. https://doi.org/10.1016/j.japb.2021.04.005
[67]
Gathara, M., Kamondo, B., Mwadalu, R., Omondi, S., Kivuti, M., Wairagu, N., et al. (2022) Influence of Soil Nutrients, Tree Age, and Sandalwood Provenances on Sandalwood Oil Yield and Quality. International Journal of Forestry Research, 2022, Article ID: 1577979. https://doi.org/10.1155/2022/1577979
[68]
Cavieres, L.A., Peñaloza, A. and Kalin Arroyo, M. (2000) Altitudinal Vegetation Belts in the High-Andes of Central Chile (33˚s). Revistachilena de historia natural, 73, 331-334. https://doi.org/10.4067/s0716-078x2000000200008
[69]
Güsewell, S. (2004) N: P Ratios in Terrestrial Plants: Variation and Functional Significance. New Phytologist, 164, 243-266. https://doi.org/10.1111/j.1469-8137.2004.01192.x
[70]
Arnesen, G., Beck, P.S.A. and Engelskjøn, T. (2007) Soil Acidity, Content of Carbonates, and Available Phosphorus Are the Soil Factors Best Correlated with Alpine Vegetation: Evidence from Troms, North Norway. Arctic, Antarctic, and Alpine Research, 39, 189-199. https://doi.org/10.1657/1523-0430(2007)39[189:sacoca]2.0.co;2.
