Conservation genetics, utilization and effects of Cyperus papyrus harvesting: making ecosystem management work in Kenyan wetlands
Terer, T. (2011). Conservation genetics, utilization and effects of Cyperus papyrus harvesting: making ecosystem management work in Kenyan wetlands. PhD Thesis. VUB Brussels University Press: Brussels. ISBN 978 90 5487 885 8. 238 pp.
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| Beschikbaar in | Auteur |
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Documenttype: Doctoraat/Thesis/Eindwerk
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| Trefwoorden |
Water bodies > Inland waters > Wetlands
Cyperus papyrus
ISW, Kenya [Marine Regions]
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| Abstract |
Wetlands are threatened ecosystems world over despite genetic resources that they hold in addition to an immense socio–economic and ecological importance to both mankind and biosphere. It is estimated that more than half of the world’s wetlands have been lost due to agricultural development including other land uses and overutilization. Papyrus swamps, mostly found in the tropical Africa and dominated by its keystone species Cyperus papyrus L. (papyrus) is under increasing threats from similar anthropogenic activities facing wetlands worldwide, yet no scientific information is available on genetic diversity and structure which are necessary for its survival in addition to information on sustainable harvesting practices. This thesis study aimed at filling some existing gaps in scientific knowledge on: genetic diversity and structure of papyrus populations across Kenyan Rift Valley and Lake Victoria sub–basins, papyrus utilization, perception on regeneration and sustainable harvesting regime. We began by investigating local utilization, perceptions on; regeneration and sustainability, threats, local ecological knowledge (LEK) and management practices relating to harvesting of papyrus in Loboi swamp, Kenya through local interviews and focused group discussions (Chapter 2). This was done with the knowledge that, a better understanding of people’s practices is crucial in sustainability of resources such as those relating to papyrus swamp. Our results showed that Cyperus papyrus supported local livelihood in social–cultural uses, as a source of income (papyrus mats are sold), cattle fodder, roofing materials, bedding materials and cooking fuel. This livelihood support revolved around basic human needs: social–spiritual fulfillment, economic empowerment, shelter, food, and energy. As such, papyrus was highly valued by the Endorois community living around Loboi swamp that have developed and instituted traditional management practices (such as rotational harvesting) to prevent overharvesting. The study further revealed important LEK relating to harvesting patterns and recovery where correlation and principal component analyses showed that experienced old harvesters avoided harvesting repeatedly at the same location, thereby allowing recovery of papyrus when compared to younger harvesters (r = 0.63, p< 0.01). The harvesters also understood the ecological needs of papyrus regeneration such as water and control proliferation of Typha into papyrus habitat during dry periods. Diversion of water for irrigation and frequent droughts were identified as major threats to the papyrus swamp. The study concluded that the documentation of site–scale papyrus users’ profile, LEK, and traditional practices are vital for the conservation and management of papyrus swamps in Kenya. Our second area of investigation was on the effects of harvesting on papyrus biomass production, stem/culm regeneration, stem–height, diameter and age structure. This was carried out through field experiments in undisturbed papyrus swamp in Lake Naivasha in order to establish sustainable harvesting regime following 6– and 12– monthly harvesting intervals in a 3 year study period (Chapter 3). The study revealed that a short harvesting lapse of 6–month significantly (Mann Whitney, Kruskal–Walis, Friedman statistics, P < 0.05) affected biomass, shoot regeneration and morphological features (e.g. height) compared to 12–month harvesting regime and non–harvested plots. Additionally and for the first time, we monitored and documented the natural regeneration of papyrus through seedling recruitment. The study underscored the significance of drawdown as a window for pulse seedling recruitment that enriches the genetic pool of papyrus swamps displaying such phenomenon. The regeneration information obtained from this particular study (Chapter 2) complements the local knowledge on recovery periods of papyrus (Chapter 3), while the documented life history of papyrus enhanced by drawdown events was crucial in the interpretation of microsatellite genetic analysis of papyrus populations (Chapters 4 and 5). This study recommended 12– monthly harvesting regime to papyrus harvesters because it allows adequate time for papyrus recovery and guarantees sustainability for swamp functioning and repository for biodiversity. The third study involved the use of microsatellite markers to assess the genetic status and structure of papyrus populations occurring in lakes, swamps and riverine habitats in Kenya (Chapters 4 and 5). The study found that most papyrus populations showed polymorphism (P) at five loci (60–100%) studied except Loboi with a marked monomorphism at all loci (P= 0%). At the lake level, all populations exhibited high clonal and genetic diversity with a low inbreeding coefficient (FIS = 0.076). However, a slightly lower clonal diversity in two Lake Victoria populations was observed and attributed these to high level of disturbances. Most of the gene diversity was portioned within populations resulting in a low overall genetic differentiation, with pairwise FST values lower between populations of the smaller Lake Naivasha (LN) than those of the larger Lake Victoria (LV) but moderate significant genetic differentiations between both lakes (AMOVA, T = 0.087, p = 0.01). The high gene flow within lakes (Nm = 32: LN, Nm = 7–12: LV) were mainly attributed to dispersal of regenerative parts (both seeds and live papyrus fragments) by water currents, wind, birds and animals while relatively low gene flow between lakes (Nm = 2.6) were attributed to historical contacts of populations through bird–animal mediated seed dispersals. This study further confirmed the occurrence of sexual reproduction and seedling recruitment (as observed in Chapter 3) among the lake populations as evident by many small clones which occurred once or few times in a 3 metre sampling intervals. This study also established that in lakes, the clonal structure was of the phalanx type though a guerrilla type was also evident in disturbed sites, suggesting combined growth strategy. The understanding of clonal structure and survival strategy obtained in Chapter 4 are important key elements in conservation of Cyperus papyrus. At large geographical scale (population across Kenya: Chapter 5), the clonal and genetic diversity varied strongly among nine populations studied. The clonal diversity (R) ranged from absent (R = 0: Loboi) to almost maximal (R= 0.98: Lake Naivasha). The study further revealed two groups of papyrus populations namely those that have few multilocus genotypes (MLGs) /clones (less than 15% of its total ramets) and those with many MLGs (> 55%). The study established that populations with few MLGs namely Loboi, Londiani–Simboiyot and Lake Jipe were characterised by large clonal sizes of up to 100 m, small to medium population areal sizes, no to low heterogeneity of genotypes as measured by pareto distribution parameter (ß Pareto = 0– 1.05), low genotypic richness (R = 0–0.13) and low effective, and observed number of alleles. On the other hand, population with many MLGs (Lake Naivasha, Lake Victoria, Ruiru, Moi–Eldoret, Nakuru–Mbaruk and Amboseli) were characterized by clonal sizes of up to 6 m, medium to large population areal sizes, high genotypic richness (R = 0.63–0.98) and heterogeneous genotypes (ß Pareto = 1.99–2.40) which occurred either few times or once. It was evident from these results that papyrus populations employed different survival reproductive strategies as indicated by varied clonal diversity (R), a genetic measure that estimate the balance of clonal and sexual reproduction over several generation. Furthermore, we found significant genetic differentiations among the nine populations (AMOVA, FST = 0.376, P = 0.001) and isolation by distance (r = 0.68, P = 0.01) an indication of little to no contacts of populations after initial seedling recruitment of the founder individual(s). The results of this study (chapter 5) suggest historical inter–basin connections and animal–bird mediation in dispersal of seeds to explain the observed gene flow (Nm) patterns (1> Nm <4). Overall, genetic studies (Chapters 4 and 5) revealed how papyrus populations are structured, clonal and genetic diversity levels including its reproductive strategies, past signatures of gene flow and genetic differentiations. All the 3 major studies considered together provide information necessary for survival and sustainability of papyrus in addition to arousing scientific curiosity for further studies on papyrus. This study obtained information that can be applied in policy implementation and local community advocacy for conservation of papyrus swamps in Kenya. This will support and safeguard local people needs that depend on papyrus for their livelihood in addition to ensuring papyrus functions for environmental sustainability as detailed in Chapter 6. |
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