An investigation of forest ecosystem health in relation to anthropogenic disturbance in the south-western Mau Forest Reserve, Kenya [Elektronische Ressource] / presented by Obati, Gilbert Obwoyere

Gilbert Parker

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• Biologie

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• Publié par: universitat_bremen
• Publié le: 01 janvier 2007
• Nombre de lectures: 43
• Langue: English
• Poids de l'ouvrage: 9 Mo

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An Investigation of Forest Ecosystem Health in
Relation to Anthropogenic Disturbance in the
Southwestern Mau Forest Reserve, Kenya
A dissertation for the Award of the Degree of
Doctor of Natural Sciences (Dr. rer. nat.)
Faculty of Chemistry and Biology
University of Bremen
Presented by
Obati, Gilbert Obwoyere An Investigation of Forest Ecosystem Health in
Relation to Anthropogenic Disturbance in the
Southwestern Mau Forest Reserve, Kenya
A dissertation for the Award of the Degree of
Doctor of Natural Sciences (Dr. rer. nat.)
Faculty of Chemistry and Biology
University of Bremen
Presented by
Obati, Gilbert Obwoyere
First Supervisor: PD Dr. Broder Breckling
Second Supervisor: Prof. Dr. Martin Diekmann
rd
Submitted on 3 August, 2007
thDate of conferrment 18 September, 2007 Gilbert Obwoyere. Obati
Declaration
Statement according to §6 Final Examination Regulation of the University of
Bremen for the Degree of Dr of Natural Science (Dr. rer. nat.).
I herewith declare and confirm that I have elaborated my dissertation titled
An Investigation of Forest Ecosystem Health in Relation
to Anthropogenic Disturbance in the South-western Mau
Forest Reserve, Kenya
Single-handed and without using other sources other than those mentioned herein.
_________________________ ___________________
Place and Date Signature
iiForest Ecosystem Health-SW Mau, Kenya
Abstract
The dissertation describes investigations carried out from September 2005 to
August 2006 to assess forest ecosystem health in relation to human disturbance in
the Southwestern Mau forest reserve Kenya. The study involved the determination
and comparison of tree species composition and structure, regeneration potential
and capacity, litter production and nutrient fluxes between disturbed and
undisturbed sites. A socioeconomic appraisal of the inhabitants was also carried
out. Forest cover change analysis of the greater Mau forest was done for the
period between 1984 and 2003 using Landsat satellite images.
A total of 24 families, 34 genera and 37 woody species comprising mainly trees
were enumerated. There were 20 families in the undisturbed sites while 21 were
present in the disturbed sites. In undisturbed sites, 30 species belonging to 29
genera were recorded while 29 species from 27 genera were tallied in the
disturbed sites. The mean species richness was higher in the disturbed sites.
Undisturbed sites had a lower proportion of shrubs and under storey trees with a
higher frequency of over storey trees. Both sites had high number of seedlings and
wildings.
Regarding survival and recruitment from seasonal seed rain, disturbed sites had
significantly higher mean species richness. Germinations from seasonal seed rain
indicated higher mean seedling species richness in disturbed plots while seedling
density was significantly higher in undisturbed plots. No significant mean
differences in species composition were recorded from the seed bank trials.
A higher amount of fine litter was collected in disturbed plots with insignificant
mean differences with regard to K, C and N content between the sites. There were
no significant mean differences in the C: P, ratios whereas undisturbed plots had
significantly lower mean C: N ratios. Within stand mean nutrient use efficiency for
C, N, P, K, and Ca were lower in the undisturbed plots.
Survey results indicated that several tree species that were once common or
dominant in the area were increasingly becoming rare. Increase in human
population, firewood collection, agricultural expansion, land subdivision among
others were ranked as important causes of forest degradation. Positive significant
correlations were reported between the definition of provision of services, forest
condition, provision of goods, the adequacy of goods provided and ecosystem
health. However, a significant negative correlation was reported for the values
attached to the current land use. The presence of disturbance indicator species like
Neoboutonia macrocalyx, Croton megalocarpus and Vernonia auriculifera in the
vegetation community indicates considerable levels of human disturbance in the
reserve representing retrogression in the vegetation succession.
The vertical stratification of the forest reserve depicts secondary growth in the
reserve. The potential for natural regeneration of trees after natural or
anthropogenic disturbance exists despite a poor soil seed bank. High litter annual
turn over in disturbed sites, coupled with lower nutrient content and nutrient use
efficiency as well as higher fine litter C: N and C: P ratios defines them as poorer
sites. A chronological degradation in the condition of the forest over time is
apparent with current land uses having negative significant effects. Thematic
change and image difference analysis indicated a significant change in closed
canopy forest.
iiiGilbert Obwoyere. Obati
Acknowledgements
First, I give honour and glory to God for his unfailing gift of life and blessings
throughout the entire project period. Secondly, my sincere gratitude is due to my
supervisors PD. Dr. Broder Breckling and Prof. Dr. Martin Diekmann for their
unconditional support and specifically Dr Breckling for his day today interactions
during the course of this project. May I take this opportunity to also sincerely
appreciate the support of Prof. Dr. Juliane Filser Head, Department of General and
Theoretical Ecology.
I would also like to extend my appreciation to colleagues at the Department of
General and Theoretical Ecology University of Bremen for their insights and
encouragement during the entire period. I am also indebted to Ms Marion Ahlbrecht
of the Department of Vegetation and Evolutionary Ecology University of Bremen
who directly assisted in the analysis of litter samples. The computer systems
administrator Mr Falko Berger was of more of a brother in all my computer related
work at the UFT, to him is a handful of thanks.
My sincere gratitude is due to Professor A A Aboud and Dr. M. Karachi of the
Department of Natural Resources Egerton University, Kenya for their valuable
support during the fieldwork stage. Am also indebted to the technicians at Kenya
Agricultural Research Institute (KARI-Njoro) National Plant Breeding Centre and
the department of Soil Science Egerton University for processing of the litter
samples.
I owe gratitude to staff of the Kenya Forest Service, Mara Mara and Itare forest
stations specifically Messrs Kevin K. Sitieney and Martin M. Marete for their tireless
efforts during the fieldwork. Likewise, I would like to thank Gladys Chepkirui and
Anita Chepkirui for their assistance in administering the questionnaires.
Am greatly indebted to my family, my wife (Rodah) and daughters (Faith and Anne)
for their constant prayers, support and encouragement. It was not easy being away
from them when in Bremen Germany.
Finally, I acknowledge the Deutscher Akademischer Austausch Dienst (DAAD)
(German Academic Exchange Service) who financed the whole project.
ivForest Ecosystem Health-SW Mau, Kenya
Dedicated to
My Late Mother
Jessicah Vihenda Obati
and my Family
Rodah Afandi Obwoyere, Faith Vihenda Obwoyere
and Anne Neema Obwoyere
vGilbert Obwoyere. Obati
Table of contents
Declaration ........................................................................................................ii
Abstract............................................................................................................iii
Acknowledgements ..........................................................................................iv
Table of contents..............................................................................................vi
List of tables .....................................................................................................ix
List of figures.................................................................................................... x
List of symbols and acronyms .........................................................................xii
1. INTRODUCTION................................................................................................. 1
1.1 STATEMENT OF THE PROBLEM .................................................... 4
1.2 CONCEPTUAL FRAMEWORK ...................................................................... 5
1.3 RESEARCH OBJECTIVES ............................................................................ 9
1.3.1 Broad objective........................................................................................ 9
1.3.2 Specific objectives................................................................................... 9
1.3.3 Hypotheses ........................................................................................... 10
2. BACKGROUND TO THE STUDY AREA.......................................................... 12
2.1 THE EAST AFRICAN MONTANE FOREST ECOREGION........................... 12
2.1.1 Vegetation and biome type.................................................................... 12
2.1.2 Biogeographical history ...................