Assessing the impacts of Silvicultural treatment systems on Ecosystem services: a case of Carbon sequestration and Biodiversity conservation Evelyn Asante-Yeboah March, 2010 Assessing the impacts of Silvicultural treatment systems on Ecosystem services: a case of Carbon sequestration and Biodiversity conservation By Evelyn Asante-Yeboah Thesis submitted to the International Institute for Geo-Information Science and Earth Observation in partial fulfilment of the requirements for the degree of Master of Science in Geo-information Science and Earth Observation, Specialization: Geo-information for Natural Resource Management Thesis Assessment Board Prof. Dr. Ir. Eric Smaling, Chairman, Degree Assessment Board, ITC (Chair) Prof. A. A. Adimaddo, KNUST (Co-Chairman) Dr. B. E. Prah, (External Examiner) Prof. S. K Oppong, Internal Examiner, KNUST Dr. E. M. Osei. Jnr, Internal Examiner, KNUST Ir. Louise van Leeuwen, Course Co-ordinator, ITC Supervisors: Ir. Louise van Leeuwen. (ITC), Prof. S.K. Oppong (KNUST) KNUST FACULTY OF GEO-INFORMATION SCIENCE AND EARTH OBSERVATION,OF THE UNIVERSITY OF TWENTE, ENSCHEDE, THE NETHERLANDS AND KWAME NKRUMAH UNIVERSITY OF SCIENCE AND TECHNOLOGY, KUMASI, GHANA Disclaimer This document describes the work undertaken as part of a programme of study at the International Institute of Geo-Information Science and Earth Observation and the Kwame Nkrumah University of Science And Technology. All views and opinions expressed in this work remain the sole responsibility of the author, and do not necessary represent those of the two institutions. iii Assessing the impacts of Silvicultural treatment systems on Ecosystem services: a case of Carbon sequestration and Biodiversity conservation Abstract Forest management practices in Ghana for many years have been based on timber production for economic benefits. Silvicultural interventions mainly logging was the key management option in Ghana for favouring desired species for high-value end use. A shift in focus under the new Forest and Wildlife policy necessitated the need to manage forests for multiple benefits. Improved Silvicultural interventions mainly the Tropical shelter wood system, Post exploitation system and Selection system were tried experimentally in Bobiri Forest reserve in Ghana in the early 1960s. The intervention involved series of different operations geared towards the removal of undesired species to favour the growth of desired species. However, the current concerns of climate change and its associated effects have necessitated the need to manage forests to make them more contemporary to current situation. In this study an attempt is made to assess the impacts of these Silvicultural treatments on carbon sequestration and biodiversity conservation 45 years after interventions. The study was conducted in Bobiri Forest reserve in Ghana. The overall objective is ‘to contribute to the adoption of forest management strategies appropriate for multiple benefits with a major focus on sustaining environmental services such as carbon sequestration and biodiversity conservation in the natural tropical forests, by evaluating the performance of three silvicultural treated systems’. 96 sample plots were located in the three silvicultural treated systems and the untreated system (control). Aboveground biomass was estimated from a three nested circular plot (with horizontal radii of 12.62m, 8m and 4m) using simple random sampling. Standard tropical allometric equations were used to derive carbon stocks from field data collected. Pixel based approach (classified image) was used for the biomass/carbon mapping. Species diversity was estimated using Shannon-Weiner index. Spectral signatures were extracted from Aster image to examine the relationship between Aster data with forest parameters. Carbon density in the total silvicultural treated systems amounted to 530.67±67Mg. ha-1 (± S.E). The density of carbon in each silvicultural treated system ranged from a high of 586.86±18Mg.ha-1 in Tropical Shelterwood system (TSS) to a low of 457.82±19 in Post Exploitation System (PES). The untreated system (control) sequestered 275.68±Mg.ha-1 of carbon. A significant difference was observed in the carbon densities and species diversity of the silvicultural treatment systems. All relationships between Aster data with forest parameters were weak and not significant. It is therefore evident that the intervention has resulted in a forest with high carbon sequestration potential with diverse structural and species composition for ecosystem functioning. However, the method of intervention mainly poison (sodium arsenide) of trees in TSS and PES is considered environmentally unacceptable. Hence, the adoption of a selection system in which intensity of harvesting can be controlled will provide the multiple benefits expected of the forest. Keywords: Forest management, silvicultural systems, carbon sequestration, species diversity vegetation indices. iv Assessing the impacts of Silvicultural treatment systems on Ecosystem services: a case of Carbon sequestration and Biodiversity conservation Acknowledgement I sincerely express my profound gratitude to the Almighty God for his blessings; guidance and gift of life granted me throughout this study. I wish to express my appreciation to Tropenbos International and ITC capacity fund for sponsoring this course. To my supervisors, Louise van Leeuwen and Prof. Samuel Kingsley Oppong, I say a big thank you for your constructive criticism and helpful advices. To Michael Weir, and all staff of ITC, NRM department, and all KNUST GIS NATUREM staff, am most grateful for your contributions. Special thanks go to Francis Kwabena Dwomoh of Forestry Research Institute of Ghana. I am most grateful for suggesting this topic, guiding me through the research work, and for the patience you had with me through out this work. I wouldn’t have come this far without your immense contribution. I owe you this work. I also say a big thank you to Patrick Vanlaake for his time and help during the proposal stage and to David Rossiter for his encouraging words. Many thanks also go to the staff and workers of Bobiri Forest reserve and to all colleagues and friends who provided support in one way or the other. Finally to the Asante-Yeboah family, I owe you many thanks for the support granted me in times of difficulties and the words of encouragement offered throughout my studies. v Assessing the impacts of Silvicultural treatment systems on Ecosystem services: a case of Carbon sequestration and Biodiversity conservation Dedication I happily dedicate this piece of work to the entire Asante-Yeboah family for their prayers, support and encouragement throughout my studies. Your toil has brought me this far!!! vi Assessing the impacts of Silvicultural treatment systems on Ecosystem services: a case of Carbon sequestration and Biodiversity conservation Table of Contents Abstract ........................................................................................................................................................ iv Acknowledgement ........................................................................................................................................ v Dedication .................................................................................................................................................... vi Table of Contents ........................................................................................................................................ vii List of Figures ................................................................................................................................................ x List of Tables ................................................................................................................................................ xi List of Acronyms .......................................................................................................................................... xii 1.0 INTRODUCTION ....................................................................................................................................... 1 1.1 Background ......................................................................................................................................... 1 1.2 Forest management practices in Ghana ............................................................................................. 1 1.3 Silvicultural systems in Ghana ............................................................................................................. 2 1.3.1 Tropical Shelterwood System (TSS) ............................................................................................. 2 1.3.2 Post Exploitation System (PES) .................................................................................................... 2 1.3.3 The (Girth Limit) Selection System (SS) ........................................................................................ 3 1.4 Forest management practices in the 21st century .............................................................................. 4 1.5 Biomass estimation and carbon sequestration .................................................................................. 4 1.6 Biodiversity and the functions of ecosystem ...................................................................................... 5 1.7 Problem statement and Justification .................................................................................................