CHAPTER ONE
INTRODUCTION
1.1 BACKGROUND OF THE STUDY
Palynology, the study of pollen grains and spores is one of the most effective tools used to
reconstruct past environment. Because exines, the tough or resistant outer shell of pollen grains
of various species are unique and can survive under favourable conditions for thousands of years,
they have served as important tools for identifying many plants that were present in the past.
Preserved pollen and spores are extracted from sediment of different environment and used to
reveal what plants were associated with a particular landscape in the past. On a large scale,
palynological studies can identify broad environmental trends. It is commonly stated that the
present condition of the biosphere is the result of the action of ecological and historical factors of
the past and the relative importance of each of these agents in shaping present day world can be
evaluated (Qian et al., 2007; Emerson and Gillespie, 2008; Alvarez et al., 2009).
Palaeoecology is defined as “the ecology of the past” (Birks and Birks, 1980). It is the
reconstruction and study of past ecosystems, including the relationships between organisms and
their environment (Robert, 1998). The most fundamental palaeoecological tenets, Hutton’s
principle of uniformitarianism emerged from the field of geology and the most common is that
“The present is the key to the past” (Tomkeieff, 1962). This means that natural processes
operating in the past are the same as those that can be observed in the present, though rates can
vary. Palynological investigations during the late Quaternary indicate that the vegetation of West
Africa has undergone considerable changes (Agwu, 1986; Sowunmi, 2004; Njokuocha 2012 ).
This is believed to be as a result of climate variability, which influences the development and
distribution of vegetation in time. Early to mid Holocene conditions in the deserts of Africa and
Asia were reported to be significantly wetter than in the late Holocene, as revealed by micro and
macro fossil remains of plants and animals from lake sediment (Agwu and Beug, 1982; Jahns,
1996).
This investigation on the Holocene vegetation was conducted by means of a sediment profile
from Ozzi Lake in Opi, Nsukka Local Government of Enugu State. Nsukka is located between
latitudes 6o 181 N and 7o 071 E and between longitudes 6o 521 E and 7o 5411 N in the
southeastern geopolitical zone of Enugu State. Nsukka area is underlain by sedimentary rock
formations whose geologic age ranges from Coniacian to Paleocene (Chima and Okpe, 2008).
The temperature range in Nsukka is between 21oC - 32oC. It has a daily maximum temperature
which is usually more than 27oC while the mean daily minimum is 21oC. The highest
temperature of 33oC is usually recorded in January while the lowest 19oC occurs in August
(Agwu, 1997). The climate has two distinct alternating dry and rainy seasons occurring within
the months of November - April and May - October respectively. Nsukka plateau in particular is
characterised by a derived savannah which
INTRODUCTION
1.1 BACKGROUND OF THE STUDY
Palynology, the study of pollen grains and spores is one of the most effective tools used to
reconstruct past environment. Because exines, the tough or resistant outer shell of pollen grains
of various species are unique and can survive under favourable conditions for thousands of years,
they have served as important tools for identifying many plants that were present in the past.
Preserved pollen and spores are extracted from sediment of different environment and used to
reveal what plants were associated with a particular landscape in the past. On a large scale,
palynological studies can identify broad environmental trends. It is commonly stated that the
present condition of the biosphere is the result of the action of ecological and historical factors of
the past and the relative importance of each of these agents in shaping present day world can be
evaluated (Qian et al., 2007; Emerson and Gillespie, 2008; Alvarez et al., 2009).
Palaeoecology is defined as “the ecology of the past” (Birks and Birks, 1980). It is the
reconstruction and study of past ecosystems, including the relationships between organisms and
their environment (Robert, 1998). The most fundamental palaeoecological tenets, Hutton’s
principle of uniformitarianism emerged from the field of geology and the most common is that
“The present is the key to the past” (Tomkeieff, 1962). This means that natural processes
operating in the past are the same as those that can be observed in the present, though rates can
vary. Palynological investigations during the late Quaternary indicate that the vegetation of West
Africa has undergone considerable changes (Agwu, 1986; Sowunmi, 2004; Njokuocha 2012 ).
This is believed to be as a result of climate variability, which influences the development and
distribution of vegetation in time. Early to mid Holocene conditions in the deserts of Africa and
Asia were reported to be significantly wetter than in the late Holocene, as revealed by micro and
macro fossil remains of plants and animals from lake sediment (Agwu and Beug, 1982; Jahns,
1996).
This investigation on the Holocene vegetation was conducted by means of a sediment profile
from Ozzi Lake in Opi, Nsukka Local Government of Enugu State. Nsukka is located between
latitudes 6o 181 N and 7o 071 E and between longitudes 6o 521 E and 7o 5411 N in the
southeastern geopolitical zone of Enugu State. Nsukka area is underlain by sedimentary rock
formations whose geologic age ranges from Coniacian to Paleocene (Chima and Okpe, 2008).
The temperature range in Nsukka is between 21oC - 32oC. It has a daily maximum temperature
which is usually more than 27oC while the mean daily minimum is 21oC. The highest
temperature of 33oC is usually recorded in January while the lowest 19oC occurs in August
(Agwu, 1997). The climate has two distinct alternating dry and rainy seasons occurring within
the months of November - April and May - October respectively. Nsukka plateau in particular is
characterised by a derived savannah which
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