Floristic Structure of Fire Experimental Plots of Olokemeji Forest Reserve, Ogun State, Nigeria

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Total enumeration of tree species was carried out fire experimental plot of Olokemeji forest reserve for relative importance value (RIV) mean heights, mean diameter at breast height and mean basal area. Three investigative plot (Plot A, B and C) were established. Plot A which represents Early Burn is burnt annually during the dry season while Plot B was burnt annually during the rainy season when the trees are still wet and Plot C serves as the protected area. Gmelina arborea had the highest relative importance value (28.31), this is followed by Dalbergia sissoo which had RIV of 10.94. Plot C recorded the highest frequency of trees with the highest tree heights, this is closely followed by Plot A and Plot B being the plot with the lowest mean height. Plot C has the highest mean diameter at breast height (DBH) of trees and it is followed by Plot B and Plot A with very close mean DBH. The highest mean basal area was also recorded in Plot C, the highest total basal area and tree volume was also recorded at Plot C as 32.2 m2 ha-1 and 188.8 m3. The size distribution of tree species depicts that Plot C has been protected just as expected Keywords: Forest, Structure, Flora, Dynamics, Fire

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... In fact, this value can be used to identify the most valuable and useful species for a cluster or an area (Whitney et al., 2018). A number of different methods can be used to determine the importance value of species according to different studies (Razavi et al., 2012;Olorunmaiye et al., 2013;Taiwo et al., 2020). However, for the current study, relative importance value (RIV) was calculated as in Eq. 5, using the relative frequency (RF) and relative dominance (RD' Eqn. ...
Homegardens are principally known as integrated man-made ecosystems with annuals and perennials where trees play a significant role in storing atmospheric carbon in the vegetation as above-ground biomass (AGB). Being one of the agroforestry systems, homegardens could ease the pressure on natural forest cover in the process of carbon sequestration and carbon storage, while reducing the greenhouse gas accumulation (CO2) in the atmosphere. Thus, they could be described as a promising approach for mitigation of climatic changes. A study was conducted to assess the tree diversity and AGB carbon stock of homegardens in Matale district, Sri Lanka. A total of 122 homegardens ranging from urban dwellings up to natural eco-systems across 05 agro-ecological regions (AER) were surveyed, capturing a vast diversity. A total of 5,140 woody trees were recorded from 100 genera and 45 families, covering 16.67 ha of homegardens. Six and three tree species were identified as vulnerable and near threatened, respectively in terms of national-level conservation status. Shannon-Wiener index (SWI) of 1.90±0.49 ranging between 0.49 and 2.83 indicated compositional diversity of the tree species. The AGB was widely varying between 0.8-139.4 Mg C/ha (mean AGB of 36.5±27.4 Mg C/ha). AGB and SWI were higher in small-scale (38.8±29.7 Mg C/ha and 1.91±0.50, respectively) than in medium-scale homegardens (28.0±14.9 Mg C/ha and 1.86±0.50, respectively). Species richness and species density were higher in small scale (<0.2 ha) homegardens compared to medium scale (0.2-0.8 ha). A considerable variation of tree diversity and AGB was observed among the homegardens in different AERs. The variation of AGB was primarily governed by tree density (trees/ha) and species diversity. Focusing on that, optimizing the potential of homegardens in terms of storing atmospheric carbon as AGB in the study area can be considered as a timely strategy in mitigating impacts of climate change and assisting domestic food security.
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The tropical forests in developing countries are faced with the problem of illegal exploitation of trees. However, dearth of empirical means of expressing the dimensions, structure, quality and quantity of a removed tree has imped conviction of offenders. This study aimed at developing a model that can effectively estimate individual tree basal area (BA) from stump diameter (Ds) for Tectona grandis stands in Omo Forest Reserve, Nigeria, for timber valuation in case of illegal felling. Thirty-six 25 m × 25 m temporary sample plots (TSPs) were laid randomly in six age strata; 26, 23, 22, 16, 14, and 12 years specifically. BA, Ds and diameter at breast height were measured in all living T. grandis trees within the 36 TSPs. Least square method was used to convert the counted stumps into harvested stem cross-sectional areas. Six basal area models were fitted and evaluated. The BA-Ds relationship was best described by power model which gave least values of Root mean square error (0.0048), prediction error sum of squares (0.0325) and Akaike information criterion (-15391) with a high adjusted coefficient of determination (0.921). This study revealed that basal area estimation was realistic even when the only information available was stump diameter. The power model was validated using independent data obtained from additional plots and was found to be appropriate for estimating the basal area of Tectona grandis stands in Omo Forest Reserve, Nigeria.
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Wetlands in Nigeria face constant threat of destruction by urbanization, road construction and agricultural activities, but the floristic compositions of these fragmented communities are unknown. A comparative assessment study of the floral of three wetlands in a forest-savanna transition ecological zone, Ibadan (70261 N, 30541 E), Oyo State, Nigeria was conducted in the dry and wet seasons of 2002 to assess their species richness, density, community structure and diversity. Thirty-eight plant species from 19 families were enumerated in the three wetlands in two seasons. Nineteen species from 13 families were enumerated in the dry season, while 14 species belonging to nine families were enumerated in the wet season. Eight families were common to both seasons. Eleyele and Apete wetlands had relatively stable flora for both seasons, while Oba dam exhibited pronounced shift in flora between the dry and wet seasons. Continuous perturbation of the three wetlands encouraged proliferation and dominance of some invasive species at the expense of indigenous species populations, leading to subtle biodiversity erosion.
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Fire is a major driving force of landscape change in the Mediterranean region. The objectives of this paper were to explore the implications of landscape change and wildfires in a region of northwestern Portugal for the diversity of breeding birds. Land use cover for the years 1958, 1968, 1983 and 1995 was obtained from aerial photography for a study area of 3700 ha. Breeding bird assemblages in each of six land use categories were characterized in 1998 using point counts. The main landscape changes in the study area across the 40 years were a decrease in the area of agricultural land and low shrublands (respectively 29% and 48%) and an increase in forests and tall shrublands (both over 95%). Bird assemblages showed increased richness and diversity across the gradient: low shrublands tall shrublands conifer mixed deciduous agricultural areas. Many of the species with narrow niche breadth (specialists) were associated with agricultural areas and deciduous forests. In spite of the low diversity of burned areas (mostly shrublands) a few specialist species depend on this habitat. Thus, the current fire regime probably contributes to maintaining bird diversity at the landscape level. There was an inverse relationship between landscape diversity and estimated bird diversity across the last 40 years. Landscape management actions to preserve bird diversity should focus on the maintenance of agricultural land and deciduous forests. In parallel, a wider use of prescribed burning and grazing is suggested. This would contribute to maintaining low shrublands in the landscape, useful both as an habitat for some bird species and as fuel breaks for preventing the occurrence of large wildfires.
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This study proposes a new metric called canopy geometric volume G, which is derived from small-footprint lidar data, for estimating individual-tree basal area and stem volume. Based on the plant allometry relationship, we found that basal area B is exponentially related to G (B = β1G3/4, where β1 is a constant) and stem volume V is proportional to G (V = β2G, where β2 is a constant). The models based on these relationships were compared with a number of models based on tree height and/or crown diameter. The models were tested over individual trees in a deciduous oak woodland in California in the case that individual tree crowns are either correctly or incorrectly segmented. When trees are incorrectly segmented, the theoretical model B = β1G3/4 has the best performance (adjusted R2, R2 a = 0.78) and the model V = β2G has the second to the best performance (R2 a = 0.78). When trees are correctly segmented, the theoretical models are among the top three models for estimating basal area (R2 a = 0.77) and stem volume (R2 a = 0.79). Overall, these theoretical models are the best when considering a number of factors such as the performance, the model parsimony, and the sensitivity to errors in tree crown segmentation. Further research is needed to test these models over sites with multiple species.
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Animal and plant life cycles are increasingly shown to depend on temperature trends and patterns. In their Perspective, Peñuelas and Filella review the evidence that global warming during the 20th century has affected the growth period of plants and the development and behavior of animals from insects to birds. The authors warn that changes in the interdependence between species could have unpredictable consequences for ecosystems, that the lengthening of the plant growing season contributes to the global increased carbon fixation, and that changes in phenology may affect not only ecosystems but also agriculture and sanitation.
Fire has been recognized as a vital agent influencing the diversity and vigor of landscapes. It is particularly important in Mediterranean ecosystems, such as those of California. This book is of interest to ecologists, policy makers, and land managers.
The diversity, relative importance, canopy height and cover of plant species in the Kwame Nkrumah University of Science and Technology (KNUST) Botanic Garden were evaluated in five 1-ha plots using a stratified random sampling technique in order to build an understanding of its floristic composition and structure in two distinct parts of the garden (cultivated and uncultivated). We recorded 184 species which belonged to 146 genera, 51 families and six growth forms. The most dominant tree species in the garden were Elaeis guineensis Jacq., Hevea brasiliensis (Willd.) Muell.-Arg. and Parkia biglobosa -(Jacq.) G. Don. with a combined importance index of 60.09 (20 % relative importance). The differences in importance value indices of species between the culti- vated and uncultivated areas of the garden were statistically insignificant (p > 0.05), suggesting the presence of a conducive growth environments for plants in both areas. The most dominant families were Fabaceae, Moraceae, Arecaceae and Euphorbiaceae whilst trees were the most predominant growth forms (62.5 %). Average crown height and percentage canopy were 28.8 ± 8.81 m and 66.4 ± 8.26 % respectively. These results show the floristic richness of the KNUST botanic garden and underscore the garden’s potential as a centre for ex-situ conservation beside its traditional roles in education, research and recreation.
Experimental manipulation of climate provides a powerful tool for studying plant community dynamics with respect to current climate change. We experimentally investigated the vegetation dynamics of a Mediterranean shrubland under directional climate change by manipulating rain and temperature at stand level throughout 7 years. We focused on seedling establishment in relation to the between-year variability of drought conditions. We also compared seedling dynamics to changes in the established adult vegetation to assess the coupling between both dynamics. We used multivariate techniques (principal response curves (PRC) and redundancy analysis (RDA)) to explore changes in the whole community, and Generalized Linear Model (GLZM) to analyse the influence of drought on the abundance and survival of the most abundant species.
Fire has played a decisive role in Post-Glacial biological and cultural evolution in the Mediterranean Region. Its evolutionary impact on plants has been manifested by feedback responses, in which the fire and its after-effects selected plants for physiological and other mechanisms that enable direct fire tolerance or permit avoidance followed by vegetative and reproductive regeneration. The dominant, sclerophyll, drought-tolerant phanerophytes of the maqui are obligatory rootsprouters, whereas the subordinate, drought-evading chamaephytes, as well as herbaceous perennials, are both vegetative and reproductive regenerators and are well adapted to new, fire-denuded habitats. Annual and perennial grass fire-followers are also able to escape high surface fire temperatures with the aid of torsion devices on seeds. Evolutionary strategies to overcome fire are closely interwoven with those against other environmental stresses such as drought and grazing. These combinations of stresses have brought about convergence in plant form and function in mediterranean climates. Fire has thus been important in the evolution of more xeric grasslands and woodlands and more mesic maqui and shrubland communities. Contrary to the present view of fire as simply destructive, both fire and grazing have favored genetical as well as ecological diversity. They should be studied as integral components of Mediterranean ecosystems and their evolution.
We are still lacking in experimental evidence of the effects of climate change on the richness of plant species under field conditions. We report a decrease in the species richness of recruited seedlings in a Mediterranean shrubland in experimentally induced drought and warming over 4 consecutive years. Drought decreased the number of emerging seedlings and their respective species richness. Warming also decreased seedling species richness, but it did not affect the number of emerging seedlings. Species that produce fewer recruits are more likely to disappear in drier or warmer scenarios. However, when the effect of induced climate treatment was greatest, the more abundant species in control stands were not necessarily the ones least affected by treatment; in other words, species-idiosyncratic responses may occur. These results show that demographic processes are sensitive to minor climate changes, with probable consequences on the diversity and structure of the future plant communities.
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