Restoration of degraded dry semideciduous forest ecosystems in Ghana: Effects of African mahogany species on soil chemistry, tree diversity and the application of leaf morphometrics for provisional seed zonation
Danquah J. A. (2012). Restoration of degraded dry semideciduous forest ecosystems in Ghana: Effects of African mahogany species on soil chemistry, tree diversity and the application of leaf morphometrics for provisional seed zonation. https://doi.org/10.14214/df.148
Abstract
The dry semideciduous forest zone is one of the most fragile and highly threatened ecosystems in Ghana. Recurrent bushfires and other anthropogenic disturbances have degraded this forest zone and converted a large proportion to savannah woodland. Moreover, the invasion of weeds following disturbances has impeded natural regeneration. Hence, the likely solution to this problem is restoration through the use of native forest tree species to catalyse natural regeneration. The use of African mahogany species in this regard has been emphasised. This study aims to (i) investigate the levels of phenotypic plasticity and ecogeographic and morphometric variation as well as similarity among populations of Khaya anthotheca and Khaya ivorensis with respect to leaf morphology as a basis for developing a preliminary framework for seed zonation for restoration; (ii) determine the effects of stand structure and native tree density on the recruitment of mahogany species in line-enrichment planting; and (iii) assess the effects of mahogany species on resident or native tree species diversity and soil chemical properties in restorations of degraded semi-deciduous forest ecosystems in Ghana. The results of the study indicated a highly significant phenotypically plastic response of leaf morphology to precipitation, temperature, altitude and latitude in Khaya ivorensis populations. In addition, it was established that leaf size in Khaya ivorensis and K. anthotheca varies inversely with latitude, annual potential evapotranspiration and aridity index. However, leaf traits vary directly with a precipitation gradient among the respective species. The results suggested a south-north clinal relationship to leaf traits, with the southern populations of the two Khaya species having larger leaf sizes than the northern populations. Thus, seeds collected from higher latitudes could be planted in the same zone or moved to lower latitude with high amounts of rainfall. However, the results from Poisson regression modelling indicated that stand basal area, growing space and crown diameter were positively associated with recruitment. However, stand dominant height was negatively associated with recruitment. The results indicated that mixed mahogany species foster the recolonisation of a diversity of native tree species and accelerate the regeneration rate in the restoration of fire-degraded dry semi-deciduous forest ecosystems compared to natural regeneration. Moreover, relatively higher amounts of Ca, Mg, base saturation, CEC, organic C and organic matter and low amounts of Al were recorded in the soils beneath mixed mahogany plantation sites compared to natural regeneration sites.
Keywords
Khaya and Entandrophragma species;
leaf morphological variation;
phenotypic plasticity;
restoration;
seed zonation;
environmental gradient;
soil chemical properties
Published 31 August 2012
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Available at https://doi.org/10.14214/df.148 | Download PDF
Original articles
Danquah, J.A. 2010. Phenotypic plasticity of leaf length to an environmental gradient in Khaya ivorensis (Meliaceae) populations in Ghana. African Journal of Environmental Science and Technology 4(12): 860-865.
https://doi.org/10.5897/AJEST 10.227
Danquah, J.A., Appiah, M., Pappinen, A. 2011. Eco-geographic variation in leaf morphology of African mahogany (Khaya anthotheca and Khaya ivorensis) provenances in Ghana. European Journal of Scientific Research 51(1): 18-28.
http://www.eurojournals.com/EJSR_51_1_02.pdf
Danquah, J.A., Appiah, M., Pappinen, A. 2011. Leaf morphometric variation in two species of African mahoganies: Khaya ivorensis and Khaya anthotheca (Meliaceae). European Journal of Scientific Research 54(3): 325-338.
http://www.eurojournals.com/EJSR_54_3_01.pdf
Danquah, J.A., Appiah, M., Pappinen, A. 2011. Enrichment planting of African mahoganies in fire-degraded dry semi-deciduous forests in Ghana: The Effect of the stand structure and species numbers on recruitment. European Journal of Scientific Research 52(2): 213-225.
http://www.eurojournals.com/EJSR_52_2_09.pdf
Danquah, J.A., Appiah, M., Pappinen, A. 2012. The Effect of African mahogany species on soil chemical properties in degraded dry semi-deciduous forest ecosystems in Ghana. International Journal of Agriculture and Biology 14: 321-328.
http://www.fspublishers.org/p_issuevol.jsp?&acc1=VOL_14_NO_3
Danquah, J.A., Appiah, M., Pappinen, A. 2011. Comparison of post-fire planted and natural dry semi-deciduous forest communities in Ghana. African Journal of Agricultural Research 6(23): 5266–5277.