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Sacred groves are remnants of primary forests with rich biological diversity, protected by indigenous communities. Their role in carbon sequestration and provision of other ecosystem services is being recognized. We investigated four sacred groves (Idanre Hills, Igbo-Olodumare, Ogun-Onire, and Osun-Osogbo) in southwestern Nigeria for biodiversity conservation, biomass production, and carbon storage. A total of 32 temporary sample plots of 800 m2 each were laid across all the sacred groves. Within each plot, all trees with dbh greater or equal to 10 cm were identified, and their diameters and heights measured. Saplings and seedlings were assessed within 100 m2 and 25 m2 sub-plots, respectively. Non-destructive methods were employed in estimating volume, biomass production, and carbon storage. Shannon–Wiener diversity index, Margalef index, and tree species richness in the four groves ranged from 2.63–3.55, 5.64–10.02, and 41–85, respectively, and differed significantly. The four groves were sanctuaries for many indigenous tree species of immense social, religious, ecological, and socio-economic importance. The high densities of seedling and sapling, together with the inverted-J tree diameter distributions, are indications of active regeneration and healthy ecosystem. Mean volume was high (range 244.99 to 343.08 m3 ha−1). The biomass (range 87.8 to 231.85 t ha−1) and carbon stock (range 43.9 to 115.9 t ha−1) of the groves revealed their potentials for climate change mitigation through atmospheric CO2 sequestration. Thus, besides being an effective biodiversity conservation method, sacred groves are important carbon sink. This calls for further conservation of sacred groves to serve as long-term carbon storage mechanism. [ABSTRACT FROM AUTHOR]

This study assessed and compared tree species diversity in a 26-year-old Gmelina arborea plantation with tree diversities in primary and degraded natural forests in southwestern Nigeria. In each forest type, a one-hectare block was divided into 400 m2 sample plots from which 4 were randomly selected, which was repeated on another one-hectare block, yielding eight 400 m2 plots per forest type. A 25 m2 quadrat was laid at the centre of each 400 m2 plot while a 4 m2 sub-quadrat was laid at the centre of each quadrat. Overstory, sapling and seedling species were inventoried in all 400 m2 plots, 25 m2 quadrats, and 4 m2 sub-quadrats, respectively. Family and species richness were significantly lower in G. arborea plantation overstory (7 families, 8 species) than in primary (8, 28) and degraded (18, 30) forest overstories. Diversity indices were also significantly lower for G. arborea plantation overstory than for primary and degraded forests. However, in the sapling layer, family and species richness in the G. arborea plantation (10, 13) were similar to those of primary (9, 15) and degraded (9, 16) forests. The species richness of G. arborea plantation seedling layer (24) was similar with that of degraded forest (25) but significantly higher than that of primary forest (18). primary (18 species), and degraded forests (25 species). Species diversity of the G. arborea sapling layerwct 2 (2.07) was significantly higher than that of its overstory (0.26) but significantly lower than those of primary (2.26) and degraded (2.44) forests. Of the species found in the G. arborea plantation seedling layer, 25% were absent in natural forests. Thus, this plantation understory harbours high biodiversity and can conserve biodiversity over time. Understory species diversity should be considered in biodiversity comparisons between plantations and natural forest. EDITED BY Nicholas Brokaw [ABSTRACT FROM AUTHOR]

Abstract: Adequate management of forest plantation requires estimation of growth and biomass yield and consequently, the fitting of functions for estimating biomass. Growth, biomass yield and biomass functions for estimating biomass of Nauclea diderrichii plantations in Omo forest reserve, Nigeria are described. Data were obtained from 30 temporary sample plots selected from stands that are 5–30 years old. A total of 81 trees were harvested for biomass estimation. Mean tree diameter at breast height (dbh), total height and stand bole volume ranged from 9.6 to 29.3cm; 9.0 to 23.6m and 23.27 to 535.52m3 ha−1, respectively while Total Above Ground Biomass (TAGB) varied from 32.5tha−1 to 287.5tha−1 between 5 and 30 years. Biomass allocations to stem, branch and foliage were 84.5%, 13.5% and 3%, respectively. All biomass components could be described precisely by dbh alone , with very low standard errors of estimates. Little improvement in the precision of the functions was achieved by including total height. In addition, the residuals of regression functions with only dbh were generally more constrained than those that included total height. Consequently, the functions with dbh alone and its derivative as independent variables were recommended for estimating biomass of opepe in Nigeria. [Copyright &y& Elsevier]

Abstract: The high productivity associated with many tropical forest plantation species has contributed to their importance in meeting the world''s growing demand for wood products. However, there is concern that their high growth rate and intensive management system might lead to site nutrients depletion. A total of 20 stands (10–28 years) of Gmelina arborea plantations in Oluwa and Omo forest reserves, Nigeria, was used to investigate the effect of Gmelina plantation development on site nutrients, aboveground productivity and nutrient accumulation. Standing biomass ranged from 81.5 to 392.1tha−1 in the youngest and oldest stands. Regardless of stand age, biomass partitioning was about 83.0, 13.5 and 3.5% to stem, branches and foliage, respectively. The size and age of trees did not significantly affect nutrient concentration in tree components. Nitrogen, Ca and Mg contents in tree tissue increased in the order of foliage>stem>branches while that of K and P increased in the order of foliage>branches>stem. Tree tissue nutrients concentration exhibited little change with stand development. Stand nutrient accumulation followed the same trend as standing biomass, with about 80% of each nutrient stored in the stem and 20% in branches and foliage. The accumulation of nutrients in stem, branches and foliage followed the order: Mg>N>Ca>P>K>Na. Though soil nutrients were slightly depleted between 10 and 19 years and re-built up afterwards, the overall effect of stand development on soil nutrients was not statistically significant, implying that the development of Gmelina plantations did not adversely affect the soil nutrient status. Consequently, productivity during the next rotation will most likely be affected by harvesting methods of current stands and management practices of the next rotation. The 20% accumulation of aboveground nutrients in branches and foliage implies that apart from the already replenished site nutrients, there will be an additional 20% nutrient input into the soil if the branches and foliage are left on the site after harvest. For long-term site quality and sustainability of production, successive plantations should be managed on 25 years rotation as lower rotation will most likely lead to steady depletion of site nutrients. [Copyright &y& Elsevier]

Above-ground biomass production was estimated for Gmelina arborea (Roxb) plantations (ages 5–21 years) in Oluwa Forest Reserve, Nigeria. A total of 120 trees were harvested and weighed to provide data for the estimation of biomass as well as for developing biomass equations. The results showed that Gmelina has high biomass yield, ranging from 83.2 t ha−1 (5 years) to 394.9 t ha−1 (21 years). Mean annual biomass increment varied from 16.2 to 20.9 t ha−1 yr−1. Average biomass allocations to different components of the tree were as follows: Stem about 84%; branch 13% and foliage 3%. The high biomass values were attributed to fast growth, high stand density (range: 837–1275 stems ha−1) and good site conditions in the study area. Biomass values of the various tree components (stem, branch and foliage) as well as total above-ground biomass (TAGB) were regressed with diameter at breast height (dbh) on the one hand (equation form 1), and with dbh and total height (in the form of D2H) on the other (equation form 2), with the aim of choosing the most suitable equation form. All equations generated had very high adjusted R2 and very low standard error of estimate. Residuals for both equation forms were normally and randomly distributed. Only little improvement in the ability of the equations to explain the variations in biomass was achieved by including the variable of total height. Considering the ease and accuracy in obtaining dbh data and the enormous time, errors and difficulty in obtaining height data, the equation form involving only dbh data as independent variable was recommended for use in estimating biomass for Gmelina in Oluwa forest reserve. [Copyright &y& Elsevier]