Goodness-of-Fit Test for Volume Equations of Three Timber Species in South East Cameroon

A study on the validity of volume equations currently used for three timber species, Entandrophragma cylindricum, Erythrophleum ivorensis and Pericopsis elata （Sapelli, Tali and Assamela respectively） in south east Cameroon, was conducted between the months of July and September, 2007 to evaluate their suitability for the site. Twenty-two percent sampling intensity was conducted within annual allowable cuts and diameter readings taken on standing trees with the aid of a wide band Relascope. A non linear regression equation model was employed to compute volume equations and the student＇s t-test for the analysis of the existing models. Based on individual tree volumes within stands, new equations for the three species were constructed. A comparison was made between the new equations and those that were being used at the site. Results indicated a total standing volume of 0.007 m3/ha obtained for the three species （Sapelli 0.003 m3/ha, Tali 0.002 m3/ha and Assamela 0.002 m3/ha）. Two new volume equation models [B] and [C] were retained for their goodness-of-fit with [B] for Assamela and [C] for Sapelli and Tali. Results also showed that a total volume of 0.005 m3/ha was underestimated for the three species （Sapelli 0.002 m3/ha, Tali 0.001 m3/ha and Assamela 0.002 m3/ha） when existing volume equations were applied. It is imperative to construct new volume equations that are compatible with the ecological characteristics of the site using representative samples. Setting-up appropriate methods for their validation shall also serve as checks to future management errors.

Biological and chemical attributes of soils under forest species in Northeast Brazil

Timber forests contribute to the sustainable development of the biomes in tropical regions.The aim of this study was to evaluate the biological and chemical properties of the soil as a consequence of the cover with native and non-native species in the Acarau basin,a transition area from the coast to the Brazilian semi-arid region.Areas planted with four native species(Anadenanthera colubrina,Astronium fraxinifolium,Handroanthus impetiginosus,Colubrina glandulosa)and three exotic species(Acacia mangium,Casuarina equisetifolia,Eucalyptus urophylla)plus a non-forested agricultural area were evaluated for organic carbon contents,and microbial and chemical soil properties.The levels of soil organic carbon were highest in A.colubrina and C.equisetifolia plantations.Low basal soil respiration was observed but the microbial biomass was particularly low in the non-forested area.In the C.equisetifolia,E.urophylla,and H.impetiginosus plantations,elevated soil metabolic quotients were found.The A.colubrina and H.impetiginosus plantations had the highest levels of easily extracted-glomalin related soil protein.Tree species affect concentrations of essential nutrients and the biological quality of the soil in different ways.They can also improve the biological and chemical properties of the soil in the coastal plains of tropical regions.

Integrating species and successional classes for wood production in a mixed forest restoration system in a neotropical region

As forests in neotropical regions,particularly in developing countries,are devastated,interventions to restore biodiversity and its ecological functions are needed.Rural producers have thus been encouraged to grow trees for wood production as an economic activity.The objective of this study was to quantify the increment of wood density of four forest species from different successional classes of a mixed system of restoration in a neotropical forest in Brazil.Tree discs were sampled at breast height and analyzed radially by X-ray densitometry to obtain apparent density and basic density.Three trees each of a species from the pioneer,early and late secondary successional stages and of the dominant species in the climax community.The radial profiles indicated increasing density from the pith to bark of trunks,except for some variations due to wood defects and growth.Average density was 0.576 g cm^(-3),0.655 g cm^(-3),0.706 g cm^(-3)and 0.775 g cm^(-3),respectively,for Peltophorum dubium,Schinus terebinthifolius,Cariniana estrellensis and Hymenaea courbaril.Radial profiles indicated higher amplitudes in the apparent densities for slow-growing species.X-ray densitometry generated parameters such as minimum,average and maximum densities,and radial density variations.These parameters are important for understanding the ecological functional role of successional classes of the Atlantic Forest from the Neotropical region.