Site classification for Eucalyptus sp. in a tropical region of Brazil.

The aim was to determine the productive capacity of a forest site by applying different methods of fitting, combined with geostatistical techniques, to stands of Eucalyptus sp. in a tropical region of Brazil. Data were collected from 845 plots of a continuous forest inventory over four years. The classification of local production capacity was performed using growth curves obtained by the guide curve (GC) method, algebraic difference approach (ADA) and generalized algebraic difference approach (GADA) methods and ordinary kriging through the spherical, exponential, and Gaussian models to determine the spatial dependence of the variables site, geographical boundaries of site index classes, and their respective areas for each hectare in an annual production unit (APU). The modified Chapman-Richards model, fitted by the generalized difference approach method (GADA), provided the best statistical results, an improvement of 12.23% and 39.80% on the ADA and GC methods, respectively. The exponential model selected to express the spatial distribution of dominant height showed a high degree of spatial dependence.

Modeling and dynamics of growth and yield of tree species in Mimosa scabrella stands.

"Bracatingais" are common forest formations formed by bracatinga (Mimosa scabrella) and secondary species, which have replaced bracatinga over time; these forests are an important source of income for small farmers. The objective of this study was to model the growth and yield volume of firewood per unit of area and to evaluate the dynamics of the stock across the years. Data from 320 plots were used to fit 12 mathematical models separately addressing the data for bracatinga and secondary species and total species. The Clutter model presented better results for bracatinga (IA = 0.954 and Syx% = 8.54) and for total species (IA = 0.917 and Syx% = 11.56). The modified Clutter model was the best for the secondary species, with IA = 0.952 and Syx% = 25.08. The volumetric estimation of these equations was used to compare the estimated volume of the bracatinga with that of the secondary species, identifying the age as between 13 and 14 years when the volume of the bracatinga is supplanted by the volume of the secondary species. Furthermore, 8 years of age was ideal for clearcutting the bracatingais.

Diametric Growth of Tree Species in the Atlantic Forest, Paraná, Brazil.

Management of remnants in Atlantic Forest is an alternative for their conservation, however, information on the growth and ecology of those species is lacking. This study aimed to describe diametric growth of Balfourodendron riedelianum, Cordia trichotoma and Ocotea diospyrifolia based on its growth rings and to verify the relationship between this growth with the environmental characteristics in different altitude levels and forest types. Diametric growth was higher for the largest tree diameters of the three species. Based on the fitted growth model, the age in which mean annual increment in diameter becomes greater than the current annual increment was 55 years for B. riedelianum (DBH = 18.27 cm), 45 years for C. trichotoma (DBH = 26.56 cm) and 44 years for O. diospyrifolia (DBH = 26.05 cm). Environmental conditions and forest types affected diametric growth of these species. B. riedelianum and O. diospyrifolia showed higher diametric growth in plain regions with higher fertility soil and few frosts. C. trichotoma was negatively affected by low water availability in winter at lower altitudes and showed higher diametric growth at higher altitudes, where soil fertility is low but there is well-drainage, high rainfall and high relative humidity during the dry season.

Sampling system for estimating woody debris in an urban mixed tropical forest.

Woody debris, defined as standing and downed deadwood, consists in an essential component of the forest carbon stock. However, few studies have been carried out to get an efficient and accurate sampling procedure for estimating it. This work proposes two methodologies to estimate the woody debris volume in a Brazilian mixed tropical forest: 1) two-stage systematic sampling, using a mixed methodology, in which the Strand's method is applied to standing dead trees and stumps, and line intercept sampling is used to fallen trees and branches; and 2) ratio estimate of the sum of cross-sectional areas of deadwood pieces and forest basal area, aiming to obtain the total woody debris volume indirectly in the natural forest. Conversions for biomass and carbon stocks were made applying the mean basic density on the estimates of deadwood volumes. Both methodologies are accurate for woody debris volume estimates, with a sampling error equal to 16.1% (methodology 1) and 5.7% (methodology 2), at a 95% probability level. Thus, the methodology 2 has potential to be used in strategic forest inventories of woody debris, such as in National Forest Inventories, due to increasing importance of its quantification in all forest ecosystems.

Floristic evolution in an agroforestry system cultivation in Southern Brazil.

Bracatinga (Mimosa scabrella Bentham) is an important pioneer tree species in Ombrophylous Mixed Forest of Brazil and is widely used as an energy source. In traditional agroforestry systems, regeneration is induced by fire, then pure and dense stands known as bracatinga stands (bracatingais) are formed. In the first year, annual crops are intercalated with the seedlings. At that time the seedlings are thinned, then the stands remain at a fallow period and cut at seven years old. The species is very important mainly for small landowners. We studied the understory species that occur naturally during the succession over several years in order to manage them rationally in the future and maintain the natural vegetation over time. Three to 20 year-old Bracatinga stands were sampled between 1998 and 2011. All tree species with diameter at breast height (DBH) ≥ 5 cm were measured.The floristic evolution was assessed with respect to Sociability Index, the Shannon Diversity Index and the Pielou Evenness Index. Graphs of rank/abundance over different age groups were evaluated using the Kolmogorov-Smirnov test. We identified 153 species dispersed throughout the understory and tend to become aggregated over time.