Selective logging has been widely employed as a management practice in tropical forests due to its reduced impact on biodiversity. However, by altering microclimatic conditions, logging could affect soil fauna responsible for nutrient cycling and the long-term dynamic of the forest. We investigated how selective logging affected termite species richness, composition, and the distribution of species in trophic groups, as well as the natural response of termites to gradients of soil conditions. Termites and edaphic variables were sampled in 32 permanent plots in southern Amazonia. Plots were subject to selective logging for 10–31 years before termite sampling. Time post-management was associated with changes in termite species composition, and wood-feeding termites were more abundant in recently logged areas. Nevertheless, most of the variation in termite species richness and composition can be attributed to the natural variation in soil clay content. Moreover, soil-dweller species, a vulnerable group strongly linked to soil decomposition, were present in all plots. These results suggest that the impact of selective logging on termite communities might be milder compared with other types of disturbance. It is likely that the decomposition process performed by termites, and consequently long-term ecosystem functioning, is preserved under selective logging.

Concentration of CO2, above and below the soil surface and δ13C values of plant tissues, soil litter and organic matter were measured in a caatinga forest of the upper Rio Negro basin in southern Venezuela. CO2, concentrations near the forest floor were consistently higher than in the atmosphere. CO2, gradient in the soil was very steep probably because of the poor aeration in this flood-prone forest. δ13C values of plant tissues showed a clear pattern with lower values in the ground herbaceous plants and under-canopy trees. Tree seedlings showed δ13C values similar to the upper-canopy trees indicating their dependence on reserves carried in the seed from the mother tree. Decomposing litter and soil organic matter also showed δ13C values similar to the upper-canopy trees. It is suggested that lower δ13C values of the shade flora result primarily from the assimilation of CO2, depleted in δ13C originating from soil respiration. Probable effects of low light intensity and physiological factors are discussed.

The floristic composition, structure, soil fertility and leaf nutrient concentrations were analysed in a monodominant forest of Brosimum rubescens Taub. located in the Areões Xavante Indigenous Reserve (14°34′S, 51°58′W). The area lies in the ecotone between Amazonian forest and cerrado in the municipality of Água Boa, Mato Grosso State, Brazil. Sixty nested plots (10 × 10m each) were located in a representative portion of the forest, giving a total sampling area of 0.6ha (40 × 150m). A total of 609 trees ≥ 5cm dbh belonging to 57 species, 46 genera and 32 families were present. The most important family was Moraceae, with B. rubescens as the dominant species with a relative dominance of 59%. The diameter distribution of B. rubescens was unbalanced, indicating an episodic recruitment that could lead to future changes in the forest structure. The high basal area per hectare of B. rubescens indicates the possibility of sustainable logging for commercial exploitation. Analysis of composite soil samples collected from the surface layer (0–10cm) of each of the 60 plots did not indicate any significant gradients in fertility within the area sampled. Mean soil pH was 4.6 and the availability of essential nutrients was very low (0.22cmol(+) kg−1 K, 0.048cmol(+) kg−1 Ca, 0.167cmol(+) kg−1 Mg, and 1.5mg kg−1 P). The higher availability of Mg in the soils in comparison with Ca was a feature observed in other monodominant forests in the Amazon region, as well as in other parts of the world. Analysis of foliar samples showed that the dominant species, B. rubescens, maintained higher foliar concentrations of K, Ca and Mg than other species in the forest. This probably indicates a competitive advantage for this species. Also, the higher concentrations of Mg in the soil did not affect its uptake of Ca or K.