Soil fertility and growth of Eucalyptus grandis in Brazil under different residue management practices

Silvicultural operations such as soil preparation, logging residue management and application of fertilisers can influence soil fertility, and hence nutrient uptake and tree growth. This paper reports the effect of site management practices of minimum and intensive cultivation of the soil on the growth of a stand of Eucalyptus grandis and soil fertility. The experimental site is a commercial plantation in the Itatinga district, São Paulo State, Brazil. This site was originally covered by climax vegetation known as ‘Cerrado\' (savanna) which is characterised by seasonal soil water deficits and very low soil fertility. The effects of complete harvest residue removal, residue retention and residue burning were assessed in a randomised block experiment. The highest productivities were obtained where the residues were retained or burned and the lowest where all the residues (slash, litter and bark) were removed. These results highlight the temporary but large release of nutrients due to burning and the effect of forest residues on tree growth. Temporary variations in organic C and N contents, exchangeable cation contents and pH were found only in the 0–5cm soil layer, except for the burned residue treatment where variations in the layer beneath (5–10cm) were also found. No modification of soil properties was found in the 10–20cm layer. It was found that burning resulted in the loss of 82% of biomass, 86% of N, 60% of P, 49% of K, 11% of Ca, 29% of Mg and 84% of S. Exchangeable K initially increased up to 0.8 years after harvesting and later decreased. Over a 21-month period, the largest rates of N mineralisation were found in the standing crop treatment (77kg ha–1 of N), followed by the treatment where the residues were retained with minimum disturbance of the site (58kg ha–1 of N). The removal or burning of the residues inhibited the N mineralisation with values of 45 and 28kg ha–1 of N respectively, recorded in these treatments. The different residue management treatments resulted in pronounced effects on the growth of E. grandis.Southern Hemisphere Forestry Journal 2007, 69(2): 95–10

Cross-sectional study defines difference in malaria morbidity in two Yanomami communities on Amazonian boundary between Brazil and Venezuela

It is well established that immunity to malaria is short-lived and is maintained by the continuous contact with the parasite. We now show that the stable transmission of malaria in Yanomami Amerindian communities maintains a degree of immunity in the exposed population capable to reduce prevalence and morbidity of malaria. We examined 508 Yanomami Amerindians living along Orinoco (407) and Mucajaí (101) rivers, on the Venezuelan and Brazilian Amazon region, respectively. At Orinoco villages, malaria was hyperendemic and presented stable transmission, while at Mucajaí villages it was mesoendemic and showed unstable transmission. The frequency of Plasmodium vivax and P. falciparum was roughly comparable in Venezuelan and Brazilian communities. Malaria presented different profiles at Orinoco and Mucajaí villages. In the former communities, malaria showed a lower prevalence (16% x 40.6%), particularly among those over 10 years old (5.2% x 34.8%), a higher frequency of asymptomatic cases (38.5% x 4.9%), and a lower frequency of cases of severe malaria (9.2% x 36.5%). Orinoco villagers also showed a higher reactivity of the immune system, measured by the frequency of splenomegaly (72.4% x 29.7%) and by the splenic index (71.4% over level 1 x 28.6), and higher prevalence (91.1% x 72.1%) and mean titer (1243 x 62) of antiplasmodial IgG antibodies, as well as a higher prevalence (77.4% x 24.7%) and mean titer (120 x 35) of antiplasmodial IgM antibodies. Our findings show that in isolated Yanomami communities the stability of malaria transmission, and the consequent continuous activation of the immune system of the exposed population, leads to the reduction of malaria prevalence and morbidity