Carbon and nitrogen mineralization in soil of leguminous trees in a degraded pasture in northern Rio de Janeiro,Brazil

Use of legume trees can improve soil quality in degraded pastures. The aim of this study was to characterize C and N mineralization kinetics and estimate the potentially mineralizable C and N in soil under Mimosa caesalpiniifolia Benth. and Acacia auriculiformis A. Cunn.ex Benth. secondary forest and pasture in red-yellow latosols in southeast Brazil. We conducted a laboratory aerobic incubation experiment using a completely randomized design of four replicates and four types of plant cover using a modified version of the Stanford and Smith technique(1972) to study C and N mineralization potential.Potentially mineralizable N(N_o) ranged from 135 to170 mg kg-~(1). The predominant form of mineral N for all types of plant cover was N-NO_3~-. M. caesalpiniifolia was the only species that had a positive influence on N mineralization. Neither of the legumes influenced C mineralization in pasture or secondary forest. The model of N mineralization corresponded to a sigmoidal curve while C mineralization corresponded to an exponential curve,revealing that the N and C mineralization processes were distinct. N mineralized by M. caesalpiniifolia(216 kg of N ha~(-1)) was adequate to meet the N requirement for a livestock-forest system.     

Effect of thinning on above-ground biomass accumulation in a Douglas-fir plantation in southern Italy

We investigated the effects of a long-term thinning experiment on the distribution of above-ground biomass of Douglas-fir(Pseudotsuga menziesii [Mirb.]Franco var. menziesii) in a plantation in southern Italy.Allometric equations were used to estimate biomass and partitioning to stem and crown compartments. Variation in biomass stock estimated with allometric equations were evaluated according to seven thinning treatments: geometric-systematic(1 row every 3), selective(light-moderate-heavy), mixed systematic-selective(1 row every 4, 1 row every 5), unthinned(control). Over the experimental period of 13 years, current annual increments of carbon were lower(3.4 Mg ha~(-1)year~(-1)) in control plots than in treated plots. At age 30, plots subjected to light selective thinning showed higher values of above-ground biomass(249.7 Mg ha~(-1)). The biomass harvested with this treatment was 29.3 Mg ha~(-1), and the mean annual increment of carbon over 13 years was 4.8 Mg ha~(-1). Our results showed that light thinning stimulated increase in carbon stock, with a minimal loss of carbon during the treatment and a current annual increment of carbon higher than in control sub-plots and sub-plots thinned using systematic methods. This treatment yielded least carbon emissions and we affirm it has discrete global warming mitigation potential.     

Comparing the use of leaf and soil analysis as N and P availability indices in a wildfire chronosequence

Two types of measures have traditionally been used to monitor changes after disturbances in the nutrient availability of forest ecosystems: (1) soil nutrient pools and transformation rates and (2) foliar nutrient content. We used a wildfire chronosequence in natural and unmanaged Pinus canariensis forests to determine which kind of measure is more effective in discriminating between disturbed and undisturbed plots and to determine whether the different availability indices provide comparable and consistent results within the chronosequence and between different sampling dates. The results showed that (1) foliar N and P concentrations were the variables that best discriminated between the plots of the chronosequence, (2) the various soil N availability indices neither showed steady relationships nor predicted the plant nutrient availability, and (3) P availability indices showed steady relationships and predicted plant nutrient availability. Due to the changing nature of the soil N pools, repeated sampling over a long period of time could yield results different from those presented here. However, the large sampling effort required would favor the use of foliar nutrient concentrations as the most desirable first approach to the community’s nutritional status, especially when time or budget constraints are relevant.     

Resistance to classical scrapie in experimentally challenged goats carrying mutation K222 of the prion protein gene

ABSTRACT: Susceptibility of sheep to scrapie, a transmissible spongiform encephalopathy of small ruminants, is strongly influenced by polymorphisms of the prion protein gene (PRNP). Breeding programs have been implemented to increase scrapie resistance in sheep populations; though desirable, a similar approach has not yet been applied in goats. European studies have now suggested that several polymorphisms can modulate scrapie susceptibility in goats: in particular, PRNP variant K222 has been associated with resistance in case-control studies in Italy, France and Greece. In this study we investigated the resistance conferred by this variant using a natural Italian goat scrapie isolate to intracerebrally challenge five goats carrying genotype Q/Q 222 (wild type) and five goats carrying genotype Q/K 222. By the end of the study, all five Q/Q 222 goats had died of scrapie after a mean incubation period of 19 months; one of the five Q/K 222 goats died after 24 months, while the other four were alive and apparently healthy up to the end of the study at 4.5 years post-challenge. All five of these animals were found to be scrapie negative. Statistical analysis showed that the probability of survival of the Q/K 222 goats versus the Q/Q 222 goats was significantly higher (p = 0.002). Our study shows that PRNP gene mutation K222 is strongly associated with resistance to classical scrapie also in experimental conditions, making it a potentially positive target for selection in the frame of breeding programs for resistance to classical scrapie in goats.     

Primary cutaneous undifferentiated round cell tumor with concurrent polymyositis in a dog

A cutaneous poorly differentiated round cell tumor with concurrent, non-suppurative, polymyositis was diagnosed in a hovawart dog. Histochemical staining, immunohistochemistry, and transmission electron microscopy findings suggested that the tumors cells were of myeloid, or possibly natural killer cell origin. The possibility that the concurrent polymyositis may represent a pre-neoplastic or paraneoplastic process is discussed.     

Determination of flagellar types by PCR-RFLP analysis of enteropathogenic Escherichia coli (EPEC) and Shiga toxin-producing E. coli (STEC) strains isolated from animals in São Paulo, Brazil

This study evaluated the polymerase chain reaction- restriction fragment length polymorphism (PCR-RFLP) analysis of fliC for typing flagella antigen (H) of Shiga toxin-producing Escherichia coli (STEC) and enteropathogenic E. coli (EPEC) strains isolated from different animals. The molecular typing of the H type was efficient in the determination of 93 (85%) strains. Two nonmotile (H-) E. coli strains showed a PCR-RFLP electrophoretic profile that did not match known H type patterns. The fliC nucleotide sequence of strains B2N and 4a revealed a nucleotide substitution at the restriction site and a nucleotide insertion that generated a stop codon, respectively. The results of this study showed that PCR-RFLP analysis of fliC is faster, less laborious and as efficient for the determination of H type E. coli isolated from animals, compared to serotyping and that it is useful in determining H type in nonmotile strains and strains expressing non-reactive H antigens. Moreover, the fliC sequence of strain B2N suggests that we could have found a new flagellin antigen type.