Risk factors associated with sero-positivity to Toxoplasma gondii in captive neotropical felids from Brazil

From September 1995 to February 2001, blood samples were collected from 865 neotropical felids belonging to 8 different species. These animals were housed in 86 institutions located in 78 cities of 20 Brazilian states. Our goal was to identify the risk factors associated with sero-positivity to Toxoplasma gondii in captive neotropical felids from Brazil. All serum samples were tested by the modified agglutination test (MAT), using formalin-fixed whole tachyzoites and mercaptoethanol. For each animal an individual questionnaire was filled with questions about tattoo number, felid species, age, sex, origin, number of animals in the group, introduction of new animals in the group, time in the institution, eating meat previously frozen for a period <7 days in the last 6 months, eating meat of run-over or euthanized animals in the last 6 months, predation of rodents or birds in the last 6 months and presence of domestic cats near the enclosures in the last 6 months. The total sero-prevalence was 55% (95% CI: 52%, 57%). We estimated a prevalence of 46% (95% CI: 40%, 54%) for jaguarundi (Puma yagouaroundi); 58% (95% CI: 53%, 63%) for ocelot (Leopardus pardalis); 50% (95% CI: 45%, 56%) for oncilla (L. tigrinus); 54% (95% CI: 46%, 62%) for margay (L. wiedii); 12% (95% CI: 4%, 31%) for Pampas-cat (L. colocolo); 83% (95% CI: 65%, 93%) for Geoffroy's-cat (L. geoffroyi); 64% (95% CI: 50%, 68%) for jaguar (Panthera onca) and 48% (95% CI: 42%, 54%) for puma (Puma concolor). Multiple logistic regression was used to evaluate the association between the variables in the questionnaire and sero-positivity to T. gondii. We concluded that the independent risk factors for toxoplasmosis were: age >3 years (OR = 4.75 [2.75; 8.2]), eating meat previously frozen for a period <7 days (OR = 2.23 [1.24; 4.01]), and consumption of animals that were run-over or euthanized (OR = 1.64; [1.14; 2.37]).     

The Sustainability of Quinoa Production in Southern Bolivia: from Misrepresentations to Questionable Solutions. Comments on Jacobsen (2011, J. Agron. Crop Sci. 197: 390–399)

Reviewing the situation of quinoa production in southern Bolivia, Jacobsen (2011, J. Agron. Crop Sci. 197: 390) argues that the booming export market has a negative effect on the environment and on the home consumption of quinoa, thereby leading to an environmental disaster in the region. In view of the scarcity of scientific knowledge on the rapid social and environmental dynamics in the region, we consider that Jacobsen’s review misrepresents the situation of quinoa production in southern Bolivia. Specifically, we argue that (i) the data presented by Jacobsen (2011, J. Agron. Crop Sci. 197: 390) do not support any drop in quinoa crop yield supposed to reflect soil degradation and (ii) his demonstration regarding home consumption of quinoa is ill‐founded from both a nutritional and a cultural point of view. We suggest that the diffusion of the arguments exposed by Jacobsen (2011, J. Agron. Crop Sci. 197: 390), because of their flaws, might have strong negative impacts on those concerned with sustainable food production and fair‐trade with developing countries. We conclude that, rather than reinforced agro‐technical controls on local farmers, the rising competition in the international quinoa market requires a shift towards an ethical economy and ethical research cooperation with quinoa producers.     

Role of waterlogging-responsive genes in shaping interspecific differentiation between two sympatric oak species

Pedunculate (Quercus robur L.) and sessile oak (Quercus petreae Matt. Liebl.) are closely related species with a widely sympatric distribution in Europe. These two oak species are also known to display different ecological features, particularly related to their adaptation to soil waterlogging. Pedunculate oak grows in humid areas and can withstand high moisture content of the soil, whereas sessile oak requires drier soil with better drainage. The main goal of this study was to explore the role of gene expression contributing to differences in terms of waterlogging tolerance between these two species. We implemented a series of experiments aimed at evaluating whether differentially expressed genes between species are associated with their ecological preferences and underlie adaptive genetic divergence. Rooted cuttings of both species were grown in hydroponic conditions and subjected to gradual root hypoxia. White roots were sampled after 6, 12, 24 and 48 h. Real-time polymerase chain reaction (qPCR) was first used to monitor the expression of 10 known waterlogging-responsive genes, to identify discriminating sampling time points along the kinetics of hypoxia. Secondly, four subtractive suppressive hybridization libraries (sessile vs. pedunculate, pedunculate vs. sessile for early and late responses) were generated to isolate differentially expressed genes between species. A total of 2160 high-quality expressed sequence tags were obtained and annotated, and a subset of 45 genes were selected for qPCR analysis in a second independent factorial experimental design applying two stress durations per two species. Significant differences of gene expression between pedunculate and sessile oaks were detected, suggesting species-specific molecular strategies to respond to hypoxia. This study revealed that the ability of pedunculate oak to maintain glycolysis and fermentation under hypoxic conditions may help explain its tolerance to waterlogging.     

Ten-year regeneration responses to varying levels of overstory retention in two productive southern British Columbia ecosystems

We investigated survival and growth responses of planted and advance natural regeneration species of varying shade tolerance to partial retention harvesting in moist warm Interior Cedar-Hemlock (ICHmw2) and dry cool Montane Spruce (MSdk) ecosystems of southeastern British Columbia, Canada. Treatments included three levels of overstory basal area retention (none, light (∼25%), or heavy (∼50%)) installed by two harvest methods (handfelled or a pushover falling technique being tested for its ability to control the spread of root disease). After 10 years, growth of both planted and natural regeneration species of varying shade tolerance tended to increase with decreasing overstory retention and associated increases in light availability. In contrast, significant survival responses to retention level were lacking except in the case of shade-intolerant western larch. Harvest method had a variable effect on regeneration survival and growth. Where significant responses did occur, they were generally attributed to harvesting effects on the characteristics of planting microsites rather than root disease spread. Natural regeneration densities at the ICHmw2 site were high at all retention levels, whereas stocking was less consistent at the MSdk site. We concluded that moderately shade-tolerant to shade-tolerant interior spruce and western redcedar can, under conditions similar to those of our study sites, be successfully established under overstories of up to approximately 25 m²/ha basal area, but that growth performance is likely to be significantly lower than in clearcuts. Despite early survival issues, conclusions regarding Douglas-fir were similar. Poorer survival and vigour of shade-intolerant western larch suggested this species is not suitable for regeneration in partial retention systems where timber production is the primary objective. Where non-timber objectives predominate, survival and acceptable growth of even a small proportion of larch could add to the diversity of the regenerating stand.     

Organic residue mass at planting is an excellent predictor of tree growth in Eucalyptus plantations established on a sandy tropical soil

Tropical plantation forests are meeting an increasing proportion of global wood demand and comprehensive studies assessing the impact of silvicultural practices on tree and soil functioning are required to achieve sustainable yields. The objectives of our study were: (1) to quantify the effects of contrasting organic residue (OR) retention methods on tree growth and soil nutrient pools over a full Eucalyptus rotation and (2) to assess the potential of soil analyses to predict yields of fast-growing plantations established on tropical sandy soils. An experiment was set up in the Congo at the harvesting of the first rotation after afforestation of a native herbaceous savanna. Six treatments were set up in 0.26 ha plots and replicated in 4 blocks, with OR mass at planting ranging from 0 to 46.5 Mg ha⁻¹. Tree growth over the whole rotation was highly dependent on OR management at planting. Over-bark trunk volume 7 years after planting ranged from 96 m³ ha⁻¹ in the treatment with forest floor and harvest residue removal at planting to 164 m³ ha⁻¹ in the treatment with the largest amount of OR. A comparison of nutrient stocks within the ecosystem at planting and at the end of the rotation suggested that nutrient contents in OR were largely involved in the different response observed between treatments. OR management treatments did not significantly modify most of the nutrient concentrations in the upper layers of the mineral soil. Conventional soil analyses performed before planting and at ages 1 and 3 years were unable to detect differences between treatments despite large differences in tree growth. In contrast, linear regressions between stand aboveground biomass at harvesting and OR mass at planting (independent variable) showed that OR mass was an excellent predictor of stand yield (R² = 0.99). A large share of soil fertility comes from organic material above the mineral soil in highly weathered sandy soils and OR mass at planting might be used in conjunction with soil analyses to assess the potential of these soils to support forest plantations.     

A variance-covariance structure to take into account repeated measurements and heteroscedasticity in growth modeling

This study proposes a within-subject variance-covariance (VC) structure to take into account repeated measurements and heteroscedasticity in a context of growth modeling. The VC structure integrates a variance function and a continuous autoregressive covariance structure. It was tested on a nonlinear growth model parameterized with data from permanent sample plots. Using a stand-level approach, basal area growth was independently modeled for red spruce (Picea rubens Sarg.) and balsam fir [Abies balsamea (L.) Mill.] in mixed stands. For both species, the implementation of the VC structure significantly improved the maximum likelihood of the model. In both cases, it efficiently accounted for heteroscedasticity and autocorrelation, since the normalized residuals no longer exhibited departures from the assumptions of independent error terms with homogeneous variances. Moreover, compared with traditional nonlinear least squares (NLS) models, models parameterized with this VC structure may generate more accurate predictions when prior information is available. This case study demonstrates that the implementation of a VC structure may provide parameter estimates that are consistent with asymptotically unbiased variances in a context of nonlinear growth modeling using a stand-level approach. Since the variances are no longer biased, the hypothesis tests performed on the estimates are valid when the number of observations is large.