Modelling Amazonian forest eddy covariance data: a comparison of big leaf versus sun/shade models for the C-14 tower at Manaus I. Canopy photosynthesis

In this study, we concentrate on modelling gross primary productivity using two simple approaches to simulate canopy photosynthesis: "big leaf" and "sun/shade" models. Two approaches for calibration are used: scaling up of canopy photosynthetic parameters from the leaf to the canopy level and fitting canopy biochemistry to eddy covariance fluxes. Validation of the models is achieved by using eddy covariance data from the LBA site C14. Comparing the performance of both models we conclude that numerically (in terms of goodness of fit) and qualitatively, (in terms of residual response to different environmental variables) sun/shade does a better job. Compared to the sun/shade model, the big leaf model shows a lower goodness of fit and fails to respond to variations in the diffuse fraction, also having skewed responses to temperature and VPD. The separate treatment of sun and shade leaves in combination with the separation of the incoming light into direct beam and diffuse make sun/shade a strong modelling tool that catches more of the observed variability in canopy fluxes as measured by eddy covariance. In conclusion, the sun/shade approach is a relatively simple and effective tool for modelling photosynthetic carbon uptake that could be easily included in many terrestrial carbon models.

Soil carbon and nitrogen in pasture soil reforested with eucalyptus and guachapele

In spite of the normally low content of organic matter found in sandy soils, it is responsible for almost the totality of cation exchange capacity (CEC), water storage and availability of plant nutrients. It is therefore important to evaluate the impact of alternative forest exploitation on the improvement of soil C and N accumulation on these soils. This study compared pure and mixed plantations of Eucalyptus grandis and Pseudosamanea guachapele, a N2-fixing leguminous tree, in relation to their effects on soil C and N stocks. The studied Planosol area had formerly been covered by Panicum maximum pasture for at least ten years without any fertilizer addition. To estimate C and N contents, the soil was sampled (at depths of 0-2.5; 2.5-5.0; 5.0-7.5; 7.5-10.0; 10.0-20.0 and 20.0-40.0 cm), in pure and mixed five-year-old tree plantations, as well as on adjacent pasture. The natural abundance 13C technique was used to estimate the contribution of the soil organic C originated from the trees in the 0-10 cm soil layer. Soil C and N stocks under mixed plantation were 23.83 and 1.74 Mg ha-1, respectively. Under guachapele, eucalyptus and pasture areas C stocks were 14.20, 17.19 and 24.24 Mg ha-1, respectively. For these same treatments, total N contents were 0.83; 0.99 and 1.71 Mg ha-1, respectively. Up to 40 % of the soil organic C in the mixed plantation was estimated to be derived from trees, while in pure eucalyptus and guachapele plantations these same estimates were only 19 and 27 %, respectively. Our results revealed the benefits of intercropped leguminous trees in eucalyptus plantations on soil C and N stocks.

Long-term C-CO2 emissions and carbon crop residue mineralization in an oxisol under different tillage and crop rotation systems

Soil C-CO2 emissions are sensitive indicators of management system impacts on soil organic matter (SOM). The main soil C-CO2 sources at the soil-plant interface are the decomposition of crop residues, SOM turnover, and respiration of roots and soil biota. The objectives of this study were to evaluate the impacts of tillage and cropping systems on long-term soil C-CO2 emissions and their relationship with carbon (C) mineralization of crop residues. A long-term experiment was conducted in a Red Oxisol in Cruz Alta, RS, Brazil, with subtropical climate Cfa (Köppen classification), mean annual precipitation of 1,774 mm and mean annual temperature of 19.2 ºC. Treatments consisted of two tillage systems: (a) conventional tillage (CT) and (b) no tillage (NT) in combination with three cropping systems: (a) R0- monoculture system (soybean/wheat), (b) R1- winter crop rotation (soybean/wheat/soybean/black oat), and (c) R2- intensive crop rotation (soybean/ black oat/soybean/black oat + common vetch/maize/oilseed radish/wheat). The soil C-CO2 efflux was measured every 14 days for two years (48 measurements), by trapping the CO2 in an alkaline solution. The soil gravimetric moisture in the 0-0.05 m layer was determined concomitantly with the C-CO2 efflux measurements. The crop residue C mineralization was evaluated with the mesh-bag method, with sampling 14, 28, 56, 84, 112, and 140 days after the beginning of the evaluation period for C measurements. Four C conservation indexes were used to assess the relation between C-CO2 efflux and soil C stock and its compartments. The crop residue C mineralization fit an exponential model in time. For black oat, wheat and maize residues, C mineralization was higher in CT than NT, while for soybean it was similar. Soil moisture was higher in NT than CT, mainly in the second year of evaluation. There was no difference in tillage systems for annual average C-CO2 emissions, but in some individual evaluations, differences between tillage systems were noticed for C-CO2 evolution. Soil C-CO2 effluxes followed a bi-modal pattern, with peaks in October/November and February/March. The highest emission was recorded in the summer and the lowest in the winter. The C-CO2 effluxes were weakly correlated to air temperature and not correlated to soil moisture. Based on the soil C conservation indexes investigated, NT associated to intensive crop rotation was more C conserving than CT with monoculture.

Bartholin's gland cysts: management with carbon-dioxide laser vaporization

PURPOSE: To evaluate the effectiveness, recurrence rate, and complications of carbon-dioxide laser vaporization in the treatment of Bartholin's gland cysts. METHODS: A retrospective study including 127 patients with symptomatic Bartholin' gland cysts submitted to carbon-dioxide laser vaporization at our institution from January 2005 to June 2011. Patients with Bartholin's gland abscesses and those suspected of having neoplasia were excluded. All procedures were performed in an outpatient setting under local anaesthesia. Clinical records were reviewed for demographic characteristics, anatomic parameters, intraoperative and postoperative complications, and follow-up data. Data were stored and analyzed in Microsoft Excel® 2007 software. A descriptive statistical analysis was performed, and its results were expressed as frequency (percentage) or mean±standard deviation. Complication, recurrence, and cure rates were calculated. RESULTS: The mean age of the patients was 37.3±9.5 years-old (range from 18 to 61 years-old). Seventy percent (n=85) of them were multiparous. The most common symptom was pain and 47.2% (n=60) of patients had a history of previous medical and/or surgical treatment for Bartholin's gland abscesses. Mean cyst size was 2.7±0.9 cm. There were three (2.4%) cases of minor intraoperative bleeding. Overall, there were 17 (13.4%) recurrences within a mean of 14.6 months (range from 1 to 56 months): ten Bartholin's gland abscesses and seven recurrent cysts requiring reintervention. The cure rate after single laser treatment was 86.6%. Among the five patients with recurrent disease that had a second laser procedure, the cure rate was 100%. CONCLUSIONS: At this institution, carbon-dioxide laser vaporization seems to be a safe and effective procedure for the treatment of Bartholin's gland cysts.

Influence of carbon source and the fermentation process on levan production by Zymomonas mobilis analyzed by the surface response method

The aim of this study is to assess sugar cane juice and sucrose as substrates, the batch and fed batch processes and their interaction in the levan production using a complete factorial design. Zymomonas mobilis was cultivated in different sugar cane juice and sucrose concentrations in two fermentation processes at 25 °C for 20 h. A complete factorial design (2³) was used to analyze the effects of the type and concentration of the substrate, as well as the batch and fed batch processes. A complete second factorial design (2²) was used to observe the importance of sugar cane juice. The results indicated that the batch process improved the levan production reaching 40.14 g/L. The addition of sugar cane juice was not statistically significant for levan formation, however sugar cane juice stimulated biomass, sorbitol and ethanol production. The best medium for levan production was 150 g/L sucrose in batch.