Resumo

BARRALES-BRITO, Edgar et al. In vitro determination of CO₂ emission in forest litter. Agrociencia [online]. 2014, vol.48, n.7, pp.679-690. ISSN 2521-9766.

Forest litter emits CO₂ into the atmosphere, but there are few studies on the subject and it is important to generate this information to improve inventories of greenhouse gases (GHGs). Methods to quantify this emission are performed in situ during long periods of measurements and others require the use of high cost instruments; some measure the loss of organic matter over time and others are indirect and are based on measurements dependent on weather conditions. The aim of this study was to generate a standardized operation protocol (PEO, its Spanish acronym) to measure the CO₂ emission potential of in vitro litter using a manometric respirometer (OxiTop OC110^®) in a maximum time of 10 d incubation. Litter samples were collected in a Quercus spp forest in Tequexquinahuac, Estado de Mexico, at the beginning of 2012. The experimental design was completely randomized, treatments were incubations (25 °C) with four litter moisture percentages (20, 40, 60 and 80 % dry weight) and four sample sizes (5, 10, 20, 40 g), and each treatment was replicated three times. Based on the data ANOVA was performed and treatment means were compared with the Tukey test (p≤0.05). The response variables were: CO₂ emission, CO₂ emission rate and percentage of oxidized carbon compared to total carbon at the start of incubation. The optimum conditions for the measurement were 10 g sample and 60 % humidity. Under these conditions the maximum CO₂ emission was recorded (23 554 mg CO₂ kg^-1) as well as the lowest standard deviation (331 mg CO₂ kg^-1), the lowest of the 16 treatments resulting from combining sample sizes and moisture percentage. In these conditions the percentage of carbon emitted compared to the initial carbon was the highest (5.26 %). The measurement of respiration in such assay depends on the humidity of the sample and the availability of oxygen present in the system, which is the condition for determining the optimal operating environment using the OxiTop OC. The data generated by OxiTop are indicators of the potential emission of CO₂ by different types of litter and have a similar value to that of the incubations performed to evaluate the potential mineralization of nitrogen.

Palavras-chave : Respirometry; CO₂; OxiTop^® (R); biogeochemistry; carbon; soil.

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