Analysis of the energy balance and CO2 flow under the influence of the seasonality of climatic elements in a mangrove ecosystem in Eastern Amazon.

An unprecedented study was carried out in a mangrove ecosystem in the northeastern coast of the Brazilian Amazon to understand the behavior of climatic elements in a year with the occurrence of El Niño (2015), associated with the seasonal function source/sink of CO2 by the ecosystem. Global radiation (Rg), net radiation (Rn), temperature, relative humidity, precipitation, horizontal wind speed and direction, as well as turbulent flows of sensible heat (H), latent heat (LE), and carbon (f_CO2) were recorded using eddy covariance, a system for studying turbulent flows of heat and gases in the atmosphere. We observed a drastic reduction in rainfall volumes, which accounts for 63.7% of the expected total according to the region's climatology. Regarding f_ CO2, the highest values of photosynthesis, autotrophic, and heterotrophic respiration of the ecosystem occurred in the wet season due to precipitation, ideal photosynthetically active radiation, lower soil salinity, and higher NDVI of the ecosystem. In the 2nd semester of the year, we observed that the decrease in cloudiness, causing a higher radiation supply in the forest canopy, accompanied by a reduction in precipitation and an increase in the value of H and soil salinity, favored the increase of foliar abscission by the dominant genus Rhizophora and Avicennia, thus influencing the reduction of magnitudes of carbon source/sink functions in the ecosystem during this season, even on high tide days.

Emisiones de dióxido de carbono en estratos de mangle en la Amazonia Oriental Brasileña

Introducción: Las emisiones de dióxido de carbono de los suelos de manglar tienen un impacto potencial en el balance global de carbono. Objetivo: Investigar la estacionalidad de las emisiones de dióxido de carbono relacionadas con diferentes estratos de la vegetación de manglar, así como las variables físico-químicas del suelo y las ambientales. Métodos: Se demarcaron nueve parcelas de 20 x 20 m (tres para cada estrato de vegetación). Las emisiones de dióxido de carbono fueron monitoreadas durante 88 días a través de la metodología de respiración basal del suelo. Resultados: Los resultados mostraron que las mayores emisiones de dióxido de carbono se presentaron en la temporada lluviosa 2017 con 21.8 (7.3 ± 3.3) mg/100 cm3 y 15.7 (5.2 ± 1.6) mg/100 cm3 en el período menos lluvioso. En análisis de componentes principales con un 56 % de varianza total, demostró que las mayores correlaciones de las emisiones de dióxido de carbono y las variables físico-químicas se dieron en el estrato adulto; la humedad del suelo, pH, materia orgánica, carbono y nitrógeno microbiano fueron las variables más correlacionadas. La prueba Kruskal-Wallis corroboró estos resultados comprobando diferencias significativas entre los estratos de vegetación y las emisiones de CO2 (P= 0.0170), y la prueba de Tukey confirmó mayor importancia estadística del manglar adulto en relación con los otros estratos (P= 0.0140). Conclusión: En las tres estaciones analizadas, las mayores emisiones acontecieron en el periodo lluvioso con promedio de 14.5 TCO2 ha/año y el estrato adulto fue el responsable de las mayores emisiones, registrando 21 TCO2 ha/año diferencia que fue estadísticamente significativa con los otros estratos (P = 0.0140).

Introduction: Carbon dioxide emissions from mangrove soils have a potential impact on the global carbon balance. They are related to anthropic actions and natural processes with interspecific interactions involving physical-chemical and environmental variables. Objective: In this research, the seasonality of carbon dioxide emissions related to different strata of mangrove vegetation, soil physical-chemical makeup and physical environmental factors were evaluated. Methods: Nine plots of 20 x 20 m were demarcated (three for each of the three vegetation strata) in the Experimental Site of the Federal Rural University of the Amazon and the Federal University of Pará in Cuiarana, Salinópolis, Pará, Brazil. Duplicate soil samples were taken from each plot during three consecutive seasonal periods and analyzed in the laboratory. Carbon dioxide emissions were monitored for 88 days through the basal breathing of the soil methodology; other variables evaluated were soil moisture and temperature, hydrogenic potential, redox potential,carbon and nitrogen of the microbial biomass, organic matter and composition of sand, silt and clay. Precipitation data was obtained from the CMORPH technique of the Climate Forecast Center - NOAA. Information on tides was obtained from the Brazilian Navy's Fundeadouro de Salinópolis. Results: The results showed that the highest carbon dioxide emissions occurred in the rainy season 2017 on average 7.5 (14.5 TCO2 ha/year) mg/100 cm3. With 10.5 mg/100 cm3 (21 TCO2 ha/year), the adult stratum was the largest source of emissions. The highest seasonal correlations of the emissions in relation to the incubation intervals occurred in the rainy season, in the adult stratum the days 1,2,3,4,3,3 and 5. Using principal component analysis (PCA) it was found that the highest correlations of carbon dioxide emissions and physical-chemical variables occurred in the adult stratum with 56 % variance. The highest correlations were found with the variables soil moisture, Ph, organic matter, carbon and microbial nitrogen. The Kruskal-Wallis test corroborated these results, indicating significant differences between vegetation strata and CO2 emissions (P= 0.0170); and the Tukey test confirmed greater statistical importance of the adult mangrove in relation to the other strata (P= 0.0140). Conclusions: In the three analyzed stations, the highest emissions occurred in the rainy period with an average of 14.5 TCO2 ha/year and the adult stratum was responsible for the highest emissions registering 21 TCO2 ha/year difference that was statistically significant with the other strata (P = 0.0140).