Balance de carbono, energía y productividad ecosistémica en la amazonía occidental empleando el método de flujos turbulentos
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Date
2019-09-03
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Pontificia Universidad Católica del Perú
Abstract
Se empleó el método de covarianza de flujos turbulentos para la determinación de
flujos netos de carbono, respiración ecosistémica y productividad primaria bruta del
bosque amazónico, en la región Madre de Dios, desde noviembre de 2016 (temporada
lluviosa) hasta octubre de 2018 (temporada seca). Para ello, se utilizó un sistema
compuesto por un anemómetro sónico, un analizador de gases infrarrojo, sensores de
radiación, humedad y temperatura ubicados sobre una plataforma, a 46 metros, sobre el
dosel del bosque. La compilación, procesamiento y análisis de datos se realizó empleando
el lenguaje de programación R y los softwares comerciales Eddy Pro y TOVI.
Se registró un 78,30 % de datos válidos en un periodo efectivo de 541 días. Las
temperaturas promedio del aire oscilaron entre 21,6 y 25,6 °C y la humedad relativa
alrededor de 80%. La distribución de patrones de viento mostró una dirección
predominante hacia el NO y velocidades entre 0,1 a 1,4 ms-1. El principal indicador de
presencia de turbulencias, u*, registró un valor promedio de 0,31 m.s-1 durante el día y
0,14 m.s-1 nocturno. Durante el día, los picos de temperatura, velocidad de viento y
temperatura, así como el mínimo de %RH, se dieron entre las 12:00 y 14:00 h.
Por otra parte, los flujos de radiación de onda corta oscilaron alrededor de 300
W.m-2 y para la onda larga en -40 W.m-2, con valores más altos durante las temporadas
secas. Para la temporada húmeda 2016-2017, se registró un flujo neto de radiación de
156,98 W.m-2 y en la temporada seca, 137,76 W.m-2. En la temporada 2017-2018, la
radiación neta fue 151,20 W.m-2 en el periodo lluvioso y 139,81 W.m-2 en el periodo seco.
La Radiación Fotosintéticamente Activa (PAR) registró un promedio diario entre 300 y
400 μmol.m-2.s-1. La distribución diaria indica que el bosque recibió radiación entre las
06:00 y 18:00 h, alcanzando picos máximos alrededor del mediodía. Durante las noches,
el bosque se comportó como un emisor de radiación.
El análisis determinó un flujo de CO2 promedio diario en -5 μmol.m-2.s-1 para las
temporadas húmedas y -4 μmol.m-2.s-1 en las temporadas lluviosas. En los flujos de
almacenamiento de CO2, se registraron valores de 2,03 μmol.m-2.s-1 en las temporadas
húmedas y 1,3 μmol.m-2.s-1 en las temporadas secas. El Intercambio Neto Ecosistémico
(NEE) osciló entre -2 y -1 μmol.m-2.s-1. El comportamiento diario, influenciado por la
actividad de la capa límite, indicó que el bosque se comporta como sumidero de carbono
durante el día y emisor durante las noches. Entre las 6:00 h y 08:00 h, la generación de turbulencias por ingreso de radiación solar en la capa límite atmosférica, generó un pulso
de CO2 con un máximo entre 6 y 9 μmol.m-2.s-1.
En el análisis de flujo y balance de energía se evaluó el calor sensible (H) y calor
latente (LE). A escala mensual, H fluctuó alrededor de 20 W.m-2 y LE alrededor de 60
W.m-2, con mayores valores durante las temporadas húmedas debido a la mayor
nubosidad, disponibilidad de H2O y menor ingreso de radiación. A nivel diario, por
presencia de radiación solar, el mayor flujo de calor se registró durante el día y los picos
se alcanzaron al mediodía. El balance de energía, como correspondencia entre la radiación
neta y H+LE, mostró rectas con pendientes entre 0,70 y 0,80. La pérdida en el balance de
energía fue causado por errores en la instrumentación, muestreo, aplicación del filtro de
turbulencias y la existencia de reservas de energía verticales que no se consideraron
puesto que no fueron registradas por los equipos.
El cálculo de la respiración ecosistémica nocturna (R) se determinó de la regresión
hiperbólica cuadrática en la relación del NEE y PAR. Durante el periodo 2016-2017, R
se situó en el intervalo de 9,49 a 11,84 μmol.m-2.s-1, mientras que en 2017-2018, estuvo
entre 7,03 y 7,88 μmol.m-2.s-1. La respiración fue más intensa durante las temporadas
lluviosas debido a la promoción de la respiración heterotrófica y mayor humedad del
suelo.
La productividad primaria bruta (GPP) se calculó como la diferencia entre los
valores de NEE y R. El cálculo mostró una fijación anual neta de 44,86 toneladas de C
por hectárea en el periodo 2016-2017 y 45,92 toneladas por hectárea durante 2017-2018.
El impacto de las variables micrometorológicas y fisiológicas, incluyendo posibles
errores por falta de continuidad de datos, pudieron afectar los promedios calculados en
GPP.
Finalmente, se modeló el comportamiento de la R en función de la temperatura
máxima diaria en cada temporada. Los resultados mostraron notable aproximación a los
resultados experimentales, por lo que existe la posibilidad de ampliar este campo en la
búsqueda de predecir el comportamiento del bosque en el futuro.
The eddy covariance method was used to determine the carbon fluxes, ecosystem respiration and gross primary productivity of a western Amazon forest, in the Madre de Dios región in Peru and its relationship with micrometeorological parameters, from November 2016 (rainy season) until October 2018 (dry season). A sonic anemometer, infrared gas analyzer, radiation, humidity and a temperature sensors were used on the platform of the SAGES flux tower, at 46 m. The compilation, processing and the analysis of data were done using the R programming language, and the commercial software packages Eddy Pro and TOVI. A 78,30% of valid data was recorded over a period of 541 days, between October 2016 and October 2018. The air temperatures ranged between 21,6 and 25,6°C while the relative humidity fluctuated around 80%. The distribution of wind patterns showed a predominant direction towards the NW and a speed interval between 0,1 to 1,4 m.s-1. The main evidence of turbulences, u*, recorded a mean value around 0,31 m.s-1 during day and around 0,14 m.s-1 during night. Throughout the day, the peaks of temperature, wind speed, temperature and the minimum of %RH were recorded between 12:00 and 14:00 h. Short wave radiation fluxes oscillated around 300 W.m-2 and for long wave around -40 W.m-2, with highest values in the dry seasons. For the 2016-2017 wet season, a net radiation flow was recorded at 156,98 W.m-2 and 137,76 W.m-2 in the dry season. For the 2017-2018 period, these values were 151,20 W.m-2 in the rainy season and 139,81 W.m-2 in the dry season. Photosyntethic Active Radiation (PAR) recorded a daily average between 300 and 400 μmol.m-2.s-1. The daily distribution indicates that the forest received radiation between 06:00 and 18:00 h, reaching maximum peaks around noon. During the night, the forest behaved like a net source of radiation. In the flux analysis, an average daily flux of CO2 was determined ranging around -5 μmol.m-2.s-1 for the wet season and -4 μmol.m-2.s-1 for the rainy seasons. Registered storage CO2 flux values were 2,03 μmol.m-2.s-1 in the wet seasons and 1,3 μmol.m-2.s-1 in the dry season. The Net Ecosystemic Exchange (NEE) oscillated between -2 and -1 μmol.m-2.s-1. The daily behavior, influenced by the activity of the boundary layer, indicated that the forest was a carbon sink during days and a constant source at nights. Around 6:00 am, the turbulence due to the entry of solar radiation into the atmospheric boundary layer caused a CO2 flush with a maximum between 6 and 9 μmol.m-2.s-1. In the flux and energy balance analysis, sensible heat (H) and latent heat (LE) were studied. On a monthly scale, H fluctuated around 20 W.m-2 and LE near 60 W.m-2, with higher values during the wet seasons due to greater cloudiness, availability of H2O and lower incoming radiation. On a daily basis, due to the presence of solar radiation, the highest heat flux was registered during the day and the peaks were reached at noon. The energy balance, as a correspondence between the net radiation and H + LE, showed slopes between 0,70 and 0,80. The loss of energy balance was caused by errors in the instrumentation, sampling, application of the turbulence filter and the presence of vertical energy reserves that were not considered and registered by the equipment. The calculation of nocturnal ecosystemic respiration (R) was determined from the quadratic hyperbolic regression of NEE vs. PAR. During the 2016-2017 period, R was in the range of 9,49 to 11,84 μmol.m-2.s-1, while in 2017-2018, it was located between 7,03 and 7,88 μmol.m-2.s-1. The magnitude of R was more intense in the rainy seasons due to promotion of heterotrophic respiration and higher humidity at soil level. Gross primary productivity (GPP) was calculated as the difference of NEE and R. The values indicated a net annual carbon fixation of 44,86 tons per hectare in the period 2016-2017 and 45,92 tons per hectare during 2017-2018. The impact of the micrometorological and physiological variables, including possible errors due to lack of data continuity, could had affected the averages in GPP. Finally, the behavior of the R was modeled using the maximum daily temperature in each season. The results showed a remarkable approximation to the experimental results, so there is the possibility of expanding this field in the search to predict the behavior of the forest in the future.
The eddy covariance method was used to determine the carbon fluxes, ecosystem respiration and gross primary productivity of a western Amazon forest, in the Madre de Dios región in Peru and its relationship with micrometeorological parameters, from November 2016 (rainy season) until October 2018 (dry season). A sonic anemometer, infrared gas analyzer, radiation, humidity and a temperature sensors were used on the platform of the SAGES flux tower, at 46 m. The compilation, processing and the analysis of data were done using the R programming language, and the commercial software packages Eddy Pro and TOVI. A 78,30% of valid data was recorded over a period of 541 days, between October 2016 and October 2018. The air temperatures ranged between 21,6 and 25,6°C while the relative humidity fluctuated around 80%. The distribution of wind patterns showed a predominant direction towards the NW and a speed interval between 0,1 to 1,4 m.s-1. The main evidence of turbulences, u*, recorded a mean value around 0,31 m.s-1 during day and around 0,14 m.s-1 during night. Throughout the day, the peaks of temperature, wind speed, temperature and the minimum of %RH were recorded between 12:00 and 14:00 h. Short wave radiation fluxes oscillated around 300 W.m-2 and for long wave around -40 W.m-2, with highest values in the dry seasons. For the 2016-2017 wet season, a net radiation flow was recorded at 156,98 W.m-2 and 137,76 W.m-2 in the dry season. For the 2017-2018 period, these values were 151,20 W.m-2 in the rainy season and 139,81 W.m-2 in the dry season. Photosyntethic Active Radiation (PAR) recorded a daily average between 300 and 400 μmol.m-2.s-1. The daily distribution indicates that the forest received radiation between 06:00 and 18:00 h, reaching maximum peaks around noon. During the night, the forest behaved like a net source of radiation. In the flux analysis, an average daily flux of CO2 was determined ranging around -5 μmol.m-2.s-1 for the wet season and -4 μmol.m-2.s-1 for the rainy seasons. Registered storage CO2 flux values were 2,03 μmol.m-2.s-1 in the wet seasons and 1,3 μmol.m-2.s-1 in the dry season. The Net Ecosystemic Exchange (NEE) oscillated between -2 and -1 μmol.m-2.s-1. The daily behavior, influenced by the activity of the boundary layer, indicated that the forest was a carbon sink during days and a constant source at nights. Around 6:00 am, the turbulence due to the entry of solar radiation into the atmospheric boundary layer caused a CO2 flush with a maximum between 6 and 9 μmol.m-2.s-1. In the flux and energy balance analysis, sensible heat (H) and latent heat (LE) were studied. On a monthly scale, H fluctuated around 20 W.m-2 and LE near 60 W.m-2, with higher values during the wet seasons due to greater cloudiness, availability of H2O and lower incoming radiation. On a daily basis, due to the presence of solar radiation, the highest heat flux was registered during the day and the peaks were reached at noon. The energy balance, as a correspondence between the net radiation and H + LE, showed slopes between 0,70 and 0,80. The loss of energy balance was caused by errors in the instrumentation, sampling, application of the turbulence filter and the presence of vertical energy reserves that were not considered and registered by the equipment. The calculation of nocturnal ecosystemic respiration (R) was determined from the quadratic hyperbolic regression of NEE vs. PAR. During the 2016-2017 period, R was in the range of 9,49 to 11,84 μmol.m-2.s-1, while in 2017-2018, it was located between 7,03 and 7,88 μmol.m-2.s-1. The magnitude of R was more intense in the rainy seasons due to promotion of heterotrophic respiration and higher humidity at soil level. Gross primary productivity (GPP) was calculated as the difference of NEE and R. The values indicated a net annual carbon fixation of 44,86 tons per hectare in the period 2016-2017 and 45,92 tons per hectare during 2017-2018. The impact of the micrometorological and physiological variables, including possible errors due to lack of data continuity, could had affected the averages in GPP. Finally, the behavior of the R was modeled using the maximum daily temperature in each season. The results showed a remarkable approximation to the experimental results, so there is the possibility of expanding this field in the search to predict the behavior of the forest in the future.
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Turbulencia, Climatología, Dióxido de carbono--Monitoreo, Bosques tropicales--Perú--Amazonía, Región.
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