Cooperative Program for Flux Tower

The long-term monitoring of the carbon, water and nutrient flows in forest plantations is extremely important to understand the use of natural resources, influence of the climatic seasonality and sustainability of such ecosystems. Accomplishment of such activity requires large sample intensity, comprising countless field and lab activities, which are usually quite burdensome. Depending on time scale and the area intended for assessment, following the field sampling methodology becomes fully unfeasible.

Due to such limitations, use of flux towers (Eddy Covariance) has become a even more robust methodology, being a standard tool for assessment of the carbon, water, and power flows between the atmosphere and different ecosystems, forests or agricultural. The towers are equipped with cutting-edge micro-meteorological equipment, positioned above thecanopy of the vegetation which is the focus of monitoring. Currently, there are over 500 flux towers spread all over the world.

This technique allows obtaining core information for enhancing the planted forest handling, with a highlight for i) continuous determination of productivity and carbon isolation in relation to the climatic variables; ii) detailed assessment of the water balance in the forest system; iii) use estimate and efficiency of water use by the eucalyptus; iv) calibration and validation of ecophysiologic models; and v) enhancement of silvicultural practices by using such models.

Thus, aimed at applying such technique to know in details the carbon, waterand power flows, throughout a complete rotation of Eucalyptus, IPEF, by means of 11 forest companies, supported by education and research institutions in Brazil, France and the United States, created the Cooperative Program EUCFLUX: Quantification of the Carbon, Water and Nutrient Balances, in the Ecosystem Scale, for a Rotation of the Eucalyptus using Flux Tower.

During 2006 and 2007, the tower installation area was chosen, the entire logistics of equipment import defined and accomplished and finally its full assembly was made. Beginning of the measurements took place in March 2008, operating with no problems until nowadays, January 2012.

Flux Tower Methodology

The technique used by the flux towers is named “Eddy Covariance” and assesses the CO2, water vapor and power exchange rates, in the interface between the atmosphere and the forest canopy, by determining the covariance between the fluctuations in the vertical wind speed and the mixture rate of such gases in the air. Such gas mix in the air is made by wind eddy, then the name of eddy covariance.

The technique allows for studying CO2, water and power exchanges, assessing the responses of the vegetation to the environmental variables, seeking to understand the control mechanisms throughout different time (from seconds to years) and spatial scales (from some meters to kilometers), so as to enhance models that work with C and H2O cycles.

The CO2 and H2O concentrations are measured in high frequency (20Hz = 20 measurements per second) using an IRGA (Infra-RedGasAnalyzer) sensor, such as Licor 7500. In turn, the scanning in the vertical windspeed is measured bya three-dimensional sonic anemometer in the same frequency (20Hz). The data are real time processed, integrated every 30 minutes and added for obtaining daily, monthly and annual estimates of the power balance, evapotranspiration and primary liquid productivity of the ecosystem (NEP = isolation of C). The technique is particularly interesting to study the physiology of the ecosystem and quantify how the carbonand water flows are affected by the environment and the weather in different time and space scales.

The towers comprise the behavior of large forested areas (150 to 200 ha), and the C flows may be divided into photosynthesis and respiration of the trees and the ground. In parallel, the nutrient flowsmay be associated with the development stage of the forest to obtain a balance, in ground level, essential for long-term sustainability analyses.

Biogeochemical Cycling

Concomitantly to use of the tower to assess the flows between the forest and the atmosphere, the project Eucflux monitors the water dynamic throughout the ground profile up to 10 meters of depth, in two places of the experimental site (medium and clayey textures), since 2008. There are also three piezometers near the tower monitoring the depth of the ground water since 2009.

Biogeochemical Cyclingis assessed, observing the dynamics of the nutrients in the ground profile, accumulation of nutrients in the tree components above and underground, mineralization rate of the undergrowth nutrients and internal translocation of nutrients in the trees. Studies related to the production rate of thin roots and their nutrient absorption features in different depths were and are being made.

Mapa da área experimental

Goals

EUCFLUX is aimed at estimating the amounts of carbon, water, power, and nutrients for a full rotation of eucalyptus clone, in ecosystem level (150 to 200 ha), using the flow tower method, to obtain the effect of the environmental variables on productivity of the forest, ground fertility and hydrous resources, aiming to:

• Measure, on a daily basis, the forest productivity, and the power, carbon and water flows throughout a rotation, capturing the seasonal effects in productivity;
• Determine carbon isolation and its allocation within the ecosystem, under and above ground;
• Determine the effects of a forest plantation on water availability;
• Determine dynamics and reserve of the nutrients (biogeochemical cycles) throughout rotation;
• Determine efficiency of water, light, nutrient use, and their seasonal standards;
• Test (calibration/validation) ecophysiological models to be used as tools for production and sustainability purposes;
• Publish scientific essays both for the Brazilian and for the international communities.

History and Participant Companies

EUCFLUX came into existence as a joint initiative of 3 research groups and the participant companies, through technical-scientific and administrative meetings held throughout 2005 and 2006. These research groups are IPEF, Esalq/USP and North Carolina State University, by means of the BEPP program, which since 2001 works in investigating subjects related to ecophysiology of Eucalyptus plantations, of the CIRAD (Centre de Coopération Internationale em Recherche Agronomique) French institute that for 5 years develops ecophysiology researches jointly with Esalq/USP, and the IAG/USP (Astronomy, Geophysics and Atmospheric Science Institute of USP) which participates of projects in other flow towers in Brazil. With this research group, companies from the forest sector that ratified their participation in the program were associated: ArcelorMittal, Fibria, Bahia Specialty Cellulose, Cenibra, Duratex, International Paper, Klabin, Suzano e V&M Florestal.

As of beginning of the measurements (March 2008) until September 2009 a seminal forest of E. grandis was studied. In September, harvesting was made and in November reform was made, with plantation of a commercial clone typical from the State of São Paulo in the whole experimental area. By the same time, a Clone Test was implemented, comprised of 10 repetitions with 16 genetic materials (2 seminal and 14 clonal) coming from different regions of Brazil, for the purpose of assessing the effect of genetic variability on productivity of the main genetic materials planted in the country currently throughout the landscape, with different productivity levels. In addition to all activities already accomplished by the main project, the following projects were proposed for Clonal Test: i) effect of genetic variability in the carbon and wood productivity allocation standards; ii) characterization of the photosynthetic capacity and efficiency of water use for the different materials; iii) assessment of the root growth front and aerial and its speed for exploitation of the ground layers and canopy structure.

EUCFLUX Tower

The flux tower technique is the most reliable method to measure CO2 and H2O exchanges in the landscape scale, being best applied in flat lands and on a single type of ground coverage (forest or agriculture), which covers an area with radius of at least 50m of the tower. These optimum conditions were found in a Duratex farm, in Itatinga (SP), near the Experimental Forest Science Station of Esalq/USP, where there is structure to support the researchers and graduation and post-graduation students.

After defining the installation site, the tower was planned and its structure was compared in Brazil, while all pieces of micrometeorological equipment were imported from the US, England and the Netherlands. Throughout 2007 the equipment was assembled with the assistance of INRA, CIRAD and USP, and a safety system, with lightning-rod, protection fences and surveillance was assembled so as to ensure continuous data gathering.

The tower, 35 meters high, had its start-up in January 2007, and started to operate continuously, as of March 1, 2008, on a forest comprised of Eucalyptus grandis with 6 years of age. During gathering and reform of the experimental area, the equipment was carefully kept in the tower aimed at ensuring the capture of the flows during such period. Now, the new planting has approximately 2 years and the tower is 22 meters high, following the micrometeorological theory that the equipment should be located in average 10 meters above the canopy and should go up as the forest grows.

Subprojects

In the Tower
The flux tower shall be an agglutinant of several researches, named subprojects, and that shall be composed throughout the years of study. Until now, the following research projects were carried out or are being carried out, and comprise the Eucflux project:

Sub-Project 1: Carbon, Water and Power Balance in Full Cycle of Eucalyptus via Flux Tower
Sub-Project 2: Environmental and physiological factors controlling GPP, NPP, NEP and Allocation of C in Eucalyptus
Sub-Project 3: Efficiency of Water, Light and Nutrient Use Throughout a Rotation of Eucalyptus
Sub-Project 4: Productivity and Efficiency of Eucalyptus Clones: Crown, Physiology and Allocation Standards
Sub-Project 5: Spatial and Temporal Variability of Eucalyptus Productivity through C Balance and MAESTRA Use
Sub-Project 6: Modeling of the growth, C cycle, Water and N using the G’Day model
Sub-Project 7: Biogeochemical Cycles in Eucalyptus due to Textural and Clonal Variability
Sub-Project 8: Direct and indirect methods for measuring water use by the Eucalyptus
Sub-Project 9: Contribution of deep thin roots in Eucalyptus nutrition in sandy and clayey grounds
Sub-Project 10: An isotropy and distribution of thin roots of Eucalyptus in a rotation
Sub-Project 11: Use of Satellite Images and Models to Simulate Growth and Transpiration of Eucalyptus
Sub-Project 12: Assessment of Vigor and Nutrition of Eucalyptus Crown with High-Resolution Multispectral Images
Sub-Project 13: Use of LIDAR Images to estimate biomass and characterize canopy and individual Eucalyptus crowns
Sub-Project 14: Assessment of Activity and Nutrition of Eucalyptus Crown with Hyperspectral Images

In Clonal Test
Sub-Project 1: Effect of Genetic Variabilityin theCarbon Allocation and Wood Productivity Standards
Sub-Project 2: Characterization of the Photosynthetic Capacity and Efficiency of Water Usefor the Different Materials
Sub-Project 3: Assessment of the Root Growth Front and Aerial and their Exploitation Speed of the Ground Layers and Canopy Structure

Several of these projects already count on scholarships, or support, from Brazil (CNPq, CAPES and FAPESP), and abroad (France and USA), and the project counts on own vehicle (Kombi).




Instituto de Pesquisas e Estudos Florestais
Via Comendador Pedro Morganti, 3500 - Bairro Monte Alegre
CEP: 13415-000 - Piracicaba, SP - Brasil
Reprodução permitida desde que citada a fonte.