**2. Methodology**

#### **2.1 Data policy and use license**

The Ameriflux platform integrates the data monitored in three biomes, with the identifications: BR-Sa1 (Amazon), BR-CST (Caatinga) and BR-Npw (Pantanal). The data from the Cerrado site (BR-BI, Bananal Island - Javaés) are available at https://daac.ornl.gov. The data made available by ORNL DAAC are shared freely, without restriction, in agreement with NASA's Earth Science Program. Ameriflux data is shared under a CC-BY-4.0 data usage license (Creative Commons by Attribution 4.0 International). The CC-BY-4.0 license specifies that data usage is free to share (copy and redistribute the material in any medium or format) and/or adapt (remix, transform and build upon the material) for any purpose. The citation of the data sites is: BR-Sa1 [18], BR-CST [19] and BR-Npw [20].

#### **2.2 Description of study áreas**

#### *2.2.1 Cerrado site*

Measurements were made at an experimental floodplain site in Cantão State Park, 260 km west of Palmas, Tocantins, Brazil, in the context of the Large-Scale Biosphere-Atmosphere Experiment in Amazonia (LBA), at a micrometeorological tower with measurements of turbulent energy fluxes and meteorological variables. The tower was located 2 km east of the Araguaia river (9° 49<sup>0</sup> 27.9" S, 50° 08' 92.8" W, at 120 m altitude), about 1 km east of Javaézinho river, on the northern border of Ilha do Bananal and south of the park. The region of the Araguaia plain, where Ilha do Bananal is located, stands out for its exuberant landscape with aspects of the Cerrado and Amazon biome with three conservation units, the Araguaia National Park, the Cantão State Park (PEC) and the Cantão Environmental Protection Area. Bananal island covers an area of about 21,000 km2 (approximately 80 x 260 km) and is the largest river island in the world, covered mostly by savannas and grasslands, in seasonal floods usually from February to June [21]. The measurement fetch area covers three types of physiognomy: cerradão and semideciduous forests (trees with an average height of about 20 m), cerrado s.s., and areas of clean field and isolated lagoons. The regional climate is hot and seasonally humid, with average annual precipitation of about 1466 mm year-1, approximately 90% of the annual rainfall in the rainy season between October and April [21] and therefore typical of the Cerrado biome in central-western Brazil. The measurements comprise the period from January 2004 to December 2006.

#### *2.2.2 Caatinga site*

The measurements were taken at a site managed by the Chico Mendes Institute for Biodiversity Conservation and the micrometeorological tower is part of the monitoring network of the National Observatory of Water and Carbon Dynamics in the Caatinga Biome (NOWCDCB) project. The period of measurements comprises January 1, 2014 to July 31, 2015. This project is located in a preserved Caatinga area (BR-CST), situated in the Pajeú river basin in Serra Talhada (7° 58<sup>0</sup> 05.20" S and 38° 23' 02.62" W, 430 m), state of Pernambuco, northeastern Brazil. The climate is classified according to Köppen as BSwh (semi-arid), being characterized as hot and semi-arid, with summer rainfall concentrated between December and May (85%) according to Alcântara et al., [22]. The average annual precipitation is approximately 640 mm, and the average monthly air temperature ranges between 23.1 and 26.7°C [22]. The native species of the site are composed of Mimosa hostilis, Mimosa verrucosa and Croton sonderianus, and it is possible to find Anadenanthera macrocarpa, *Spondias tuberosa*, Caesalpinia pyramidalis and Ziziphus joazeiro, with a height of about 8.0 m [22].

#### *2.2.3 Pantanal site*

The study was conducted at the Brazilian Northern Pantanal Wetland (BR-Npw) flux tower (**Figure 1**) located approximately 35 km SE of Pocone, Mato Grosso, Brazil (16<sup>o</sup> 29<sup>0</sup> 53.71" S: 56<sup>o</sup> 24<sup>0</sup> 45.91" W; 120 m altitude). The site is part of a research station managed by the Federal University of Mato Grosso (UFMT) within a national reserve managed by the Brazilian Social Service of Commerce (SESC Pantanal) [23, 24]. Our data were collected from 1 January 2015 to 31 December 2016. Micrometeorological variables were measured 20 m aboveground, close to the eddy covariance sensors. Air temperature (*Ta*, °C) and relative humidity (*RH*, %) were measured using a thermohygrometer (HMP45AC, Vaisala Inc., Woburn, MA, USA). Precipitation (*Ppt*, mm) was measured 2 m above the ground using a micrometeorological station (WXT520, Vaisala Inc., Helsinki, Finland) installed in an open area to avoid interception by the tower or tree canopy. The flood stage was determined by measuring water levels (*WL*) above the ground at the study site. These inundation

*The Relevance of Maintaining Standing Forests for Global Climate Balance: A Case Study… DOI: http://dx.doi.org/10.5772/intechopen.110533*

**Figure 1.** *Location of the study sites.*

levels ( 1%) were measured along with water temperature ( 0.3°C using a CTD-10 [Decagon Devices Inc., Pullman, WA, USA], 0.05% full scale at 20°C) in 2015 and 2016. Due to instrument malfunction in 2014, the data for this year are not available. The start of each flood cycle began with the first reading of standing water at the site and ended when sensors indicated the absence of standing water. These flood cycles were then compared to the stage of the Cuiaba River collected by the RPPN-SESC Pantanal park rangers (pers. comm.) approximately 1 km away.

#### *2.2.4 Amazonia site*

Measurements were made at a site located in the Tapajós National Forest (FNT, 2° 51' S, 54° 58' W), which is situated near the Santarém-Cuiabá Highway (BR-163), at km 67. The NTF is bounded by the Tapajós River to the west and the BR-163 highway to the east, extending 50 km to 150 km south of the city of Santarém-PA. On the eastern side of the BR-163 highway the landscape is extensively developed for agriculture. The tower was installed approximately 6 km west of the BR-163 highway. The data analyzed are CO2 and energy fluxes associated with meteorological measurements. Measurements range from January 2009 to December 2011, with daily and monthly averages of hourly data. CO2 fluxes were measured at 58 m using a closed path analyzer (LICOR- 6262) and a Campbell CSAT3 Anemometer was used for the three-dimensional wind measurements. The 65 m micrometeorological tower is located in an area emerging from within a primary forest with a closed canopy of approximately 40 m in height, and can reach up to 55 m with some emergent trees [25]. **Figure 1** shows the location of the four study sites.

#### **2.3 Instrumentation and data processing**

Site instrumentations are given in previous publications [21, 22, 24, 26]. The gaps arising from the exclusion of spurious data during the rigorous screening process, were filled using the gap-filling algorithm of marginal distribution sampling (MDS) described by Reichstein et al. [27], which takes into account the covariation of fluxes with meteorological variables and also the temporal self-correlation of fluxes. In this algorithm, three conditions are identified with their respective procedures: when flux data are missing, but meteorological data are available (Rg, Ta and VPD): the missing data is replaced by the average value under similar meteorological conditions in a 7 day window. If similar conditions are not available, the window is increased to 14 days; (2) when only radiation values are available: the missing data is replaced by the average value under similar meteorological conditions within a 7-day window; (3) when no meteorological data is available: the missing value is replaced by the average value of the last hour, thus considering the diurnal variability of each variable. If, after these steps, the data are not filled, the procedure is repeated with larger window sizes until the value can be filled. For filling the gaps, an automated online tool made available by the Max Plank Institute (Max Planck Institute for Biogeochemistry http://www.bgc-jena.mpg.de/�MDIwork/eddyproc/) was used.

#### **2.4 Fluxes partitioning**

Gross primary productivity (GPP) and ecosystem respiration (Reco) were partitioned from the CO2 flux data (NEE). For the Cerrado and Pantanal sites, NEE is given as a proxy measure of turbulent flux (Fc). At the other sites NEE is composed of turbulent flux + storage. We used a nighttime-based flow partitioning method [27]. Since GPP =0 in night time, NEE corresponds to:

$$NEE = R\_{\text{avg}}\text{, for right hours}\tag{1}$$

$$NEE = R\_{eco} - GPP,\\
\text{for daytime hours} \tag{2}$$

Reco (μmol m�<sup>2</sup> s �2 ) being the sum of autotrophic and heterotrophic respiration. Reco and GPP were calculated using the online tool provided by the Max Plank Institute (Max Planck Institute for Biogeochemistry - http://www.bgc-jena.mpg.de/� MDIwork/eddyproc/).

Diurnal corrections for missing NEE data were modeled based on diurnal data using the common rectangular hyperbolic light response curve model [28, 29]:

$$NEE = \frac{a \cdot \beta \cdot R\_{\text{g}}}{a \cdot R\_{\text{g}} + \beta} + \gamma \tag{3}$$

where α (μmol C J�<sup>1</sup> ) is the light utilization efficiency and represents the initial slope of the light response curve, β (μmol C m�<sup>2</sup> s �1 ) is the maximum canopy CO2 uptake rate at light saturation, γ (μmol C m�<sup>2</sup> s �1 ) is the ecosystem respiration and Rg (W m�<sup>2</sup> ) is the global radiation. GPP was calculated as:

$$\text{GPP} = \text{NEE} + \text{R}\_{\text{eco}} \tag{4}$$

*The Relevance of Maintaining Standing Forests for Global Climate Balance: A Case Study… DOI: http://dx.doi.org/10.5772/intechopen.110533*
