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1. Effects of experimental nitrogen deposition on soil organic carbon storage in Southern California drylands

Author

Püspök, Johann F, Zhao, Sharon, Calma, Anthony D, Vourlitis, George L, Allison, Steven D, Aronson, Emma L, Schimel, Joshua P, Hanan, Erin J, and Homyak, Peter M

Subjects
Life on Land, Carbon, Soil, Nitrogen, Ecosystem, Biomass, Minerals, Calcium, Soil Microbiology, atmospheric nitrogen deposition, carbon use efficiency, extracellular enzymes, fertilization, mineral-associated organic matter, particulate organic matter, soil acidification, soil microbes, Environmental Sciences, Biological Sciences, Ecology
Abstract

Atmospheric nitrogen (N) deposition is enriching soils with N across biomes. Soil N enrichment can increase plant productivity and affect microbial activity, thereby increasing soil organic carbon (SOC), but such responses vary across biomes. Drylands cover ~45% of Earth's land area and store ~33% of global SOC contained in the top 1 m of soil. Nitrogen fertilization could, therefore, disproportionately impact carbon (C) cycling, yet whether dryland SOC storage increases with N remains unclear. To understand how N enrichment may change SOC storage, we separated SOC into plant-derived, particulate organic C (POC), and largely microbially derived, mineral-associated organic C (MAOC) at four N deposition experimental sites in Southern California. Theory suggests that N enrichment increases the efficiency by which microbes build MAOC (C stabilization efficiency) if soil pH stays constant. But if soils acidify, a common response to N enrichment, then microbial biomass and enzymatic organic matter decay may decrease, increasing POC but not MAOC. We found that N enrichment had no effect on C fractions except for a decrease in MAOC at one site. Specifically, despite reported increases in plant biomass in three sites and decreases in microbial biomass and extracellular enzyme activities in two sites that acidified, POC did not increase. Furthermore, microbial C use and stabilization efficiency increased in a non-acidified site, but without increasing MAOC. Instead, MAOC decreased by 16% at one of the sites that acidified, likely because it lost 47% of the exchangeable calcium (Ca) relative to controls. Indeed, MAOC was strongly and positively affected by Ca, which directly and, through its positive effect on microbial biomass, explained 58% of variation in MAOC. Long-term effects of N fertilization on dryland SOC storage appear abiotic in nature, such that drylands where Ca-stabilization of SOC is prevalent and soils acidify, are most at risk for significant C loss.

Published
2023

3. Gap-filling eddy covariance methane fluxes: Comparison of machine learning model predictions and uncertainties at FLUXNET-CH4 wetlands

Author

Irvin, Jeremy, Zhou, Sharon, McNicol, Gavin, Lu, Fred, Liu, Vincent, Fluet-Chouinard, Etienne, Ouyang, Zutao, Knox, Sara Helen, Lucas-Moffat, Antje, Trotta, Carlo, Papale, Dario, Vitale, Domenico, Mammarella, Ivan, Alekseychik, Pavel, Aurela, Mika, Avati, Anand, Baldocchi, Dennis, Bansal, Sheel, Bohrer, Gil, Campbell, David I, Chen, Jiquan, Chu, Housen, Dalmagro, Higo J, Delwiche, Kyle B, Desai, Ankur R, Euskirchen, Eugenie, Feron, Sarah, Goeckede, Mathias, Heimann, Martin, Helbig, Manuel, Helfter, Carole, Hemes, Kyle S, Hirano, Takashi, Iwata, Hiroki, Jurasinski, Gerald, Kalhori, Aram, Kondrich, Andrew, Lai, Derrick YF, Lohila, Annalea, Malhotra, Avni, Merbold, Lutz, Mitra, Bhaskar, Ng, Andrew, Nilsson, Mats B, Noormets, Asko, Peichl, Matthias, Rey-Sanchez, A Camilo, Richardson, Andrew D, Runkle, Benjamin RK, Schäfer, Karina VR, Sonnentag, Oliver, Stuart-Haëntjens, Ellen, Sturtevant, Cove, Ueyama, Masahito, Valach, Alex C, Vargas, Rodrigo, Vourlitis, George L, Ward, Eric J, Wong, Guan Xhuan, Zona, Donatella, Alberto, Ma Carmelita R, Billesbach, David P, Celis, Gerardo, Dolman, Han, Friborg, Thomas, Fuchs, Kathrin, Gogo, Sébastien, Gondwe, Mangaliso J, Goodrich, Jordan P, Gottschalk, Pia, Hörtnagl, Lukas, Jacotot, Adrien, Koebsch, Franziska, Kasak, Kuno, Maier, Regine, Morin, Timothy H, Nemitz, Eiko, Oechel, Walter C, Oikawa, Patricia Y, Ono, Keisuke, Sachs, Torsten, Sakabe, Ayaka, Schuur, Edward A, Shortt, Robert, Sullivan, Ryan C, Szutu, Daphne J, Tuittila, Eeva-Stiina, Varlagin, Andrej, Verfaillie, Joeseph G, Wille, Christian, Windham-Myers, Lisamarie, Poulter, Benjamin, and Jackson, Robert B

Subjects
Earth Sciences, Agricultural, Veterinary and Food Sciences, Biological Sciences, Machine Learning and Artificial Intelligence, Networking and Information Technology R&D (NITRD), Bioengineering, Machine learning, time series, imputation, gap-filling, methane, flux, wetlands, Agricultural and Veterinary Sciences, Meteorology & Atmospheric Sciences, Agricultural, veterinary and food sciences, Biological sciences, Earth sciences
Abstract

Time series of wetland methane fluxes measured by eddy covariance require gap-filling to estimate daily, seasonal, and annual emissions. Gap-filling methane fluxes is challenging because of high variability and complex responses to multiple drivers. To date, there is no widely established gap-filling standard for wetland methane fluxes, with regards both to the best model algorithms and predictors. This study synthesizes results of different gap-filling methods systematically applied at 17 wetland sites spanning boreal to tropical regions and including all major wetland classes and two rice paddies. Procedures are proposed for: 1) creating realistic artificial gap scenarios, 2) training and evaluating gap-filling models without overstating performance, and 3) predicting half-hourly methane fluxes and annual emissions with realistic uncertainty estimates. Performance is compared between a conventional method (marginal distribution sampling) and four machine learning algorithms. The conventional method achieved similar median performance as the machine learning models but was worse than the best machine learning models and relatively insensitive to predictor choices. Of the machine learning models, decision tree algorithms performed the best in cross-validation experiments, even with a baseline predictor set, and artificial neural networks showed comparable performance when using all predictors. Soil temperature was frequently the most important predictor whilst water table depth was important at sites with substantial water table fluctuations, highlighting the value of data on wetland soil conditions. Raw gap-filling uncertainties from the machine learning models were underestimated and we propose a method to calibrate uncertainties to observations. The python code for model development, evaluation, and uncertainty estimation is publicly available. This study outlines a modular and robust machine learning workflow and makes recommendations for, and evaluates an improved baseline of, methane gap-filling models that can be implemented in multi-site syntheses or standardized products from regional and global flux networks (e.g., FLUXNET).

Published
2021

5. Identifying dominant environmental predictors of freshwater wetland methane fluxes across diurnal to seasonal time scales

Author

Knox, Sara H, Bansal, Sheel, McNicol, Gavin, Schafer, Karina, Sturtevant, Cove, Ueyama, Masahito, Valach, Alex C, Baldocchi, Dennis, Delwiche, Kyle, Desai, Ankur R, Euskirchen, Eugenie, Liu, Jinxun, Lohila, Annalea, Malhotra, Avni, Melling, Lulie, Riley, William, Runkle, Benjamin RK, Turner, Jessica, Vargas, Rodrigo, Zhu, Qing, Alto, Tuula, Fluet‐Chouinard, Etienne, Goeckede, Mathias, Melton, Joe R, Sonnentag, Oliver, Vesala, Timo, Ward, Eric, Zhang, Zhen, Feron, Sarah, Ouyang, Zutao, Alekseychik, Pavel, Aurela, Mika, Bohrer, Gil, Campbell, David I, Chen, Jiquan, Chu, Housen, Dalmagro, Higo J, Goodrich, Jordan P, Gottschalk, Pia, Hirano, Takashi, Iwata, Hiroki, Jurasinski, Gerald, Kang, Minseok, Koebsch, Franziska, Mammarella, Ivan, Nilsson, Mats B, Ono, Keisuke, Peichl, Matthias, Peltola, Olli, Ryu, Youngryel, Sachs, Torsten, Sakabe, Ayaka, Sparks, Jed P, Tuittila, Eeva‐Stiina, Vourlitis, George L, Wong, Guan X, Windham‐Myers, Lisamarie, Poulter, Benjamin, and Jackson, Robert B

Subjects
Earth Sciences, Climate Change Impacts and Adaptation, Environmental Sciences, Carbon Dioxide, Ecosystem, Fresh Water, Methane, Seasons, Wetlands, eddy covariance, generalized additive modeling, lags, methane, mutual information, predictors, random forest, synthesis, time scales, wetlands, Biological Sciences, Ecology, Biological sciences, Earth sciences, Environmental sciences
Abstract

While wetlands are the largest natural source of methane (CH4 ) to the atmosphere, they represent a large source of uncertainty in the global CH4 budget due to the complex biogeochemical controls on CH4 dynamics. Here we present, to our knowledge, the first multi-site synthesis of how predictors of CH4 fluxes (FCH4) in freshwater wetlands vary across wetland types at diel, multiday (synoptic), and seasonal time scales. We used several statistical approaches (correlation analysis, generalized additive modeling, mutual information, and random forests) in a wavelet-based multi-resolution framework to assess the importance of environmental predictors, nonlinearities and lags on FCH4 across 23 eddy covariance sites. Seasonally, soil and air temperature were dominant predictors of FCH4 at sites with smaller seasonal variation in water table depth (WTD). In contrast, WTD was the dominant predictor for wetlands with smaller variations in temperature (e.g., seasonal tropical/subtropical wetlands). Changes in seasonal FCH4 lagged fluctuations in WTD by ~17 ± 11 days, and lagged air and soil temperature by median values of 8 ± 16 and 5 ± 15 days, respectively. Temperature and WTD were also dominant predictors at the multiday scale. Atmospheric pressure (PA) was another important multiday scale predictor for peat-dominated sites, with drops in PA coinciding with synchronous releases of CH4 . At the diel scale, synchronous relationships with latent heat flux and vapor pressure deficit suggest that physical processes controlling evaporation and boundary layer mixing exert similar controls on CH4 volatilization, and suggest the influence of pressurized ventilation in aerenchymatous vegetation. In addition, 1- to 4-h lagged relationships with ecosystem photosynthesis indicate recent carbon substrates, such as root exudates, may also control FCH4. By addressing issues of scale, asynchrony, and nonlinearity, this work improves understanding of the predictors and timing of wetland FCH4 that can inform future studies and models, and help constrain wetland CH4 emissions.

Published
2021

10. Diversity-productivity relationships of savanna ecosystems in the Cerrado-Pantanal transition of southern Mato Grosso, Brazil.

Author

Vourlitis, George L., Pinto Jr, Osvaldo Borges, Dalmagro, Higo J., Arruda, Paulo H., and de Almeida Lobo, Francisco

Subjects
SWAMPS, SAVANNAS, RIPARIAN forests, TREE growth, CERRADOS, FOREST productivity
Abstract

Productivity and ecosystem carbon (C) storage are often positively associated with species and/or structural diversity; however, positive relationships in tropical forests and woodlands are not universal and the strength of this relationship may be affected by climate. Diversity-productivity relationships were evaluated in upland and seasonally flooded savanna (Cerrado) of the Cuiaba Basin and Northern Pantanal in southern Mato Grosso, Brazil. Data on wood C increment, tree species composition, and alpha diversity were measured over a 10-year period in nine communities located in the Cerrado-Pantanal transition zone. Communities were composed of a wide spectrum of tropical savanna physiognomies, including mixed grassland (campo sujo), typical wooded savanna (stricto sensu), dense wooded savanna (cerrado denso), seasonal forest (mata seca and mata ciliar), and riparian forest (mata de galeria). We hypothesized that tree species richness and diversity would increase from grassland to forest. We further hypothesized that there would be a positive relationship between woody C storage and diversity, but the strength of this relationship would be higher in wet years and wetter environments, such as the Pantanal, due to an increase in water availability. We found that tree species richness and diversity did not increase from mixed grasslands to forests, as mixed grasslands and riparian forests had similarly low levels of tree species richness and diversity compared to the other physiognomies. However, the rate of annual aboveground wood C increment was positively related to species richness and alpha diversity, and the positive relationship was primarily observed during wet years when the annual precipitation was at, or above, the long-term average for the region. Presumably, the impact of structural and species diversity on productivity declines during dry years when water availability becomes a more important control on stem C increment for tree species in the Cerrado-Pantanal transition. These data suggest that maintenance of diversity in these Cerrado woodlands and forests is important for maximizing aboveground C gain. However, climate change, which is causing warming and drying for the region, may limit the importance of diversity on wood C storage. [ABSTRACT FROM AUTHOR]

Published
2024
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19. Early stage litter decomposition across biomes

Author

Caliman, Adriano, Paquette, Alain, Gutiérrez-Girón, Alba, Humber, Alberto, Valdecantos, Alejandro, Petraglia, Alessandro, Alexander, Heather, Augustaitis, Algirdas, Saillard, Amélie, Fernández, Ana Carolina Ruiz, Sousa, Ana I., Lillebø, Ana I., da Rocha Gripp, Anderson, Francez, André-Jean, Fischer, Andrea, Bohner, Andreas, Malyshev, Andrey, Andrić, Andrijana, Smith, Andy, Stanisci, Angela, Seres, Anikó, Schmidt, Anja, Avila, Anna, Probst, Anne, Ouin, Annie, Khuroo, Anzar A., Verstraeten, Arne, Palabral-Aguilera, Arely N., Stefanski, Artur, Gaxiola, Aurora, Muys, Bart, Bosman, Bernard, Ahrends, Bernd, Parker, Bill, Sattler, Birgit, Yang, Bo, Juráni, Bohdan, Erschbamer, Brigitta, Ortiz, Carmen Eugenia Rodriguez, Christiansen, Casper T., Carol Adair, E., Meredieu, Céline, Mony, Cendrine, Nock, Charles A., Chen, Chi-Ling, Wang, Chiao-Ping, Baum, Christel, Rixen, Christian, Delire, Christine, Piscart, Christophe, Andrews, Christopher, Rebmann, Corinna, Branquinho, Cristina, Polyanskaya, Dana, Delgado, David Fuentes, Wundram, Dirk, Radeideh, Diyaa, Ordóñez-Regil, Eduardo, Crawford, Edward, Preda, Elena, Tropina, Elena, Groner, Elli, Lucot, Eric, Hornung, Erzsébet, Gacia, Esperança, Lévesque, Esther, Benedito, Evanilde, Davydov, Evgeny A., Ampoorter, Evy, Bolzan, Fabio Padilha, Varela, Felipe, Kristöfel, Ferdinand, Maestre, Fernando T., Maunoury-Danger, Florence, Hofhansl, Florian, Kitz, Florian, Sutter, Flurin, Cuesta, Francisco, de Almeida Lobo, Francisco, de Souza, Franco Leandro, Berninger, Frank, Zehetner, Franz, Wohlfahrt, Georg, Vourlitis, George, Carreño-Rocabado, Geovana, Arena, Gina, Pinha, Gisele Daiane, González, Grizelle, Canut, Guylaine, Lee, Hanna, Verbeeck, Hans, Auge, Harald, Pauli, Harald, Nacro, Hassan Bismarck, Bahamonde, Héctor A., Feldhaar, Heike, Jäger, Heinke, Serrano, Helena C., Verheyden, Hélène, Bruelheide, Helge, Meesenburg, Henning, Jungkunst, Hermann, Jactel, Hervé, Shibata, Hideaki, Kurokawa, Hiroko, Rosas, Hugo López, Rojas Villalobos, Hugo L., Yesilonis, Ian, Melece, Inara, Van Halder, Inge, Quirós, Inmaculada García, Makelele, Isaac, Senou, Issaka, Fekete, István, Mihal, Ivan, Ostonen, Ivika, Borovská, Jana, Roales, Javier, Shoqeir, Jawad, Lata, Jean-Christophe, Theurillat, Jean-Paul, Probst, Jean-Luc, Zimmerman, Jess, Vijayanathan, Jeyanny, Tang, Jianwu, Thompson, Jill, Doležal, Jiří, Sanchez-Cabeza, Joan-Albert, Merlet, Joël, Henschel, Joh, Neirynck, Johan, Knops, Johannes, Loehr, John, von Oppen, Jonathan, Þorláksdóttir, Jónína Sigríður, Löffler, Jörg, Cardoso-Mohedano, José-Gilberto, Benito-Alonso, José-Luis, Torezan, Jose Marcelo, Morina, Joseph C., Jiménez, Juan J., Quinde, Juan Dario, Alatalo, Juha, Seeber, Julia, Stadler, Jutta, Kriiska, Kaie, Coulibaly, Kalifa, Fukuzawa, Karibu, Szlavecz, Katalin, Gerhátová, Katarína, Lajtha, Kate, Käppeler, Kathrin, Jennings, Katie A., Tielbörger, Katja, Hoshizaki, Kazuhiko, Green, Ken, Yé, Lambiénou, Pazianoto, Laryssa Helena Ribeiro, Dienstbach, Laura, Williams, Laura, Yahdjian, Laura, Brigham, Laurel M., van den Brink, Liesbeth, Rustad, Lindsey, Zhang, Lipeng, Morillas, Lourdes, Xiankai, Lu, Carneiro, Luciana Silva, Di Martino, Luciano, Villar, Luis, Bader, Maaike Y., Morley, Madison, Lebouvier, Marc, Tomaselli, Marcello, Sternberg, Marcelo, Schaub, Marcus, Santos-Reis, Margarida, Glushkova, Maria, Torres, María Guadalupe Almazán, Giroux, Marie-Andrée, de Graaff, Marie-Anne, Pons, Marie-Noëlle, Bauters, Marijn, Mazón, Marina, Frenzel, Mark, Didion, Markus, Wagner, Markus, Hamid, Maroof, Lopes, Marta L., Apple, Martha, Schädler, Martin, Weih, Martin, Gualmini, Matteo, Vadeboncoeur, Matthew A., Bierbaumer, Michael, Danger, Michael, Liddell, Michael, Mirtl, Michael, Scherer-Lorenzen, Michael, Růžek, Michal, Carbognani, Michele, Di Musciano, Michele, Matsushita, Michinari, Zhiyanski, Miglena, Pușcaș, Mihai, Barna, Milan, Ataka, Mioko, Jiangming, Mo, Alsafran, Mohammed, Carnol, Monique, Barsoum, Nadia, Tokuchi, Naoko, Eisenhauer, Nico, Lecomte, Nicolas, Filippova, Nina, Hölzel, Norbert, Ferlian, Olga, Romero, Oscar, Pinto, Osvaldo B., Jr, Peri, Pablo, Weber, Paige, Vittoz, Pascal, Turtureanu, Pavel Dan, Fleischer, Peter, Macreadie, Peter, Haase, Peter, Reich, Peter, Petřík, Petr, Choler, Philippe, Marmonier, Pierre, Muriel, Priscilla, Ponette, Quentin, Guariento, Rafael Dettogni, Canessa, Rafaella, Kiese, Ralf, Hewitt, Rebecca, Rønn, Regin, Adrian, Rita, Kanka, Róbert, Weigel, Robert, Gatti, Roberto Cazzolla, Martins, Rodrigo Lemes, Georges, Romain, Meneses, Rosa Isela, Gavilán, Rosario G., Dasgupta, Sabyasachi, Wittlinger, Sally, Puijalon, Sara, Freda, Sarah, Suzuki, Satoshi, Charles, Sean, Gogo, Sébastien, Drollinger, Simon, Mereu, Simone, Wipf, Sonja, Trevathan-Tackett, Stacey, Löfgren, Stefan, Stoll, Stefan, Trogisch, Stefan, Hoeber, Stefanie, Seitz, Steffen, Glatzel, Stephan, Milton, Sue J., Dousset, Sylvie, Mori, Taiki, Sato, Takanori, Ise, Takeshi, Hishi, Takuo, Kenta, Tanaka, Nakaji, Tatsuro, Michelan, Thaisa Sala, Camboulive, Thierry, Mozdzer, Thomas J., Scholten, Thomas, Spiegelberger, Thomas, Zechmeister, Thomas, Kleinebecker, Till, Hiura, Tsutom, Enoki, Tsutomu, Ursu, Tudor-Mihai, di Cella, Umberto Morra, Hamer, Ute, Klaus, Valentin H., Rêgo, Vanessa Mendes, Di Cecco, Valter, Busch, Verena, Fontana, Veronika, Piscová, Veronika, Carbonell, Victoria, Ochoa, Victoria, Bretagnolle, Vincent, Maire, Vincent, Farjalla, Vinicius, Zhou, Wenjun, Luo, Wentao, McDowell, William H., Hu, Yalin, Utsumi, Yasuhiro, Kominami, Yuji, Zaika, Yulia, Rozhkov, Yury, Kotroczó, Zsolt, Tóth, Zsolt, Djukic, Ika, Kepfer-Rojas, Sebastian, Schmidt, Inger Kappel, Larsen, Klaus Steenberg, Beier, Claus, Berg, Björn, and Verheyen, Kris

Published
2018
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24. Patterns of water and heat flux across a biome gradient from tropical forest to savanna in Brazil

Author

da Rocha, Humberto R., Manzi, Antonio O., Cabral, Osvaldo M., Miller, Scott D., Goulden, Michael L., Saleska, Scott R., R.-Coupe, Natalia, Wofsy, Steven C., Borma, Laura S., Artaxo, P., Vourlitis, George, Nogueira, José S., Cardoso, Fernando L., Nobre, Antonio D., Kruijt, Bart, Freitas, Helber C., von Randow, Celso, Aguiar, Renata G., and Maia, Jair F.

Subjects
tropical forest, evaporation, cerrado, savanna, Amazonia
Abstract

We investigated the seasonal patterns of water vapor and sensible heat flux along a tropical biome gradient from forest to savanna. We analyzed data from a network of flux towers in Brazil that were operated within the Large-Scale Biosphere-Atmosphere Experiment in Amazonia (LBA). These tower sites included tropical humid and semideciduous forest, transitional forest, floodplain (with physiognomies of cerrado), and cerrado sensu stricto. The mean annual sensible heat flux at all sites ranged from 20 to 38 Wm−2, and was generally reduced in the wet season and increased in the late dry season, coincident with seasonal variations of net radiation and soil moisture. The sites were easily divisible into two functional groups based on the seasonality of evaporation: tropical forest and savanna. At sites with an annual precipitation above 1900 mm and a dry season length less than 4 months (Manaus, Santarem and Rondonia), evaporation rates increased in the dry season, coincident with increased radiation. Evaporation rates were as high as 4.0 mm d−1 in these evergreen or semidecidous forests. In contrast, ecosystems with precipitation less than 1700 mm and a longer dry season (Mato Grosso, Tocantins and São Paulo) showed clear evidence of reduced evaporation in the dry season. Evaporation rates were as low as 2.5 mm d−1 in the transitional forests and 1 mm d−1 in the cerrado. The controls on evapotranspiration seasonality changed along the biome gradient, with evaporative demand (especially net radiation) playing a more important role in the wetter forests, and soil moisture playing a more important role in the drier savannah sites.

Published
2009

35. Enhanced net CO2 exchange of a semideciduous forest in the southern Amazon due to diffuse radiation from biomass burning.

Author

Rodrigues, Simone, Cirino, Glauber, Moreira, Demerval, Pozzer, Andrea, Palácios, Rafael, Lee, Sung-Ching, Imbiriba, Breno, Nogueira, José, Vitorino, Maria Isabel, and Vourlitis, George

Subjects
BIOMASS burning, CARBONACEOUS aerosols, ATMOSPHERIC aerosols, RADIATION, SOLAR radiation, ATMOSPHERIC circulation, DECIDUOUS forests
Abstract

Carbon cycling in the Amazon fundamentally depends on the functioning of ecosystems and atmospheric dynamics, which are highly intricate. Few studies have hitherto investigated or measured the radiative effects of aerosols on the Amazon and Cerrado. This study examines the effects of atmospheric aerosols on solar radiation and their effects on net ecosystem exchange (NEE) in an area of semideciduous tropical forest in the north of Mato Grosso. Our results show that for a relative irradiance (f) 1.10–0.67, a decrease in incident solar radiation is associated with a reduction in the NEE. However, an average increase of 25 %–110 % in NEE was observed when pollution levels and aerosol optical depth (AOD) were above ≈1.25 and f < 0.5. The increase NEE was attributed to the increase of up to 60 % in the diffuse fraction of photosynthetically active radiation. The change in AOD and f was mainly attributable to biomass burning organic aerosols from fires. Important influences on vapor pressure deficit (VPD) as well as air temperature (Tair) and canopy (LC T), induced by the interaction between solar radiation and high aerosol load in the observation area, were also noticed. On average, a cooling of about 3–4 ∘ C was observed for Tair and LC T , and a decrease of up to 2–3 hPa was observed for VPD. Given the long-distance transport of aerosols emitted by burning biomass, significant changes in atmospheric optical properties and irradiance will impact the CO 2 flux of semideciduous forests distributed in the region. [ABSTRACT FROM AUTHOR]

Published
2024
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39. Enhanced net CO2 exchange of a semi-deciduous forest in the southern Amazon due to diffuse radiation from biomass burning

Author

Rodrigues, Simone, Cirino, Glauber, Moreira, Demerval, Palácios, Rafael, Nogueira, José, Vitorino, Maria Isabel, and Vourlitis, George

Abstract

Atmospheric processes and climate are closely linked to the carbon cycle in the Amazon region as a consequence of the strong biosphere-atmosphere coupling. The radiative effects of aerosols and clouds are still unknown for a wide variety of species and types of vegetation present in Amazonian biomes. This study examines the effects of atmospheric aerosols on solar radiation and their effects on Net Ecosystem Exchange (NEE) in an area of semideciduous tropical forest in the North of Mato Grosso State. Our results show a reduction in the NEE with a decrease in incident solar radiation of ≈ 40 % and relative irradiance between 1.10–0.67. However, an average increase of 35–70 % in NEE was observed when pollution levels (Aerosol Optical Depth) were above ≈ 1.25. The increase NEE was attributed to the increase of up to 60 % in the diffuse fraction of Photosynthetically Active Radiation. These results were mainly attributable to the biomass burning organic aerosols from fires. Important influences on temperature and relative humidity of the air, induced by the interaction between solar radiation and high aerosol load in the observation area, were also noticed; an average cooling of ≈ 3.0 °C and 10 %, respectively. Given the long-distance transport of aerosols emitted by burning biomass, significant changes in CO2 flux can occur over large areas of the Amazon, with important effects on the potential for CO2 absorption on ecosystems of semideciduous forests distributed in the region.

Published
2023

42. Tara (Caesalpinia spinosa) in Natural and Agroforestry Systems under an Altitudinal Gradient in the Peruvian Andes: Responses to Soil and Climate Variation

Author

Murga-Orrillo, Hipolito, primary, Abanto-Rodriguez, Carlos, additional, Fernandes Silva Dionisio, Luiz, additional, Chu-Koo, Fred William, additional, Schwartz, Gustavo, additional, Nuñez Bustamante, Ever, additional, Stewart, Paul Michael, additional, Santos Silva Amorim, Ricardo, additional, Vourlitis, George Louis, additional, De Almeida Lobo, Francisco, additional, and Bardales-Lozano, Ricardo Manuel, additional

Published
2023
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48. Examining Decomposition and Nitrogen Mineralization in Five Common Urban Habitat Types across Southern California to Inform Sustainable Landscaping

Author

Vourlitis, George L., primary, van der Veen, Emma Lousie, additional, Cangahuala, Sebastian, additional, Jaeger, Garrett, additional, Jensen, Colin, additional, Fissore, Cinzia, additional, Wood, Eric M., additional, Abraham, Joel K., additional, Whittemore, Kevin S., additional, Slaven, Elijah, additional, VanOverbeke, Dustin, additional, Blauth, James, additional, Braker, Elizabeth, additional, Karnovsky, Nina, additional, and Meyer, Wallace M., additional

Published
2022
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