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17. Aboveground biomass density models for NASA's Global Ecosystem Dynamics Investigation (GEDI) lidar mission

Author

Duncanson, L, Duncanson, L, Kellner, JR, Armston, J, Dubayah, R, Minor, DM, Hancock, S, Healey, SP, Patterson, PL, Saarela, S, Marselis, S, Silva, CE, Bruening, J, Goetz, SJ, Tang, H, Hofton, M, Blair, B, Luthcke, S, Fatoyinbo, L, Abernethy, K, Alonso, A, Andersen, HE, Aplin, P, Baker, TR, Barbier, N, Bastin, JF, Biber, P, Boeckx, P, Bogaert, J, Boschetti, L, Boucher, PB, Boyd, DS, Burslem, DFRP, Calvo-Rodriguez, S, Chave, J, Chazdon, RL, Clark, DB, Clark, DA, Cohen, WB, Coomes, DA, Corona, P, Cushman, KC, Cutler, MEJ, Dalling, JW, Dalponte, M, Dash, J, de-Miguel, S, Deng, S, Ellis, PW, Erasmus, B, Fekety, PA, Fernandez-Landa, A, Ferraz, A, Fischer, R, Fisher, AG, García-Abril, A, Gobakken, T, Hacker, JM, Heurich, M, Hill, RA, Hopkinson, C, Huang, H, Hubbell, SP, Hudak, AT, Huth, A, Imbach, B, Jeffery, KJ, Katoh, M, Kearsley, E, Kenfack, D, Kljun, N, Knapp, N, Král, K, Krůček, M, Labrière, N, Lewis, SL, Longo, M, Lucas, RM, Main, R, Manzanera, JA, Martínez, RV, Mathieu, R, Memiaghe, H, Meyer, V, Mendoza, AM, Monerris, A, Montesano, P, Morsdorf, F, Næsset, E, Naidoo, L, Nilus, R, O'Brien, M, Orwig, DA, Papathanassiou, K, Parker, G, Philipson, C, Phillips, OL, Pisek, J, Poulsen, JR, Pretzsch, H, Rüdiger, C, Duncanson, L, Duncanson, L, Kellner, JR, Armston, J, Dubayah, R, Minor, DM, Hancock, S, Healey, SP, Patterson, PL, Saarela, S, Marselis, S, Silva, CE, Bruening, J, Goetz, SJ, Tang, H, Hofton, M, Blair, B, Luthcke, S, Fatoyinbo, L, Abernethy, K, Alonso, A, Andersen, HE, Aplin, P, Baker, TR, Barbier, N, Bastin, JF, Biber, P, Boeckx, P, Bogaert, J, Boschetti, L, Boucher, PB, Boyd, DS, Burslem, DFRP, Calvo-Rodriguez, S, Chave, J, Chazdon, RL, Clark, DB, Clark, DA, Cohen, WB, Coomes, DA, Corona, P, Cushman, KC, Cutler, MEJ, Dalling, JW, Dalponte, M, Dash, J, de-Miguel, S, Deng, S, Ellis, PW, Erasmus, B, Fekety, PA, Fernandez-Landa, A, Ferraz, A, Fischer, R, Fisher, AG, García-Abril, A, Gobakken, T, Hacker, JM, Heurich, M, Hill, RA, Hopkinson, C, Huang, H, Hubbell, SP, Hudak, AT, Huth, A, Imbach, B, Jeffery, KJ, Katoh, M, Kearsley, E, Kenfack, D, Kljun, N, Knapp, N, Král, K, Krůček, M, Labrière, N, Lewis, SL, Longo, M, Lucas, RM, Main, R, Manzanera, JA, Martínez, RV, Mathieu, R, Memiaghe, H, Meyer, V, Mendoza, AM, Monerris, A, Montesano, P, Morsdorf, F, Næsset, E, Naidoo, L, Nilus, R, O'Brien, M, Orwig, DA, Papathanassiou, K, Parker, G, Philipson, C, Phillips, OL, Pisek, J, Poulsen, JR, Pretzsch, H, and Rüdiger, C

Abstract

NASA's Global Ecosystem Dynamics Investigation (GEDI) is collecting spaceborne full waveform lidar data with a primary science goal of producing accurate estimates of forest aboveground biomass density (AGBD). This paper presents the development of the models used to create GEDI's footprint-level (~25 m) AGBD (GEDI04_A) product, including a description of the datasets used and the procedure for final model selection. The data used to fit our models are from a compilation of globally distributed spatially and temporally coincident field and airborne lidar datasets, whereby we simulated GEDI-like waveforms from airborne lidar to build a calibration database. We used this database to expand the geographic extent of past waveform lidar studies, and divided the globe into four broad strata by Plant Functional Type (PFT) and six geographic regions. GEDI's waveform-to-biomass models take the form of parametric Ordinary Least Squares (OLS) models with simulated Relative Height (RH) metrics as predictor variables. From an exhaustive set of candidate models, we selected the best input predictor variables, and data transformations for each geographic stratum in the GEDI domain to produce a set of comprehensive predictive footprint-level models. We found that model selection frequently favored combinations of RH metrics at the 98th, 90th, 50th, and 10th height above ground-level percentiles (RH98, RH90, RH50, and RH10, respectively), but that inclusion of lower RH metrics (e.g. RH10) did not markedly improve model performance. Second, forced inclusion of RH98 in all models was important and did not degrade model performance, and the best performing models were parsimonious, typically having only 1-3 predictors. Third, stratification by geographic domain (PFT, geographic region) improved model performance in comparison to global models without stratification. Fourth, for the vast majority of strata, the best performing models were fit using square root transformation of field AG

Published
2022

20. Effects of harvesting and drought on C[O.sub.2] and [H.sub.2]O fluxes in an aspen-dominated western boreal plain forest: early chronosequence recovery

Author

Petrone, R.M., Chasmer, L., Hopkinson, C., Silins, U., Landhausser, S.M., Kljun, N., and Devito, K.J.

Subjects
Plant-water relationships -- Health aspects, Droughts -- Health aspects, Harvesting -- Health aspects, Carbon dioxide -- Health aspects, Taigas -- Environmental aspects -- Health aspects, Earth sciences
Abstract

This study examines the hydrological recovery of two regenerating boreal trembling aspen (Populus tremuloides Michx.) dominated stands and the sensitivity of that regeneration to drought within the first 5 years of establishment. The results indicate that evapotranspiration fluxes and water-use efficiency rebounded quickly as a result of new vegetation foliage growth and wet conditions found within the first 2 years following the harvest. However, a period of dry years had a significant influence on rates of postharvest growth, carbon dioxide (C[O.sub.2]), and water fluxes at these sites. The northern study area (NSA) and southern study area (SSA) were harvested in the winters of 2007 and 2008, respectively. The first and second years of regeneration at the SSA and NSA, respectively, were marked by an early spring thaw and higher-than-normal precipitation, while air temperatures remained slightly above the 30-year normal. During this period, mean measured height of vegetation tripled at both sites, and cumulative evapotranspiration was approximately 60% of that prior to harvest by the end of the second year of growth. By the third year (2009), the NSA became a sink for atmospheric C[O.sub.2] during the snow free season (days of the year 128- 238) despite low precipitation during the latter half of the summer. Volumetric soil moisture content in 2009 was the highest (on average) of the 5 years examined due to heavy snowfall and a late start to the growing season (where air temperatures consistently exceeded 0°C), resulting in sustained productivity. However, cumulative annual precipitation also declined to 79% and 57% in 2009 and 2010, respectively, of the 30-year normal for that region, leading to significant (lagged) declines in forest productivity at the NSA in 2010 and 2011. This resulted in the site becoming a source of C[O.sub.2] to the atmosphere during the 2010 and 2011 growing seasons (annual balance was not measured). Throughout the drought period (2009, 2010, and 2011), mean stand height increased by only 15%, 11%, and 14%, respectively, compared with the mean stand height in 2008. Water-use efficiency also declined in 2010 and 2011, whereas differences in light-use efficiency did not vary significantly because foliage was maintained (i.e., leaves did not abscise as a result of drought). The results of this study indicate that regenerating aspen stands are sensitive to drought and respond relatively quickly to changes in the soil moisture regime. This is important because regional drying as a result of predicted climatic changes combined with increased industrial activity may result in significant decline in productivity within these stands over broad regions. Key words: trembling aspen, evapotranspiration, net ecosystem exchange, water-use efficiency, harvest. Cette etude s'interesse a la recuperation hydrologique de deux peuplements boreaux en regeneration domines par le peuplier faux-tremble (Populus tremuloides Michx.) ainsi qu'a la sensibilite de la regeneration a la secheresse au cours des cinq annees suivant son etablissement. Les resultats de cette etude indiquent que le flux d'evapotranspiration (ET) et l'efficacite d'utilisation de l'eau (EUE) se sont rapidement retablis avec la croissance du feuillage de la nouvelle vegetation et les conditions humides observees au cours des deux premieres annees apres la recolte. Cependant, une periode d'annees seches a eu une influence significative sur les taux de croissance postrecolte, de dioxyde de carbone (C[O.sub.2]) et de flux de l'eau dans ces sites. L'aire d'etude septentrionale (AES) et l'aire d'etude meridionale (AEM) ont ete recoltees respectivement durant les hivers 2007 et 2008. La premiere annee de regeneration dans l'AEM et la seconde dans l'AES ont ete marquees par un degel printanier hatif et des precipitations plus elevees que la normale tandis que les temperatures de l'air sont demeurees legerement au-dessus de la normale 30 ans. Durant cette periode, la hauteur moyenne mesuree de la vegetation a triple dans les deux sites et, a la fin de la deuxieme annee de croissance, la valeur cumulative de ET correspondait a environ 60 % de la valeur prerecolte. A la troisieme annee (2009), l'AES est devenue un puits pour le C[O.sub.2] atmospherique pendant la saison exempte de neige (jours de l'annee 128-238) malgre les faibles precipitations durant la derniere moitie de l'ete. Au cours des cinq annees de l'etude, l'humidite volumique du sol (Hv) a ete la plus elevee en 2009 (en moyenne) a cause des chutes de neige importantes et du debut tardif de la saison de croissance (lorsque la temperature de l'air etait constamment au-dessus de 0°C), entrainant une production soutenue. Cependant, la precipitation annuelle cumulative a aussi diminue, atteignant seulement 79 % (2009) et 57 % (2010) de la normale 30 ans dans cette region, ce qui a entraine un declin important (differe) de la production de la foret dans l'AES en 2010 et 2011. Ce site est par consequent devenu une source de C[O.sub.2] atmospherique durant les saisons de croissance de 2010 et 2011 (le bilan annuel n'a pas ete mesure). Durant la periode de secheresse (2009, 2010 et 2011) la hauteur moyenne du peuplement a augmente de seulement 15 % (2009), 11 % (2010) et 14 % (2011) par rapport a 2008. L'EUE a aussi diminue en 2010 et 2011 tandis que les differences dans l'efficacite d'utilisation de la lumiere n'ont pas varie de facon significative parce que le feuillage s'est maintenu (c.-a-d. que les feuilles ne sont pas tombees a cause de la secheresse). Les resultats de cette etude indiquent que les peuplements de peuplier faux-tremble en regeneration sont sensibles a la secheresse et reagissent assez rapidement aux variations du regime d'humidite du sol. Cela est important etant donne que des conditions regionales plus seches a cause des changements climatiques a venir combinees a l'activite industrielle accrue pourraient engendrer un declin de la productivite dans ces peuplements sur de vastes etendues. [Traduit par la Redaction] Mots-cles : peuplier faux-tremble, evapotranspiration, echanges nets de l'ecosysteme, efficacite d'utilisation de l'eau, recolte., Introduction The northern boreal forest covers approximately 29% of North America (Brandt 2009) and is a significant sink for atmospheric carbon dioxide (C[O.sub.2]) due to broad area coverage and the [...]

Published
2015
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21. Chapter 15: Tidal Wetlands and Estuaries. Second State of the Carbon Cycle Report

Author

Windham-Myers, L., primary, Cai, W.-J., additional, Alin, S., additional, Andersson, A., additional, Crosswell, J., additional, Dunton, K. H., additional, Hernandez-Ayon, J. M., additional, Herrmann, M., additional, Hinson, A. L., additional, Hopkinson, C. S., additional, Howard, J., additional, Hu, X., additional, Knox, S. H., additional, Kroeger, K., additional, Lagomasino, D., additional, Megonigal, P., additional, Najjar, R., additional, Paulsen, M.-L., additional, Peteet, D., additional, Pidgeon, E., additional, Schäfer, K., additional, Tzortziou, M., additional, Wang, Z. A., additional, and Watson, E. B., additional

Published
2018
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31. Influences of vegetation structure and elevation on C[O.sub.2] uptake in a mature jack pine forest in Saskatchewan, Canada

Author

Chasmer, L., Kljun, N., Barr, A., Black, A., Hopkinson, C., McCaughey, H., and Treitz, P.

Subjects
Saskatchewan -- Environmental aspects, Jack pine -- Environmental aspects -- Measurement, Coniferous forests -- Environmental aspects -- Measurement, Forest dynamics -- Influence -- Measurement -- Environmental aspects, Atmospheric carbon dioxide -- Measurement -- Environmental aspects, Earth sciences, Influence, Measurement, Environmental aspects
Abstract

Carbon dioxide, water vapour, and energy fluxes vary spatially and temporally within forested environments. However, it is not clear to what extent they vary as a result of variability in the spatial distribution of biomass and elevation. The following study presents a new methodology for extracting changes in the structural characteristics of vegetation and elevation within footprint areas, for direct comparison with eddy covariance (EC) C[O.sub.2] flux concentrations. The purpose was to determine whether within-site canopy structure and local elevation influenced C[O.sub.2] fluxes in a mature jack pine (Pinus banksiana Lamb.) forest located in Saskatchewan, Canada. Airborne light detection and ranging (lidar) was used to extract tree height, canopy depth, foliage cover, and elevation within 30 min flux footprints. Within-footprint mean structural components and elevation were related to 30 min mean net ecosystem productivity (NEP) and gross ecosystem production (GEP). NEP and GEP were modeled using multiple regression, and when compared with measured fluxes, almost all periods showed improvements in the prediction of flux concentration when canopy structure and elevation were included. Increased biomass was related to increased NEP and GEP in June and August when the ecosystem was not limited by soil moisture. On a daily basis, fractional cover and elevation had varying but significant influences on C[O.sub.2] fluxes. Le dioxyde de carbone, la vapeur d'eau et les flux d'energie varient dans l'espace et le temps dans les environnements forestiers. Cependant, nous ne savons pas dans quelle mesure ils varient en fonction de la variation des gradients de biomasse et d'altitude. Cette etude presente une nouvelle methode pour extraire les caracteristiques de la structure de la vegetation et les changements d'altitude a partir d'empreintes pour etablir des comparaisons directes avec des concentrations de flux de C[O.sub.2] calculees par la methode de covariance des turbulences. Le but de l'etude etait de determiner si la structure de la canopee a l'interieur d'une station et 'altitude locale influencent les flux de C[O.sub.2] dans une foret mature de pin gris situee en Saskatchewan, an Canada. Un lidar aeroporte a ete utilise pour estimer la hauteur des arbres, la profondeur de la canopee, la couverture foliacee et l'altitude dans des empreintes de flux de 30 minutes. Les composantes structurales moyennes et l'altitude issues de ces empreintes ont ete reliees aux valeurs moyennes sur des periodes de 30 minutes de la productivity nette de l'ecosysteme (PNE) et de la production brute de l'ecosysteme (PBE). La PNE et la PBE ont ete modelisees a l'aide d'une regression multiple et, lorsqu'elles on ete comparees aux flux mesures, la prevision des concentrations de flux a ete amelioree pour presque toutes les periodes quand la structure de la canopee et l'altitude etaient incluses dans le modele. L'augmentation de la biomasse etait reliee a des augmentations de PNE et de PBE en juin et en aout lorsque la teneur en eau du sol ne limitait pas le fonctionnement de l'ecosysteme. Sur une base journaliere, la proportion de couverture et l'altitude avaient une influence variable, mais significative, sur les flux de C[O.sub.2]. [Traduit par la Redaction], Introduction The eddy covariance (EC) method is commonly used to measure the direction and movement of energy and trace gas (e.g., water, C[O.sub.2]) concentrations throughout ecosystems (Baldocchi 2008). Networks of [...]

Published
2008

35. Twenty-three unsolved problems in hydrology (UPH)–a community perspective

Author

Blöschl, G., Bierkens, M. F. P., Chambel, A., Cudennec, C., Destouni, G., Fiori, A., Kirchner, J. W., McDonnell, J. J., Savenije, H. H. G., Sivapalan, M., Stumpp, C., Toth, E., Volpi, E., Carr, G., Lupton, C., Salinas, J., Széles, B., Viglione, A., Aksoy, H., Allen, S. T., Amin, A., Andréassian, V., Arheimer, B., Aryal, S. K., Baker, V., Bardsley, E., Barendrecht, M. H., Bartosova, A., Batelaan, O., Berghuijs, W. R., Beven, K., Blume, T., Bogaard, T., Borges de Amorim, P., Böttcher, M. E., Boulet, G., Breinl, K., Brilly, M., Brocca, L., Buytaert, W., Castellarin, A., Castelletti, A., Chen, X., Chen, Y., Chifflard, P., Claps, P., Clark, M. P., Collins, A. L., Croke, B., Dathe, A., David, P. C., de Barros, F. P. J., de Rooij, G., Di Baldassarre, G., Driscoll, J. M., Duethmann, D., Dwivedi, R., Eris, E., Farmer, W. H., Feiccabrino, J., Ferguson, G., Ferrari, E., Ferraris, S., Fersch, B., Finger, D., Foglia, L., Fowler, K., Gartsman, B., Gascoin, S., Gaume, E., Gelfan, A., Geris, J., Gharari, S., Gleeson, T., Glendell, M., Gonzalez Bevacqua, A., González-Dugo, M. P., Grimaldi, S., Gupta, A. B., Guse, B., Han, D., Hannah, D., Harpold, A., Haun, S., Heal, K., Helfricht, K., Herrnegger, M., Hipsey, M., Hlaváčiková, H., Hohmann, C., Holko, L., Hopkinson, C., Hrachowitz, M., Illangasekare, T. H., Inam, A., Innocente, C., Istanbulluoglu, E., Jarihani, B., Kalantari, Z., Kalvans, A., Khanal, S., Khatami, S., Kiesel, J., Kirkby, M., Knoben, W., Kochanek, K., Kohnová, S., Kolechkina, A., Krause, S., Kreamer, D., Kreibich, H., Kunstmann, H., Lange, H., Liberato, M. L. R., Lindquist, E., Link, T., Liu, J., Loucks, D. P., Luce, C., Mahé, G., Makarieva, O., Malard, J., Mashtayeva, S., Maskey, S., Mas-Pla, J., Mavrova-Guirguinova, M., Mazzoleni, M., Mernild, S., Misstear, B. D., Montanari, A., Müller-Thomy, H., Nabizadeh, A., Nardi, F., Neale, C., Nesterova, N., Nurtaev, B., Odongo, V. O., Panda, S., Pande, S., Pang, Z., Papacharalampous, G., Perrin, C., Pfister, L., Pimentel, R., Polo, M. J., Post, D., Prieto Sierra, C., Ramos, M. -H, Renner, M., Reynolds, J. E., Ridolfi, E., Rigon, R., Riva, M., Robertson, D. E., Rosso, R., Roy, T., Sá, J.H.M., Salvadori, G., Sandells, M., Schaefli, B., Schumann, A., Scolobig, A., Seibert, J., Servat, E., Shafiei, M., Sharma, A., Sidibe, M., Sidle, R. C., Skaugen, T., Smith, H., Spiessl, S. M., Stein, L., Steinsland, I., Strasser, U., Su, B., Szolgay, J., Tarboton, D., Tauro, F., Thirel, G., Tian, F., Tong, R., Tussupova, K., Tyralis, H., Uijlenhoet, R., van Beek, R., van der Ent, R. J., van der Ploeg, M., Van Loon, A. F., van Meerveld, I., van Nooijen, R., van Oel, P. R., Vidal, J. -P, von Freyberg, J., Vorogushyn, S., Wachniew, P., Wade, A. J., Ward, P., Westerberg, I. K., White, C., Wood, E. F., Woods, R., Xu, Z., Yilmaz, K. K., Zhang, Y., Blöschl, G., Bierkens, M. F. P., Chambel, A., Cudennec, C., Destouni, G., Fiori, A., Kirchner, J. W., McDonnell, J. J., Savenije, H. H. G., Sivapalan, M., Stumpp, C., Toth, E., Volpi, E., Carr, G., Lupton, C., Salinas, J., Széles, B., Viglione, A., Aksoy, H., Allen, S. T., Amin, A., Andréassian, V., Arheimer, B., Aryal, S. K., Baker, V., Bardsley, E., Barendrecht, M. H., Bartosova, A., Batelaan, O., Berghuijs, W. R., Beven, K., Blume, T., Bogaard, T., Borges de Amorim, P., Böttcher, M. E., Boulet, G., Breinl, K., Brilly, M., Brocca, L., Buytaert, W., Castellarin, A., Castelletti, A., Chen, X., Chen, Y., Chifflard, P., Claps, P., Clark, M. P., Collins, A. L., Croke, B., Dathe, A., David, P. C., de Barros, F. P. J., de Rooij, G., Di Baldassarre, G., Driscoll, J. M., Duethmann, D., Dwivedi, R., Eris, E., Farmer, W. H., Feiccabrino, J., Ferguson, G., Ferrari, E., Ferraris, S., Fersch, B., Finger, D., Foglia, L., Fowler, K., Gartsman, B., Gascoin, S., Gaume, E., Gelfan, A., Geris, J., Gharari, S., Gleeson, T., Glendell, M., Gonzalez Bevacqua, A., González-Dugo, M. P., Grimaldi, S., Gupta, A. B., Guse, B., Han, D., Hannah, D., Harpold, A., Haun, S., Heal, K., Helfricht, K., Herrnegger, M., Hipsey, M., Hlaváčiková, H., Hohmann, C., Holko, L., Hopkinson, C., Hrachowitz, M., Illangasekare, T. H., Inam, A., Innocente, C., Istanbulluoglu, E., Jarihani, B., Kalantari, Z., Kalvans, A., Khanal, S., Khatami, S., Kiesel, J., Kirkby, M., Knoben, W., Kochanek, K., Kohnová, S., Kolechkina, A., Krause, S., Kreamer, D., Kreibich, H., Kunstmann, H., Lange, H., Liberato, M. L. R., Lindquist, E., Link, T., Liu, J., Loucks, D. P., Luce, C., Mahé, G., Makarieva, O., Malard, J., Mashtayeva, S., Maskey, S., Mas-Pla, J., Mavrova-Guirguinova, M., Mazzoleni, M., Mernild, S., Misstear, B. D., Montanari, A., Müller-Thomy, H., Nabizadeh, A., Nardi, F., Neale, C., Nesterova, N., Nurtaev, B., Odongo, V. O., Panda, S., Pande, S., Pang, Z., Papacharalampous, G., Perrin, C., Pfister, L., Pimentel, R., Polo, M. J., Post, D., Prieto Sierra, C., Ramos, M. -H, Renner, M., Reynolds, J. E., Ridolfi, E., Rigon, R., Riva, M., Robertson, D. E., Rosso, R., Roy, T., Sá, J.H.M., Salvadori, G., Sandells, M., Schaefli, B., Schumann, A., Scolobig, A., Seibert, J., Servat, E., Shafiei, M., Sharma, A., Sidibe, M., Sidle, R. C., Skaugen, T., Smith, H., Spiessl, S. M., Stein, L., Steinsland, I., Strasser, U., Su, B., Szolgay, J., Tarboton, D., Tauro, F., Thirel, G., Tian, F., Tong, R., Tussupova, K., Tyralis, H., Uijlenhoet, R., van Beek, R., van der Ent, R. J., van der Ploeg, M., Van Loon, A. F., van Meerveld, I., van Nooijen, R., van Oel, P. R., Vidal, J. -P, von Freyberg, J., Vorogushyn, S., Wachniew, P., Wade, A. J., Ward, P., Westerberg, I. K., White, C., Wood, E. F., Woods, R., Xu, Z., Yilmaz, K. K., and Zhang, Y.

Abstract

QC 20210112

Published
2019
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36. Twenty-three unsolved problems in hydrology (UPH)–a community perspective

Author

Blöschl, G. Bierkens, M. F. P. Chambel, A. Cudennec, C. Destouni, G. Fiori, A. Kirchner, J. W. McDonnell, J. J. Savenije, H. H. G. Sivapalan, M. Stumpp, C. Toth, E. Volpi, E. Carr, G. Lupton, C. Salinas, J. Széles, B. Viglione, A. Aksoy, H. Allen, S. T. Amin, A. Andréassian, V. Arheimer, B. Aryal, S. K. Baker, V. Bardsley, E. Barendrecht, M. H. Bartosova, A. Batelaan, O. Berghuijs, W. R. Beven, K. Blume, T. Bogaard, T. Borges de Amorim, P. Böttcher, M. E. Boulet, G. Breinl, K. Brilly, M. Brocca, L. Buytaert, W. Castellarin, A. Castelletti, A. Chen, X. Chen, Y. Chen, Y. Chifflard, P. Claps, P. Clark, M. P. Collins, A. L. Croke, B. Dathe, A. David, P. C. de Barros, F. P. J. de Rooij, G. Di Baldassarre, G. Driscoll, J. M. Duethmann, D. Dwivedi, R. Eris, E. Farmer, W. H. Feiccabrino, J. Ferguson, G. Ferrari, E. Ferraris, S. Fersch, B. Finger, D. Foglia, L. Fowler, K. Gartsman, B. Gascoin, S. Gaume, E. Gelfan, A. Geris, J. Gharari, S. Gleeson, T. Glendell, M. Gonzalez Bevacqua, A. González-Dugo, M. P. Grimaldi, S. Gupta, A. B. Guse, B. Han, D. Hannah, D. Harpold, A. Haun, S. Heal, K. Helfricht, K. Herrnegger, M. Hipsey, M. Hlaváčiková, H. Hohmann, C. Holko, L. Hopkinson, C. Hrachowitz, M. Illangasekare, T. H. Inam, A. Innocente, C. Istanbulluoglu, E. Jarihani, B. Kalantari, Z. Kalvans, A. Khanal, S. Khatami, S. Kiesel, J. Kirkby, M. Knoben, W. Kochanek, K. Kohnová, S. Kolechkina, A. Krause, S. Kreamer, D. Kreibich, H. Kunstmann, H. Lange, H. Liberato, M. L. R. Lindquist, E. Link, T. Liu, J. Loucks, D. P. Luce, C. Mahé, G. Makarieva, O. Malard, J. Mashtayeva, S. Maskey, S. Mas-Pla, J. Mavrova-Guirguinova, M. Mazzoleni, M. Mernild, S. Misstear, B. D. Montanari, A. Müller-Thomy, H. Nabizadeh, A. Nardi, F. Neale, C. Nesterova, N. Nurtaev, B. Odongo, V. O. Panda, S. Pande, S. Pang, Z. Papacharalampous, G. Perrin, C. Pfister, L. Pimentel, R. Polo, M. J. Post, D. Prieto Sierra, C. Ramos, M. H. Renner, M. Reynolds, J. E. Ridolfi, E. Rigon, R. Riva, M. Robertson, D. E. Rosso, R. and Blöschl, G. Bierkens, M. F. P. Chambel, A. Cudennec, C. Destouni, G. Fiori, A. Kirchner, J. W. McDonnell, J. J. Savenije, H. H. G. Sivapalan, M. Stumpp, C. Toth, E. Volpi, E. Carr, G. Lupton, C. Salinas, J. Széles, B. Viglione, A. Aksoy, H. Allen, S. T. Amin, A. Andréassian, V. Arheimer, B. Aryal, S. K. Baker, V. Bardsley, E. Barendrecht, M. H. Bartosova, A. Batelaan, O. Berghuijs, W. R. Beven, K. Blume, T. Bogaard, T. Borges de Amorim, P. Böttcher, M. E. Boulet, G. Breinl, K. Brilly, M. Brocca, L. Buytaert, W. Castellarin, A. Castelletti, A. Chen, X. Chen, Y. Chen, Y. Chifflard, P. Claps, P. Clark, M. P. Collins, A. L. Croke, B. Dathe, A. David, P. C. de Barros, F. P. J. de Rooij, G. Di Baldassarre, G. Driscoll, J. M. Duethmann, D. Dwivedi, R. Eris, E. Farmer, W. H. Feiccabrino, J. Ferguson, G. Ferrari, E. Ferraris, S. Fersch, B. Finger, D. Foglia, L. Fowler, K. Gartsman, B. Gascoin, S. Gaume, E. Gelfan, A. Geris, J. Gharari, S. Gleeson, T. Glendell, M. Gonzalez Bevacqua, A. González-Dugo, M. P. Grimaldi, S. Gupta, A. B. Guse, B. Han, D. Hannah, D. Harpold, A. Haun, S. Heal, K. Helfricht, K. Herrnegger, M. Hipsey, M. Hlaváčiková, H. Hohmann, C. Holko, L. Hopkinson, C. Hrachowitz, M. Illangasekare, T. H. Inam, A. Innocente, C. Istanbulluoglu, E. Jarihani, B. Kalantari, Z. Kalvans, A. Khanal, S. Khatami, S. Kiesel, J. Kirkby, M. Knoben, W. Kochanek, K. Kohnová, S. Kolechkina, A. Krause, S. Kreamer, D. Kreibich, H. Kunstmann, H. Lange, H. Liberato, M. L. R. Lindquist, E. Link, T. Liu, J. Loucks, D. P. Luce, C. Mahé, G. Makarieva, O. Malard, J. Mashtayeva, S. Maskey, S. Mas-Pla, J. Mavrova-Guirguinova, M. Mazzoleni, M. Mernild, S. Misstear, B. D. Montanari, A. Müller-Thomy, H. Nabizadeh, A. Nardi, F. Neale, C. Nesterova, N. Nurtaev, B. Odongo, V. O. Panda, S. Pande, S. Pang, Z. Papacharalampous, G. Perrin, C. Pfister, L. Pimentel, R. Polo, M. J. Post, D. Prieto Sierra, C. Ramos, M. H. Renner, M. Reynolds, J. E. Ridolfi, E. Rigon, R. Riva, M. Robertson, D. E. Rosso, R.

Abstract

This paper is the outcome of a community initiative to identify major unsolved scientific problems in hydrology motivated by a need for stronger harmonisation of research efforts. The procedure involved a public consultation through online media, followed by two workshops through which a large number of potential science questions were collated, prioritised, and synthesised. In spite of the diversity of the participants (230 scientists in total), the process revealed much about community priorities and the state of our science: a preference for continuity in research questions rather than radical departures or redirections from past and current work. Questions remain focused on the process-based understanding of hydrological variability and causality at all space and time scales. Increased attention to environmental change drives a new emphasis on understanding how change propagates across interfaces within the hydrological system and across disciplinary boundaries. In particular, the expansion of the human footprint raises a new set of questions related to human interactions with nature and water cycle feedbacks in the context of complex water management problems. We hope that this reflection and synthesis of the 23 unsolved problems in hydrology will help guide research efforts for some years to come.

Published
2019
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39. Impacts of a weather event on shelf circulation and CO2 and O2 dynamics on the Louisiana shelf during summer 2009

Author

Huang, W.-J., Cai, W.-J., Wang, Y., and Hopkinson, C. S.

Abstract

While much is known about the physics of coastal currents, much less is known about the biogeochemical effects of surface currents on shelf carbon dioxide (CO2) and oxygen distribution and dynamics. The Mississippi and Atchafalaya River plume is usually observed along the Louisiana shelf with easterly winds. Such a typical pattern was observed in August 2007, i.e. a plume of low salinity and low partial pressure of CO2 (pCO2), indicating high biological production on the inner shelf; and higher salinity and pCO2 on the outer shelf. This high biological production induced by riverine nitrogen flux thus provided major organic matter sources for the shelf-wide hypoxia (dissolved oxygen [DO] < 2 mg L−1) accompanied by high dissolved inorganic carbon (DIC) concentrations in the bottom water. The slope of the DO and DIC relationship also demonstrated Redfield-type respiration in this shelf-wide hypoxia. In contrast, summer 2009 was an abnormal season characterized by a cool temperature in the central North America. Our observation and satellite chlorophyll a patterns both displayed a greatly distinct situation, i.e., the river plume was relocated to the eastern part of the Louisiana shelf; and high salinity and high pCO2 values occurred in surface waters of the western inner shelf. This plume relocation shifted the Louisiana shelf from a normally weak CO2 sink (as in 2007) to a strong CO2 source for the atmosphere. Although riverine nitrogen flux was enough to support a shelf-wide hypoxia in 2009, the plume relocation changed the location of high biological production and resulted in a limited hypoxic area. Furthermore, DIC concentration in bottom waters was higher than those predicted by the Redfield ratio, most likely because of much rapid O2 compensation than CO2 loss during air–sea exchange. Numerical models indicate such relocation of plume was mostly affected by the shelf circulation dominated by southerly and southwesterly winds. Consequently, we conclude that wind-forcing and shelf circulation are critical factors that influence the plume trajectories and the associated biogeochemical properties in coastal waters.

Published
2018

43. Fluvial carbon export from a lowland Amazonian rainforest in relation to atmospheric fluxes

Author

Vihermaa, LE, Waldron, S, Domingues, T, Grace, J, Cosio, EG, Limonchi, F, Hopkinson, C, da Rocha, HR, and Gloor, E

Abstract

We constructed a whole carbon budget for a catchment in the Western Amazon Basin, combining drainage water analyses with eddy covariance measured terrestrial CO2 fluxes. As fluvial C export can represent permanent C export it must be included in assessments of whole site C balance, but is rarely done. The footprint area of the flux tower is drained by two small streams (~5-7 km2) from which we measured the dissolved inorganic carbon (DIC), dissolved organic carbon (DOC), particulate organic carbon (POC) export and CO2 efflux. The EC measurements showed the site C balance to be +0.7 ± 9.7 Mg C ha-1 yr-1 (a source to the atmosphere) and fluvial export was 0.3 ± 0.04 Mg C ha-1 yr-1. Of the total fluvial loss 34% was DIC, 37% DOC and 29% POC. The wet season was most important for fluvial C export. There was a large uncertainty associated with the EC results and with previous biomass plot studies (-0.5 ± 4.1 Mg C ha-1 yr-1), hence it cannot be concluded with certainty whether the site is C sink or source. The fluvial export corresponds to only 3-7 % of the uncertainty related to the site C balance, thus other factors need to be considered to reduce the uncertainty and refine the estimated C balance. However, stream C export is significant, especially for almost neutral sites where fluvial loss may determine the direction of the site C balance. The fate of C downstream then dictates the overall climate impact of fluvial export.

Published
2016

50. Remote sensing of ecosystem trajectories as a proxy indicator for watershed water balance.

Author

Chasmer, L. E., Devito, K. J., Hopkinson, C. D., and Petrone, R. M.

Subjects
REMOTE sensing, ECOSYSTEM dynamics, WATERSHEDS, WATER balance (Hydrology), SPATIOTEMPORAL processes
Abstract

Abstract: Ecosystem trajectories are inextricably linked to hydrology; however, water availability is not easily observed within the landscape. The response of vegetation to soil water availability may provide an indicator of local hydrology and the resilience or sensitivity of ecosystems to long‐term changes in water balance. In this study, vegetation trajectories derived from Landsat Modified Soil Adjusted Vegetation Index over a 22‐year period are used as an indicator of spatio‐temporal changes of watershed water balance and surface water storage within 6 proximal watersheds of the Boreal Plains ecozone of Alberta, Canada. The interactions between hydrology, topography, geology, and land cover type are examined as they relate to vegetation change. In this study, we find that run‐off ratio (run‐off/precipitation) is greater within watersheds with greater variability of relief, compared within subhumid, wetland‐dominated watersheds (average = 0.35, 0.20, respectively), which experience lagged run‐off response. A 2‐year drought had a greater impact on vegetation trajectories within variable relief watersheds containing a high proportion of coarse‐grain surficial geology, compared with peatland‐dominated watersheds. The drought extended for an additional 1 to 2 years within 3 subhumid watersheds, reducing watershed run‐off to less than 50 mm per water year (November to October) in 2 watersheds. However, proportional area of decline of Modified Soil Adjusted Vegetation Index was significantly less within these watersheds. The results of this study indicate that wetlands play an important role for local water balance and ecosystem maintenance during periods of water stress and should be considered within land use planning and reclamation strategies of the Boreal Plains. [ABSTRACT FROM AUTHOR]

Published
2018
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