The net ecosystem exchange of carbon dioxide was measured by eddy covariance methods for 3 years in two old-growth forest sites near Santarém, Brazil. Carbon was lost in the wet season and gained in the dry season, which was opposite to the seasonal cycles of both tree growth and model predictions. The 3-year average carbon loss was 1.3 (confidence interval: 0.0 to 2.0) megagrams of carbon per hectare per year. Biometric observations confirmed the net loss but imply that it is a transient effect of recent disturbance superimposed on long-term balance. Given that episodic disturbances are characteristic of old-growth forests, it is likely that carbon sequestration is lower than has been inferred from recent eddy covariance studies at undisturbed sites.

Abstract. We used eddy covariance to measure the net exchange of CO2 between the atmosphere and an old-growth tropical forest in Pari, Brazil from 1 July 2000 to 1 July 2001. The mean air temperature and daily temperature range varied little year-round; the rainy season lasted from late December to around July. Daytime CO2 uptake under high irradiance averaged 16-19 mol.m-2.s-1. Light was the main controller of CO2 exchange, accounting for 48% of the half-hour-to-half-hour variance. The rate of canopy photosynthesis at a given irradiance was lower in the afternoon than the morning. This photosynthetic inhibition was probably caused by high evaporative demand, high temperature, an intrinsic circadian rhythm, or a combination of the three. Wood increment increased from January to May, suggesting greater rates of carbon sequestration during the wet season. However, the daily net CO2 exchange measured by eddy covariance revealed the opposite trend, with greater carbon accumulation during the dry season. A reduction in respiration during the dry season was an important cause of this seasonal pattern. The surface litter was desiccated in the dry season, and the seasonal pattern of respiration appears to be a direct result of reduced forest floor decomposition during drought. In contrast, canopy photosynthesis was not directly reduced by the dry season, probably because deep rooting allows the forest to avoid drought stress

We used the eddy covariance technique from July 2000 to July 2001 to measure the fluxes of sensible heat, water vapor, and CO2 between an old‐growth tropical forest in eastern Amazonia and the atmosphere. Precipitation varied seasonally, with a wet season from mid‐December 2000 to July 2001 characterized by successive rainy days, wet soil, and, relative to the dry season, cooler temperatures, greater cloudiness, and reduced incoming solar and net radiation. Average evapotranspiration decreased from 3.96 ± 0.65 mm/d during the dry season to 3.18 ± 0.76 mm/d during the wet season, in parallel with decreasing radiation and decreasing water vapor deficit. The average Bowen ratio was 0.17 ± 0.10, indicating that most of the incoming radiation was used for evaporation. The Bowen ratio was relatively low during the early wet season (December–March), as a result of increased evaporative fraction and reduced sensible heat flux. The seasonal decline in Bowen ratio and increase in evaporative fraction coincided with an increase in ecosystem CO2 assimilation capacity, which we attribute to the growth of new leaves. The evaporative fraction did not decline as the dry season progressed, implying that the forest did not become drought stressed. The roots extracted water throughout the top 250 cm of soil, and water redistribution, possibly by hydraulic lift, partially recharged the shallow soil during dry season nights. The lack of drought stress during the dry season was likely a consequence of deep rooting, and possibly vertical water movement, which allowed the trees to maintain access to soil water year round.

We used two independent approaches, biometry and micrometeorology, to determine the net ecosystem production (NEP) of an old growth forest in Pará, Brazil. Biometric inventories indicated that the forest was either a source or, at most, a modest sink of carbon from 1984 to 2000 (+0.8 ± 2 Mg C·ha −1 ·yr −1 ; a positive flux indicates carbon loss by the forest, a negative flux indicates eScholarship provides open access, scholarly publishing services to the University of California and delivers a dynamic research platform to scholars worldwide.carbon gain). Eddy covariance measurements of CO 2 exchange were made from July 2000 to July 2001 using both open-and closed-path gas analyzers. The annual eddy covariance flux calculated without correcting for the underestimation of flux on calm nights indicated that the forest was a large carbon sink (−3.9 Mg C·ha −1 ·yr −1 ). This annual uptake is comparable to past reports from other Amazonian forests, which also were calculated without correcting for calm nights. The magnitude of the annual integral was relatively insensitive to the selection of open-versus closedpath gas analyzer, averaging time, detrending, and high-frequency correction. In contrast, the magnitude of the annual integral was highly sensitive to the treatment of calm nights, changing by over 4 Mg C·ha −1 ·yr −1 when a filter was used to replace the net ecosystem exchange (NEE) during nocturnal periods with u* < 0.2 m/s. Analyses of the relationship between nocturnal NEE and u* confirmed that the annual sum needs to be corrected for the effect of calm nights, which resulted in our best estimate of the annual flux (+0.4 Mg C·ha −1 ·yr −1 ). The observed sensitivity of the annual sum to theu* filter is far greater than has been previously reported for temperate and boreal forests. The annual carbon balance determined by eddy covariance is therefore less certain for tropical than temperate forests. Nonetheless, the biometric and micrometeorological measurements in tandem provide strong evidence that the forest was not a strong, persistent carbon sink during the study interval.Abstract. We used two independent approaches, biometry and micrometeorology, to determine the net ecosystem production (NEP) of an old growth forest in Parai, Brazil. Biometric inventories indicated that the forest was either a source or, at most, a modest sink of carbon from 1984 to 2000 (+0.8 ? 2 Mg C-ha-l*yr-'; a positive flux indicates carbon loss by the forest, a negative flux indicates carbon gain). Eddy covariance measurements of CO2 exchange were made from July 2000 to July 2001 using both open-and closed-path gas analyzers. The annual eddy covariance flux calculated without correcting for the underestimation of flux on calm nights indicated that the forest was a large carbon sink (-3.9 Mg C.ha-1-yr-'). This annual uptake is comparable to past reports from other Amazonian forests, which also were calculated without correcting for calm nights. The magnitude of the annual integral was relatively insensitive to the selection of ope...

Through their synergies, trade-offs, and contradictions, the sustainable development goals (SDGs) have the potential to lead to environmental justices and injustices. Yet, environmental justice (EJ), and social justice more broadly, are not currently embedded within the language and spirit of the SDGs. We part from the premise that "many 'environmental' problems are, by their very nature, problems of justice" (Lele, Wiley Interdiscip Rev Water 4:e1224, 2017). We review progress in EJ frameworks in recent years, arguing for the need to move beyond a focus on the four principles of mainstream EJ (distribution, procedure, recognition, and capabilities) towards a more intersectional decolonial approach to environmental justice that recognises the indispensability of both humans and non-humans. EJ frameworks, and the SDGs should recognise power dynamics, complex interactions among injustices, and listens to the different 'senses of justice' and desires of theorists, activists, and other stakeholder from the Global South. We analyze how EJ frameworks are, or fail to be, incorporated in the SDGs with a focus on the food-water-health nexus (SDG2, 3, 6); climate-energy (SDG7, 13), conservation (SDG14, 15); and poverty and inequality (SDG1, 10). We call attention to the 'elephant in the room'-the failure to go beyond GDP but instead include economic growth as a goal (SDG8). We argue that sustainable degrowth and intersectional decolonial environmental justices would create better conditions for the transformative changes needed to reach the broader aim of the SDGs: to leave no one behind.

Abstract

Background

Climate change and high rates of global carbon emissions have focussed attention on the need for high-quality monitoring systems to assess how much carbon is present in terrestrial systems and how these change over time. The choice of system to adopt should be guided by good science. There is a growing body of scientific and technical information on ground-based and remote sensing methods of carbon measurement. The adequacy and comparability of these different systems have not been fully evaluated.

Methods

A systematic review will compare methods of assessing carbon stocks and carbon stock changes in key land use categories, including, forest land, cropland, grassland, and wetlands, in terrestrial carbon pools that can be accounted for under the Kyoto protocol (above- ground biomass, below-ground biomass, dead wood, litter and soil carbon). Assessing carbon in harvested wood products will not be considered in this review.

Discussion

Developing effective mitigation strategies to reduce carbon emissions and equitable adaptation strategies to cope with increasing global temperatures will rely on robust scientific information that is free from biases imposed by national and commercial interests. A systematic review of the methods used for assessing carbon stocks and carbon stock changes will contribute to the transparent analysis of complex and often contradictory science.

A 35‐year controlled burning experiment in Minnesota oak savanna showed that fire frequency had a great impact on ecosystem carbon (C) stores. Specifically, compared to the historical fire regime, fire suppression led to an average of 1.8 Mg·ha−1·yr−1 of C storage, with most carbon stored in woody biomass. Forest floor carbon stores were also significantly impacted by fire frequency, but there were no detectable effects of fire suppression on carbon in soil and fine roots combined, or in woody debris. Total ecosystem C stores averaged ∼110 Mg/ha in stands experiencing presettlement fire frequencies, but ∼220 Mg/ha in stands experiencing fire suppression. If comparable rates of C storage were to occur in other ecosystems in response to the current extent of fire suppression in the United States, fire suppression in the USA might account for 8–20% of missing global carbon.

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