Fossil actinomycete filaments and fungal hyphae in dicotyledonous wood from the Eocene London Clay, Isle-of-Sheppey, Kent, England

Two types of filamentous microfossil are preserved within vessel elements and rays of pyritized and partly carbonized twigs from the Lower Eocene London Clay. The first type, probably a Streptomyces -like actinomycete, is slender (<1 µm) with branches and some regular septation. Wider filaments (>2 µm) are fungal hyphae; no reproductive structures are preserved. These filamentous organisms probably started growing saprophytically after the death of the twigs; the fungi created lysis tracks on cell walls. Both are seen to pass through pyrite crystals that fill the lumina of some vessel elements, showing that they are not Recent contaminants.  © 2003 The Linnean Society of London, Botanical Journal of the Linnean Society , 2003, 142 , 383–394.     

Tube structures of probable microbial origin in the Neoarchean Carawine Dolomite, Hamersley Basin, Western Australia

The ~2.63 Ga Carawine Dolomite, Hamersley Basin, Western Australia, preserves tube structures of probable microbial origin that formed in a low energy environment. The tubes are 0.4–1.8 cm in diameter and at least 10–16 cm long in outcrop. The tubes are defined by dark, 45-µm-thick dolomicritic walls, whereas the tube fill and host rock are composed of 30 µm, cloudy dolomite crystals and rare 170- to 425-µm-wide, dark well-sorted clasts. Closely spaced, rarely discontinuous laminae coat the insides of tubes; less closely spaced, peaked, discontinuous laminae coat the outsides of tubes. The laminae on the outsides of tubes are often intercalated with mammilate structures. The presence of probable microbial coatings on both the insides and the outsides of the tube walls requires that the tubes formed above the sediment–water interface. These tube structures probably formed during gas-charged fluid escape, similar to tubes observed in ancient and modern hydrocarbon seeps and cylindrical water transfer structures in sandstones. The laminae that coat the tubes have very similar geometries to modern biofilms that form in both turbulent and laminar flow, and their geometries probably reflect flow conditions during the fluid escape. The identification of these structures suggests that the preserved interaction between fluid escape and microbial growth in carbonates may be more common than previously thought.     

Feulgen-positive staining of the cell nuclei in fossilized leaf and fruit tissues of the Lower Eocene Myrtaceae

The Feulgen reaction and the staining of preparations with two DNA-specific fluorochromes, Hoechst 33258 and 4',6-diamidino-2-fenilindol (DAPI), were used to study the preservation of DNA in the fossilized leaf and fruit tissues of the Lower Eocene Myrtaceae, Paramyrtacicarpus plurilocularis and Paramyrtaciphyllum agapovii collected in Yakutia (Siberia, Russia). It was shown that chromatin structures of the fossilized plants form stable red-purple complexes with the Schiff's fuchsin sulphuric acid reagent in situ . This coloration is specific for DNA, in particular, for the deoxyribose residues. It means that the cell nuclei of these 53–55 Myr old plants preserve a part of the deoxyribose backbone of DNA molecules. On the other hand, there was no, or only a very weak, staining of the cell nucleus with fluorochromes DAPI or Hoechst 33258, which specifically bind to the double-stranded DNA and do not bind to either the single-stranded DNA or RNA molecules. The stainability of fossil plant cell preparations with alcian blue shows that there are also polysaccharides containing carboxyl groups in the cell walls of fossilized leaf and fruit tissues of the Lower Eocene Myrtaceae.  © 2006 The Linnean Society of London, Botanical Journal of the Linnean Society , 2006, 150 , 315–321.     

Formation of mineral phosphate microtubes in the presence of halophilic cyanobacteriumMicrocoleus chthonoplastes

In a culture of filamentous cyanobacteriumMicrocoleus chthonoplastes under high phosphorus content and the presence of NaF, formation of aggregated microtubes of 0.8–1.0 m in diameter was obtained. Microtubes contain calcium and phosphorus. These filamentous structures do not represent fossilized bacteria.     

Microtubules in basalt glass from Hawaii Scientific Driling Project #2 phase 1 core and Hilina slope, Hawaii: evidence of the occurrence and behavior of endolithic microorganisms

Elongate, fine tubes, ~1 µm wide and up to 200 µm long, extend from fractured surfaces, vesicle walls, and internal fractures into fragments of basalt glass in samples from the Hawaii Scientific Drilling Project #2 phase 1 (HSDP #2₁) core and the Hilina slope, Hawaii. Several features indicate that these tubes are microbial endolithic microborings: the tubes resemble many described microborings from oceanic basalt glass, their formation is postdepositional but restricted to certain but different ranges of time in the two sets of samples, and they are not uniformly distributed throughout glass fragments. Microtubules record several characteristic behaviors including boring into glass, mining, seeking olivine, and avoiding plagioclase. They also are highly associated with a particular form of glass-replacing smectite. Evidence of behavior should join morphological and geochemical criteria in indicating microbial alteration of basalt glass.
In some samples, steeply conical tubes, ~10–20 µm in diameter tapering to 1 µm and commonly filled with smectite, appear to be modifications or elaborations of the microtubules. These also curve toward olivine and are associated with replacement smectite. In HSDP #2₁ samples, microtubules initiated at margins of shards before palagonite replaced those margins and are preserved during palagonitization. In fact, microtubules appear to have provided routes that enhanced the efficiency of water's reaching of unaltered glass. In Hilina Slope samples, the microtubules appear to postdate palagonitization because they initiate at the boundary between palagonite and unaltered sideromelane.
Preservation of microtubules during palagonitization in samples together with recognition of other associated characteristics representing behavior suggests that such features may be recognizable in more heavily altered ancient rocks.     

Fast Pyrolysis Behavior of Banagrass as a Function of Temperature and Volatiles Residence Time in a Fluidized Bed Reactor

A reactor was designed and commissioned to study the fast pyrolysis behavior of banagrass as a function of temperature and volatiles residence time. Four temperatures between 400 and 600°C were examined as well as four residence times between ~1.0 and 10 seconds. Pyrolysis product distributions of bio-oil, char and permanent gases were determined at each reaction condition. The elemental composition of the bio-oils and chars was also assessed. The greatest bio-oil yield was recorded when working at 450°C with a volatiles residence time of 1.4 s, ~37 wt% relative to the dry ash free feedstock (excluding pyrolysis water). The amounts of char (organic fraction) and permanent gases under these conditions are ~4 wt% and 8 wt% respectively. The bio-oil yield stated above is for ''dry'' bio-oil after rotary evaporation to remove solvent, which results in volatiles and pyrolysis water being removed from the bio-oil. The material removed during drying accounts for the remainder of the pyrolysis products. The ''dry'' bio-oil produced under these conditions contains ~56 wt% carbon which is ~40 wt% of the carbon present in the feedstock. The oxygen content of the 450°C, 1.4 s ''dry'' bio-oil is ~38 wt%, which accounts for ~33 wt% of the oxygen in the feedstock. At higher temperature or longer residence time less bio-oil and char is recovered and more gas and light volatiles are produced. Increasing the temperature has a more significant effect on product yields and composition than increasing the volatiles residence time. At 600°C and a volatiles residence time of 1.2 seconds the bio-oil yield is ~21 wt% of the daf feedstock, with a carbon content of 64 wt% of the bio-oil. The bio-oil yield from banagrass is significantly lower than from woody biomass or grasses such as switchgrass or miscanthus, but is similar to barley straw. The reason for the low bio-oil yield from banagrass is thought to be related to its high ash content (8.5 wt% dry basis) and high concentration of alkali and alkali earth metals (totaling ~2.8 wt% relative to the dry feedstock) which are catalytic and increase cracking reactions during pyrolysis.     

Widespread decreases in topsoil inorganic carbon stocks across China's grasslands during 1980s–2000s

Soil carbon (C) stocks consist of inorganic and organic components, ~1.7 times larger than the total of the C stored in vegetation and the atmosphere together. Significant soil C losses could thus offset any C sink in vegetation, creating a positive feedback to climate change. However, compared with the susceptible sensitivity of organic matter decay to climate warming, soil inorganic carbon (SIC) stocks are often assumed to be relatively stable. Here, we evaluated SIC changes across China's grasslands over the last two decades using data from a recent regional soil survey during 2001–2005 and historical national soil inventory during the 1980s. Our results showed that SIC stocks in the top 10 cm decreased significantly between the two sampling periods, with a mean rate of 26.8 (95% confidence interval: 15.8–41.7) g C m^?2 yr^?1. The larger decreases in SIC stocks were observed in those regions with stronger soil acidification and richer soil carbonates. The lost SIC could be released to the atmosphere as carbon dioxide, redistributed to the deeper soil layer, and transferred to the nearby regions. The fraction of soil carbonates entering into the atmosphere may diminish the strength of terrestrial C sequestration and amplify the positive C‐climate feedback.     

Preservation of overmature,ancient, sedimentary organic matter in carbonate concretions during outcrop weathering

Concretions are preferentially cemented zones within sediments and sedimentary rocks. Cementation can result from relatively early diagenetic processes that include degradation of sedimentary organic compounds or methane as indicated by significantly ¹³C‐depleted or enriched carbon isotope compositions. As minerals fill pore space, reduced permeability may promote preservation of sediment components from degradation during subsequent diagenesis, burial heating and outcrop weathering. Discrete and macroscopic organic remains, macro and microfossils, magnetic grains, and sedimentary structures can be preferentially preserved within concretions. Here, Cretaceous carbonate concretions of the Holz Shale are shown to contain relatively high carbonate‐free total organic carbon (TOC) contents (up to ~18.5 wt%) compared to the surrounding host rock (with <2.1 wt%). TOC increases with total inorganic carbon (TIC) content, a metric of the degree of cementation. Pyrite contents within concretions generally correlate with organic carbon contents. Concretion carbonate carbon isotope compositions (δ¹³C_carb) range from ?22.5 to ?3.4‰ (VPDB) and do not correlate strongly with TOC. Organic carbon isotope compositions (δ¹³C_org) of concretions and host rock are similar. Thermal maturity data indicate that both host and concretion organic matter are overmature and have evolved beyond the oil window maturity stage. Although the organic matter in general has experienced significant oxidative weathering, concretion interiors exhibit lower oxygen indices relative to the host. These results suggest that carbonate concretions can preferentially preserve overmature, ancient, sedimentary organic matter during outcrop weathering, despite evidence for organic matter degradation genetic mechanisms. As a result, concretions may provide an optimal proxy target for characterization of more primary organic carbon concentrations and chemical compositions. In addition, these findings indicate that concretions can promote delayed oxidative weathering of organic carbon in outcrop and therefore impact local chemical cycling.     

Stomatal length and frequency as a measure of ploidy level in black wattle, Acacia mearnsii (de Wild)

The length and frequency of stomata on leaf surfaces were examined as rapid techniques for future identification of ploidy level of Acacia mearnsii (de Wild). Diploid (2 n  = 2 x  = 26) and tetraploid (2 n  = 4 x  = 52) plants were germinated from chipped seed at 25°C and grown under nursery conditions. After one month, measurements showed that the mean stomatal length was 27.17 ± 0.474 µm for diploids and 40.24 ± 0.521 µm for tetraploids and these differed significantly from each other ( P  < 0.001). The frequency of stomata per leaf surface was shown to decrease significantly ( P  < 0.001) as the ploidy level increased, with a mean of 22.11 ± 0.495 for diploids and 10.26 ± 0.495 for tetraploids. It was concluded that stomatal length and stomatal frequency are rapid indirect methods to identify ploidy level in black wattle.  © 2003 The Linnean Society of London, Botanical Journal of the Linnean Society , 2003, 141 , 177–181.     

Trafficking of yellow-fluorescent-protein-tagged mu1 subunit of clathrin adaptor AP-1 complex in living cells

Clathrin adaptor protein AP-1 complex is thought to function in forming clathrin-coated vesicles at the trans -Golgi network (TGN) and mediating transport of cargo between the TGN and endosomes. To study trafficking of AP-1 in living cells, yellow fluorescent protein (YFP) was inserted in the middle of µ1 A subunit of AP-1. When expressed in a tetracycline-dependent manner in HeLa cells, YFP-µ1 was efficiently incorporated into the AP-1 complex, replacing endogenous µ1 in most of cellular AP-1. Time-lapse imaging revealed that YFP-µ1/AP-1 departs from TGN as isolated vesicles and spherical structures, or varicosities, associated with fine tubular processes. Typically, several vesicles or varicosities were seen moving sequentially along the same 'tracks' from TGN to cell periphery. These data suggest that AP-1 may function after formation of Golgi transport intermediates in facilitating their intracellular movement. Mutagenesis of YFP-µ1 determined that the structural requirements for its binding to tyrosine-containing sequence motifs are similar to those previously defined in µ2 subunit of AP-2. Moreover, the carboxyl-terminal half of µ2 could replace the corresponding fragment of µ1 without loss of the ability of the resulting µ1-YFP-µ2 chimeric protein to incorporate into AP-1 and bind tyrosine-containing motifs. Mutations that abolish binding capacity for tyrosine motifs did not mistarget AP-1 in the cell, suggesting that AP-1 interactions with this type of sorting signals are not essential for membrane docking of AP-1 at the TGN. Altogether, this study demonstrates that YFP-tagged µ1 protein can serve as a useful tool for visualizing the dynamics of AP-1 in living cells and for the structure-function analysis of µ1–cargo interactions.     

Chamaebotrys prolifera sp. nov. (Rhodymeniaceae, Rhodophyta) from Puerto Rico, Caribbean Sea, based on morphology and small subunit rDNA sequences

A new rhodymeniacean species, Chamaebotrys prolifera , is described from a shallow water habitat in Puerto Rico, representing the first occurrence of the genus in the Atlantic Ocean. Plants, to 5 cm across, are decumbent and comprised of compressed vesicles that are originally proliferously branched at the perimeter. Older vesicles become branched from their dorsal surfaces as well. Branches are septate at their origin and become irregularly shaped with age. Anastomoses between adjacent vesicles is common. Individual vesicles measure to 15 mm in broadest dimension. Vesicle walls consist of two layers of medullary cells and two layers of cortical cells. Tetrasporangia, which occur in diffuse nemathecia, are spherical, to 30 µm in diameter and are cut off terminally from an inner cortical cell. Cystocarps are hemispherical measuring to 800 µm in diameter and 350 µm in height. Spermatangia are apparently cut off randomly from outer cortical cells across the thallus surface. Molecular evidence confirms placement of Chamaebotrys within the Rhodymeniaceae.     

An isotopic and geochemical study of carbonate-clay mineralization in basaltic caves: abiotic versus microbial processes

Stable isotope and geochemical data are used here to differentiate between contemporaneous abiotic and microbial processes leading to formation of modern carbonate‐ (calcite, aragonite and magnesite) and silicate‐rich (kerolite) mineralization in basaltic sea caves on the island of Kauai, Hawaii. Strontium isotope and Ca/Sr ratios in meteoric water and cave carbonates suggest that the majority of Sr and Ca are derived from rock–water interaction within the host basalts situated above the caves. Oxygen and hydrogen isotope ratios and chemical compositions of cave and surface waters indicate that evaporation does not control cave‐water composition. However, evaporation of drops and thin films of water in microenvironments can lead to precipitation of some phases. This behaviour is suggested by the covariance in δ¹⁸O and δ¹³C values of some carbonates, especially magnesite, which is considered to be a late‐stage evaporative precipitate. Modelling of water evolution suggests that evaporation can be a cause of supersaturation for magnesite, kerolite and some Ca carbonates. However, the highly elevated δ¹³C values (up to +8.2) of some Ca carbonates, compared to average dissolved inorganic carbon δ¹³C values (~?12), are best explained as the product of microbial photosynthesis, in particular by cyanobacteria, present in the upper layers of active microbial mats on cave surfaces. The preferential uptake of ¹²C by cyanobacteria is recorded in the low δ¹³C values (?29.1 to ?22.6) of organic matter in mats and mineralized microbialites. The resulting ¹³C‐enrichment of dissolved inorganic carbon is recorded in the elevated δ¹³C values of these Ca carbonates. A positive correlation exists between the δ¹³C values of the carbonates and coexisting organic matter. The large enrichment in ¹³C of carbonate minerals, relative to dissolved inorganic carbon, and its covariance with the δ¹³C values of coexisting organic matter are useful for identification of carbonate‐rich mineralization resulting from autotrophic microbial activity.     

Proposed molten globule intermediates in fd phage penetration and assembly

The fd filamentous phage can be contracted to short rods called I-forms and to spheroidal particles called S-forms. The conversions from fd----I-forms----S-forms were previously suggested to mimic steps in fd penetration. The same conversions, in reverse order, were suggested to mimic steps in fd assembly. The I-forms and S-forms bind the hydrophobic probe, 1-anilino-napthalene-8-sulfonate (ANS); under the same conditions, fd binds this probe very poorly. Rigidly packed side chains in fd and nonrigidly packed side chains in I-forms and S-forms would explain the differences in ANS binding. A compilation of the properties of I-forms and S-forms indicate that: (i) they have compact structures; (ii) they have secondary structures of the same type as native phage; (iii) they have non-native morphologies; and (iv) they may have nonrigid side chain packing. These are the properties of molten globules.     

Microbialite taphonomy and biogenicity: new insights from NanoSIMS

We here show that nano‐scale mapping of elements commonly utilized in biological cycles provides a promising new additional line of evidence when evaluating the extent of the contribution of biology to microbialites. Our case study comes from Lake Clifton in Western Australia, a unique environment where living domical and conical microbialites occur in close proximity to ≤4000‐year‐old fossilized equivalents. The outer margins of a partially lithified, actively growing Lake Clifton microbialite are characterized by abundant filamentous cyanobacteria within a loosely cemented aragonite matrix. Nano‐scale chemical maps have been successfully matched to specific morphological features such as trichomes, sheaths and putative extracellular polymeric substances (EPS). A suite of elements (C, O, Mg, N, Si, S) is concentrated within cyanobacterial sheaths, with carbon, magnesium, nitrogen and sulfur also enriched within trichomes and putative EPS. Calcium distribution highlights the sites of aragonite mineralization. In contrast, the fossilized Lake Clifton microbialite contains only rare, extensively degraded cyanobacterial filaments, the mean diameter of which is <50% of the living equivalents. Nevertheless, nano‐scale chemical maps can again be matched with morphological features. Here, poorly preserved filamentous microfossils are highlighted by enrichments in nitrogen and sulfur. Magnesium is no longer concentrated within the filaments, instead it co‐occurs with calcium and oxygen in the calcite cement. Extension of this study to a ∼2720‐million‐year‐old stromatolitic microbialite from the Tumbiana Formation of Western Australia shows that similar nano‐scale signals, in particular nitrogen and sulfur enrichments, are characteristic of stromatolite laminations, even when morphological microfossils are absent. The close similarities of nano‐scale elemental distributions in organic material from modern and ancient microbialites show that this technique provides a valuable addition to the morphological investigation of such structures, particularly in non‐fossiliferous ancient examples.     

Gravisusception by buoyancy: a mechanism ubiquitous among fungi?

Gravitropism is ubiquitous among the fungal taxa; however, the mechanism(s) of gravisusception have overall remained obscure so far. In the vegetative sporangiophore of the zygomycete Phycomyces blakesleeanus some 200 large lipid globules form a conspicuous spherical complex which is positioned in a dense mesh of filamentous actin about 100 microm below the growing tip of the apex. Experimental suppression of that complex by transient growth at low temperature greatly diminishes the gravitropic response of the sporangiophore. With respect to size and abundance of the globules, the complex of lipid globules meets basic physical criteria for a possible function of gravisusception. Accumulations of similar lipid globules of critical size are documented in the apex of gravitropically growing hyphae of the endomycorrhizal fungus Gigaspora margarita (Glomeromycota) and have been described in the hyphal apices of members of various fungal phyla. We suppose that--in contrast to plants which use starch as a carbon storage and amyloplasts as statoliths--the fungi utilise the buoyancy of carbon-storing oil droplets for gravisusception.     

Carbon burial by shallow lakes on the Yangtze floodplain and its relevance to regional carbon sequestration

Floodplain lakes may play an important role in the cycling of organic matter at the landscape scale. For those lakes on the middle and lower reaches of the Yangtze (MLY) floodplain which are subjected to intense anthropogenic disturbance, carbon burial rates should, theoretically, be substantial due to the high nutrient input, increased primary production and high sediment accumulation rates. There are more than 600 lakes >1 km² on the Yangtze floodplain including 18 lakes >100 km² and most are shallow and eutrophic. ²¹⁰Pb‐dated cores were combined with total organic carbon (TOC) analyses to determine annual C accumulation rates (C AR; g C m^?2 yr^?1) and the total C stock (since ~1850). The sediment TOC content is relatively low with an average <2% in most lakes. C AR ranged from ~5 to 373 g C m^?2 yr^?1, resulting in C standing stocks of 0.60–15.3 kg C m^?2 (mean: ~5 kg C m^?2) since ~1850. A multicore study of Chaohu lake (770 km²) indicated that spatial variability of C burial was not a significant problem for regional upscaling. The possible effect of changes in lake size and catchment land use on C burial was examined at Taibai lake and indicated that lake shrinkage and declining arable agriculture had limited effects on C AR. The organic C standing stock in individual lakes is, however, significantly dependent on lake size, allowing a simple linear scaling for all the MLY lakes. Total regional C sequestration was ~80 Tg C since ~1850, equivalent to ~11% of C sequestration by soils, but in ~3% of the land area. Shallow lakes from MLY are a substantial regional C sink, although strong mineralization occurs due to their shallow nature and their role as C sinks is threatened due to lake drainage.     

CRYSTALLOGRAPHY AND DIAGENESIS IN FOSSIL CRANIID BRACHIOPODS

Abstract:  One of the fundamental questions in biomineralization is how organisms control crystallographic orientation during biomineral production. The understanding of how diagenetic changes influence the preservation of original crystallographic patterns in fossilized biomineral structures provides a priori fundamental information for such an assessment. Fossil craniid brachiopods Petrocrania scabiosa (Late Ordovician) and Crania craniolaris (Late Cretaceous) are analysed using electron backscattered diffraction (EBSD) to provide crystallographic data at high spatial resolution in the structural context. EBSD analyses show that P. scabiosa maintains most of the original crystallographic signature, including data from individual calcite tablets and laminae, while C. craniolaris only retains fragmentary crystallographic data reflecting the crystallographic continuity of tablets across laminae. Data show that the preservation of the original crystallographic signature is independent of that of shell ultrastructure and geological time. In addition, results allow us to propose a series of steps in the evolution of 'crystallographic loss' due to diagenesis.     

Methanobactin-promoted dissolution of Cu-substituted borosilicate glass

Mineral weathering plays an important role in the global cycling of carbon and metals and there is an increasing realization that subsurface microbial activity may be a key factor controlling specific biogeochemical reactions and their rates. Methanobactin (mb) is an extracellular copper-binding compound excreted by methanotrophs to acquire copper for the regulation of methane oxidation. Bioavailable Cu regulates the expression and activity of pMMO vs. sMMO (particulate vs. soluble methane monooxygenase, respectively), key enzymes responsible for bacterial methane oxidation. In this study, we investigate the effect of mb on the dissolution of Cu-substituted borosilicate glass at low temperature and near neutral pH conditions, using batch dissolution experiments. Methanobactin promotes the dissolution of Cu-substituted glasses at rates faster than control experiments. Glasses with lower concentrations of copper (80 p.p.m.) or no copper are dissolved more rapidly by mb than those with more abundant copper (800 p.p.m.). Within the first 2 h of reaction, mb sorption onto glass surfaces limits mass transfer of Cu into solution, and at higher concentrations (100 µmol) of the ligand, inhibits dissolution rates of all glass formulations. These results suggest that both the concentration of mb in solution and the solid phase Cu concentration impact silicate weathering rates and related cycling of carbon in near-surface geological settings.     

Carbon stock loss from deforestation through 2013 in Brazilian Amazonia

The largest carbon stock in tropical vegetation is in Brazilian Amazonia. In this ~5 million km² area, over 750 000 km² of forest and ~240 000 km² of nonforest vegetation types had been cleared through 2013. We estimate current carbon stocks and cumulative gross carbon loss from clearing of premodern vegetation in Brazil's ‘Legal Amazonia’ and ‘Amazonia biome’ regions. Biomass of ‘premodern’ vegetation (prior to major increases in disturbance beginning in the 1970s) was estimated by matching vegetation classes mapped at a scale of 1 : 250 000 and 29 biomass means from 41 published studies for vegetation types classified as forest (2317 1‐ha plots) and as either nonforest or contact zones (1830 plots and subplots of varied size). Total biomass (above and below‐ground, dry weight) underwent a gross reduction of 18.3% in Legal Amazonia (13.1 Pg C) and 16.7% in the Amazonia biome (11.2 Pg C) through 2013, excluding carbon loss from the effects of fragmentation, selective logging, fires, mortality induced by recent droughts and clearing of forest regrowth. In spite of the loss of carbon from clearing, large amounts of carbon were stored in stands of remaining vegetation in 2013, equivalent to 149 Mg C ha^?1 when weighted by the total area covered by each vegetation type in Legal Amazonia. Native vegetation in Legal Amazonia in 2013 originally contained 58.6 Pg C, while that in the Amazonia biome contained 56 Pg C. Emissions per unit area from clearing could potentially be larger in the future because previously cleared areas were mainly covered by vegetation with lower mean biomass than the remaining vegetation. Estimates of original biomass are essential for estimating losses to forest degradation. This study offers estimates of cumulative biomass loss, as well as estimates of premodern carbon stocks that have not been represented in recent estimates of deforestation impacts.     

Foliar and ecosystem respiration in an old-growth tropical rain forest

Foliar respiration is a major component of ecosystem respiration, yet extrapolations are often uncertain in tropical forests because of indirect estimates of leaf area index (LAI). A portable tower was used to directly measure LAI and night-time foliar respiration from 52 vertical transects throughout an old-growth tropical rain forest in Costa Rica. In this study, we (1) explored the effects of structural, functional and environmental variables on foliar respiration; (2) extrapolated foliar respiration to the ecosystem; and (3) estimated ecosystem respiration. Foliar respiration temperature response was constant within plant functional group, and foliar morphology drove much of the within-canopy variability in respiration and foliar nutrients. Foliar respiration per unit ground area was 3.5 ± 0.2  µ mol CO₂ m⁻² s⁻¹, and ecosystem respiration was 9.4 ± 0.5  µ mol CO₂ m⁻² s⁻¹[soil = 41%; foliage = 37%; woody = 14%; coarse woody debris (CWD) = 7%]. When modelled with El Niño Southern Oscillation (ENSO) year temperatures, foliar respiration was 9% greater than when modelled with temperatures from a normal year, which is in the range of carbon sink versus source behaviour for this forest. Our ecosystem respiration estimate from component fluxes was 33% greater than night-time net ecosystem exchange for the same forest, suggesting that studies reporting a large carbon sink for tropical rain forests based solely on eddy flux measurements may be in error.