Bulk Organic Matter (bulk + organic_matter)

Distribution by Scientific Domains

Selected Abstracts

Water vapour isotopic exchange by epiphytic bromeliads in tropical dry forests reflects niche differentiation and climatic signals

ABSTRACT The 18O signals in leaf water (,18Olw) and organic material were dominated by atmospheric water vapour 18O signals (,18Ovap) in tank and atmospheric life forms of epiphytic bromeliads with crassulacean acid metabolism (CAM), from a seasonally dry forest in Mexico. Under field conditions, the mean ,18Olw for all species was constant during the course of the day and systematically increased from wet to dry seasons (from 0 to +6,), when relative water content (RWC) diminished from 70 to 30%. In the greenhouse, progressive enrichment from base to leaf tip was observed at low night-time humidity; under high humidity, the leaf tip equilibrated faster with ,18Ovap than the other leaf sections. Laboratory manipulations using an isotopically depleted water source showed that ,18Ovap was more rapidly incorporated than liquid water. Our data were consistent with a Craig,Gordon (C-G) model as modified by Helliker and Griffiths predicting that the influx and exchange of ,18Ovap control ,18Olw in certain epiphytic life forms, despite progressive tissue water loss. We use ,18Olw signals to define water-use strategies for the coexisting species which are consistent with habitat preference under natural conditions and life form. Bulk organic matter (,18Oorg) is used to predict the ,18Ovap signal at the time of leaf expansion. [source]

Are environmental conditions recorded by the organic matrices associated with precipitated calcium carbonate in cyanobacterial microbialites?

GEOBIOLOGY, Issue 2 2006
ABSTRACT The amino acid composition of organic matrices associated with calcium carbonate precipitates in microbialites built by different Phormidium species (cyanobacteria) has been compared for samples recovered in lagoonal settings from two regions of the Southern Tropical Pacific separated by more than 4000 km: New Caledonia (Nouméa lagoon) and French Polynesia (Tikehau atoll). Calcium carbonate precipitation in these microbial structures was observed mainly in the interior of the domes and clearly separated from the photosynthetically active surface layer. This study focuses on the hydrolysable amino acid composition of the associated organic matrices that are typically rich in cysteine, leucine, alanine and arginine in New Caledonia, whereas they are particularly rich in dicarboxylic amino acids in French Polynesia. This striking difference is seemingly related to different environmental conditions that characterize the two reef settings. The high cysteine content suggests an origin from metallothioneins produced by the cyanobacteria and/or by epiphytic diatoms that were observed on the top layer, as the result of the input of metals from terrestrial origin in the Nouméa lagoon. In addition, we analysed the bulk organic matter of the photosynthetically active surface layer and of the interior of the domes. The former showed remarkable variations of amino acid composition throughout the year 2001, which may potentially reflect the impact of climatological events (e.g. cyclones) and/or a much stronger seasonality in New Caledonia than in French Polynesia. Although the mechanisms behind the differences remain elusive, our study clearly shows that environmental conditions can be reflected by amino acid compositions, particularly for the organic matrices associated with carbonate precipitates. [source]

Multi-component stable isotope records from Late Weichselian and early Holocene lake sediments at Imio,ki, Poland: palaeoclimatic and methodological implications,

Karina Apolinarska
Abstract Late Weichselian and early Holocene climatic and environmental changes are inferred from stable carbon and oxygen isotope records obtained on bulk and biogenic carbonates from the sediment sequence of Lake Lednica, western Poland. Along with sediment and pollen stratigraphic data, a wide range of carbonate components occurring in the sediments was analysed for ,13C and ,18O, including shells of several gastropod species and the bivalve genus Pisidium, carapaces of the ostracod subfamily Candoninae and oogonia of the aquatic macrophyte genus Chara. The development of catchment soils and the onset of authigenic carbonate production in response to the climatic amelioration during the Late Weichselian are clearly reflected by rising carbonate content, distinct isotopic shifts in bulk carbonates and decreasing ,13C values of bulk organic matter in the sediments. The GI-1/GS-1 (the Bølling,Allerød Interstadial complex/Younger Dryas Stadial) and the GS-1/Preboreal transitions are marked by significant shifts in ,18O values of 2,3,, as well as by distinct changes in carbonate content, indicative of a decrease and a subsequent increase in mean annual temperature. Corresponding ,13C records reflect primarily changes in aquatic productivity, with favourable conditions for phytoplankton and macrophytes during GI-1 and the Preboreal resulting in persistent 13C enrichment. The Younger Dryas Stadial is characterised by depletions in 13C and 18O, with indications of a climatic tripartition. Consistent offsets in ,13C and ,18O between records obtained on specific carbonate components reflect vital effects in combination with seasonal characteristics and habitat preferences of the respective carbonate-precipitating biota. Largely parallel first-order variations in ,13C and ,18O of the different carbonate components demonstrate that individual isotope records may provide important palaeoclimatic information, although more detailed reconstructions can be obtained from multi-component analysis. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Assessment of ,13C and C/N ratios in bulk organic matter as palaeosalinity indicators in Holocene and Lateglacial isolation basin sediments, northwest Scotland,

Elizabeth A. V. Mackie
Abstract Carbon isotopes (,13C) and C/N ratios from bulk organic matter have recently been used as alternative proxies for relative sea-level (RSL) reconstruction where there are problems associated with conventional biological indictors. A previous study on a single isolation basin (Upper Loch nan Eala) in northwest Scotland has shown a clear relationship between ,13C, C/N ratios and palaeosalinity from Younger Dryas and Holocene aged sediments. In this paper we present results of ,13C and C/N ratio analyses from other isolation basins in northwest Scotland over the Holocene and the Lateglacial period in order to validate this technique. The results from the Holocene sequences support the earlier findings that this technique can be used to identify RSL change from isolation basins over the Holocene in this region. The relationship between ,13C, C/N ratios and RSL change is not apparent in sediments of Lateglacial age. Other environmental variables such as atmospheric CO2 concentration, poor vegetation development and temperature influence ,13C values during this period. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Bulk organic ,13C and C/N ratios as palaeosalinity indicators within a Scottish isolation basin,

Elizabeth A. V. Mackie
Abstract Microfossils in isolation basin sediments are frequently used to reconstruct sea-level change, but preservation problems and non-analogue situations can limit their usefulness. Here we investigate the potential of stable carbon isotopes (,13C) and C/N ratios from bulk organic matter, as an alternative proxy of salinity within isolation basin sediments from a basin in northwest Scotland. Within the Holocene sediment ,13C and C/N are determined largely by the mean weighted values of the predominant source of the organic material. Analysis of modern materials and comparison with the diatom record shows that the marine parts of the sequence are dominated by high ,13C and variable C/N. In the fresh water sequences the organic material is a mixture of both freshwater aquatic and terrestrial plant input that have relatively low ,13C and high C/N. The application of ,13C and C/N ratios in the studied basin in general follow the environmental change recorded by the diatoms and shows the potential of bulk organic matter in the investigation of salinity change in isolation basins. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Leaf respiratory CO2 is 13C-enriched relative to leaf organic components in five species of C3 plants

Cheng-yuan Xu
Summary ,,Here, we compared the carbon isotope ratios of leaf respiratory CO2 (,13CR) and leaf organic components (soluble sugar, water soluble fraction, starch, protein and bulk organic matter) in five C3 plants grown in a glasshouse and inside Biosphere 2. One species, Populus deltoides, was grown under three different CO2 concentrations. ,,The Keeling plot approach was applied to the leaf scale to measure leaf ,13CR and these results were compared with the ,13C of leaf organic components. ,,In all cases, leaf respiratory CO2 was more 13C-enriched than leaf organic components. The amount of 13C enrichment displayed a significant species-specific pattern, but the effect of CO2 treatment was not significant on P. deltoides. ,,In C3 plant leaves, 13C-enriched respiratory CO2 appears widespread. Among currently hypothesized mechanisms contributing to this phenomenon, non-statistical carbon isotope distribution within the sugar substrates seems most likely. However, caution should be taken when attempting to predict the ,13C of leaf respiratory CO2 at the ecosystem scale by upscaling the relationship between leaf ,13CR and ,13C of leaf organic components. [source]

Does the 13C of foliage-respired CO2 and biochemical pools reflect the 13C of recently assimilated carbon?

ABSTRACT Isotopic labelling experiments were conducted to assess relationships among 13C of recently assimilated carbon (,CA), foliage respiration (,CF), soluble carbohydrate (,CSC), leaf waxes (,CLW) and bulk organic matter (,COM). Slash pine, sweetgum and maize were grown under 13C depleted CO2 to label biomass and then placed under ambient conditions to monitor the loss of label. In pine and sweetgum, ,CF of labelled plants (,,44 and ,35,, respectively) rapidly approached control values but remained depleted by ,4,6, after 3,4 months. For these tree species, no or minimal label was lost from ,CSC, ,CLW and ,COM during the observation periods. ,CF and ,CSC of labelled maize plants rapidly changed and were indistinguishable from controls after 1 month, while ,CLW and ,COM more slowly approached control values and remained depleted by 2,6,. Changes in ,CF in slash pine and sweetgum fit a two-pool exponential model, with the fast turnover metabolic pool (,3,4 d half-life) constituting only 1,2% of the total. In maize, change in ,CF fits a single pool model with a half-life of 6.4 d. The 13C of foliage respiration and biochemical pools reflect temporally integrated values of ,CA, with change in isotopic composition dampened by the size of metabolic carbon reserves and turnover rates. [source]

Changes in 13C/12C of oil palm leaves to understand carbon use during their passage from heterotrophy to autotrophy,

Emmanuelle Lamade
The carbon isotope composition of leaf bulk organic matter was determined on the tropical tree Elaeis guineensis Jacq. (oil palm) in North Sumatra (Indonesia) to get a better understanding of the changes in carbon metabolism during the passage from heterotrophy to autotrophy of the leaves. Leaf soluble sugar (sucrose, glucose and fructose) contents, stomatal conductance and dark respiration, as well as leaf chlorophyll and nitrogen contents, were also investigated. Different growing stages were sampled from leaf rank ,6 to rank 57. The mean values for the ,13C of bulk organic matter were ,29.01,±,0.9, for the leaflets during the autotrophic stage, ,27.87,±,1.08, for the petioles and ,28.17,±,1.09, for the rachises, which are in the range of expected values for a C3 plant. The differences in ,13C among leaf ranks clearly revealed the changes in the origin of the carbon source used for leaf growth. Leaves were 13C-enriched at ranks below zero (around ,27,). During this period, the ,spear' leaves were completely heterotrophic and reserves from storage organs were mobilised for the growth of these young emerging leaves. 13C-depletion was then observed when the leaf was expanding at rank 1, and there was a continuous decrease during the progressive passage from heterotrophy until reaching full autotrophy. Thereafter, the ,13C remained more or less constant at around ,29.5,. Changes in sugar content and in ,13C related to leaf ranks showed an interesting similarity of the passage from heterotrophy to autotrophy of oil palm leaves to the budburst of some temperate trees or seed germination reported in the literature. Copyright © 2009 John Wiley & Sons, Ltd. [source]