scholarly journals Leaf waxes in litter and topsoils along a European transect

2016 ◽  
Author(s):  
Imke Schäfer ◽  
Verena Lanny ◽  
Jörg Franke ◽  
Timothy I. Eglinton ◽  
Michael Zech ◽  
...  
Keyword(s):  
Chain Length ◽  
Deciduous Forest ◽  
Soil Depth ◽  
Large Species ◽  
Alkanoic Acid ◽  
Climate Conditions ◽  
Leaf Wax ◽  
Leaf Waxes ◽  
Forest Sites ◽  
Alkanoic Acids

Abstract. Lipid biomarkers are increasingly used to reconstruct past environmental and climate conditions. Leaf wax derived long chain n-alkanes and n-alkanoic acids may have great potential for reconstructing past changes in vegetation, but the factors that affect the leaf wax distribution in fresh plant material, as well as in soils and sediments are not yet fully understood and need further research. We systematically investigated the influence of vegetation and soil depth on leaf waxes in litter and topsoils along a European transect. Our deciduous forest sites are often dominated by the n-C27 alkane and n-C28 alkanoic acid. Conifers produce few n-alkanes, but show high abundances of the C24 n-alkanoic acid. Grasslands are characterized by relatively high amounts of C31 and C33 n-alkanes and C32 and C34 n-alkanoic acids. Chain length ratios thus may allow to distinguish between different vegetation types, but caution must be exercised given the large species-specific variability of chain length patterns. An updated endmember model with a new n-alkane ratio is provided to illustrate, and tentatively account for, degradation effects on n-alkanes.

scholarly journals Leaf waxes in litter and topsoils along a European transect

SOIL ◽  
2016 ◽  
Vol 2 (4) ◽  
pp. 551-564 ◽  
Author(s):  
Imke K. Schäfer ◽  
Verena Lanny ◽  
Jörg Franke ◽  
Timothy I. Eglinton ◽  
Michael Zech ◽  
...  
Keyword(s):  
Chain Length ◽  
Deciduous Forest ◽  
Soil Depth ◽  
Large Species ◽  
Alkanoic Acid ◽  
Climate Conditions ◽  
Leaf Wax ◽  
Leaf Waxes ◽  
Forest Sites ◽  
Alkanoic Acids

Abstract. Lipid biomarkers are increasingly used to reconstruct past environmental and climate conditions. Leaf-wax-derived long-chain n-alkanes and n-alkanoic acids may have great potential for reconstructing past changes in vegetation, but the factors that affect the leaf wax distribution in fresh plant material, as well as in soils and sediments, are not yet fully understood and need further research. We systematically investigated the influence of vegetation and soil depth on leaf waxes in litter and topsoils along a European transect. The deciduous forest sites are often dominated by the n-C27 alkane and n-C28 alkanoic acid. Conifers produce few n-alkanes but show high abundances of the C24 n-alkanoic acid. Grasslands are characterized by relatively high amounts of C31 and C33 n-alkanes and C32 and C34 n-alkanoic acids. Chain length ratios thus may allow for distinguishing between different vegetation types, but caution must be exercised given the large species-specific variability in chain length patterns. An updated endmember model with the new n-alkane ratio (n-C31 + n-C33) / (n-C27 + n-C31 + n-C33) is provided to illustrate, and tentatively account for, degradation effects on n-alkanes.

scholarly journals Improvement of modelling plant responses to low soil moisture in JULESvn4.9 and evaluation against flux tower measurements

2020 ◽  
Author(s):  
Anna B. Harper ◽  
Karina E. Williams ◽  
Patrick C. McGuire ◽  
Maria Carolina Duran Rojas ◽  
Debbie Hemming ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Land Surface ◽  
Deciduous Forest ◽  
Soil Depth ◽  
Regional Climate ◽  
Moisture Stress ◽  
Plant Responses ◽  
Soil Moisture Stress ◽  
Forest Sites ◽  
The Impact

Abstract. Drought is predicted to increase in the future due to climate change, bringing with it a myriad of impacts on ecosystems. Plants respond to drier soils by reducing stomatal conductance, in order to conserve water and avoid hydraulic damage. Despite the importance of plant drought responses for the global carbon cycle and local/regional climate feedbacks, land surface models are unable to capture observed plant responses to soil moisture stress. We assessed the impact of soil moisture stress on simulated gross primary productivity (GPP) and latent energy flux (LE) in the Joint UK Land Environment Simulator (JULES) vn4.9 on seasonal and annual timescales, and evaluated ten different representations of stress in the model. For the default configuration, GPP was more realistic in temperate biome sites than in the tropics or high latitudes/cold region sites, while LE was best simulated in temperate and high latitude/cold sites. Errors not due to soil moisture stress, possibly linked to phenology, contributed to model biases for GPP in tropical savannah and deciduous forest sites. We found that three alternative approaches to calculating soil moisture stress produced more realistic results than the default parameterization for most biomes and climates. All of these involved increasing the number of soil layers from 4 to 14, and the soil depth from 3m to 10.8m. In addition, we found improvements when soil matric potential replaced volumetric water content in the stress equation, when the onset of stress was delayed, and when roots extended deeper into the soil. For LE, the biases were highest in the default configuration in temperate mixed forests, with overestimation occurring during most of the year. At these sites, reducing soil moisture stress (with the new parameterizations mentioned above) increased LE and made the simulation worse. Further evaluation into the reason for the high bias in LE at many of the sites would enable improvements in both carbon and energy fluxes with new parameterizations for soil moisture stress.

scholarly journals Distinguishing between old and modern permafrost sources with compound-specific δ<sup>2</sup>H analysis

2017 ◽  
Author(s):  
Jorien E. Vonk ◽  
Tommaso Tesi ◽  
Lisa Bröder ◽  
Henry Holmstrand ◽  
Gustaf Hugelius ◽  
...  
Keyword(s):  
Isotope Composition ◽  
Quantitative Measure ◽  
The Arctic ◽  
Near Surface ◽  
Leaf Wax ◽  
Leaf Waxes ◽  
Shelf Slope ◽  
Alkanoic Acids ◽  
Long Chain ◽  
Ice Complex

Abstract. Pleistocene ice complex permafrost deposits contain roughly a quarter of the organic carbon (OC) stored in permafrost terrain. When permafrost thaws, its OC is remobilized into the (aquatic) environment where it is available for degradation, transport or burial. Aquatic or coastal environments contain sedimentary reservoirs that can serve as archives of past climatic change. As permafrost thaw is increasing throughout the Arctic, these reservoirs are important locations to assess the fate of remobilized permafrost OC. We here present compound-specific deuterium (δ2H) analysis on leaf waxes as a tool to distinguish between OC released from thawing Pleistocene permafrost (Ice Complex Deposits; ICD) and from thawing Holocene permafrost (from near-surface soils). Bulk geochemistry (%OC, δ13C, %total nitrogen; TN) was analyzed as well as the concentrations and δ2H signatures of long-chain n-alkanes (C21 to C33) and mid/long-chain n-alkanoic acids (C16 to C30) extracted from both ICD-PF samples (n = 9) and modern vegetation/O-horizon (Topsoil-PF) samples (n = 9) from across the northeast Siberian Arctic. Results show that these Topsoil-PF samples have higher %OC, higher OC/TN values, and more depleted δ13C-OC values than ICD-PF samples, suggesting that these former samples trace a fresher soil and/or vegetation source. Median concentrations of high-molecular weight n-alkanes (sum of C25-C27-C29-C31) were 210 ± 350 µg/gOC (median ± IQR) for Topsoil-PF and 250 ± 81 µg/gOC for ICD-PF samples. Long-chain n-alkanoic acids (sum of C22-C24-C26-C28) were more abundant than long-chain n-alkanes, both in Topsoil-PF samples (4700 ± 3400 µg/gOC) and in ICD samples (6630 ± 3500 µg/gOC). Whereas the two investigated sources differ on the bulk geochemical level, they are, however, virtually indistinguishable when using leaf wax concentrations and ratios. However, on the molecular-isotope level, leaf wax biomarker δ2H values are statistically different between Topsoil-PF and ICD-PF. The mean δ2H value of C29 n-alkane was −246 ± 13 ‰ (mean ± stdev) for Topsoil-PF and −280 ± 12 ‰ for ICD-PF, whereas the C31 n-alkane was −247 ± 23 ‰ for Topsoil-PF and −297 ± 15 ‰ for ICD-PF. The C28 n-alkanoic acid δ2H value was −220 ± 15 ‰ for Topsoil-PF and −267 ± 16 ‰ for ICD-PF. With a dynamic isotopic range (difference between two sources) of 34 to 50 ‰, the isotopic fingerprints of individual, abundant, biomarker molecules from leaf waxes can thus serve as end-members to distinguish between these two sources. We tested this molecular δ2H tracer along with another source-distinguishing approach, dual-carbon (δ13C-δ14C) isotope composition of bulk OC, for a surface sediment transect in the Laptev Sea. Results show that general offshore patterns along the shelf-slope transect are similar, but the source apportionment between the approaches vary, which may highlight the advantages of either. The δ2H molecular approach has the advantage that it circumvents uncertainties related to a marine end-member, yet the δ13C-δ14C approach has the advantage that it represents the bulk OC fraction thereby avoiding issues related to the molecular-bulk upscaling challenge. This study indicates that the application of δ2H leaf wax values has potential to serve as a complementary quantitative measure of the source and differential fate of OC thawed out from different permafrost compartments.

scholarly journals Current, steady-state and historical weathering rates of base cations at two forest sites in northern and southern Sweden: a comparison of three methods

2020 ◽  
Vol 17 (2) ◽  
pp. 281-304 ◽  
Author(s):  
Sophie Casetou-Gustafson ◽  
Harald Grip ◽  
Stephen Hillier ◽  
Sune Linder ◽  
Bengt A. Olsson ◽  
...  
Keyword(s):  
Steady State ◽  
Soil Depth ◽  
Base Cations ◽  
Base Cation ◽  
Mineral Weathering ◽  
Soil Horizon ◽  
Soil Horizons ◽  
Weathering Rate ◽  
Weathering Rates ◽  
Forest Sites

Abstract. Reliable and accurate methods for estimating soil mineral weathering rates are required tools in evaluating the sustainability of increased harvesting of forest biomass and assessments of critical loads of acidity. A variety of methods that differ in concept, temporal and spatial scale, and data requirements are available for measuring weathering rates. In this study, causes of discrepancies in weathering rates between methods were analysed and were classified as being either conceptual (inevitable) or random. The release rates of base cations (BCs; Ca, Mg, K, Na) by weathering were estimated in podzolised glacial tills at two experimental forest sites, Asa and Flakaliden, in southern and northern Sweden, respectively. Three different methods were used: (i) historical weathering since deglaciation estimated by the depletion method, using Zr as the assumed inert reference; (ii) steady-state weathering rate estimated with the PROFILE model, based on quantitative analysis of soil mineralogy; and (iii) BC budget at stand scale, using measured deposition, leaching and changes in base cation stocks in biomass and soil over a period of 12 years. In the 0–50 cm soil horizon historical weathering of BCs was 10.6 and 34.1 mmolc m−2 yr−1, at Asa and Flakaliden, respectively. Corresponding values of PROFILE weathering rates were 37.1 and 42.7 mmolc m−2 yr−1. The PROFILE results indicated that steady-state weathering rate increased with soil depth as a function of exposed mineral surface area, reaching a maximum rate at 80 cm (Asa) and 60 cm (Flakaliden). In contrast, the depletion method indicated that the largest postglacial losses were in upper soil horizons, particularly at Flakaliden. With the exception of Mg and Ca in shallow soil horizons, PROFILE produced higher weathering rates than the depletion method, particularly of K and Na in deeper soil horizons. The lower weathering rates of the depletion method were partly explained by natural and anthropogenic variability in Zr gradients. The base cation budget approach produced significantly higher weathering rates of BCs, 134.6 mmolc m−2 yr−1 at Asa and 73.2 mmolc m−2 yr−1 at Flakaliden, due to high rates estimated for the nutrient elements Ca, Mg and K, whereas weathering rates were lower and similar to those for the depletion method (6.6 and 2.2 mmolc m−2 yr−1 at Asa and Flakaliden). The large discrepancy in weathering rates for Ca, Mg and K between the base cation budget approach and the other methods suggests additional sources for tree uptake in the soil not captured by measurements.

scholarly journals Modern isotope hydrology and controls on δD of plant leaf waxes at Lake El'gygytgyn, NE Russia

2013 ◽  
Vol 9 (1) ◽  
pp. 335-352 ◽  
Author(s):  
K. M. K. Wilkie ◽  
B. Chapligin ◽  
H. Meyer ◽  
S. Burns ◽  
S. Petsch ◽  
...  
Keyword(s):  
Sediment Cores ◽  
Winter Precipitation ◽  
Mean Value ◽  
Great Promise ◽  
Plant Leaf ◽  
Hydrologic Processes ◽  
Leaf Waxes ◽  
Lake El’Gygytgyn ◽  
Alkanoic Acids ◽  
Hydrogen Isotope Ratios

Abstract. Stable isotope data from lipid biomarkers and diatom silica recovered from lake sediment cores hold great promise for paleoclimate and paleohydrological reconstructions. However, these records rely on accurate calibration with modern precipitation and hydrologic processes and only limited data exist on the controls on the δD values for n-alkanoic acids from plant leaf waxes. Here we investigate the stable isotopic composition of modern precipitation, streams, lake water and ice cover, and use these data to constrain isotope systematics of the Lake El'gygytgyn Basin hydrology. Compound-specific hydrogen isotope ratios determined from n-alkanoic acids from modern vegetation are compared with modern precipitation and lake core top sediments. Multi-species net (apparent) fractionation values between source water (precipitation) and modern vegetation (e.g., &amp;varepsilon;wax/precip mean value is −107 ± 12‰) agree with previous results and suggest a consistent offset between source waters and the δD values of alkanoic acids. We conclude that although there may be some bias towards a winter precipitation signal, overall δD values from leaf wax n-alkanoic acids record annual average precipitation within the El'gygytgyn Basin. A net fractionation calculated for 200-yr-integrated lake sediments yields &amp;varepsilon;30/precip = −96 ± 8‰ and can provide robust net "apparent" fractionation to be used in future paleohydrological reconstructions.

Antifungal properties of 2-alkynoic acids and their methyl esters

1978 ◽  
Vol 24 (5) ◽  
pp. 593-597 ◽  
Author(s):  
Herman Gershon ◽  
Larry Shanks
Keyword(s):  
Candida Albicans ◽  
Chain Length ◽  
Inverse Relationship ◽  
Methyl Esters ◽  
Trichoderma Viride ◽  
Trichophyton Mentagrophytes ◽  
Weight Basis ◽  
Alkanoic Acids ◽  
Mucor Mucedo ◽  
Partition Behavior

Thirteen 2-alkynoic acids and their methyl esters (C3–C12, C14, C16, and C18) were tested against Aspergillus niger, Trichoderma viride, and Myrothecium verrucaria in Sabouraud dextrose agar at pH 4.0 and 5.6. Toxicity to Candida albicans, Trichophyton mentagrophytes, and Mucor mucedo was determined in the same medium at pH 5.6 and 7.0 in the absence and presence of 10% beef serum. The fungitoxicity of the acids was influenced by chain length, pH of the medium, and absence or presence of adsorbents. The toxicity of the esters was influenced primarily by chain length and to a lesser extent by the pH of the medium and the presence of beef serum. The order of activity of the 2-alkynoic acids is C10 = C11 = C12 > C14 = C16 > C9 > C8 > C7.When compared with other fatty acid analogs, the order of fungitoxicity on a weight basis is 2-alkynoic acids > 2-alkenoic acids > alkanoic acids > 2-bromoalkanoic acids > 2-fluoroalkanoic acids. There is an inverse relationship between chain length and pKa of the acids, suggesting that partition behavior is a fundamental determinant of fungitoxicity along with the effect of adsorbents.

scholarly journals Surface soil organic carbon in temperate and subtropical oriental oak stands of East China

2016 ◽  
Vol 46 (5) ◽  
pp. 621-628 ◽  
Author(s):  
Wenjuan Yu ◽  
Timothy J. Fahey ◽  
Hongzhang Kang ◽  
Pisheng Zhou
Keyword(s):  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Isotopic Composition ◽  
Climatic Factors ◽  
Soil Depth ◽  
East China ◽  
Clear Trend ◽  
Mineral Horizon ◽  
Forest Sites ◽  
Surface Mineral

Forest ecosystems contain large amounts of soil organic carbon (SOC), which is a major component of biogeochemical cycles that may be sensitive to environmental change. We used a combination of nuclear magnetic resonance (NMR) spectroscopy and elemental and isotopic composition to examine the influence of soil properties and climatic factors on the quantity and degree of decomposition of SOC for organic and surface mineral horizons in seven oriental oak (Quercus variabilis Blume) forest sites arranged across a 11o latitudinal gradient in East China. Lacking Oa horizons, the two southernmost sites contained lower amounts of SOC in the forest floor horizon, but otherwise, latitudinal trends were not consistent. The SOC stock in the 0–10 cm mineral horizon exhibited no clear trend along the gradient and had a negative association with clay + silt content. Based on a higher alkyl/O-alkyl (A/O) ratio and alkyl/methoxyl (A/M) ratio, the SOC at the 0–10 cm depth appeared to be relatively more decomposed in three of the four southern subtropical sites. However, the degree of SOC degradation also decreased strongly with increasing soil pH (R2 = 0.90, P = 0.001). Soil organic carbon exhibited increases in δ13C and δ15N and decreases in the C/N ratio with depth for all the seven sites, indicating an increase in its extent of decomposition. Our analysis indicated that the A/M ratio from NMR provided the best indication of the extent of SOC degradation along the latitudinal transect, whereas the elemental and isotopic composition better reflected patterns with soil depth.

scholarly journals HÁBITAT DE Hodomys alleni (RODENTIA: MURIDAE) EN LA SELVA BAJA CADUCIFOLIA EN LA REGIÓN CENTRAL DE COLIMA, MÉXICO

2015 ◽  
Vol 5 (1) ◽  
pp. 63
Author(s):  
Paulina Arias-Caballero de Miguel ◽  
Daniela Medellín ◽  
Yolanda Domínguez Castellanos ◽  
Gerardo Ceballos
Keyword(s):  
Deciduous Forest ◽  
Soil Depth ◽  
Total Sample ◽  
Dry Forest ◽  
Tree Cover ◽  
Conservation Strategies ◽  
Mexican Pacific ◽  
La Selva ◽  
Brosimum Alicastrum ◽  
Depth Feature

RESUMENSon pocas las áreas de selva baja caducifolia y selva mediana subcaducifolia en México y en este tipo de vegetación se encuentra uno de los pocos géneros monotípico de roedores, Hodomys alleni, una especie endémica de los bosques secos tropicales del Pacífico mexicano y también es una especie amenazada debido a la pérdida de su hábitat. El estudio se realizó en la selva baja de Colima, México, se capturaron 303 individuos, incluyendo 11 especies de roedores y 1 marsupial, H. alleni está representado sólo por un 17% de la muestra total. Los resultados revelaron que la distribución y selección del sitio de construcción de madrigueras de H. alleni están directamente relacionados con la profundidad del suelo, característica que resultó ser la más importante en determinar dicha selección. También se estableció una relación entre la muestra de 65 madrigueras y su ubicación en el suelo (43% huecos en el suelo, 51% en la base del árbol o tocón con materiales orgánicos y 6% entre las rocas sin material orgánico) todas estas estrechamente relacionadas con la profundidad del suelo, cubierta arbórea y área de suelo desnudo. 491 individuos de árboles fueron cuantificados constando de 60 especies. De las cuales 9 especies representan el 50% de la muestra total, siendo Acacia macilenta la especie más abundante y Albizia sp., Bursera sp., y Brosimum alicastrum las especies encontradas con mayor frecuencia alrededor de las madrigueras. Por otra parte las etapas reproductivas de H. alleni parecen estar fuertemente relacionadas con la estacionalidad (lluvias y secas), como en muchas otras especies que habitan en los bosques tropicales secos. Por otro lado, se encontraron hembras con mayor peso corporal y mayor longitud durante la estación seca y en ambas temporadas en comparación con los machos. Sin embargo, se necesitan más estudios para recopilar nueva información que pueda fortalecer nuestro objetivo de crear estrategias de conservación para estas y otras especies que dependen fuertemente de la estructura y la estacionalidad de estas pocas y frágiles selvas secas que aún perduran.Palabras clave: Hodomys alleni, selva baja, selva mediana, madrigueras, Colima.ABSTRACTFew areas of deciduous forest and deciduous tropical forest in Mexico and in this type of vegetation is one of the few monotypic genera of rodents, Hodomys alleni, an endemic species of tropical dry forests of the Mexican Pacific and is also a kind threatened due to habitat loss. The study was conducted in the lowland rainforest of Colima, Mexico, 303 individuals were captured, including 11 species of rodents and one marsupial, H. alleni is represented only 17% of the total sample. The results revealed that the distribution and site selection burrowing H. alleni are directly related to soil depth feature that proved to be the most important in determining that selection. A relationship between sample 65 burrows and its location on the ground (43% holes in the ground, 51% at the base of the tree or stump with organic materials and 6% among the rocks without organic material) was also established these closely related to soil depth, tree cover and area of bare ground. 491 trees were quantified individuals comprising 60 species. Of which 9 species represent 50% of the total sample, being the most abundant haggard Acacia and Albizia species sp., Bursera sp., and Brosimum alicastrum species most frequently found around the burrows. Moreover reproductive stages of H. alleni appear to be strongly related to the seasonality (rainy and dry), as in many other species that live in dry tropical forests. Furthermore, females have a greater and longer body weight were found in the dry season and in both seasons compared with males. However, more studies are needed to gather new information that can strengthen our goal of creating conservation strategies for these and other species that depend heavily on the structure and seasonality of these few and fragile dry forest that still survive.Key words: Hodomys alleni, deciduous forest, semi deciduous forest, burrows, Colima.

scholarly journals Heritability of the structures and 13C fractionation in tomato leaf wax alkanes: a genetic model system to inform paleoenvironmental reconstructions

2017 ◽  
Author(s):  
Amanda L.D. Bender ◽  
Daniel H. Chitwood ◽  
Alexander S. Bradley
Keyword(s):  
Plant Communities ◽  
Genetic Model ◽  
Average Chain Length ◽  
Implicit Assumption ◽  
Tomato Cultivar ◽  
Environmental Variance ◽  
Leaf Wax ◽  
Tomato Species ◽  
Leaf Waxes ◽  
Paleoclimate Proxy

AbstractLeaf wax n-alkanes are broadly used to reconstruct paleoenvironmental information. However, the utility of the n-alkane paleoclimate proxy is modulated by the extent to which genetic as well as environmental factors influence the structural and isotopic variability of leaf waxes. In paleoclimate applications, there is an implicit assumption that most variation of leaf wax traits through a time series can be attributed to environmental change and that biological sources of variability within plant communities are small. For example, changes in hydrology affect the δ2 H of waxes though rainwater and the δ13C of leaf waxes by changing plant communities (i.e., C3 versus C4 input). Here we test the assumption of little genetic control over 5 C variation of leaf wax by presenting the results of an experimental greenhouse growth study in which we estimate the role of genetic variability on structural and isotopic leaf wax traits in a set of 76 introgression lines (ILs) between two interfertile Solanum (tomato) species: S. lycopersicum cv M82 (hereafter cv M82) and S. pennellii. We found that the leaves of S. pennellii, a wild desert tomato relative, produces significantly more iso-alkanes than cv M82, a domesticated tomato cultivar adapted to water-replete conditions; we introduce a methylation index to summarize the ratio of branched (iso- and anteiso-) to total alkanes. Between S. pennellii and cv M82, the iso-alkanes were found to be enriched in 13C by 1.2–1.4%o over n-alkanes. By modeling our results from the ILs, we report the broad-sense heritability values (H2) of leaf wax traits to describe the degree to which genetic variation contributes to variation of these traits. Individual carbon isotope values of alkanes are of low heritability (H2 = 0.13–0.19), suggesting that δ13C of leaf waxes from this study are strongly influenced by environmental variance, which supports the interpretation that variation in the 5 C of wax compounds recorded in sediments reflects paleohydrological changes. Average chain length (ACL) values of n-alkanes are of intermediate heritability (H2 = 0.30), suggesting that ACL values are strongly influenced by genetic cues.

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