Constant Climatic Conditions Research Articles

Variation in fern species richness, assemblages and morphology along a tropical riparian humidity gradient: an example from Borneo

ABSTRACT Riparian vegetation experiences a little spatial distance humidity gradient, especially in the hyper-humid tropics. In Borneo, with almost no seasons and rather constant local climatic conditions, the riparian plant species show a wide range of morphological and physiological adaptations. This study assesses the adaptation strategies of ferns along a riparian humidity gradient in the submontane forest of Sarawak, Malaysia (Borneo). The species richness and cover, morphological traits, leaf area, leaf perimeter, leaf dissection, leaf elongation ratio, and stomatal density of 63 fern species were surveyed in six study areas along six stream transects. Significant trends in species richness and species cover were identified along the six transects, and changes in morphological traits such as leaf area, leaf perimeter, and leaf dissection were also discovered. With increasing distance from the streams (i.e. decreasing humidity), ferns tended to show longer leaves and a lower stomatal density. We conclude that the morphological traits of fronds change significantly within a short tropical riparian humidity gradient. This reveals variations in the energy investment and adaptation efficiency of ferns within a tropical forest microsite.

Deep CO2 release and the carbon budget of the central Apennines modulated by geodynamics

Recent studies increasingly recognize the importance of critical-zone weathering during mountain building for long-term CO2 drawdown and release. However, the focus on near-surface weathering reactions commonly does not account for CO2 emissions from the crust, which could outstrip CO2 drawdown where carbonates melt and decarbonize during subduction and metamorphism. We analyse water chemistry from streams in Italy’s central Apennines that cross a gradient in heat flow and crustal thickness with relatively constant climatic conditions. We quantify the balance of inorganic carbon fluxes from near-surface weathering processes, metamorphism and the melting of carbonates. We find that, at the regional scale, carbon emissions from crustal sources outpace near-surface fluxes by two orders of magnitude above a tear in the subducting slab characterized by heat flow greater than 150 mW m–2 and crustal thickness of less than 25 km. By contrast, weathering processes dominate the carbon budget where crustal thickness exceeds 40 km and heat flow is lower than 30 mW m–2. The observed variation in metamorphic fluxes is one to two orders of magnitude larger than that of weathering fluxes. We therefore suggest that geodynamic modulations of metamorphic melting and decarbonation reactions are an efficient process by which tectonics can regulate the inorganic carbon cycle.

What makes soil landscape robust? Landscape sensitivity towards land use changes in a Swiss southern Alpine valley

Landscape sensitivity is a concept referring to the likelihood that changes in land use may affect in an irreversible way physical and chemical soil properties of the concerned landscape. The objective of this study is to quantitatively assess the sensitivity of the southern Alpine soil landscape regarding land use change-induced perturbations. Alpine soil landscapes can be considered as particularly sensitive to land use changes because their effects tend to be enhanced by frequent extreme climatic and topographic conditions as well as intense geomorphologic activity. In detail, the following soil key properties for soil vulnerability were analysed: (i) soil texture, (ii) bulk density, (iii) soil organic carbon (SOC), (iv) saturated hydraulic conductivity (Ksat), (v) aggregate stability and (vi) soil water repellency (SWR). The study area is characterized by a steep, east-west oriented valley, strongly anthropized in the last centuries followed by a progressive abandonment. This area is particularly suitable due to constant lithological conditions, extreme topographic and climatic conditions as well as historic land use changes. The analysis of land use change effects on soil properties were performed through a linear mixed model approach due to the nested structure of the data. Our results show a generally high stability of the assessed soils in terms of aggregate stability and noteworthy thick soils. The former is remarkable, since aggregate stability, which is commonly used for detecting land use-induced changes in soil erosion susceptibility, was always comparably high irrespective of land use. The stability of the soils is mainly related to a high amount of soil organic matter favouring the formation of stable soil aggregates, decreasing soil erodibility and hence, reducing soil loss by erosion. However, the most sensitive soil property to land use change was SWR that is partly influenced by the amount of soil organic carbon and probably by the quality and composition of SOM.

A 576 m long creep and shrinkage specimen – Long‐term deformation of a semi‐integral concrete bridge with a massive solid cross‐section

AbstractFor creep and shrinkage investigations, relatively small cylindrical specimens are generally exposed to constant climatic conditions. The derived mainly empirical prediction models are used for the calculation of large engineering structures with massive cross‐sections. In this paper, the expected values of the material models according to fib Model Code 2010 and Eurocode 2 are compared with monitoring data, which were acquired over a period of more than 12 years during a structural health monitoring of a large viaduct. It was found that in addition to the measured continuous increase in the viscous deformations, seasonal fluctuations due to climatic influences could also be detected. The numerical calculations show that the material models differ significantly in their magnitude and time course of the predicted viscous concrete deformations. In comparison with the monitoring data, a good agreement was achieved when using the material models according to Eurocode 2. The models of the fib Model Code 2010, on the other hand, underestimated the deformations of the massive bridge girder.

Numerical investigation of a new combined energy system includes parabolic dish solar collector, Stirling engine and thermoelectric device

According to new findings, the use of clean energy sources such as solar energy to supply energy (both electricity and heat) to human societies is essential. On the other hand, choosing the appropriate technology to convert solar energy into useful energy in the form of individual or combined systems is a fundamental issue. Individual solar energy systems have inherently low performance. However, their use in hybrid energy systems with other energy generation devices is key solution and shows high performance. The present work provides the performance of a new combined energy system composed of the parabolic dish solar collector (PDC), Stirling engine (SE) and thermoelectric device (TD) under various parameters. Sun is the main source of energy in this system, where, sunlight is focused on the PDC focal point by the parabolic shaped mirrors. Thus, the useful thermal power is produced by PDC and then feeds to the SE. The operating fluid of the engine is heated by this heat and converted into mechanical energy. Then, the mechanical energy is converted into electricity by a generator connected to the SE and the excess heat is lost from the engine. The exhaust of the SE transferred to the TEG hot end and produces further electricity. In addition, the TEC module absorbs the cooled environment heat and produces cooling energy (by consuming electricity from the TEG). Therefore, the proposed combined process provides the electricity, heat and cooling. The paper is based on the following three scenarios: (1) the system performance is evaluated under constant climatic conditions, (2) climate data from five various cities in Europe and Asia are used for system operation and (3) this scenario presents the general comparison between the two different hybrid energy systems driven by PDC and linear Fresnel reflector (LFR). In addition, multi-objective optimization is provided to obtain the optimal performance of the developed hybrid system. The optimization results showed that, the optimum total output electricity and overall efficiency were 26.21 kW and 39.17%, respectively. It was also found that, average daily useful power generated by PDC in Moscow on 14-June is 373.97 W/m2, which is about 11.1%, 1.55%, 33.3% and 14.23% more than Tehran, Beijing, Geneva and Kiev, respectively. Furthermore, increasing the temperature of PDC absorber improves the performance of SE and TD and subsequently improves the overall operation. Also, in terms of the PDC numbers, the system in the cities of Tehran, Beijing and Moscow has a better justification compared to the other two cities (Geneva and Kiev).

DynaGraM: A process-based model to simulate multi-species plant community dynamics in managed grasslands

Permanent grasslands host a high plant diversity, which sustains many ecosystem services. Thus, understanding how composition of the plant community responds to different management practices under given soil and climatic conditions is crucial for making best use of grasslands. modeling approaches may be used to explain the manifold interactions involved to sustain this diversity. We developed the dynamic, process-based ecological model DynaGraM to simulate the seasonal aboveground vegetation dynamics of semi-natural grasslands. The model allows specifying plant community by any number of species. The predictive power of the model was assessed by simulating the dynamics of a virtual mountain grassland in response to four typical management scenarios under constant climatic conditions over several decades. In our experiments, we modelled an assemblage of seven species representing contrasted plant functional types. We compared model outputs to compositions inferred from floristic records conducted in the French Jura Mountains. Irrespective of initial conditions, the simulated community converged to four distinct compositions that primarily reflected management. Overall, the results matched the functional composition inferred for each of the scenarios from the botanical records. Convergence in functional composition was reached in less than 15 years under grazing scenarios, but not less than 50 years under mowing scenarios. At quasi-equilibrium, the highest vegetation diversity was obtained for extensive grazing and the lowest for extensive mowing. Overall, this study introduces a novel and relatively simple approach to model competition and adaptation processes in plant community dynamics, thus providing a response to the key challenge of modeling multi-species grasslands.

Changes in population dynamics regimes as a result of both multistability and climatic fluctuation

The paper proposes a mathematical model that describes mouse-like rodent population dynamics. The model is examined through analytical and numerical methods. Changes in the population parameter values lead to a complex evolution of dynamic regimes observed, namely periodic, quasi-periodic and chaotic oscillations, as well as changes in dynamic regimes caused by multistability and external factors. Multistability consists in the existence of various dynamic regimes under the same values of parameters; a transition to these regimes is determined by the initial conditions. An approach is proposed to study multistability by analysing annual population surveys and the model parameter estimates corresponding to the real data set, as well as environmental factors that influence both the birth rate and self-regulation. The adequacy of the results obtained is illustrated by comparing the simulations with the real dynamics of the bank vole population (Myodes glareolus) as a typical example of mouse-like rodents under non-constant environmental conditions. The model study shows that external factors lead to a significant change in attraction basins of coexisting dynamic regimes and shift in model parameter values over the parametric space, which results in a trajectory transition from one dynamic regime to another. As a result, the population size shifts between attraction basins of different dynamic regimes. In certain years, the population size can be attracted to an area of parameter values with similar regimes (the same period of cycles). In particular, the real dynamics of the bank vole population can be represented by a sequence of alternating transients that lead to fluctuations with 3-, 6-, 7- or 14-year periods under constant climatic conditions.

The well-behaved killer: Late Pleistocene humans in Eurasia were significantly associated with living megafauna only

The end of the Pleistocene was characterized by an intense, highly selective extinction event, affecting large-bodied terrestrial mammals worldwide. This period coincides with two major events, the last glacial period, and the dispersal of technologically advanced Homo sapiens outside the Old World. Upper Paleolithic hunters were armed with advanced, projectile weapons, and were able to dispatch prey as large as mammoths. As human population size was rapidly expanding, and hence means meat consumption rate was also growing, Paleolithic hunters are often held responsible for the extinction of mammalian megafauna. Yet, whether human focused on megafauna as prey, and drove them to extinction, remains uncertain. Here we model spatial and temporal patterns in habitat suitability for 24 megafauna species and Homo sapiens in Eurasia. We find that within land patches most suitable for humans, the identity of the most abundant herbivorous mammals switched from warm adapted species (such as the wild boar) to cold adapted species (reindeer) as climate switched from mild to cold conditions. Importantly, extinct herbivorous megafauna species were consistently rare within habitat patches optimal for humans. This suggests that humans may have settled under relatively constant climatic conditions, and possibly behaved as efficient predators, exploiting their prey in a cost-effective manner. These results are in accordance with evidence coming from the archaeological record, where medium sized living herbivore species are overrepresented in comparison of their natural abundance. For Late Pleistocene megafauna in Eurasia, human hunting may have been just an additional, non-decisive extinction factor.

Evaluation of Equilibrium Moisture Content and Chemical Composition in Torrefied Birch Wood

Birch wood veneer shorts from the plywood production plant in Latvia were fractionated to 0.63-2.00 mm and torrefied 30 min at 250, 260, 270, 280, 290 and 300 °C. The evaluation of hydrophobicity to untreated and torrefied birch wood was studied at constant climatic conditions (65±2% relative humidity, 22.8±0.3 °C) while standard chemical analysis methods were used to ascertain the structural and physical changes. Torrefaction process has a strong effect on the equilibrium moisture content of the fuel. The equilibrium moisture content of the torrefied wood decreased by 34% and more compared to the raw wood. Compositional analysis showed that the hemicelluloses are thermally more unstable than cellulose and lignin. During torrefaction process, hemicelluloses were almost removed, but extensive cellulose and light lignin degradation occurred only at torrefaction temperature of 300 °C. As the optimal torrefaction temperature can be considered 280 °C, where equilibrium moisture content of fuel was 5.9% and higher heating value 20.1 MJ/kg.

Biotic and Climatic Velocity Identify Contrasting Areas of Vulnerability to Climate Change

Metrics that synthesize the complex effects of climate change are essential tools for mapping future threats to biodiversity and predicting which species are likely to adapt in place to new climatic conditions, disperse and establish in areas with newly suitable climate, or face the prospect of extirpation. The most commonly used of such metrics is the velocity of climate change, which estimates the speed at which species must migrate over the earth’s surface to maintain constant climatic conditions. However, “analog-based” velocities, which represent the actual distance to where analogous climates will be found in the future, may provide contrasting results to the more common form of velocity based on local climate gradients. Additionally, whereas climatic velocity reflects the exposure of organisms to climate change, resultant biotic effects are dependent on the sensitivity of individual species as reflected in part by their climatic niche width. This has motivated development of biotic velocity, a metric which uses data on projected species range shifts to estimate the velocity at which species must move to track their climatic niche. We calculated climatic and biotic velocity for the Western Hemisphere for 1961–2100, and applied the results to example ecological and conservation planning questions, to demonstrate the potential of such analog-based metrics to provide information on broad-scale patterns of exposure and sensitivity. Geographic patterns of biotic velocity for 2954 species of birds, mammals, and amphibians differed from climatic velocity in north temperate and boreal regions. However, both biotic and climatic velocities were greatest at low latitudes, implying that threats to equatorial species arise from both the future magnitude of climatic velocities and the narrow climatic tolerances of species in these regions, which currently experience low seasonal and interannual climatic variability. Biotic and climatic velocity, by approximating lower and upper bounds on migration rates, can inform conservation of species and locally-adapted populations, respectively, and in combination with backward velocity, a function of distance to a source of colonizers adapted to a site’s future climate, can facilitate conservation of diversity at multiple scales in the face of climate change.

Long-term settlement behavior of loose-fill cellulose insulation under different types of exposure

In a long-term settling test with loose-fill cellulose insulation under three different types of climatic and mechanical exposure (standard climate, outdoor climate and dynamic vibration) the influence of different impacts on the settlement behavior was compared. Strongest settling was observed in outdoor climate, followed by dynamic vibration at a clearly lower level while least settling occurred under constant standard climatic conditions. A correlation between the progress of settling in outdoor climate and the climate data showed a tendency to accelerated settling, especially when the material is drying.

Abrupt changes in the rate of Andean Plateau uplift from reversible jump Markov Chain Monte Carlo inversion of river profiles

Knowledge of the rate of surface uplift of the central Andean Plateau provides important boundary conditions for regional geodynamic models and paleoclimate reconstructions. Here we present a fully nonlinear inverse method to extract the rock uplift history of the central Andean Plateau from the Cotahuasi River and its tributaries. Our approach is based on an analytical solution to the stream power model that relates elevation to rock uplift history under the assumptions of constant climatic conditions in space and time and spatially invariant rock uplift. We use a Bayesian framework that allows us to quantify the full state of knowledge of model parameters (i.e., uncertainties, trade-offs). The erosional efficiency defines the landscape response time, and this must be determined using independent data. Therefore, using thermochronometric data from the Cotahuasi–Ocoña Canyon, which record rapid fluvial incision at ~13–10Ma, we calibrate our results to infer a rock uplift history for the north-central Andean Plateau. We infer a pulse of rock uplift between 25 and 10Ma at rates as high as 0.25km/My. However, the rock uplift rate inferred during this pulse is not as high as is predicted if the central Andean Plateau grew as a result of loss of unstable lithospheric mantle. Therefore, our results are more consistent with models requiring gradual uplift of the central Andean Plateau.

How the root zone modifies soil wettability: Model experiments with alfalfa and wheat

AbstractTo investigate the effect of plants on soil water repellency (SWR), two column experiments with wheat (Triticum aestivum) and alfalfa (Medicago sativa) with a growing period of three months had been carried out under constant and near‐natural climatic conditions. Model soils with defined wettability were created by mixing a natural sandy loam subsoil with different proportions of a wettable and a hydrophobized pure quartz sand, resulting in a wettable model soil and three model soils with increasing level of subcritical SWR (initial contact angle CA > 0° and < 90°). Results showed a significant decrease of the mean CA after the experiments compared to the initial CA while the mean CA was constant for plant free columns used as a reference. CA as a function of depth in some cases showed a depth dependent variation with decreased CA at the bottom or as well at top and bottom. The deviation from the initial CA was most pronounced for wheat under constant climatic conditions. Changes in CA could be related to changes in pH, i.e., CA was decreased and pH increased. Subcritical WR at the beginning of the growth period affected significantly the moisture content profiles during the entire growing season as well as plant dry mass production. We expect that plant root exudates of plants widely used for foot production cause directly or indirectly pH‐related modifications of the WR level in the root zone dependent on plant species and the ambient climatic conditions.

Adapting agricultural land management to climate change: a regional multi-objective optimization approach

In several regions of the world, climate change is expected to have severe impacts on agricultural systems. Changes in land management are one way to adapt to future climatic conditions, including land-use changes and local adjustments of agricultural practices. In previous studies, options for adaptation have mostly been explored by testing alternative scenarios. Systematic explorations of land management possibilities using optimization approaches were so far mainly restricted to studies of land and resource management under constant climatic conditions. In this study, we bridge this gap and exploit the benefits of multi-objective regional optimization for identifying optimum land management adaptations to climate change. We design a multi-objective optimization routine that integrates a generic crop model and considers two climate scenarios for 2050 in a meso-scale catchment on the Swiss Central Plateau with already limited water resources. The results indicate that adaptation will be necessary in the study area to cope with a decrease in productivity by 0–10 %, an increase in soil loss by 25–35 %, and an increase in N-leaching by 30–45 %. Adaptation options identified here exhibit conflicts between productivity and environmental goals, but compromises are possible. Necessary management changes include (i) adjustments of crop shares, i.e. increasing the proportion of early harvested winter cereals at the expense of irrigated spring crops, (ii) widespread use of reduced tillage, (iii) allocation of irrigated areas to soils with low water-retention capacity at lower elevations, and (iv) conversion of some pre-alpine grasslands to croplands.

Extinctions in North America's Late Glacial landscapes

The end of the Pleistocene was characterized by an intense, highly selective extinction event, affecting large-bodied terrestrial mammals worldwide. This period coincides with two major events, the last glacial period, and the dispersal of technologically advanced Homo sapiens outside the Old World. Upper Paleolithic hunters were armed with advanced, projectile weapons, and were able to dispatch prey as large as mammoths. As human population size was rapidly expanding, and hence means meat consumption rate was also growing, Paleolithic hunters are often held responsible for the extinction of mammalian megafauna. Yet, whether human focused on megafauna as prey, and drove them to extinction, remains uncertain. Here we model spatial and temporal patterns in habitat suitability for 24 megafauna species and Homo sapiens in Eurasia. We find that within land patches most suitable for humans, the identity of the most abundant herbivorous mammals switched from warm adapted species (such as the wild boar) to cold adapted species (reindeer) as climate switched from mild to cold conditions. Importantly, extinct herbivorous megafauna species were consistently rare within habitat patches optimal for humans. This suggests that humans may have settled under relatively constant climatic conditions, and possibly behaved as efficient predators, exploiting their prey in a cost-effective manner. These results are in accordance with evidence coming from the archaeological record, where medium sized living herbivore species are overrepresented in comparison of their natural abundance. For Late Pleistocene megafauna in Eurasia, human hunting may have been just an additional, non-decisive extinction factor.

Net ammonification as influenced by plant diversity in experimental grasslands

Previous plant diversity experiments have mainly reported positive correlations between diversity and N mineralization. We tested whether this relationship can be explained by plant diversity-induced changes i) in the quantity or quality of organic matter or ii) in microclimatic conditions of central European grassland mixtures.We measured ex-situ net ammonification in a laboratory incubation of aboveground plant material and soil sampled in differently diverse plant mixtures. Secondly, in-situ net ammonification was assessed in a field incubation with mineralization cores containing standardized material in four treatments: soil only (control), and soil mixed with field-fresh plant tissue (grass, legume, or tall herb). We used 82 plots with varying species numbers (1, 2, 4, 8, 16, and 60) and numbers of functional groups (1–4; grasses, short herbs, tall herbs, and legumes). We determined the soil water content, total N concentrations of plant and soil, and NH4–N release rates.In the ex-situ incubation under constant climatic conditions, functional group or plant species richness did not influence net ammonification rate constants (k) or the proportion of the organic N pool involved in ammonification (NH4–N0). The presence of legumes in plant mixtures significantly increased NH4–N0 and decreased k indicating elevated N leaching risks in legume-containing grassland mixtures. Mean in-situ net ammonification rates in the mineralization cores decreased in the following order: mixtures of soil with grasses (0.30 ± standard error 0.01 mg NH4–N (g Ninitial)−1 d−1) > tall herbs (0.25 ± 0.01) > legumes (0.22 ± 0.01) > control (0.07 ± 0.00). The type of incubated plant tissue also influenced the soil water content in the mineralization cores at the end of field incubation, likely because of different water retention capacities of the different plant tissue/soil mixtures. Significant plant functional group and species richness effects explained up to 13% of the variance of in-situ net ammonification rates. Because the effect of plant species richness disappeared if the type of incubated plant tissue and the soil water content were accounted for in a sequential ANCOVA, we infer that the soil water content was the main driver underlying the plant species richness effect.

Multiscale prediction of viscoelastic properties of softwood under constant climatic conditions

This paper covers the development and validation of a multiscale homogenization model for linear viscoelastic properties of wood. Starting point is the intrinsic structural hierarchy of wood, which is accounted for by several homogenization steps. Using the correspondence principle, an existing homogenization model for the prediction of elastic properties of wood is adapted herein for upscaling of viscoelastic characteristics. Accordingly, self-consistent, Mori–Tanaka, and unit-cell-based techniques are employed, leading to pointwise defined tensorial creep and relaxation functions in the Laplace-Carson domain. Subsequently, these functions are back-transformed into the time domain by means of the Gaver-Stehfest algorithm. With this procedure the orthotropic macroscopic creep behavior of wood can be derived from the isotropic shear behavior of the lignin-hemicellulose phase. A comparison of model predictions for viscoelastic properties of softwood with corresponding experimentally derived values yields very promising results and confirms the suitability of the model.

The influence of changes in glacier extent and surface elevation on modeled mass balance

Abstract. Glaciers are widely recognized as unique demonstration objects for climate change impacts, mostly due to the strong change of glacier length in response to small climatic changes. However, glacier mass balance as the direct response to the annual atmospheric conditions can be better interpreted in meteorological terms. When the climatic signal is deduced from long-term mass balance data, changes in glacier geometry (i.e. surface extent and elevation) must be considered as such adjustments form an essential part of the glacier reaction to new climatic conditions. In this study, a set of modelling experiments is performed to assess the influence of changes in glacier geometry on mass balance for constant climatic conditions. The calculations are based on a simplified distributed energy/mass balance model in combination with information on glacier extent and surface elevation for the years 1850 and 1973/1985 for about 60 glaciers in the Swiss Alps. The results reveal that over this period about 50–70% of the glacier reaction to climate change (here a one degree increase in temperature) is "hidden" in the geometric adjustment, while only 30–50% can be measured as the long-term mean mass balance. For larger glaciers, the effect of the areal change is partly reduced by a lowered surface elevation, which results in a slightly more negative balance despite a potential increase of topographic shading. In view of several additional reinforcement feedbacks that are observed in periods of strong glacier decline, it seems that the climatic interpretation of long-term mass balance data is rather complex.

RELATIONSHIPS BETWEEN SOIL CHARACTERISTICS AND LEAF NUTRIENT CONCENTRATIONS IN GRAPEVINE

The results of a study investigating the relationships between different soil chemical-physical characteristics and nutrient concentrations in leaf tissues of grapevine (Vitis vinifera L.) are reported. The main feature of the experimental site, its high soil spatial variability, allowed examination of the variables of interest while keeping constant crop variety, plant age, climatic conditions and agronomic techniques management, the variability of which is often cause of data misinterpretation. The research was carried out on a winegrape vineyard, cv. Trebbiano Toscano grafted on 1103P rootstock, in Southern Italy. Ten areas characterised by different soil average fertility were selected within the experimental field and, within each area, two representative plants were chosen as test plants. Soil samples at three depths and leaf blades at three sampling times (end of bloom, fruit set and veraison) were collected. In the soil, total N content was positively correlated with organic C, available P and exchangeable K and inversely related to total CaC0 3 content. Among the leaf mineral nutrients, P showed the highest variation in relation to soil parameters (positive correlation with N content, organic C, available P; negative with CaC0 3 ) at the end of bloom and at veraison. Total leaf N was positively correlated with soil organic C and available P only at veraison. Moreover, in this stage, a higher Ca and Mg leaf content was observed in the areas characterised by a lower chemical fertility (lower total N and organic C; higher CaCO 3 ). Principal component analysis clearly discriminated areas of different soil fertility and underlined the variation in tissue nutrient concentrations as a function of soil chemical and physical properties.

Oxygen and carbon isotope composition of Callovian–Lower Oxfordian (Middle–Upper Jurassic) belemnite rostra from central Poland: A record of a Late Callovian global sea-level rise?

Oxygen and carbon isotope data of well-preserved and stratigraphically well-dated belemnite rostra are presented from a Callovian–Lower Oxfordian succession of the Polish Jura Chain (south-central Poland) that was deposited in a deep shelf environment. Palaeotemperatures calculated from belemnite δ 18O values (9 to 14 °C) indicate relatively constant climatic conditions during studied Callovian and Early Oxfordian intervals. Belemnite δ 13C temporal trends, which are interpreted to record primary variation in the isotope composition of dissolved inorganic carbon reservoir, display a prominent positive carbon isotope shift (up to around 1.7‰ VPDB) in the Upper Callovian. This excursion is preceded and followed by a drop in average δ 13C values of belemnite rostra of around 1‰. The Late Callovian carbonate carbon isotope excursion is likely linked to the enhanced storage of organic carbon in shelf sediments during a global sea-level rise. The presented data are not compatible with the theory of prolonged global glaciation at the Middle–Late Jurassic transition.