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1. Ten years ago Gannes et al. (1997 , Stable isotopes in animal ecology: assumptions, caveats, and a call for laboratory experiments. Ecology, 78, 1271-1276, 1998) identified four major areas requiring further research in experimental animal isotopic ecology: (i) the dynamics of isotopic incorporation, (ii) mixing models, (iii) the problem of routing, and (iv) trophic discrimination factors. 2. Differences in isotopic incorporation rates among tissues seem to be explained by variation in protein turnover. The application of multi-compartment models to isotopic incorporation data has revealed that different inferences can be derived between these and one-compartment models. 3. A variety of mixing models of varying degrees of complexity and realism are used to find the contribution of isotopic sources to the elements in an organism's tissues. The use of these models demands the use of tissue to diet discrimination factors that are rarely measured experimentally. 4. Mixing models assume that assimilated nutrients are disassembled into their elemental components and that these elements are reassembled into biomolecules. This assumption is unrealistic as macromolecules are routed differentially into tissues. Isotopic routing is an area that isotopic ecologists have neglected in their experimental and modelling research. 5. Isotopic ecologists are just beginning to understand why ¹⁵N biomagnifies along trophic chains, and to explore the factors that determine the degree of ¹⁵N biomagnification. We review the hypotheses that explain why ¹⁵N biomagnifies up trophic chains. 6. The use of compound-specific isotopic analyses is opening new fruitful areas of research at the intersection of nutritional and isotopic ecology.

Understanding lifetime space use by pelagic animals is pivotal for ecology and fisheries management, but electronic tags are costly, labour‐intensive and rarely able to capture juvenile movement. We implemented an iso‐logging workflow that converts stable isotope chronologies in eye lenses into continuous migration tracks, and demonstrate its application to skipjack tuna (Katsuwonus pelamis). The δ13C and δ15N of muscle from 1122 skipjack were combined with oceanographic predictors in a geostatistical model to produce isoscapes of the western Pacific. Then, a newly developed dry‐and‐scrape protocol was applied to eye lenses from 33 adult skipjack and yielded high‐resolution δ13C and δ15N time series. These isotope ratios were normalised to muscle–lens offsets and ontogenetic enrichment, and a Bayesian state‐space model was used to estimate lifetime migration tracks for each individual. Ensemble reconstructions exposed two migration habits: most fish caught in the western tropical Pacific were lifelong residents, whereas several North Pacific fish had migrated there from tropical nurseries. This provides the first direct evidence of partial migration in a highly migratory pelagic fish. We show that the reconstruction of migration by iso‐logging is a powerful approach for reconstructing the lifetime migration history of pelagic fish. This approach could be applied to a variety of other marine organisms, possibly providing a breakthrough for behavioural ecology studies of marine ecosystems. 要旨 外洋性の高度回遊性魚類において、その生涯にわたる移動履歴を理解することは、生態学および資源管理の観点から重要な課題である。本研究では、外洋性魚類の移動履歴追跡手法として一般的なBio‐loggingに比べて、簡易的かつ低コストに、そしてより長期(ほぼ一生涯)の移動履歴を復元できるIso‐loggingのワークフローを確立し、外洋性の高度回遊性魚類であるカツオ(Katsuwonus pelamis)にこれを適用した。 西部太平洋の広域で採捕されたカツオの筋肉の炭素・窒素安定同位体比(δ13C・δ15N)を地理統計モデルで解析することで、当該海域における同位体比の空間分布(Isoscapes)を構築した。続いて、新たに開発した魚類の水晶体の分割手法を33個体のカツオ成魚に適用し、δ13C・δ15Nの時系列変化を個体ごとに高時間解像度で復元した。これらの同位体データをIsoscapesと直接比較できるように補正し、状態空間モデルにより各個体の生涯の移動履歴を推定した。 Iso‐loggingによる移動履歴復元により、西部太平洋の熱帯域のカツオでは2つの異なる回遊パターンを持つ個体(熱帯域に生涯残留する個体と、日本近海まで北上する個体)が同一個体群内に存在していることが明らかになった。このことから、外洋性の高度回遊性魚類において部分回遊が存在することが本研究で初めて明らかになった。 本研究の結果から、Iso‐loggingを用いた移動履歴推定が外洋性魚類の生涯スケールの移動履歴推定に有効であることが示された。本手法は、水晶体を持つあらゆる海洋生物に適用可能であることから、今後の移動・回遊に関する生態学的研究におけるブレイクスルーとなることが期待される。

Soil respiration is the largest flux of carbon (C) from terrestrial ecosystems to the atmosphere. Here, we tested the hypothesis that photosynthesis affects the diurnal pattern of grassland soil-respired CO₂ and its C isotope composition (δ¹³CSR). A combined shading and pulse-labelling experiment was carried out in a mountain grassland. δ¹³CSR was monitored at a high time resolution with a tunable diode laser absorption spectrometer. In unlabelled plots a diurnal pattern of δ¹³CSR was observed, which was not explained by soil temperature, moisture or flux rates and contained a component that was also independent of assimilate supply. In labelled plots δ¹³CSR reflected a rapid transfer and respiratory use of freshly plant-assimilated C and a diurnal shift in the predominant respiratory C source from recent (i.e. at least 1 d old) to fresh (i.e. photoassimilates produced on the same day). We conclude that in grasslands the plant-derived substrates used for soil respiratory processes vary during the day, and that photosynthesis provides an important and immediate C source. These findings indicate a tight coupling in the plant-soil system and the importance of plant metabolism for soil CO₂ fluxes.

•Rising atmospheric CO₂ (cₐ) is expected to promote tree growth and lower water loss via changes in leaf gas exchange. However, uncertainties remain if gas-exchange regulation strategies are homeostatic or dynamical in response to increasing cₐ, as well as evolving climate and pollution inputs. • Using a suite of tree ring-based δ13C-derived physiological parameters (Δ13C, ci , iWUE) and tree growth from a mesic, low elevation stand of canopy-dominant Tsuga canadensis in north-eastern USA, we investigated the influence of rising cₐ, climate and pollution on, and characterised the dynamical regulation strategy of, leaf gas exchange at multidecadal scales. • Isotopic and growth time series revealed an evolving physiological response in which the species shifted its leaf gas-exchange strategy dynamically (constant ci ; constant ci/cₐ; constant cₐ − ci ) in response to rising cₐ, moisture availability and site conditions over 111 yr. Tree iWUE plateaued after 1975, driven by greater moisture availability and a changing soil biogeochemistry that may have impaired a stomatal response. • Results suggested that trees may exhibit more complex physiological responses to the changing environmental conditions over multidecadal periods, and complicating the parameterisation of Earth system models and the estimation of future carbon sink capacity and water balance in midlatitude forests and elsewhere.

Improvement in crop water-use efficiency (WUE) is a critical priority for regions facing increased drought or diminished groundwater resources. Despite new tools for the manipulation of stomatal development, the engineering of plants with high WUE remains a challenge. We used Arabidopsis epidermal patterning factor (EPF) mutants exhibiting altered stomatal density to test whether WUE could be improved directly by manipulation of the genes controlling stomatal density. Specifically, we tested whether constitutive overexpression of EPF2 reduced stomatal density and maximum stomatal conductance (g w(max)) sufficiently to increase WUE. We found that a reduction in g w(max) via reduced stomatal density in EPF2-overexpressing plants (EPF2OE) increased both instantaneous and long-term WUE without altering significantly the photosynthetic capacity. Conversely, plants lacking both EPF1 and EPF2 expression (epf1epf2) exhibited higher stomatal density, higher g w(max) and lower instantaneous WUE, as well as lower (but not significantly so) long-term WUE. Targeted genetic modification of stomatal conductance, such as in EPF2OE, is a viable approach for the engineering of higher WUE in crops, particularly in future high-carbon-dioxide (CO2) atmospheres.

As a representative warm-season grass, Bermudagrass [ (L). .] is widely used in turf systems. However, low temperature remarkably limits its growth and distribution. ABA is a crucial phytohormone that has been reported to regulate much important physiological and biochemical processes in plants under abiotic stress. Therefore, the objective of this study was to figure out the effects of ABA on the cold-sensitive (S) and cold-resistant (R) Bermudagrass genotypes response to cold stress. In this study, the plants were treated with 100 μM ABA solution and exposed to 4°C temperature. After 7 days of cold treatment, the electrolyte leakage (EL), malonaldehyde (MDA) and H O content were significantly increased in both genotypes compared with control condition, and these values were higher in R genotype than those of S genotype, respectively. By contrast, exogenous ABA application decreased the electrolyte leakage (EL), MDA and H O content in both genotypes compared with those plants without ABA treatment under cold treatment condition. In addition, exogenous ABA application increased the levels of chlorophyll fluorescence transient curve for both genotypes, and it was higher in R genotype than that of S genotype. Analysis of photosynthetic fluorescence parameters revealed that ABA treatment improved the performance of photosystem II under cold condition, particularly for the R genotype. Moreover, cold stress significantly increased δ13C values for both genotypes, while it was alleviated by exogenous ABA. Additionally, exogenous ABA application altered the expression of ABA- or cold related genes, including , , and . In summary, exogenous ABA application enhanced cold resistance of both genotypes by maintaining cell membrane stability, improving the process of photosystem II, increasing carbon isotopic fractionation under cold stress, and more prominently in R genotype compared with S genotype.

Species-specific responses of plant intrinsic water-use efficiency (iWUE) to multiple environmental drivers associated with climate change, including soil moisture (θ), vapor pressure deficit (D), and atmospheric CO2 concentration (c a), are poorly understood. We assessed how the iWUE and growth of several species of deciduous trees that span a gradient of isohydric to anisohydric water-use strategies respond to key environmental drivers (θ, D and c a). iWUE was calculated for individual tree species using leaf-level gas exchange and tree-ring δ13C in wood measurements, and for the whole forest using the eddy covariance method. The iWUE of the isohydric species was generally more sensitive to environmental change than the anisohydric species was, and increased significantly with rising D during the periods of water stress. At longer timescales, the influence of c a was pronounced for isohydric tulip poplar but not for others. Trees’ physiological responses to changing environmental drivers can be interpreted differently depending on the observational scale. Care should be also taken in interpreting observed or modeled trends in iWUE that do not explicitly account for the influence of D.

Tropical low‐cloud feedback is the largest source of uncertainty in climate sensitivity, yet multi‐century records of surface shortwave radiation are scarce. We calibrate Porites coral δ13C against satellite photosynthetically available radiation (PAR) and reconstruct monthly PAR for the northern South China Sea during the Medieval Climate Anomaly (1129–1264 CE) and the Little Ice Age (1631–1771 CE). After correcting for the Suess effect and propagating errors via Monte Carlo resampling techniques, annual PAR during the Little‐Ice‐Age is ∼22% lower and seasonality slightly weaker. The dimming aligns with regional proxies for cooler, wetter conditions and is best explained by brighter low clouds, likely boosted by volcanic aerosol–cloud interactions. CMIP6/PMIP4 past1000 simulations, however, yield <0.2% change over the same interval, indicating that current models understate volcanic microphysics and tropical low‐cloud sensitivity. The coral PAR record thus provides a quantitative pre‐industrial target for evaluating tropical cloud processes and reducing uncertainty in equilibrium climate sensitivity.

The study presents the results of investigations into various types of anhydrous pyrolysis aimed at determining the kinetic parameters of hydrocarbon generation processes from source rocks. Surface outcrop samples from the Silesian, Dukla, and Skole units, characterized by a low level of thermal maturity, were used as experimental material. The samples predominantly represented the Menilite Beds from the aforementioned three units, but also included Istebna, Lgota, Verovice, and Spas beds, which exhibit significantly lower parameters that describe generation properties. The anhydrous pyrolysis experiments provided information on the rate of organic matter decomposition (TG/DSC), the degree of conversion (Rock-Eval), the quality of the obtained products (Py/GC), and the isotopic composition of the gaseous products (Py/GC/IRMS). Chromatographic analyses confirmed the oil-prone nature of kerogen contained in the Menilites from the Dukla Unit (Tylawa area), the Silesian Unit (Iwonicz fold), and the Skole Unit, revealing an equal share of all hydrocarbon fractions: C1–C9, C10–C15, and C15+. Through the integration of pyrolytic studies conducted on potential source rocks in the polish Outer Carpathians, a new type of information was obtained regarding the rate of organic matter decomposition, as well as the fractional and isotopic composition of the pyrolysis products. The set of obtained results was used to estimate the activation energy and characterize the potential source levels. The innovative aspect of this approach involved the isotopic characterization of gaseous products generated during thermal degradation of the source rocks. These data were subsequently used to establish genetic correlations with natural gases accumulated in hydrocarbon reservoirs of the Carpathian region. It has been demonstrated that pyrolysis using PY-GC-IRMS can yield results comparable to those obtained through generation in natural geological conditions.

We present a conceptual model linking dry-mass allocational allometry, hydraulic limitation, and vertical stratification of environmental conditions to patterns in vertical tree growth and tree height. Maximum tree height should increase with relative moisture supply and both should drive variation in apparent stomatal limitation. Carbon isotope discrimination (Δ) should not vary with maximum tree height across a moisture gradient when only hydraulic limitation or allocational allometry limit height, but increase with moisture when both hydraulic limitation and allocational allometry limit maximum tree height. We quantified tree height and Δ along a gradient in annual precipitation from 300 to 1600 mm from mallee to temperate rain forest in southeastern Australia; Eucalyptus on this gradient span almost the entire range of tree heights found in angiosperms worldwide. Maximum tree height showed a strong, nearly proportional relationship to the ratio of precipitation to pan evaporation. Δ increased with ln  P / E p , suggesting that both hydraulic limitation and allocational allometry set maximum tree height. Coordinated shifts in several plant traits should result in different species having an advantage in vertical growth rate at different points along a rainfall gradient, and in maximum tree height increasing with relative moisture supply, photosynthetic rate, nutrient supply, and xylem diameter.