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The Andean margin of Central Chile (∼32°40′–34°30′S) records abundant Cenozoic arc magmatic activity with variable compositional characteristics. This is examined through the analysis of an extensive database of new and published whole‐rock geochemistry and Sr‐Nd isotopic compositions, in addition to zircon Hf and O isotopic compositions. The whole‐rock data record an increasing assimilation of continental crust material that developed through the compressional regime set in the margin in the Early Miocene that led to the construction of the modern Andes. The same is recorded by the Hf and O isotopic compositions, but these also allow identification of components involved in the magma genesis: (a) the sub arc mantle derived primary magmas, (b) a late Paleozoic—Early Triassic crystalline component, as that currently outcropping immediately to the east of the study area, (c) a deep enriched component, which likely corresponds to the Cuyania terrane, a Grenville age basement recognized further east in this Andean region, and (d) a deep juvenile low‐δ18O component, interpreted here as basement with oceanic crust affinities. This latter component reveals a possible composite nature for the Chilenia terrane, the postulated Grenville age basement in the region. The Cenozoic Andean arc magmas correspond to the differentiated products of an extensive intra‐crustal re‐working, taking place along tens of kilometers below their emplacement level, and whose main imprint is on the magmatic isotopic composition. Our results document the role of the continental crust, particularly regarding its evolving architecture and constitution, over the composition of arc magmas.

Plant C and N isotope values often correlate with rainfall on global and regional scales. This study examines the relationship between plant isotopic values and rainfall in the Eastern Mediterranean region. The results indicate significant correlations between both C and N isotope values and rainfall in C₃ plant communities. This significant relationship is maintained when plant communities are divided by plant life forms. Furthermore, a seasonal increase in C isotope values is observed during the dry season while N isotope values remain stable across the wet and dry seasons. Finally, the isotopic pattern in plants originating from desert environments differs from those from Mediterranean environments because some desert plants obtain most of their water from secondary sources, namely water channeled by local topographic features rather than direct rainfall. From these results it can be concluded that water availability is the primary factor controlling C and N isotope variability in plant communities in the Eastern Mediterranean.

Changing precipitation and temperature are principal drivers for nutrient cycling dynamics in drylands. Foliar isotopic carbon (C) and nitrogen (N) composition (δ 13 C and δ 15 N) are often used to describe the plant’s water use efficiency and nitrogen use strategy in plant ecology research. However, the drivers and mechanisms under differential foliar δ 13 C and δ 15 N among plant species and communities are largely unknown for arid high-elevation regions. This study collected 462 leaf samples of ten top-dominant plant species (two or three replicates per species) across 16 sites in 2005 and 2010 to measure the community-weighted means (CWMs) of foliar δ 13 C and δ 15 N, northeastern Qaidam Basin, Qinghai-Tibetan Plateau. Our results showed that the CWM of foliar δ 15 N was higher in 2005 than in 2010 and was lower in the warm-dry season (July and August) than the cool-wet one (June and September) in 2010. Similarly, the CWM of foliar δ 13 C was higher in 2005 than in 2010, but no difference between warm-dry and cool-wet seasons in 2010. C 4 plants have higher δ 13 C and generally grow faster than C 3 species under warm-wet weathers. This might be why the CWM of foliar δ 13 C was high, while the CWM of foliar δ 15 N was low in the wet sampling year (2010). The general linear mixed models revealed that soil moisture was the most critical driver for the CWM of foliar δ 15 N, which explained 42.1% of the variance alone. However, the total soluble salt content was the crucial factor for the CWM of foliar δ 13 C, being responsible for 29.7% of the variance. Growing season temperature (GST) was the second most vital factor and explained 28.0% and 21.9% of the variance in the CWMs of foliar δ 15 N and δ 13 C. Meanwhile, remarkable differences in the CWMs of foliar δ 15 N and δ 13 C were also found at the species level. Specifically, Kalidium gracile and Salsola abrotanoides have higher foliar δ 15 N, while Ephedra sinica and Tamarix chinensis have lower foliar δ 15 N than other species. The foliar δ 13 C of Calligonum Kozlov and H. ammodendron was the highest among the ten species. Except for the foliar δ 13 C of E. sinica was higher than Ceratoide latens between the two sampling years or between the cool-wet and warm-dry seasons, no significant difference in foliar δ 13 C was found for other species. Overall, the CWMs of foliar δ 15 N and δ 13 C dynamics were affected by soil properties, wet-dry climate change, and species identity in high-elevation deserts on the Qinghai Tibetan Plateau.

Key message Natural Mongolian pine trees of different ages consistently use shallow water throughout the main growing season; therefore, water stored in the shallow soil layer is vital for maintaining their viability. Mongolian pine ( Pinus sylvestris var. mongolica ) plantations in sandy regions often experience dieback after 30–35 years of growth due to water deficiency, whereas natural Mongolian pine forests remain healthy during the same growth stage. However, the water use strategies of natural Mongolian pines remains unclear. Therefore, δ 2 H and δ 18 O in twig xylem water, soil water and groundwater were analyzed in 10–20, 20–30 and 30–50-year-old natural Mongolian pine trees to identify their water sources. In addition, needle δ 13 C was measured simultaneously to assess water use efficiency. Results showed that pine trees of different ages utilized soil water from the same depth. During the growing season (June–August), all pine trees utilized water from 0 to 20 cm soil depth, regardless of the soil water condition. During the end of growing season (September and October), even though soil moisture content in the 0–20 cm depth was higher, pine trees of different ages utilized water from the 0–60 cm soil depth in September and switched to utilize water from the 20–80 cm soil depth in October. There were no significant differences in needle δ 13 C among the sampling dates for trees in each age group, indicating that pine trees can absorb sufficient water to satisfy their water requirements regardless of age. These findings suggest that water stored in the shallow soil layer (0–20 cm) plays an important role in supporting tree transpiration during the growing season (June–August). Therefore, the stability of shallow soil is vital for maintaining the viability of natural Mongolian pine forests.

We review the biochemical and physiological bases of the use of carbon and nitrogen isotopic compositions as an approach for environmental and ecological studies. Biochemical processes commonly observed in the biosphere, including the decarboxylation and deamination of amino acids, are the key factors in this isotopic approach. The principles drawn from the isotopic distributions disentangle the complex dynamics of the biosphere and allow the interactions between the geosphere and biosphere to be analyzed in detail. We also summarize two recently examined topics with new datasets: the isotopic compositions of individual biosynthetic products (chlorophylls and amino acids) and those of animal organs for further pursuing the basis of the methodology. As a tool for investigating complex systems, compound-specific isotopic analysis compensates the intrinsic disadvantages of bulk isotopic signatures. Chlorophylls provide information about the particular processes of various photoautotrophs, whereas amino acids provide a precise measure of the trophic positions of heterotrophs. The isotopic distributions of carbon and nitrogen in a single organism as well as in the whole biosphere are strongly regulated, so that their major components such as amino acids are coordinated appropriately rather than controlled separately.

An experimental study of the main factors affecting the accuracy of oxygen and carbon isotopic analysis in carbonates dispersed in silicate matrix is carried out. Artificial 1, 2, 5, and 10% mixtures of quartz with carbonates with different isotopic parameters (KH-2, Ko, MCA-8) were analyzed by continuous flow isotope ratio mass spectrometry (CF IRMS). It is established that, in addition to the influence of the instrumental nonlinearity, the results are affected by two factors: trace amounts of CO 2 , constantly present in the system (the blank effect) and the presence of chemically neutral silicate particles (the matrix effect). The blank effect depends on the isotopic parameters of the sample and has very little influence on the estimated carbonate content in the rock. The matrix effect, on the contrary, strongly affects the estimated carbonate content, and produces the isotopic shift towards underestimated contents of heavy 13 C and 18 O isotopes. It is shown that this effect is related to the processes occurring near the CO 2 –acid–quartz interface, which are accompanied by kinetic fractionation of carbon and oxygen isotopes. Both effects are dependent on the amount of silicate matrix in the system and most clearly manifested during analysis of carbonate-poor rocks. When the carbonate content in the rock is about 1–2%, deviations from the true δ 13 C and δ 18 O values can reach the first ppm, while carbonate content obtained by chromatographic peak calibration can be underestimated by 20–40%.

In this paper, we report for the first time the δ 13 C and δ 15 N data for PM 2.5 and PM 10 aerosols collected in Tanzania during May-August 2011 together with total carbon (TC) and nitrogen (TN) contents. Mean TC concentrations were 6.5±2.1 µg m −3 in PM 2.5 and 9.2±3.5 µg m −3 in PM 10 . δ 13 C of TC ranged from −26.1 to −20.6‰ with a mean of −23.6‰ in PM 2.5 and from −24.4 to −22.4‰ with a mean of −23.6‰ in PM 10 . We found substantially greater δ 13 C values in PM 2.5 samples during dry season as well as strong positive correlation between levoglucosan (and nss-K + ) and TC in PM 2.5 . These results suggest a significant contribution from burning of C 4 plants to fine organic aerosol formation. TN contents showed a mean of 0.7±0.3 µg m −3 in PM 2.5 and 0.8±0.2 µg m −3 in PM 10 . δ 15 N ranged from +13.4 to +22.1‰ with a mean of +16.2±2.7‰ in PM 2.5 and +10.4 to +18.7‰ with a mean of +13.7±2.2‰ in PM 10 . δ 15 N showed higher ratios in fine particles than coarse particles in both wet and dry season. The relatively high δ 15 N values suggest isotopic enrichment of 15 N in aerosols via exchange reaction between NH 3 (gas) and (particle). We found a strong correlation between TN and (r 2 =0.94 in PM 2.5 and r 2 =0.86 in PM 10 ) and (r 2 =0.48 in PM 2.5 and r 2 =0.55 in PM 10 ). We also found that organic nitrogen is less significant than inorganic nitrogen in the Morogoro aerosols. Based on stable carbon isotopic composition, contributions of burning C 3 plants to TC were estimated to range from 42 to 74% in PM 2.5 and from 39 to 64% in PM 10, whereas those of C 4 ranged from 26 to 58% in PM 2.5 and from 36 to 61% in PM 10 . These results suggest that burning activities of C 3 and C 4 plants contribute to organic aerosol formation in Tanzania.

Hydrogen and oxygen isotopes in atmospheric water vapor (δv) and precipitation (δp or δr) were continuously measured using a laser-based water isotope spectrometer in Guangzhou, southeastern China, from March 2016 to February 2018. The measurements were conducted to investigate the variations in water isotopes in the hydrological cycle under the subtropical monsoon climate. The isotopic composition ranged from −24.4‰ to −11.1‰ for δ18O in water vapor (δ18Ov) and from −11.5‰ to 2.3‰ for δ18O in precipitation (δ18Or). The values of δv and δr were enriched during the dry season and depleted during the wet season, exhibiting systematic seasonal variation. A negative correlation was observed between monthly δv and precipitation amount, indicating that the values of δv exhibits an ‘amount effect’. However, a corresponding amount effect was not observed in the values of δr. The mean difference between δv and δr was −9.7‰ for δ18O and −76‰ for δD, suggesting that equilibrium fractionation is the dominant process during precipitation. The local meteoric vapor line (LMVL) for Guangzhou (δD = 6.6δ18O − 6.4) exhibited a slope similar to that of the equilibrium local meteoric vapor line (ELMVL) but with an intercept difference of 8.6. This difference in intercepts can be attributed to the vertical profile of δv. The δD-q (q refers to water vapor concentration) relationship is useful for identifying water vapor sources and tracking isotopic changes during atmospheric transport and precipitation. The local water vapor was found to originate primarily from the mixing of oceanic air masses. Data points falling between the oceanic source mixing line and the Rayleigh curve likely reflect post-condensation processes, such as raindrop re-evaporation or mixing with surrounding ambient vapor. Short periods of heavy precipitation were observed to cause severe depletion in δv, resulting in values falling below the Rayleigh curve.

We examined the trophic levels of deep-sea benthic foraminifera and metazoans based on stable carbon and nitrogen isotopic compositions of soft tissue to evaluate the role of foraminifera in deep-sea benthic ecosystems. Living benthic foraminifera and metazoans were collected from 2 bathyal sites in Sagami Bay, Japan (water depths 750 and 1430 m) on 3 occasions (April 2004, November 2004 and August 2005). Both carbon and nitrogen isotopic compositions significantly differed among the analysed foraminiferal species. At the deeper site δ15N of the benthic foraminifera ranged from 6.7 to 11.0‰ (typically 7 to 10‰) with considerable interspecies variations. This implies that most benthic foraminifera utilize primarily surface sediments (4.5‰) or particulate organic matter (6.4‰) as their food sources. Many metazoan meiobenthic organisms, in particular polychaetes of meiofaunal size, some harpacticoid copepods, and kinorhynchs (examined only at the shallower site), exhibited δ15N heavier than foraminifera, suggesting that they occupy higher trophic levels than benthic foraminifera. Macro- and megabenthos (spatangoids, ophiuroids and Dentalioida) exhibited δ15N of 10 to 14‰, suggesting they belong in trophic levels 1 to 2 steps higher than metazoan meiobenthos and benthic foraminifera. Similar isotopic trends were observed at the shallower site. Combining the isotopic evidences and the observations on gut contents of some metazoan meiobenthos, together with previous experimental results, the benthic foraminifera in the bathyal Sagami Bay are considered a bridge in the energy flow from phytodetritus and sediments to metazoans.

Prosopis tamarugo Phil. is a strict phreatophyte tree species endemic to the \"Pampa del Tamarugal\", Atacama Desert. The extraction of water for various uses has increased the depth of the water table in the Pampa aquifers threatening its conservation. This study aimed to determine the effect of the groundwater table depth on the water relations of P. tamarugo and to present thresholds of groundwater depth (GWD) that can be used in the groundwater management of the P. tamarugo ecosystem. Three levels of GWD, 11.2 ± 0.3 m, 10.3 ± 0.3 m, and 7.1 ± 0.1 m, (the last GWD being our reference) were selected and groups of four individuals per GWD were studied in the months of January and July of the years 2011 through 2014. When the water table depth exceeded 10 m, P. tamarugo had lower pre-dawn and mid-day water potential but no differences were observed in minimum leaf stomatal resistance when compared to the condition of 7.1 m GWD; the leaf tissue increased its δ(13)C and δ(18)O composition. Furthermore, a smaller green canopy fraction of the trees and increased foliage loss in winter with increasing water table depth was observed. The differences observed in the physiological behavior of P. tamarugo trees, attributable to the ground water depth; show that increasing the depth of the water table from 7 to 11 m significantly affects the water status of P. tamarugo. The results indicate that P. tamarugo has an anisohydric stomatal behavior and that given a reduction in water supply it regulates the water demand via foliage loss. The growth and leaf physiological activities are highly sensitive to GWD. The foliage loss appears to prevent the trees from reaching water potentials leading to complete loss of hydraulic functionality by cavitation. The balance achieved between water supply and demand was reflected in the low variation of the water potential and of the variables related to gas exchange over time for a given GWD. This acclimation capacity of P. tamarugo after experiencing increases in GWD has great value for the implementation of conservation strategies. The thresholds presented in this paper should prove useful for conservation purposes of this unique species.