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To understand the metabolic adjustments and nitrogen excretion in haemolymph of mature Eriocheir sinensis during the reproductive migration from fresh water to seawater, haemolymph metabolic variations and nitrogenous wastes were determined after gradual acclimation of females and males from fresh water to different salinities (7, 14, 21, 28 and 35). Total protein content in both female and male crabs was reduced with increased salinity. The contents of lipids including triglyceride and cholesterol significantly decreased at salinities of 0-21, suggesting the lipids of E. sinensis might be mobilized to produce energy for osmoregulation and gonad development at a different salinity. Interestingly, the lipid levels in the females were higher than those in the males, implying the females need to store more lipids to prepare for reproduction. The glucose level was low in this study, which was related to the diet with high protein. Haemolymph urea and uric acid level together decreased at first and then increased, indicating that E. sinensis could regulate the nitrogen excretion pattern by inhibiting or activating ureogenesis and uricogenesis to acclimate to a different osmotic environment. Notably, the females might be more tolerant to salinity increase and have a faster metabolic reorganization than males. These facts could indicate that a different strategy has been employed in mature E. sinensis when encountering salinity stress during the reproductive migration form fresh water to seawater.

Cardisoma armatum is a typical member of the Gecarcinidae which show significant behavioral, morphological, physiological, and/or biochemical adaptations permitting extended activities on the land. The special gills (branchiostegal lung) of C. armatum play an important role in maintaining osmotic pressure balance and obtaining oxygen to adapt to the terrestrial environment. However, adaptive molecular mechanisms responding to air exposure in C. armatum are still poorly understood. In this study, transcriptomic analysis and histological analysis were conducted on the gills to test adaptive capabilities over 8 h between the aerial exposure (AE) and the water immersion (WI) group. Differentially expressed genes (DEGs) related to terrestrial adaptation were categorized into four broad categories: ion transport , acid-base balance, energy metabolism and immune response. This is the first research to reveal the molecular mechanism of terrestrial adaptation in C. armatum, and will provide new insight into the molecular genetic basis of terrestrial adaptation in crabs.

Although the representative species of Sesarmidaes, mudflat crab Parasesarma pictum and P. affine, are primarily herbivorous crabs, very little information is available about these transcriptomes. To identify the key genes those are responsible for the digestion systems in these crabs, we investigated transcriptomic profiles of the hepatopancreas in P. pictum and P. affine. Hundreds of unigenes in P. pictum and P. affine were classified related to food digestion and absorption by blast annotation, and many of them were annotated as digestive enzymes that played key roles during food digestion process. Remarkably, we presented the first report that these two Parasesarma genus species had four types of alpha amylase genes and two types of EGs. This transcriptomic information about P. pictum and P. affine will be helpful in further study of crustacean biology and the molecular basis of the herbivorous diet in crabs.

Procambarus clarkii is an important model crustacean organism in many researches. Ammonia nitrogen is one of common contaminants in aquatic environment, influencing the health of aquatic organisms. The primary objective of this study was to investigate molecular mechanisms on ammonia stress in gills of P. clarkii to provide new insights into the strategies of aquatic animals in responding to high concentration of ammonia in the environment. Procambarus clarkii were randomly assigned into two groups (ammonia stress group, AG; control group, CG), and gill samples were dependently excised from AG and CG. Then response mechanisms on ammonia stress were investigated based on transcriptome data of P. clarkii. 9237 differentially expressed genes were identified in ammonia stress group. The genes of ion transport enzymes (NKA and SLC6A5S) were significantly up-regulated. Whereas the immune-related genes (e.g. MAP3K7, HSP70, HSP90A, CTSF, CTSL1, CHI and CTL4) and pathways were significantly up-regulated, which played an important role in reacting to ammonia stress. Procambarus clarkii may enhance immune defense to counteract ammonia toxicity by the up-regulation of immune-related genes and signaling pathways. The activities of ion transport enzymes are changed to mobilise signal transduction and ion channel regulation for adapting to ammonia environment. These previous key genes play an important role in resistance to ammonia stress to better prepare for survival in high concentration of ammonia.

Reproduction and development are the most important stages in the life of aquatic animals, which are also the most sensitive stages to environmental stress. As a migratory crab, parent Eriocheir sinensis need to migrate to estuary (brackish water) for reproduction, and megalopas need to migrate to freshwater for development. Yangtze River estuary is located at the junction of the Yangtze River and the East China Sea, and the salinity of different regions varies greatly (salinity 0-30‰). Therefore, salinity is one of the key environmental factors affecting E. sinensis. In this study, the salinity preference of parent and megalopas E. sinensis was observed and analyzed by the six-chambered and seven-chambered devices of laboratory experiments. Two groups of alternative salinity were set for parent crabs (7, 14, 21, 28, and 35 ‰) and megalopas (0, 5, 10, 15, 20, 25, and 30‰). The results indicated that males showed no obvious preference for salinity, while females had obvious preference for different salinity and stronger dependence and tolerance to saltwater. Megalopas showed a significant preference for low salinity which was beneficial to migrating to freshwater quickly. It was speculated that the behavior of megalopas tending to freshwater was an inherited behavior in the evolutionary process rather than influenced by environment. The salinity preference of E. sinensis might change the position of spawning grounds and migratory routes, and then the annual fluctuation of salinity in Yangtze River estuary will affect the change of E. sinensis resources.

Crabs feed on a wide range of items and display diverse feeding strategies. The primary objective of this study was to investigate 10 digestive enzyme genes in representative crabs to provide insights into the genetic basis of feeding habits among crab functional groups. Crabs were classified into three groups based on their feeding habits: herbivores (HV), omnivores (OV), and carnivores (CV). To test whether crabs' feeding adaptations matched adaptive evolution of digestive enzyme genes, we examined the 10 digestive enzyme genes of 12 crab species based on hepatopancreas transcriptome data. Each of the digestive enzyme genes was compared to orthologous sequences using both nucleotide- (i.e., PAML and Datamonkey) and protein-level (i.e., TreeSAAP) approaches. Positive selection genes were detected in HV crabs (AMYA, APN, and MGAM) and CV crabs (APN, CPB, PNLIP, RISC, TRY, and XPD). Additionally, a series of positive selection sites were localized in important functional regions of these digestive enzyme genes. This is the first study to characterize the molecular basis of crabs' digestive enzyme genes based on functional feeding group. Our data suggest that HV crabs have evolved an enhanced digestion capacity for carbohydrates, and CV crabs have acquired digestion capacity for proteins and lipids.

A thinning study was established in 1967 in moist mixed forests on the Priest River Experimental Forest in northern Idaho, USA. The study design included three thinning intensities: low, moderate, and high intensity (1,976, 988, and 494 trees ha–1). This study examined short-term (11 years) and long-term (50 years) thinning effects on residual stand characteristics, growth, and yield. Since regeneration may occur after thinning, understory change was also addressed. Thinning decreased stand density immediately but improved the growth of residual trees. Shade-tolerant species were favored in all the thinnings and dominated 50 years after thinning. Unthinned stands had higher total and merchantable volume than all thinned stands both 11 years and 50 years post treatment. Regeneration and nontree vegetation richness increased shortly after thinning, whereas nontree vegetation cover decreased sharply 50 years after treatment. The stands developed into multistrata forests with shade-tolerant species in both the overstory and understory. This is contrary to current thinning practice favoring shade-intolerant species, but demonstrates the resilience of moist Northern Rockies forests to partial overstory disturbances. In this study, thinning favoring shade-tolerant species in these mixed forests has a more significant effect on forest structure dynamics than timber production.

Eriocheir sinensis is an important economic species in China, which is easily affected by pH changes. However, the molecular mechanism of the pH stress response in E. sinensis is still unclear. Therefore, this study aimed to examine the molecular response mechanism of E. sinensis based on pH variation surveillance, histopathological evaluation and transcriptomic analyses. Firstly, pH variation surveillance showed that E. sinensis could actively regulate the pH of its environment. Meanwhile, the histopathological evaluation suggested that pH stress seriously damaged the gills, especially at high pH. Finally, transcriptome analysis showed that the expression of genes related to ion transport, immune stress, and energy metabolism significantly changed. Many genes played an important role in the pH response of E. sinensis, such as carbonic anhydrase (CA), mitochondrial proton/calcium exchanger protein (LETM1), recombinant sodium/hydrogen exchanger 3 (SLC9A3/NHE3), heat shock protein 90 alpha family class a member (HSP90A), alkylglycerone phosphate synthase (AGPS), succinate-CoA ligase ADP-forming subunit beta (LSC2), and superoxide dismutase (SOD). Our study revealed the molecular response mechanism of E. sinensis in response to pH stress, thus providing a basis for further research on the molecular mechanism of response to pH stress in aquatic animals.

Copper (Cu2+), which represents a major physiological challenge for crab culture, is ubiquitous in the aquatic culture environment, and gills are the first organs that come into direct contact with the environment. However, the molecular basis of the response of crabs to Cu2+ stress remains unclear. Here, we conducted a transcriptome and differential expression analysis on the gills from Chinese mitten crab unexposed and exposed to Cu2+ for 24 h. The comparative transcriptome analysis identified 2486 differentially expressed genes (DEGs). GO functional analysis and KEGG pathway analysis revealed some DEGs, which were mostly related to immunity, metabolism, osmotic regulation, Cu2+ homeostasis regulation, antioxidant activity, and detoxification process. Some pathways related to humoral and cellular immunity, such as phagosome, peroxisome, lysosome, mTOR signaling pathway, PI3K-Akt signaling pathway, Toll-like receptor signaling pathway, and T cell receptor signaling pathway were enhanced under Cu2+ stress. In addition, Cu2+ stress altered the expression patterns of key phagocytosis and apoptosis genes (lectin, cathepsin L, Rab7, and HSP70), confirming that Cu2+ can induce oxidative stress and eventually even apoptosis. Histological analysis revealed that the copper can induce damage at the cellular level. This comparative transcriptome analysis provides valuable molecular information to aid future study of the immune mechanism of Chinese mitten crab in response to Cu2+ stress and provides a foundation for further understanding of the effects of metal toxicity.

As fatty acids are one of the most crucial biomolecules transferred across the aquatic food webs, they are claimed to be bioindicators of stressors. Among the various environmental stressors, food shortage is of prime importance. Lower food availability can affect fatty acid metabolism of organisms. We investigated the effects of short-term starvation on fatty acid metabolism of Daphnia magna neonates and juveniles. The results revealed that the total fatty acid content in neonates and juveniles of daphnids both rapidly declined within 24 h of starvation, and it remained constant after the following 24 h of starvation. In addition, the fatty acid profiles in neonates or juveniles fed for 24 h were not significantly different from that in the fasting individuals, while the feeding daphnids presented notably higher fatty acid saturation and lower unsaturation in relative to the fasting daphnids within the next 24 h. D. magna neonate increased its special need for C16:1n7 over food transformation, and its C16:1n7 content was elevated the most when fed for 48 h, much higher than the other fatty acids. Time-course changes in fatty acid content in starved D. magna showed that the dietary polyunsaturated α-linolenic acid, i.e. C18:3n3, could be considered as the potential biomarker in either neonates or juveniles to respond to the abiotic food shortage. This study could offer insights into the assessment of food-deprived stress in terms of fatty acid metabolism for distinct ages of cladocerans.

Olfaction plays a central role in mating, spawning, obtaining food and escaping predators, which is essential for survival and reproduction of animals. The nature of the olfactory perception in crabs, which is a major group of crustaceans, has remained elusive. This project aims to explore the molecular mechanism of olfaction in crabs and further improve our understanding of olfactory perception in crustaceans. The olfactory receptors and ingestion-related gene expression in Eriocheir japonica sinensis were studied by transcriptomic techniques. The de novo assembly, annotation and functional evaluation were performed with bioinformatics tools. A series of chemosensory receptors associated with olfaction were identified including 33 EsIRs, 24 EsIGluRs, 58 EsVIGluRs, 1 EsOR and 1 EsGC-D. We found IRs were key odorant receptors demonstrating a specific species evolutionary trend in crustaceans. Furthermore, we identified ORs in E. j. sinensis and Litopenaeus vannamei. The incomplete EsOR and LvOR1 structures implied that ORs exist in crustaceans, and may have been degenerated or even lost in the olfactory evolutionary process. In addition, comparative transcriptome analysises demonstrated two possible olfactory transduction pathways of E. j. sinensis: the cGMP-mediated olfactory pathway related to vegetable odor molecules and the cAMP-mediated olfactory pathway related to meat odor molecules. The above results were consistent with its omnivorous ingestion of E. j. sinensis. Our study revealed the unique olfactory molecular mechanism of omnivorous crabs and provided valuable information for further functional research on the chemoreception mechanisms in crustaceans.

A tree crown is a mass of foliage and significantly correlated to biomass and growth of other parts of a tree. Crown width (CW) is defined as an average of two crown diameters perpendicular to each other, obtained from measurements of four crown radii (crown components). The CW is often used as a covariate predictor in various forest models and therefore, its accurate estimate can be useful for forest management. Although various CW models have been developed so far, all of them lack a detailed investigation of the additivity properties of crown components and inherent correlations among the components and total CW. This study compared three alternative procedures of developing the systems of CW models: nonlinear simultaneous equations (NSE), disaggregated model structure with both one-step proportional weighting system (DMS&OSPWS), and two-step proportional weighting system, and aggregated model structure with one constraint on the total CW. Other two commonly used additivity methods: adjustment in proportion and ordinary least square with separating regression were also evaluated. The comparisons were based on the analyses of data obtained from 2207 trees of Mongolian oak (Quercus mongolica Fisch.) on 116 permanent sample plots located in northern China. Results showed that each method ensured a summation of crown components equal to twice as much as the total CW. The NSE better accounted for the inherent correlations among the crown components and total CW. Out of the model structures evaluated, DMS&OSPWS provided the best performance. This article emphasized more on the methodology and it was expected that the method could be applied by other researchers to develop similar systems of the CW models for other species as well.

As a commonly used phthalate compound, di(n-butyl) phthalate (DBP) is an emerging group of polyvinyl chloride plasticizers. The acute toxicity of DBP has been extensively studied using the aquatic indicator organism, Daphnia magna. However, little is known about chronic and transgenerational toxicity of DBP. In this study, acute LC50 values were 3.04 mg/L (24 h) and 2.55 mg/L (48 h). Chronic toxicity tests in the case of maternal exposure to DBP revealed that DBP had negligible effects on growth and reproduction of F3 generation of D. magna, although the growth rate of body length and the intrinsic rate of increase were prominently reduced, to a pretty small extent. At specific concentrations, DBP generated beneficial effects on the parental generation of D. magna and no obvious impacts on the F1 generation. This study showed that maternal exposure to DBP did not cause any transgenerational effects on D. magna.

Di-(2-ethylhexyl) phthalate (DEHP) is a plasticizer used in the polyvinyl chloride industry worldwide. DEHP exists in the aquatic environments for decades. However, the toxicological effects of DEHP to aquatic organisms have not been adequately researched. We investigated acute toxicity, oxidative damage, antioxidant enzyme activities, and gene expression patterns of antioxidant enzymes in juvenile and adult Daphnia magna exposed to DEHP. We found that the median lethal concentrations (LC50) of DEHP for juveniles exposed for 24 and 48 h were 0.83 and 0.56 mg L−1, respectively. The LC50 of DEHP in adults exposed for 24 and 48 h were 0.48 and 0.35 mg L−1. Daphnia magna that was exposed to DEHP had increased malondialdehyde levels for 24 h and lower total antioxidant capacity compared with the control. Activity levels of antioxidant enzymes superoxide dismutase and phase II detoxifying enzyme glutathione S-transferases were significantly higher upon initial exposure for 24 h, and enzyme activity was then diminished at high concentrations and prolonged exposure for 48 h. Gene expression levels of cat and gst were notably reduced or increased upon DEHP exposure. These findings suggest that DEHP can cause biochemical and physiological effects in juvenile and adult D. magna by inhibiting enzymes, an increase in lipid peroxidation levels and changes both transcription levels of enzymes (cat, gst). On the whole, juveniles and adults both responded similarly to DEHP. Our findings will contribute to the understanding of toxic mechanisms in phthalate esters and the evaluation of environmental risks in aquatic ecosystems.

The asphalt binders could be modified to improve road perfo rmances by using various methods, and the reinforcement mechanisms are obviously different and quietly affect the road performances. According to the composite reinforcement theory, nano-CaCO3 particles, CaCO3 whiskers, and aramid fibers were used as reinforcements to prepare modified asphalt binders, and the conventional technical performances and dynamic shear rheometer (DSR) rheological properties were measured and investigated. In addition, scanning electron microscopy (SEM) was applied to observe the interfaces between reinforcements and asphalt matrixes and the different reinforcement mechanisms were analyzed. The test results showed that the use of nano-CaCO3 particles, CaCO3 whiskers, and aramid fibers can improve the high-temperature stability of modified asphalt binders by different reinforcement mechanisms. The nano-CaCO3 particles were still effective under high-temperature conditions and could last for a long time through the principle of dispersion enhancement. The CaCO3 whiskers segregate easily and cannot be well dispersed in asphalt binders. The aramid fibers played an important role of stress transmission and fiber reinforcement in asphalt binders, and 2 mm-aramid fibers hold the best reinforcement effects. The conclusions can provide a reference for the selection and application of modifiers in the preparation of modified asphalt in laboratory and engineering projects.

Dibutyl phthalate (DBP) poses a severe threat to aquatic ecosystems, introducing hazards to both aquatic species and human health. The ecotoxic effects of DBP on aquatic organisms have not been fully investigated. This study investigates acute toxicity, oxidative damage, and antioxidant enzyme parameters in neonate and adultDaphnia magnaexposed to DBP. The obtained results show comparable DBP toxic responses in neonates and adults. The median lethal concentrations (LC50) of DBP in neonates exposed for 24 and 48 h were 3.48 and 2.83 mg/L, respectively. The LC50of adults for the same DBP exposure durations were 4.92 and 4.31 mg/L, respectively. Increased hydrogen peroxide and malondialdehyde were found in neonates and adults at both 24 and 48 h, while the total antioxidant capacity decreased. Superoxide dismutase activity increased significantly in neonates and adults exposed to 0.5 mg/L DBP, and subsequently diminished at higher DBP concentrations and prolonged exposure. Catalase and glutathione S-transferases activities both decreased markedly in neonates and adults. The changes observed were found to be time and concentration dependent. Overall, these data indicated that the acute toxic effects of DBP exposure on neonates were more pronounced than in adults, and oxidative injury may be the main mechanism of DBP toxicity. These results provide a functional link for lipid peroxidation, antioxidant capacity, and antioxidant enzyme levels in theDaphnia magnaresponse to DBP exposure.

Di-2-ethylhexyl phthalate (DEHP) is a toxic organic compound. It has been shown to exert negative effects on non-targeted aquatic organisms. In order to study the toxicological effects of DEHP on marine microalgae, we investigated cell growth, oxidative damage and antioxidant enzyme activities of Dunaliella salina under DEHP treatment. After exposure to DEHP of 10 to 800 mg/L for 7 days, D. salina growth was gradually inhibited with the increase in DEHP concentration. After D. salina was exposed to 400 mg/L DEHP for 4 days, the contents of malondialdehyde and hydrogen peroxide in D. salina were significantly increased as compared with those in the control group. After 6 days of exposure to DEHP at 10 to 400 mg/L, glutathione peroxidase activity in D. salina was significantly reduced in the 10 and 40 mg/L DEHP groups. Exposure of D. salina to 100 to 400 mg/L DEHP resulted in significantly higher inhibition of total superoxide dismutase in D. salina (p

Due to the existence of the nanoparticles (NPs) agglomeration phenomena in nanometer silica (SiO2) modified asphalt binder, solvent-free SiO2 nanofluids (NFs) were applied in asphalt modification to solve this issue in this research. The main objective is to investigate the rheological properties of SiO2 NFs modified asphalt binder. Solvent-free SiO2 NFs were manufactured based on SiO2 nanoparticles (NPs) by surface functionalization, and subsequently utilized to modify base asphalt binder with various dosages of 1 wt%, 3 wt% and 5 wt%. Fourier transform infrared spectrometer (FTIR), X-ray diffractometer (XRD), scanning electron microscope (SEM) and thermogravimetric analyzer (TGA) were conducted to investigate the microstructure characteristics and thermal stability of SiO2 NFs. The results prove that the successfully manufactured SiO2 NFs are suitable as a modifier to blend with asphalt binder. In addition, the compatibility between SiO2 NFs and base asphalt binder was also observed by SEM, indicating that the dispersion of SiO2 NFs and the compatibility with asphalt binder are much better than SiO2 NPs. Moreover, the tests of rheological property such as temperature sweep (TS), multiple stress creep recovery (MSCR), linear amplitude sweep (LAS), frequency sweep (FS) and bending beam rheometer (BBR) were executed to analyze the rutting, fatigue and crack resistances of asphalt binder effected by the SiO2 NFs. A series of test results manifest that the addition of SiO2 NFs slightly reduces the rutting resistance at high temperatures, but is favorable to improving the fatigue life and low-temperature crack resistance of asphalt binder.

Individual tree growth models are flexible and commonly used to represent growth dynamics for heterogeneous and structurally complex uneven-aged stands. Besides traditional statistical models, the rapid development of nonparametric and nonlinear machine learning methods, such as random forest (RF), boosted regression tree (BRT), cubist (Cubist) and multivariate adaptive regression splines (MARS), provides a new way for predicting individual tree growth. However, the application of these approaches to individual tree growth modelling is still limited and short of a comparison of their performance. The objectives of this study were to compare and evaluate the performance of the RF, BRT, Cubist and MARS models for modelling the individual tree diameter growth based on tree size, competition, site condition and climate factors for larch&ndash, spruce&ndash, fir mixed forests in northeast China. Totally, 16,619 observations from long-term sample plots were used. Based on tenfold cross-validation, we found that the RF, BRT and Cubist models had a distinct advantage over the MARS model in predicting individual tree diameter growth. The Cubist model ranked the highest in terms of model performance (RMSEcv [0.1351 cm], MAEcv [0.0972 cm] and R2cv [0.5734]), followed by BRT and RF models, whereas the MARS ranked the lowest (RMSEcv [0.1462 cm], MAEcv [0.1086 cm] and R2cv [0.4993]). Relative importance of predictors determined from the RF and BRT models demonstrated that the competition and tree size were the main drivers to diameter growth, and climate had limited capacity in explaining the variation in tree diameter growth at local scale. In general, the RF, BRT and Cubist models are effective and powerful modelling methods for predicting the individual tree diameter growth.

Dibutyl phthalate (DBP) poses a severe threat to aquatic ecosystems, introducing hazards to both aquatic species and human health. The ecotoxic effects of DBP on aquatic organisms have not been fully investigated. This study investigates acute toxicity, oxidative damage, and antioxidant enzyme parameters in neonate and adult Daphnia magna exposed to DBP. The obtained results show comparable DBP toxic responses in neonates and adults. The median lethal concentrations (LC50) of DBP in neonates exposed for 24 and 48 h were 3.48 and 2.83 mg/L, respectively. The LC50 of adults for the same DBP exposure durations were 4.92 and 4.31 mg/L, respectively. Increased hydrogen peroxide and malondialdehyde were found in neonates and adults at both 24 and 48 h, while the total antioxidant capacity decreased. Superoxide dismutase activity increased significantly in neonates and adults exposed to 0.5 mg/L DBP, and subsequently diminished at higher DBP concentrations and prolonged exposure. Catalase and glutathione S-transferases activities both decreased markedly in neonates and adults. The changes observed were found to be time and concentration dependent. Overall, these data indicated that the acute toxic effects of DBP exposure on neonates were more pronounced than in adults, and oxidative injury may be the main mechanism of DBP toxicity. These results provide a functional link for lipid peroxidation, antioxidant capacity, and antioxidant enzyme levels in the Daphnia magna response to DBP exposure.

International audience; AbstractKey messageNatural regeneration patterns of conifer species were studied. Seedling regeneration follows patterns responding to stand structure and site condition factors along shade and drought tolerance gradients. Our findings can assist in adaptive forest management for maintaining sustainable regeneration and plant biodiversity.ContextSeedling regeneration can vary with stand factors of overstory trees and understory non-tree vegetation and site conditions.AimsNatural seedling regeneration patterns of coniferous species were investigated using Forest Inventory and Analysis (FIA) data of 10 common species across the Inland Northwest, USA.MethodsZero-inflated negative binomial models were developed to understand the responses of natural regeneration to stand factors and site conditions.ResultsSeedling occurrence varies along shade and drought tolerance gradients responding to stand structure and site conditions. Two moderate shade-tolerant species of different drought tolerance contributed as a transition. Strong response patterns were revealed for seedling density, in which seedling density was improved with the presence of conspecific trees while limited by competition, especially from the understory vegetation layer.ConclusionOverstory structure and understory vegetation could improve or hinder natural regeneration of coniferous tree species given different shade tolerance and site conditions. Our findings can be effectively implemented in adaptive forest management for maintaining sustainable regeneration of specific conifers in broad temperate mixed forests.

We investigated the variability of the relationships between climate and tree-ring growth along an altitudinal gradient and the temporal instability of the relationships under warming for Changbai larch ( Larix olgensis Henry) in northeast of China. Growth response of trees to climate has been found to vary with elevation, but their relationships might also be altered with ongoing global climate change. We developed residual chronologies of tree-ring growth parameters at three sites to investigate variability of the interactions between climate and tree-ring growth for Changbai larch (Larix olgensis Henry) along an altitudinal gradient on the northern slopes of the Changbai Mountains area in Northeastern China. The results indicate that temperature and precipitation are linked differently to the formation of the annual ring width of Changbai larch at different elevations. Tree-ring density of Changbai larch is mainly positively associated with temperature while negatively responding to precipitation. The relationships between temperature and tree-ring growth became unstable, however, after the notable warming of the late 1980s in the study area. Tree-ring width decreased at low elevation under drought stress, whereas showed more positive sensitivity to warming at higher altitudes. We found that the tree-ring density relationship with temperature also became unstable under the rising temperature regime. These findings could be applied in simulating tree-ring growth and forest distribution under various climatic and environmental scenarios.

Climate change is expected to substantially affect forest site productivity. However, its effects may vary depending on the climate scenario, region and tree species. We chose Larix olgensis in northeast China to investigate the responses of forest site productivity to regional climate change using a generalized additive model (GAM). Based on site index data and climate variables from 335 townships across the Jilin Province, we developed a climate-sensitive forest site index model, which accounted for 72.9% of the variation in the site index at the referred age of 20 (SI20). Our results indicated that climatic and geographic factors significantly affect forest site productivity. The geographic location, mean annual temperature, mean annual precipitation and mean temperature differential were found to be statistically significant explanatory variables. We predict that the change of mean SI20 would vary from 0.3 m to -0.8 m (2.2% to -5.9%) by 2050 and from 0.5 m to -1.6 m (3.7% to -11.8%) by 2070 under three BC-RCP scenarios with rising temperature and increasing precipitation. Our study suggests that climate is an important factor affecting forest site productivity. Future climate changes could affect the forest site productivity both positively and negatively for Larix olgensis in northeast China. The relationship between climate and forest site productivity has strong implications for adaptive forest management and needs to be considered in forest management planning under future climate change.

2,3,4-Trimethyl aryl isoprenoid (AIP) hydrocarbons as well as their 2,3,6 homologues were found in most Paleocene crude oils from the Jianghan Basin, China. We interpret their concurrence as evidence for the presence of both purple sulfur bacteria (PSB, family of Chromatiaceae) and green sulfur bacteria (GSB, family of Chlorobiaceae) in the water body during deposition. The GSB and PSB contributions are also evidenced by the presence of the monoaromatic carotenoid derivatives chlorobactane and okenane as well as C40 diaromatic carotenoid derivatives, including isorenieratane and renierapurpurane. The presence of related biomarkers of gammacerane, phytane and methyl trimethyltridecyl chromans (MTTCs) in the oil samples implies that these prolific photosynthetic sulfur bacteria grew in a mesosaline condition, which is consistent with their niches above and below the oxic–anoxic chemocline in a stratified water column. Thus, the general presence of 2,3,6-AIPs, chlorobactane, and isorenieratane sourced from G...

We used bulk rock (BR), solvent extracted BR, isolated kerogen, and bitumen from a mature Salgan Shale as reactants during gold-tube simulation experiments to investigate the contribution of insoluble kerogen to late-stage gas generation at high thermal stress. We measured the gas yields and stable carbon isotopic compositions of methane, ethane, and propane. The high methane yield ([Formula: see text] methane yield at 600°C) in BR series demonstrated the huge potential for late methane generation. The maximum methane yield (normalized to total organic compound) in the bitumen series is twice more than that in the BR series. This phenomenon is interpreted by the high availabilities of hydrogen. However, bitumen only takes up a very small proportion of the overall BR, and generated gas from bitumen cracking is limited. Thus, in mature Salgan Shale, kerogen cracking contributes more hydrocarbon gases than that from bitumen cracking. Meanwhile, generated gas from kerogen cracking is very dry and enriched in the [Formula: see text] isotope, whereas gas cracked from retained oil is much wetter and associated with much lighter [Formula: see text] values. Mature kerogen cracking is also helpful to enlarge the shale gas reserve at high maturities especially when the retained oil is limited.