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SignificanceEstimates of nutrient allocation in different plant tissues and the relationships between the nutrient contents and photosynthetic capacity are critical to predicting ecosystem carbon sequestration under global change. Here, we provide an assessment of large-scale patterns of community-level nitrogen and phosphorus concentrations in different plant tissues and then examine how nutrient allocations are coupled with plant productivity. The results show that nutrient concentrations in leaves are less responsive to abiotic environments than those in woody stems and roots (stable leaf nutrient concentration hypothesis); the relationships between vegetation primary productivity and leaf nutrient contents are stronger when less nutrients are allocated to the woody tissues (productivity–nutrient allocation hypothesis) and are stronger in deciduous than in evergreen vegetation (productivity–leaf lifespan hypothesis).

Hanging glaciers hold the absolute dominant number in West China and their changes had important influences on local hydrology, sea-level rise and natural hazards (snow/ice avalanches). However, logistic and operational difficulties have resulted in the lack of in-situ-measured data, leaving us with poor knowledge of the changing behaviors of this type of glacier. Here, we presented the spatiotemporal pattern of seasonal and annual mass changes of a mid-latitude hanging glacier in the Tien Shan based on repeated terrestrial laser scanning (TLS) surveys during the period 2016–2018. The distributed glacier surface elevation changes exhibited highly spatiotemporal variability, and the winter elevation changes showed slight surface lowering at the upper elevations and weak thickening at the glacier terminus, which was contrary to altitudinal elevation changing patterns at the summer and annual scales. Mass balance processes of the hanging glacier mainly occurred during summer and the winter mass balance was nearly balanced (−0.10 ± 0.15 m w.e.). The glacier exhibited more rapid mass loss than adjacent other morphological glacier and the estimated response time of the glacier to climate change was very short (6–9 years), indicating hanging glaciers will experience rapid wastage and disappearance in the future even with climate change mitigation.

An experimental study of the adsorption performances of NH3 on several commercial activated carbons was described. Firstly, the specific surface area, pore size distribution and morphological structure of the activated carbons have been characterized by N2 adsorption, Scanning Electron Microscope (SEM), and X-ray diffraction (XRD). The adsorption capacities of four kinds of activated carbons were compared based on adsorption isotherms at 30℃. Results show that a type of activated carbon MSC30 with high adsorption capacity of NH3 is a promising adsorbent for NH3 because of its large specific surface area and high pore volume. Secondly, the effect of adsorption temperature on the adsorption capacity of NH3 on MSC30 was investigated. A modified Dubinin-Astakhov equation was employed to describe the adsorption isotherms, with the reliability and accuracy evaluation. The isosteric heat of adsorption of MSC30-NH3 as a function of the amount adsorbed was calculated applying the Clausius-Clapeyron equation with isotherms obtained at 20℃ and 30℃. Thirdly, a packed-bed type adsorber was used to evaluate the influence of cycle time on the system cooling performance (coefficient of performance, specific cooling performance, and volumetric cooling performance) of the MSC30-NH3 pair at the evaporating temperatures of 5℃, 10℃ and 15℃ with a fixed adsorption/condensing temperature and desorption temperature of 30?C and 80℃, respectively. Finally, a long term operation without degradation for MSC30-NH3 adsorption was experimentally demonstrated from the 80 consecutive adsorption-desorption cycles.

The clean wall condition in tokamak devices can be achieved by utilizing the active chemical property of lithium (Li). This also exposes Li to air contamination even when protected by inert gas. To determine whether air contamination affects the retention of hydrogen isotopes in Li, the desorption performances of deuterium (D2) in liquid Li with D/Li ratios of 4.1 mol.%, 2.5 mol.%, and 0.6 mol.% were compared. At a D/Li ratio as low as 0.6 mol.%, the results revealed a significant change in the desorption temperature of D2 by Li contaminants. The ratio of contaminants to D2 in Li was discovered to be important. In this regard, the influence of N2, O2, and H2O (accounting for 15 mol.% of D2) on the desorption performance of D2 in liquid Li was discussed. Both H2O and N2 preabsorbed in liquid Li could react with D2, leading to the changed desorption temperature of D2. Notably, the H2O present in Li consumed all of D2 via reaction, whereas the same amount of N2 as H2O could only react with a part of D2. However, the effect of O2 on the desorption temperature and the effect of impurities on the desorption amount of D2 were not obvious. The impacts of the findings of this work on the retention and extraction of hydrogen isotopes in Li may be further explored to prompt the application of Li in fusion devices.

AbstractThe long half‐life of 129I makes it useful for dating marine sediments aged 2–90 Ma. However, the lack of initial value dating hinders its application for dating terrestrial sediments. A large scatter of 129I/127I in prenuclear terrestrial samples has been reported; however, the key influencing factors remain unclear. This study presented iodine isotope data from three Argentine Entisol profiles and developed an iodine‐source model to determine the influence of the source on iodine isotopic composition. The temporal patterns demonstrated clear climate modulations in natural terrestrial iodine isotopes over the last ∼15 Kyr. The model identified rock weathering as a major source of iodine in continental sediments. Higher 129I/127I ratios at mid‐high latitudes arise from weak geomagnetic shielding of cosmic rays and thus a high production rate, implying limited meridional diffusion of atmospheric iodine. These findings reveal that environmental factors are significant for constraining the initial value of terrestrial 129I.

Carbon storage is an important component of ecosystem services. Under climate warming and human activities, land use/land cover (LULC) have been undergoing tremendous change, leading to spatio-temporal variations in carbon storage. Based on seven series of LULC data and combined with carbon module of Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) model, spatial-temporal changes in LULC types and carbon storage were analyzed and estimated for Heilongjiang Province, Northeast China. Results show varied carbon storage among different types of LULC. Forest and cropland are the dominant LULC types in Heilongjiang Province, Northeast China, accounting for 46–49% (20.90 × 104–22.12 × 104km2) and 30–37% (13.56 × 104–16.70 × 104km2) of the total area. Areal extents of forest, grassland, and unused land declined from 1980 to 2015, by 1.22, 0.84, and 1.11 × 104km2, respectively; while those of cropland and construction land expanded, by 3.14 and 0.08 × 104km2, respectively. From 1980 to 2015, carbon storage displayed consistent change trends with those of LULC types: carbon storage of forest, grassland, and unused land decreased by 236.22, 116.61 and 21.82 × 106 Mg C, respectively; and those of cropland and construction land increased by 414.65 and 0.99 × 106 Mg C, respectively. The total carbon storage in the study region was 6,863.06 × 106–6,907.64 × 106 Mg C, for which the forest, cropland, and grassland were the major contributor (6,778.75 × 106–6,840.57 × 106 Mg C). Due to the conversion of large extents of forest, grassland, and unused land to cropland, which facilitated the formation of carbon sinks and thus enlarged the carbon storage by 45.36 × 106 Mg C from 1980 to 2015. Frequent forest fires, urban expansion, farmland reclamation, and engineering construction were the important factors of changes in the LULC, accelerating permafrost degradation and leading to obvious changes in the total carbon storage in the Heilongjiang Province, Northeast China. Therefore, the estimation of carbon storage in different LULC types can provide important data support and have important implications for evaluation of ecosystem services and carbon cycle.

Understanding the variation in stomatal characteristics in relation to climatic gradients can reveal the adaptation strategies of plants, and help us to predict their responses to future climate changes. In this study, we investigated stomatal density (SD) and stomatal length (SL) in 150 plant species along an elevation gradient (540-2357 m) in Changbai Mountain, China, and explored the patterns and drivers of stomatal characteristics across species and plant functional types (PFTs: trees, shrubs, and herbs). The average values of SD and SL for all species combined were 156 mm(-2) and 35 µm, respectively. SD was higher in trees (224 mm(-2)) than in shrubs (156 mm(-2)) or herbs (124 mm(-2)), and SL was largest in herbs (37 µm). SD was negatively correlated with SL in all species and PFTs (P < 0.01). The relationship between stomatal characteristics and elevation differed among PFTs. In trees, SD decreased and SL increased with elevation; in shrubs and herbs, SD initially increased and then decreased. Elevation-related differences in SL were not significant. PFT explained 7.20-17.6% of the total variation in SD and SL; the contributions of CO2 partial pressure (P CO2), precipitation, and soil water content (SWC) were weak (0.02-2.28%). Our findings suggest that elevation-related patterns of stomatal characteristics in leaves are primarily a function of PFT, and highlight the importance of differences among PFTs in modeling gas exchange in terrestrial ecosystems under global climate change.

Accurately predicting oilfield development indicators (such as oil production, liquid production, current formation pressure, water cut, oil production rate, recovery rate, cost, profit, etc.) is to realize the rational and scientific development of oilfields, which is an important basis to ensure the stable production of the oilfield. Due to existing oilfield development index prediction methods being difficult to accurately reflect the complex nonlinear problem in the oil field development process, using the artificial neural network, which can predict the oilfield development index with the function of infinitely close to any non-linear function, will be the most ideal prediction method at present. This article summarizes four commonly used artificial neural networks: the BP neural network, the radial basis neural network, the generalized regression neural network, and the wavelet neural network, and mainly introduces their network structure, function types, calculation process and prediction results. Four kinds of artificial neural networks are optimized through various intelligent algorithms, and the principle and essence of optimization are analyzed. Furthermore, the advantages and disadvantages of the four artificial neural networks are summarized and compared. Finally, based on the application of artificial neural networks in other fields and on existing problems, a future development direction is proposed which can serve as a reference and guide for the research on accurate prediction of oilfield development indicators.