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An algorithm based on the spectral segment fusion combination and deep residual network is proposed to improve the recognition accuracy of the objects of interest in the WHU-Hi dataset, particularly for cruciferous plants. The accuracy of the objects of interest was effectively improved, as well as the recognition accuracy of other ground objects, and the time efficiency was improved as well. The optimal combination of spectral segments was determined, and spatial and spectral information was extracted from the deep residual network for ground object recognition research. Experimental results showed that the classification accuracy of the cruciferous plants of interest, namely, pak choi, Brassica chinensis, and small Brassica chinensis, increased from 81.36%, 84.2%, and 83.8% to 98.32%, 99.22%, and 98.35%, respectively. In addition, the accuracy of interested trees and grass also increased from 77.6% and 89.09% to 99.12% and 98.33%, respectively, and the overall accuracy, KAPPA, and average accuracy of the three datasets were all improved. The time efficiency was also improved by an order of magnitude. [ABSTRACT FROM AUTHOR]

• Semantic-based segmentation (Semseg) methods are presented in deep learning architecture. • A comparative study is presented for reviewed paper based on performance. • Existing challenges, problems in DL-based semantic segmentation approaches are discussed. • The challenges of Semseg applications are mentioned for other researchers. • Prospect for future work in this area for stable medical image segmentation. Semantic-based segmentation (Semseg) methods play an essential part in medical imaging analysis to improve the diagnostic process. In Semseg technique, every pixel of an image is classified into an instance, where each class is corresponded by an instance. In particular, the semantic segmentation can be used by many medical experts in the domain of radiology, ophthalmologists, dermatologist, and image-guided radiotherapy. The authors present perspectives on the development of an architectural, and operational mechanism of each machine learning-based semantic segmentation approach with merits and demerits. In this regard, researchers have proposed different Semseg methods and examined their performance in a variety of applications such as medical image analysis (e.g., medical image classification and segmentation). A review of recent advances in Semseg techniques are presented in this paper by applying computational image processing and machine learning methods. This article is further presented a comprehensive investigation on how different architectures are helpful for medical image segmentation. Finally, advantages, open challenges, and possible future directions are elaborated in the discussion part, beneficial to the research community to understand the significance of the available medical imaging segmentation technology based on Semseg and thus deliver robust segmentation solutions. Fig. 3: An overview of a latest trend to show the methodological evolution in the development of semantic-based segmentation models for medical images [Display omitted] [ABSTRACT FROM AUTHOR]

Aiming at the detection difficulties in camouflage target detection, such as the high similarity between the target and its background, serious damage to the edge, and strong concealment of the target, a camouflage target detection algorithm YOLO of camouflage object detection based on strong semantic information and feature fusion is proposed. First, the attention mechanism convolutional block attention module (CBAM) is constructed to highlight the important channel features and target spatial locations to further aggregate rich semantic information from the high-level feature map. Then the atrous spatial pyramid pooling module is constructed to repeatedly sample the multiscale feature maps to expand the receptive field of the neural network, reduce feature sparsity in the process of convolution, and ensure dense features and multiscale contextual semantic information enter the feature fusion module. Finally, the attention skip-connections are constructed based on the CBAM module for fusing the original feature maps extracted by the backbone network to the corresponding detection outputs so as to eliminate the redundant features as well as enrich the target information of the network outputs. In order to fully verify the performance of the proposed algorithm, a camouflage target detection dataset named strong camouflage efficiency target dataset (SCETD) is constructed. Experimental results on SCETD show that the precision and recall of the proposed algorithm achieve 96.1% and 87.1%, respectively. The AP0.5 and AP0.5 : 0.95 achieve 92.3% and 54.4%, respectively. The experimental results prove the effectiveness of the proposed method in detecting camouflage targets. [ABSTRACT FROM AUTHOR]

In high-resolution remote sensing images, the problems of large scale variation, large intra-class variance of background, small variability and irregularity of arrangement between different targets always exist in remote sensing images, making the modeling between targets and background more difficult and the target detection task more difficult. However, general target detection methods mainly use convolutional layers of different scales to enhance the target's perceptual domain and fuse different scale features to solve the scale variation problem, without considering the other two problems prevalent in remote sensing scenes of earth observation. In order to solve the above two problems, this paper proposes a semantic correction and focusing network (SCFNet) from the perspective of modeling the relationship between background and target and target to target. The network consists of two core modules the Local Correction Module (LCM) calculates the similarity of local features through the global features of the image to correct the local features and exclude the non-relevant The Non-local Focus Module (NLFM) enhances the recognition of target features by obtaining the non-local dependencies and the corrected local features from the LCM. To demonstrate the effectiveness and robustness of our proposed method, we conducted extensive experiments on two publicly popular large remote sensing multi-target detection datasets, namely DIOR and DOTA. the experimental results show that our SCFNet achieves best-in-class performance and significant accuracy improvement on the datasets. [ABSTRACT FROM AUTHOR]

Considering the relatively poor real-time performance when extracting transform-domain image features and the insufficiency of spatial domain features extraction, a no-reference remote sensing image quality assessment method based on gradient-weighted spatial natural scene statistics is proposed. A 36-dimensional image feature vector is constructed by extracting the local normalized luminance features and the gradient-weighted local binary pattern features of local normalized luminance map in three scales. First, a support vector machine classifier is obtained by learning the relationship between image features and distortion types. Then based on the support vector machine classifier, the support vector regression scorer is obtained by learning the relationship between image features and image quality scores. A series of comparative experiments were carried out in the optics remote sensing image database, the LIVE database, the LIVEMD database, and the TID2013 database, respectively. Experimental results show the high accuracy of distinguishing distortion types, the high consistency with subjective scores, and the high robustness of the method for remote sensing images. In addition, experiments also show the independence for the database and the relatively high operation efficiency of this method. © The Authors. Published by SPIE under a Creative Commons Attribution 4.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI. [DOI: 10.1117/1.JEI.28.1.013033] [ABSTRACT FROM AUTHOR]

To solve the problems of occlusion and fast motion of small targets in unmanned aerial vehicle target tracking, an adaptive algorithm that fuses the improved color histogram tracking response and the correlation filter tracking response based on multichannel histogram of oriented gradient features is proposed to realize small target tracking with high accuracy. The state judgment index is used to determine whether the target is in a fast motion or an occlusion state. In the fast motion state, the search area is enlarged, and the color optimal model that suppresses the suspected area is used for rough detection. Then, redetection in the location of multiple peaks in the rough detection response is carried out using the correlation filter to accurately locate the target. In an occlusion state, the model stops updating, the search area is expanded, and the current color model is used for rough detection. Then, redetection in the place of multiple peaks in the rough detection response is carried out using the correlation filter to accurately locate the target. Experimental results show that the proposed method can track small targets accurately. The frame rate of the proposed method is 40.23 frames/s, indicating usable real-time performance. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI. [DOI: 10 .1117/1.JEI.27.5.053010] [ABSTRACT FROM AUTHOR]

Peach stones (PS) modified by citric acid (MPS) were used to remove heavy metals and methylene blue (MB) from wastewater. The effects of experimental factors such as pH, adsorbent dosage and contact time, etc. were conducted. Moreover, the adsorption kinetics and isotherm studies also were investigated. According to the Langmuir isotherm model, the maximum adsorption capacities of Pb2+, Cd2+, Cu2+ and MB were 118.76, 37.48, 32.22 and 178.25 mg/g, respectively. Finally, column experiments were also carried out to investigate the adsorption of Pb2+ and MB. All results indicated that PS has a good potential for the treatment of wastewater. [ABSTRACT FROM AUTHOR]

Carbon dioxide (CO2) enhancement ( eCO2) and N addition ( aN) have been shown to increase net primary production (NPP) and to affect water-use efficiency (WUE) for many temperate ecosystems, but few studies have been made on subtropical tree species. This study compared the responses of NPP and WUE from a mesocosm composing five subtropical tree species to eCO2 (700 ppm), aN (10 g N m−2 yr−1) and eCO2 × aN using open-top chambers. Our results showed that mean annual ecosystem NPP did not changed significantly under eCO2, increased by 56% under aN and 64% under eCO2 × aN. Ecosystem WUE increased by 14%, 55%, and 61% under eCO2, aN and eCO2 × aN, respectively. We found that the observed responses of ecosystem WUE were largely driven by the responses of ecosystem NPP. Statistical analysis showed that there was no significant interactions between eCO2 and aN on ecosystem NPP ( P = 0.731) or WUE ( P = 0.442). Our results showed that increasing N deposition was likely to have much stronger effects on ecosystem NPP and WUE than increasing CO2 concentration for the subtropical forests. However, different tree species responded quite differently. aN significantly increased annual NPP of the fast-growing species ( Schima superba). Nitrogen-fixing species ( Ormosia pinnata) grew significantly faster only under eCO2 × aN. eCO2 had no effects on annual NPP of those two species but significantly increased annual NPP of other two species ( Castanopsis hystrix and Acmena acuminatissima). Differential responses of the NPP among different tree species to eCO2 and aN will likely have significant implications on the species composition of subtropical forests under future global change. [ABSTRACT FROM AUTHOR]

To investigate the effects of multiple environmental conditions on greenhouse gas ( CO2, N2O, CH4) fluxes, we transferred three soil monoliths from Masson pine forest ( PF) or coniferous and broadleaved mixed forest ( MF) at Jigongshan to corresponding forest type at Dinghushan. Greenhouse gas fluxes at the in situ (Jigongshan), transported and ambient (Dinghushan) soil monoliths were measured using static chambers. When the transported soil monoliths experienced the external environmental factors (temperature, precipitation and nitrogen deposition) at Dinghushan, its annual soil CO2 emissions were 54% in PF and 60% in MF higher than those from the respective in situ treatment. Annual soil N2O emissions were 45% in PF and 44% in MF higher than those from the respective in situ treatment. There were no significant differences in annual soil CO2 or N2O emissions between the transported and ambient treatments. However, annual CH4 uptake by the transported soil monoliths in PF or MF was not significantly different from that at the respective in situ treatment, and was significantly lower than that at the respective ambient treatment. Therefore, external environmental factors were the major drivers of soil CO2 and N2O emissions, while soil was the dominant controller of soil CH4 uptake. We further tested the results by developing simple empirical models using the observed fluxes of CO2 and N2O from the in situ treatment and found that the empirical models can explain about 90% for CO2 and 40% for N2O of the observed variations at the transported treatment. Results from this study suggest that the different responses of soil CO2, N2O, CH4 fluxes to changes in multiple environmental conditions need to be considered in global change study. [ABSTRACT FROM AUTHOR]

Highlights: [•] Subtropical and tropical forest showed different temporal variations in carbon fluxes. [•] Seasonal variation in NEE of tropical forest was driven by ER. [•] Seasonal variation in NEE of subtropical forest was driven by both GPP and ER. [•] Annual rainfall drives interannual variation in subtropical or tropical forest. [ABSTRACT FROM AUTHOR]

Abstract: Chemical concentrations and export rates from surface water were analyzed in Houzhai Karst Basin (HKB, area 80.65km2 in total), southwest China, for the past two decades from 1986 to 2007. Surface water chemistry was dominated by ions of calcium (Ca2+), magnesium (Mg2+), bicarbonate (HCO3 −) and sulfate (SO4 2−), which together made up 96% (by weight) of the total dissolved solids measured in this study. Seasonal variability of chemical export rates was positively correlated with surface runoff discharge, with the concentrations generally diluting at high discharge. From 1986 to 2007, as a result of the responses of karst weathering to climatic factors, the concentrations of Ca2+, Mg2+, HCO3 −, and SO4 2− slowly increased in surface water. By contrast, changes in the concentrations of sodium (Na+), potassium (K+), and chloride (Cl−) showed a slowly decreasing pattern. We also found that the annual dissolved inorganic carbon (DIC) flux ranged from 10.1 to 34.1gCm−2 yr−1, with an average value of 24.2gCm−2 yr−1. Rainfall had the most important influence on DIC flux, although water pH may greatly affect the proportions of the three fractions (CO2, HCO3 −, CO3 2−) of DIC. High water temperature in the wet season may reduce the solubility of CO2 in water and consequently affect DIC export rate, but this effect is much smaller than that of rainfall. Based on the chemical mass balance in surface water, our results indicate that high concentrations of SO4 2− by the large gypsum (CaSO4·2H2O) dissolution offset some anions such as HCO3 − in karst water, which can partly explain why carbon uptake is often overestimated by the empirical model using concentrations of HCO3 − in this karst water. It is concluded that the fluvial flux of DIC from karst water is important to the regional or national carbon budgets. [Copyright &y& Elsevier]

Abstract: This paper reports the results of soil respiration (SR, including heterotrophic and autotrophic respiration), in a presumably successional series (early, middle and advanced) of subtropical forests in Dinghushan Biosphere Reserve in Guangdong Province, China. A static chamber method was used to characterize SR in dynamics of diurnal and seasonal patterns. The relationships of SR with soil temperature (ST) at 5cm depth and with soil moisture (SM) at 0–10cm depth were studied in order to estimate the annual SR of each of the forests. The annual SR in a climax forest community, monsoon evergreen broad-leaved forest (MEBF) was estimated as 1163.0gCm−2 year−1 and in its successional communities, coniferous and broad-leaved mixed forest (MF) and the Masson pine forest (MPF) were 592.1gCm−2 year−1, 1023.7gCm−2 year−1, respectively. In addition, removal of surface litter led to the reduction of annual SR by 27–45% in those three forests. Analysis of the results indicated that the annual SR was highly correlated with both ST and SM. Furthermore, ST and SM themselves were highly correlated with each other across season in this study area. Thus for seasonal predictive SR model, either ST or SM could be integrated. However, for SR daily change prediction, both ST and SM were required because of confounding effects of ST and SM on a diurnal time scale. The Q 10 values of SR derived from ST dependence function were 2.37, 2.31 and 2.25 in the three forests: MPF, MF and MEBF, respectively, suggesting a decreasing trend of the Q 10 with the degree of forest succession. [Copyright &y& Elsevier]

Soil respiration (heterotropic and autotropic respiration, Rg) and aboveground litter fall carbon were measured at three forests at different succession (early, middle and advanced) stages in Dinghushan Biosphere Reserve, Southern China. It was found that the soil respiration increases exponentially with soil temperature at 5 cm depth ( Ts) according to the relation Rg= a exp( bTs), and the more advanced forest community during succession has a higher value of a because of higher litter carbon input than the forests at early or middle succession stages. It was also found that the monthly soil respiration is linearly correlated with the aboveground litter carbon input of the previous month. Using measurements of aboveground litter and soil respiration, the net primary productions (NPPs) of three forests were estimated using nonlinear inversion. They are 475, 678 and 1148 g C m−2 yr−1 for the Masson pine forest (MPF), coniferous and broad-leaf mixed forest (MF) and subtropical monsoon evergreen broad-leaf forest (MEBF), respectively, in year 2003/2004, of which 54%, 37% and 62% are belowground NPP for those three respective forests if no change in live plant biomass is assumed. After taking account of the decrease in live plant biomass, we estimated the NPP of the subtropical MEBF is 970 g C m−2 yr−1 in year 2003/2004. Total amount of carbon allocated below ground for plant roots is 388 g C m−2 yr−1 for the MPF, 504 g C m−2 yr−1 for the coniferous and broad-leaf MF and 1254 g C m−2 yr−1 for the subtropical MEBF in 2003/2004. Our results support the hypothesis that the amount of carbon allocation belowground increases during forest succession. [ABSTRACT FROM AUTHOR]

Several thymidine analogues substituted with closo- and nido-carborane at the N-3 position were synthesized. The nido-carboranyl thymidine analogues were designed to be effective substrates for human thymidine kinase 1 in combination with an increased water solubility sufficient for clinical application in boron neutron capture therapy. This was done because N-3 substituted closo-carboranyl thymidine analogues previously synthesized in our laboratories were good TK1 substrates but were poorly water-soluble. Newly synthesized zwitterionic amino nido- and the corresponding neutral closo-m-carboranyl thymidine analogues exhibited excellent TK1 phosphorylation rates up to 75% relative to thymidine, indicating that these compounds were good substrates for thymidine kinase 1. Thin layer chromatographic studies were indicative of increased hydrophilicity of the synthesized nido-carboranyl thymidine analogues compared with their closo-carboranyl counterparts and previously reported closo-carboranyl thymidine analogues. [Copyright &y& Elsevier]

Boron neutron capture therapy (BNCT) is a chemoradio-therapeutic method for the treatment of cancer. It depends on the selective targeting of tumor cells by boron-containing compounds. One category of BNCT agents with potential to selectively target tumor cells may be thymidine derivatives substituted at the 3′-position with appropriate boron moieties. Thus, several thymidine analogues were synthesized with a carborane cluster bound to the 3′-position either through an ether or a carbon linkage. The latter are the first reported carborane-containing nucleosides in which the carboranyl entity is directly linked to the carbohydrate portion of the nucleoside by a carbon–carbon bond. Low but significant phosphorylation rates in the range of 0.18% that of thymidine were observed for the carbon-linked 3′-carboranyl thymidine analogues in phosphoryl transfer assays using recombinant preparations of thymidine kinases 1 (TK1) and thymidine kinases 2 (TK2). Some of the ether-linked 3′-carboranyl thymidine analogues appeared to be slightly unstable under acidic as well as phosphoryl transfer assay conditions and were, if at all, poor substrates for TK1. [Copyright &y& Elsevier]

Fusing the pertinence of natural scene statistics-based methods and the ubiquity of convolutional neural network-based methods, a no-reference image quality assessment (IQA) method fusing deep learning and statistical visual features for no-reference image quality assessment (FDSVIQA) is proposed. For the statistical visual features, a local normalized luminance map and a local normalized local binary pattern (LBP) map of the image are constructed, and the local normalized luminance features and the gradient-weighted local normalized LBP features are extracted on the two maps, respectively. These two kinds of features are concatenated to build the image statistical visual features. For deep learning, the local normalized luminance block and the localized normalized LBP block are input into a double-path deep learning network, and the statistical visual features are input into the deep learning network to be integrated with the depth features. After learning and training, IQA is achieved. The performance of the proposed FDSVIQA algorithm is tested on the Laboratory for Image and Video Engineering (LIVE), LIVE Multiply Distorted Image Quality Database, and Multiply Distortion Optics Remote Sensing Image databases. Experimental results show that the FDSVIQA algorithm has excellent subjective and objective consistency and good robustness for both distorted natural images and distorted remote sensing images. In addition, the FDSVIQA has database independence. [ABSTRACT FROM AUTHOR]

Interspecific variations in phenotypic plasticity of trees that are affected by climate change may alter the ecosystem function of forests. Seedlings of four common tree species (Castanopsis fissa , Michelia macclurei , Dalbergia odorifera and Ormosia pinnata) in subtropical plantations of southern China were grown in the field under rainout shelters and subjected to changing precipitation (48 L of water every 4 days in the dry season, 83 L of water every 1 day in the wet season; 4 g m−2 year−1 of nitrogen (N)), low N deposition (48 L of water every 2 days in the dry season, 71 L of water every 1 day in the wet season; 8 g m−2 year−1 N), high N deposition (48 L of water every 2 days in the dry season, 71 L of water every 1 day in the wet season; 10 g m−2 year−1 N) and their interactive effects. We found that the changes in seasonal precipitation reduced the light-saturated photosynthetic rate (A sat) for C. fissa due to declining area-based foliar N concentrations (Na). However, we also found that the interactive effects of changing precipitation and N deposition enhanced A sat for C. fissa by increasing foliar Na concentrations, suggesting that N deposition could alleviate N limitations associated with changing precipitation. Altered precipitation and high N deposition reduced A sat for D. odorifera by decreasing the maximum electron transport rate for RuBP regeneration (J max) and maximum rate of carboxylation of Rubisco (V cmax). Ormosia pinnata under high N deposition exhibited increasing A sat due to higher stomatal conductance and V cmax. The growth of D. odorifera might be inhibited by changes in seasonal precipitation and N deposition, while O. pinnata may benefit from increasing N deposition in future climates. Our study provides an important insight into the selection of tree species with high capacity to tolerate changing precipitation and N deposition in subtropical plantations. [ABSTRACT FROM AUTHOR]

Tropical and subtropical forests play a crucial role in global carbon (C) pools, and their responses to warming can significantly impact C‐climate feedback and predictions of future global warming. Despite earth system models projecting reductions in land C storage with warming, the magnitude of this response varies greatly between models, particularly in tropical and subtropical regions. Here, we conducted a field ecosystem‐level warming experiment in a subtropical forest in southern China, by translocating mesocosms (ecosystem composed of soils and plants) across 600 m elevation gradients with temperature gradients of 2.1°C (moderate warming), to explore the response of ecosystem C dynamics of the subtropical forest to continuous 6‐year warming. Compared with the control, the ecosystem C stock decreased by 3.8% under the first year of 2.1°C warming; but increased by 13.4% by the sixth year of 2.1°C warming. The increased ecosystem C stock by the sixth year of warming was mainly attributed to a combination of sustained increased plant C stock due to the maintenance of a high plant growth rate and unchanged soil C stock. The unchanged soil C stock was driven by compensating and offsetting thermal adaptation of soil microorganisms (unresponsive soil respiration and enzyme activity, and more stable microbial community), increased plant C input, and inhibitory C loss (decreased C leaching and inhibited temperature sensitivity of soil respiration) from soil drying. These results suggest that the humid subtropical forest C pool would not necessarily diminish consistently under future long‐term warming. We highlight that differential and asynchronous responses of plant and soil C processes over relatively long‐term periods should be considered when predicting the effects of climate warming on ecosystem C dynamics of subtropical forests. [ABSTRACT FROM AUTHOR]

Nitrogen (N) deposition usually increases plant tissue N concentrations and thus phosphorus (P) demand in young and/or N‐limited forests, but the N deposition effect on plant P demand has rarely been assessed in N‐saturated forests.Impacts of 18‐year external N additions (Control: 0, Low N: 50, Moderate N:100 and High N: 150 kg N ha−1 year−1) on leaf P of four plant life‐forms (tree, shrub, herb and liana), P fractions of bulk and rhizosphere soils were examined in a N‐saturated mature tropical forest in southern China.Leaf N, P and N: P ratios of all plant life‐forms remained stable under three N additions. Among soil P fractions, moderate labile organic P increased by 25%–33% across three N additions; and soil total P was increased by 11.76% under Low N, and 8.87% under High N, compared with the control. The PLS‐PM results showed that path coefficient of microbial community to available P significantly increased and of inorganic P to available P significantly decreased under N additions than control. N additions improved soil P availability through microbe‐mediated P transformation: Low N significantly increased soil microbial taxonomic diversity, and a higher microbial diversity could enlarge the sources of nutrient acquisition and stimulate decomposition of recalcitrant organic matters; while High N significantly decreased soil microbial taxonomic diversity, the remaining microorganisms that were screened by N‐rich environments had the characteristics of resisting the N addition effects and maintained efficient P acquisition.Synthesis. Our findings provide a novel line of evidence that long‐term N deposition did not increase plant P demand in a N‐saturated mature tropical forest. The underlying mechanism is that plants did not increase N uptakes therefore nor increase P uptakes (a stable leaf N: P stoichiometry) in an already N‐saturated ecosystem. Different N addition rates regulated soil P transformation via microbial community transition. These findings help improve the understanding of plant P acquisition and modelling of biogeochemical N–P cycling and vegetation productivity in N‐rich forest ecosystems, particularly considering the fact that chronic N deposition may likely lead to soil N richness and even saturation of many forests in the future. [ABSTRACT FROM AUTHOR]

Competition for light has traditionally been considered as the main mechanism for exclusion of Pinus massoniana during succession in subtropical forest ecosystems. However, both long-term inventories and a seedling cultivation experiment showed that growth of mature individuals and young seedlings of P. massoniana was not limited by available light, but was strongly influenced by stoichiometric homoeostasis. This is supported by the results of homoeostatic regulation coefficients for nitrogen (HN) and phosphorus (HP) estimated using the measured data from six transitional forests across subtropical China. Among three dominant tree species in subtropical forests, P. massoniana and Castanopsis chinensis had the lowest values of HP and HN, respectively. Therefore P. massoniana cannot survive in the advanced stage due to soil phosphorus limitation and C. chinensis cannot successfully grow in the pioneer stage due to soil nitrogen limitation. Our results support that stoichiometric homeostasis is the main reason for gradual exclusion of P. massoniana from the transitional forest and the eventual elimination from the advanced forest during the subtropical forest succession. Therefore greater attention should be paid to stoichiometric homeostasis as one of the key mechanisms for species exclusion during forest succession. [ABSTRACT FROM AUTHOR]

Climate change globally affects soil microbial community assembly across ecosystems. However, little is known about the impact of warming on the structure of soil microbial communities or underlying mechanisms that shape microbial community composition in subtropical forest ecosystems. To address this gap, we utilized natural variation in temperature via an altitudinal gradient to simulate ecosystem warming. After 6 years, microbial co‐occurrence network complexity increased with warming, and changes in their taxonomic composition were asynchronous, likely due to contrasting community assembly processes. We found that while stochastic processes were drivers of bacterial community composition, warming led to a shift from stochastic to deterministic drivers in dry season. Structural equation modelling highlighted that soil temperature and water content positively influenced soil microbial communities during dry season and negatively during wet season. These results facilitate our understanding of the response of soil microbial communities to climate warming and may improve predictions of ecosystem function of soil microbes in subtropical forests. [ABSTRACT FROM AUTHOR]

The Chinese mugwort (Artemisia argyi Lév. et Vaniot) is an important traditional Chinese medicine plant that is ubiquitously disturbed in Asia. However, the molecular mechanisms that reflect the natural evolution of Artemisia argyi remain unclear. In this study, a high-quality draft assembly of the allotetraploid A. argyi (ArteW1-Tongbai) was conducted utilizing PacBio long-read sequencing and Hi-C technologies. The assembly is about 7.20 Gb with a contig N50 length of 0.87 Mb. The allotetraploid genome of ArteW1-Tongbai is highly heterozygous and rich in repeat sequences (the heterozygous ratio is 1.36%, and the repeat rate is 86.26%). A total of 139,245 protein-coding genes were identified. The KEGG enrichment analysis revealed that 846 species-specific genes were related to the biosynthesis of secondary metabolites. The plants with allopolyploid genomes can potentially exhibit a better adaptive capacity to environmental stresses and accumulation of secondary metabolites. Therefore, the genome assembly serves as a valuable reference for Artemisia, the genus characterized by species richness and diverse specialized metabolites. [ABSTRACT FROM AUTHOR]

In cognitive radio (CR) network, to improve spectrum sensing performance to primary user (PU) and decrease energy wastage of secondary user (SU) in cooperative spectrum sensing, an energy harvesting-based weighed cooperative spectrum sensing is proposed in this paper. The SU harvests the radio frequency (RF) energy of the PU signal and then converts the RF energy into the electric energy to supply the power used for energy detection and cooperation. The time switching model and power splitting model are developed to realize the notion. In the time switching model, the SU performs either spectrum sensing or energy harvesting at any time, while in the power splitting model, the received PU signal is split into two signal streams, one for spectrum sensing and the other one for energy harvesting. A joint optimization problem is formulated to maximize the spectrum access probability of the SU by jointly optimizing sensing time, number of cooperative SUs and splitting factor. The simulation results have shown that compared to the traditional cooperative spectrum sensing, the proposed energy harvesting-based weighed cooperative spectrum sensing can decrease the energy wastage obviously while guaranteeing the maximum spectrum access probability. [ABSTRACT FROM AUTHOR]

Phosphorus (P) is often one of the most limiting nutrients in highly weathered soils of humid tropical forests and may regulate the responses of carbon (C) feedback to climate warming. However, the response of P to warming at the ecosystem level in tropical forests is not well understood because previous studies have not comprehensively assessed changes in multiple P processes associated with warming. Here, we detected changes in the ecosystem P cycle in response to a 7‐year continuous warming experiment by translocating model plant‐soil ecosystems across a 600‐m elevation gradient, equivalent to a temperature change of 2.1°C. We found that warming increased plant P content (55.4%) and decreased foliar N:P. Increased plant P content was supplied by multiple processes, including enhanced plant P resorption (9.7%), soil P mineralization (15.5% decrease in moderately available organic P), and dissolution (6.8% decrease in iron‐bound inorganic P), without changing litter P mineralization and leachate P. These findings suggest that warming sustained plant P demand by increasing the biological and geochemical controls of the plant‐soil P‐cycle, which has important implications for C fixation in P‐deficient and highly productive tropical forests in future warmer climates. [ABSTRACT FROM AUTHOR]

Soil phosphorus (P) availability often limits plant productivity. Classical theories suggest that total P content declines at the temporal scale of pedogenesis, and ecosystems develop toward the efficient use of scarce P during succession. However, the trajectory of ecosystem P within shorter time scales of succession remains unclear. We analyzed changes to P pools at the early (I), middle (II), and late (III) stages of growth of plantation forests (PFs) and the successional stages of natural forests (NFs) at 1969 sites in China. We found significantly lower P contents at later growth stages compared to earlier ones in the PF (p <.05), but higher contents at late successional stages than in earlier stages in the NF (p <.05). Our results indicate that increasing P demand of natural vegetation during succession, may raise, retain, and accumulate P from deeper soil layers. In contrast, ecosystem P in PF was depleted by the more rapidly increasing demand outpacing the development of a P‐efficient system. We advocate for more studies to illuminate the mechanisms for determining the divergent changes, which would improve forest management and avoid the vast degradation of PF ecosystems suffering from the ongoing depletion of P. [ABSTRACT FROM AUTHOR]

Background and aims: As a significant land carbon sink, highly acid subtropical forests in southern China continued to accumulate a significant amount of soil carbon under elevated acid deposition, yet the mechanism of how soil organic carbon (SOC) and its two components: particulate (POC) and mineral-associated (MAOC) organic carbon increased remain unclear. We aim to assess which mechanism and drivers dominated the accumulation of SOC and its two fractions under elevated acid deposition.We conducted a 11-year field acid addition experiment to study how acid deposition affected the accumulation of SOC and its fractions. Lignin phenols and amino sugars were used as two tracers for plant- and microbe-derived carbon.We found that both POC (0–20 cm) and MAOC (10–20 cm) were significantly increased by acid addition. Acid addition significantly reduced the contributions of fungal-, bacterial- or total microbial residue carbon to SOC but significantly increased the plant-derived soil carbon in both soil depths. The increase of lignin phenol and suppressed soil organic matter decomposition from soil microbes suggested that soil POC increased with acid addition. Soil acidification strongly enhanced MAOC accumulation through increased lignin and mineral protection by iron-aluminum oxides and cations.Our results showed that increased mineral protection of plant-derived carbon was the dominant driver of the increased SOC sequestration under acid addition. This finding identified the dominant pathway for SOC accumulation in a highly acidic subtropical forest and provides new insights into understanding how plant-soil-mineral interact under increasing acid deposition in the region.Methods: As a significant land carbon sink, highly acid subtropical forests in southern China continued to accumulate a significant amount of soil carbon under elevated acid deposition, yet the mechanism of how soil organic carbon (SOC) and its two components: particulate (POC) and mineral-associated (MAOC) organic carbon increased remain unclear. We aim to assess which mechanism and drivers dominated the accumulation of SOC and its two fractions under elevated acid deposition.We conducted a 11-year field acid addition experiment to study how acid deposition affected the accumulation of SOC and its fractions. Lignin phenols and amino sugars were used as two tracers for plant- and microbe-derived carbon.We found that both POC (0–20 cm) and MAOC (10–20 cm) were significantly increased by acid addition. Acid addition significantly reduced the contributions of fungal-, bacterial- or total microbial residue carbon to SOC but significantly increased the plant-derived soil carbon in both soil depths. The increase of lignin phenol and suppressed soil organic matter decomposition from soil microbes suggested that soil POC increased with acid addition. Soil acidification strongly enhanced MAOC accumulation through increased lignin and mineral protection by iron-aluminum oxides and cations.Our results showed that increased mineral protection of plant-derived carbon was the dominant driver of the increased SOC sequestration under acid addition. This finding identified the dominant pathway for SOC accumulation in a highly acidic subtropical forest and provides new insights into understanding how plant-soil-mineral interact under increasing acid deposition in the region.Results: As a significant land carbon sink, highly acid subtropical forests in southern China continued to accumulate a significant amount of soil carbon under elevated acid deposition, yet the mechanism of how soil organic carbon (SOC) and its two components: particulate (POC) and mineral-associated (MAOC) organic carbon increased remain unclear. We aim to assess which mechanism and drivers dominated the accumulation of SOC and its two fractions under elevated acid deposition.We conducted a 11-year field acid addition experiment to study how acid deposition affected the accumulation of SOC and its fractions. Lignin phenols and amino sugars were used as two tracers for plant- and microbe-derived carbon.We found that both POC (0–20 cm) and MAOC (10–20 cm) were significantly increased by acid addition. Acid addition significantly reduced the contributions of fungal-, bacterial- or total microbial residue carbon to SOC but significantly increased the plant-derived soil carbon in both soil depths. The increase of lignin phenol and suppressed soil organic matter decomposition from soil microbes suggested that soil POC increased with acid addition. Soil acidification strongly enhanced MAOC accumulation through increased lignin and mineral protection by iron-aluminum oxides and cations.Our results showed that increased mineral protection of plant-derived carbon was the dominant driver of the increased SOC sequestration under acid addition. This finding identified the dominant pathway for SOC accumulation in a highly acidic subtropical forest and provides new insights into understanding how plant-soil-mineral interact under increasing acid deposition in the region.Conclusion: As a significant land carbon sink, highly acid subtropical forests in southern China continued to accumulate a significant amount of soil carbon under elevated acid deposition, yet the mechanism of how soil organic carbon (SOC) and its two components: particulate (POC) and mineral-associated (MAOC) organic carbon increased remain unclear. We aim to assess which mechanism and drivers dominated the accumulation of SOC and its two fractions under elevated acid deposition.We conducted a 11-year field acid addition experiment to study how acid deposition affected the accumulation of SOC and its fractions. Lignin phenols and amino sugars were used as two tracers for plant- and microbe-derived carbon.We found that both POC (0–20 cm) and MAOC (10–20 cm) were significantly increased by acid addition. Acid addition significantly reduced the contributions of fungal-, bacterial- or total microbial residue carbon to SOC but significantly increased the plant-derived soil carbon in both soil depths. The increase of lignin phenol and suppressed soil organic matter decomposition from soil microbes suggested that soil POC increased with acid addition. Soil acidification strongly enhanced MAOC accumulation through increased lignin and mineral protection by iron-aluminum oxides and cations.Our results showed that increased mineral protection of plant-derived carbon was the dominant driver of the increased SOC sequestration under acid addition. This finding identified the dominant pathway for SOC accumulation in a highly acidic subtropical forest and provides new insights into understanding how plant-soil-mineral interact under increasing acid deposition in the region. [ABSTRACT FROM AUTHOR]

Summary: Elucidating the effects of atmospheric nitrogen (N) deposition on fine root dynamics and the potential underlying mechanisms is required to understand the changes in belowground and aboveground carbon storage. However, research on these effects in forests has mostly involved direct understory addition of N and has ignored canopy interception and processing of N.Here, we conducted a field experiment comparing the effects of canopy addition of N (CAN) with those of understory addition of N (UAN) at three N‐addition rates (0, 25 and 50 kg N ha–1 yr–1) on fine root dynamics in a temperate deciduous forest.Fine root production and biomass were significantly higher with CAN than with UAN. At the same N‐addition rate, increases in fine root production with CAN were at least two‐fold greater than with UAN. At the high N‐addition rate and relative to the control, fine root biomass was significantly increased by CAN (by 23.5%) but was significantly decreased by UAN (by 12.2%).Our results indicate that traditional UAN may underestimate the responses of fine root dynamics to atmospheric N deposition in forest ecosystems. Canopy N processes should be considered for more realistic assessments of the effects of atmospheric N deposition in forests. [ABSTRACT FROM AUTHOR]

The present paper reports a novel adsorbent that is synthesized with chitosan and zirconium ions through a simple method, for the removal of Cr (VI) ions from solutions. In this study, the effects of solution pH, absorbent dosage, contact time, and initial concentration were evaluated through a series of experiments. The modified chitosan was also characterized by SEM-EDS, FTIR, TG, and XPS. It is found that the Cr (VI) adsorption capacity by Zr-CS of 230.41 mg/g, was achieved at pH 4.5. The adsorption results indicated that the adsorption process was in line with Langmuir isotherm at 25°C. At the same time, the kinetic studies indicated that the adsorption process followed a pseudo-second-order model. Therefore, Zr-CS is a very promising adsorbent for the treatment of chromium-containing wastewater. XPS and element spectrum images, however, showed the difference between the adsorbent before and after Cr (VI) adsorption. According to the data, the adsorption should include electrostatic interaction between protonated amino and Cr (VI) as well as complexation of Zr with Cr (VI). According to the experimental data, it is believed that zirconium-modified chitosan adsorbent is an effective adsorbent for removing chromium ions in the solution. [ABSTRACT FROM AUTHOR]

The relationship between the kinetic energy of waterdrops (rainfall and throughfall) and sediment yield (suspended solid (SS) and bed load (BL)) was studied in paired watersheds (one without vegetation and the other covered by an eucalyptus (Eucalyptus exserta) plantation) in Guangdong Province, Southern China. The results showed that there was a significant correlation between the kinetic energy of waterdrops and sediment yield in both watersheds. Sediment yield in the unvegetated watershed is significantly affected by the kinetic energy of atmospheric raindrops. Sediment yield in the plantation watershed, however, is significantly related to the kinetic energy of throughfall waterdrops, but not to the atmospheric rainfall intensity or the rainfall kinetic energy. When rainfall amount is greater than 5 mm, and their intensities are less than 20 mm h−1, the single-layer eucalyptus plantations significantly increased the kinetic energy of waterdrops to the land surface, and consequently, accelerated soil erosion. However, these plantations do have positive impacts on the reduction of soil erosion for the rainfall events of larger intensities (particularly >40 mm h−). Management implications of these results are discussed in the context of soil protection xxxxxxxxand ecosystem rehabilitation. [Copyright &y& Elsevier]

Warming may have profound effects on nitrogen (N) cycling by changing plant N demand and underground N supply. However, large uncertainty exists regarding how warming affects the integrated N dynamic in tropical forests. We translocated model plant‐soil ecosystems from a high‐altitude site (600 m) to low‐altitude sites at 300 and 30 m to simulate warming by 1.0°C and 2.1°C, respectively, in tropical China. The effects of experimental warming on N components in plant, soil, leaching, and gas were studied over 6 years. Our results showed that foliar δ15N values and inorganic N (NH4‐N and NO3‐N) leaching were decreased under warming, with greater decreases under 2.1°C of warming than under 1.0°C of warming. The 2.1°C of warming enhanced plant growth, plant N uptake, N resorption, and fine root biomass, suggesting higher plant N demand. Soil total N concentrations, NO3‐N concentrations, microbial biomass N and arbuscular mycorrhizal fungal abundance were decreased under 2.1°C of warming, which probably restricted bioavailable N supply and arbuscular mycorrhizal contribution of N supply to plants. These changes in plants, soils and leaching indicated more closed N cycling under warming, the magnitude of which varied over time. The closed N cycling became pronounced during the first 3 years of warming where the sustained reductions in soil inorganic N could not meet plant N demand. Subsequently, the closed N cycling gradually mitigated, as observed by attenuated positive responses of plant growth and less negative responses of microbial biomass N to warming during the last 3 years. Overall, the more closed N cycling under warming could facilitate ecosystem N retention and affect production in these tropical forests, but these effects would be eventually mitigated with long‐term warming probably due to the restricted plant growth and microbial acclimation. [ABSTRACT FROM AUTHOR]

• Reco in summer and autumn largely depends on the substrate availability. • Reco in spring and winter is limited by soil temperature and moisture. • Enhanced GEP was not sufficient to compensate for increased Reco during winter. • Larger GEP ratios in autumn and winter means more days at high photosynthetic rate. • Higher NEP accumulated in cold and dry seasons than those in warm and wet seasons. Precipitation and energy are vital factors profoundly affecting carbon and water fluxes in subtropical forest ecosystems. However, knowledge of the seasonality of ecosystem productivity and water fluxes and their dominant controlling factors remains understudied. Based on 12 years (2003–2014) of eddy-covariance measurements, we examined how the seasonal carbon flux components and evapotranspiration respond to climatic variability in a subtropical forest ecosystem. Our results showed that both the magnitude and the percentage of gross ecosystem productivity (GEP) and ecosystem respiration (Reco) in winter increased. The enhanced GEP during winter and dampened Reco in summer and autumn were not sufficient to compensate for the decreased GEP in spring, summer and autumn, and simultaneously increased Reco in spring and winter. Thus, net ecosystem productivity (NEP) slightly diminished during the study period, and the majority of annual net carbon gains occurred in winter and spring with high water use efficiency. In addition, solar radiation predominantly contributed to GEP in spring and winter, while soil moisture is the main contributor in summer. ET greatly determined the GEP in autumn due to both were well-coupled. The vapor pressure deficit (VPD) was a major driver of Reco in summer and autumn inferred that Reco largely depends on substrate availability. However, Reco was mainly attributed to the soil environmental conditions (moisture and temperature) in spring and winter. Our results highlighted that the different extents and asynchronous responses of ecosystem carbon assimilation and respiration to altered energy and moisture availability determined the seasonal patterns of carbon and water fluxes, thus having important implications for assessing or projecting subtropical forest ecosystem responses to current climate change. [ABSTRACT FROM AUTHOR]

• Translocating tree species from a cooler high-elevation site to warmer low-elevation sites; • The growth of arbuscular mycorrhizal trees would benefit from translocation treatment; • Ectomycorrhizal trees were more tolerant of soil water deficit. Arbuscular mycorrhizal (AM) and ectomycorrhizal (EcM) trees are commonly represented in tropical forests, but their response to warming is generally not known. We conducted a long-term (9-year) field experiment in subtropical China by translocating AM tree species (Machilus breviflora and Schima superba) and EcM tree species (Syzygium rehderianum and Castanopsis hystrix) from a cooler high-elevation site (300 m) to a 1 °C warmer low-elevation site (30 m). Here, we report leaf chemical and physiological data from the last three years (Years 7–9) of the translocation experiment. Translocation to warmer site induced higher air (T air) and soil (T soil) temperatures, but lower soil volumetric water content (SVWC). Translocation treatment significantly increased the light-saturated photosynthetic rate (A sat) for AM trees due to higher stomatal conductance (g s) and Rubisco carboxylation capacity (V cmax), generating increased growth in AM trees. Translocation treatment reduced the maximum efficiency of photosynthetic quantum yield (F v /F m) and growth in EcM trees. Translocation treatment increased leaf turgor loss point (TLP) in AM trees, but reduced TLP in EcM trees. Translocation treatment increased foliar nitrogen (N) concentrations and phosphorus (P) concentrations for AM trees. In EcM trees, stable foliar N and P concentrations were related to higher N and P resorption efficiencies. Translocation treatment was more beneficial for the growth of AM trees than EcM trees, while EcM trees were more tolerant of soil water deficit. Differential responses to these co-occurring climate drivers may alter the composition of tree functional groups and ecosystem function in tropical forests in response to future warmer and drier climate conditions. [ABSTRACT FROM AUTHOR]

Intensification of the Earth's hydrological cycle amplifies the interannual variability of precipitation, which will significantly impact the terrestrial carbon (C) cycle. However, it is still unknown whether previously observed relationship between soil respiration (Rs) and precipitation remains applicable under extreme precipitation change. By analyzing the observations from a much larger dataset of field experiments (248 published papers including 151 grassland studies and 97 forest studies) across a wider range of precipitation manipulation than previous studies, we found that the relationship of Rs response with precipitation change was highly nonlinear or asymmetric, and differed significantly between grasslands and forests, between moderate and extreme precipitation changes. Response of Rs to precipitation change was negatively asymmetric (concave‐down) in grasslands, and double‐asymmetric in forests with a positive asymmetry (concave‐up) under moderate precipitation changes and a negative asymmetry (concave‐down) under extreme precipitation changes. In grasslands, the negative asymmetry in Rs response was attributed to the higher sensitivities of soil moisture, microbial and root activities to decreased precipitation (DPPT) than to increased precipitation (IPPT). In forests, the positive asymmetry was predominantly driven by the significant increase in microbial respiration under moderate IPPT, while the negative asymmetry was caused by the reductions in root biomass and respiration under extreme DPPT. The different asymmetric responses of Rs between grasslands and forests will greatly improve our ability to forecast the C cycle consequences of increased precipitation variability. Specifically, the negative asymmetry of Rs response under extreme precipitation change suggests that the soil C efflux will decrease across grasslands and forests under future precipitation regime with more wet and dry extremes. [ABSTRACT FROM AUTHOR]

Selecting suitable species for vegetation restoration presents a notable challenge for land managers and scientists. Recently developed trait‐based approaches may be an effective means of overcoming this challenge. However, we lack a trait‐based species screening model that can be used to select potential species for restoration of degraded ecosystems.Here, we developed a species screening model based on quantitative trait‐based theory and a maximum entropy algorithm. The objective was to select more species that have comparable restoration abilities to the target species that have high survival rates for vegetation restoration based on species' functional traits. Thus, species diversity will be improved to facilitate restoration. We also developed a software platform that can be used to implement the model. We then applied our model and software platform to select species for restoration efforts in a tropical coral island which is part of Hainan Island, China.As a prerequisite, we started with three target species which have high potential for restoring the island. Likewise, 66 non‐native species were selected as the potential species pool. For each species, we identified and measured 28 traits that are strongly associated with harsh environments. Harsh environments are those with drought stress, high temperatures, intensive UV radiation, lack of real soil and nutrients, and high salinity and alkalinity. Then, our software platform was used to run the species selection model. Finally, 12 out of 66 species being identified as suitable species for restoration.We transplanted seedlings of all 66 species to the island to monitor seedlings survival. We found that the 12 species identified from our model had high survival rates, which ranged from 86% to 91%. In contrast, the mean survival rate for species not identified from our model was less than 40%. These results suggest that our species screening procedure was appropriate for selecting candidate species for use in vegetation restoration.We show that by using species natural history information, as well as functional trait data, candidate species for restoration efforts can be successfully identified in a timely manner. Importantly, our proposed method is faster and less costly than more commonly used 'trial‐and‐error' method. The most time‐consuming aspect of our approach is the need to measure the functional traits of target and potential species. Ultimately, we provide a protocol for using functional traits to quickly select a large number of suitable species for restoring degraded ecosystems. We expect that this work will be important for future vegetation restoration efforts in tropical islands, and perhaps other ecosystems as well. We also expect that our model will help prevent the invasive species and promote specific ecosystem functions. A free Plain Language Summary can be found within the Supporting Information of this article. [ABSTRACT FROM AUTHOR]

The potential of modified peach stone for Cr (VI) removal from wastewater was explored in this work. The properties of the materials were characterized by SEM, TGA, FT-IR, EDX and elemental analysis. It was found that 3 g/L EPS was good enough for removal of Cr (VI) in feed solution, with the maximum adsorption capacity was 24.68 mg/g. The pseudo-second-order kinetic model and Langmuir adsorption model was well fitted with adsorption data. In addition, EPS could be reused for sustainable operation for a number of cycles. All results confirm that EPS has potential for the removal of Cr (VI). [ABSTRACT FROM AUTHOR]

Asymbiotic nitrogen (N) fixation (ANF) is an important source of N in pristine forests and is predicted to decrease with N deposition. Previous studies revealing N fixation in response to N deposition have mostly applied understory N addition approaches, neglecting the key processes (for example, N retention and uptake) occurring in forest canopy. This study evaluated the effects of N deposition on N fixation in the soil, forest floor, mosses, and canopy leaves in a temperate forest (in central China) and a tropical forest (in southern China) with different treatments: control, understory N addition, and canopy N addition. Results showed that total ANF rates were higher in the temperate forest (2.57 ± 0.19 mg N m−2 d−1) than in the tropical forest (1.34 ± 0.09 mg N m−2 d−1). N addition inhibited the soil, forest floor, moss, and foliar N fixation in the temperate forest, whereas it inhibited only the soil N fixation in the tropical forest. Compared to canopy N addition, understory N addition overestimated the inhibitory effects of N deposition on total ANF slightly in the tropical forest (by 35%) but severely in the temperate forest (by 375–472%) due to neglecting canopy retention of N. In summary, our findings indicate that ANF has different rates and sensitivities to N addition between tropical and temperate forests and that understory N addition overestimates the N deposition effects on ANF in forests, particularly in the temperate forest. These findings are important for our accurate understanding and estimate of terrestrial N fixation under N deposition scenarios. [ABSTRACT FROM AUTHOR]

Nitrogen (N) addition drives ecosystems toward phosphorus (P) limitation has gained increasing recognition, whereas how P addition affects ecosystem N-cycling processes remains elusive. We performed a meta-analysis of 1826 observational data from 222 independent studies to evaluate the responses of plant N pools, soil N pools, and N fluxes to P addition at the global scale. The results suggested that P addition had an overall positive effect on plant N uptake and ecosystem N retention, which were mainly reflected in increases of plant N pools (i.e., aboveground/belowground biomass and belowground biomass-N) and microbial N transformation (i.e., net N mineralization and nitrification), and decrease of soil N leaching (i.e., nitrate-N and total dissolved N). The contribution of microbial processes to plant N uptake was greater in the mid−/high-latitude ecosystems (≥30°) than in the low-latitude ecosystems (<30°), and the sensitivities of most N-cycling variables to P addition were stronger in the most/moderately acidic soils (pH < 6.5) or strongly/intermediately weathered soils than in the neutral/alkaline soils or slightly weathered soils. Our meta-analysis highlighted the key role of soil microbes in promoting plant N uptake, and identified several important soil properties (i.e., soil N status, initial pH, and weathering degree) regulating the N-cycling responses to P addition and should be incorporated into the nutrient-cycling models of terrestrial ecosystems. • Phosphorus addition enhances nitrogen retention in ecosystems. • Microbial nitrogen transformation is stimulated by phosphorus addition. • Soil nitrogen status regulates the nitrogen-cycling response to phosphorus addition. [ABSTRACT FROM AUTHOR]

Soil organic carbon (SOC) plays critical roles in stabilizing atmospheric CO2 concentration, but the mechanistic controls on the amount and distribution of SOC on global scales are not well understood. In turn, this has hampered the ability to model global C budgets and to find measures to mitigate climate change. Here, based on the data from a large field survey campaign with 2600 plots across China's forest ecosystems and a global collection of published data from forested land, we find that a low litter carbon-to-nitrogen ratio (C/N) and high wetness index (P/PET, precipitation-to-potential-evapotranspiration ratio) are the two factors that promote SOC accumulation, with only minor contributions of litter quantity and soil texture. The field survey data demonstrated that high plant diversity decreased litter C/N and thus indirectly promoted SOC accumulation by increasing the litter quality. We conclude that any changes in plant-community composition, plant-species richness and environmental factors that can reduce the litter C/N ratio, or climatic changes that increase wetness index, may promote SOC accumulation. The study provides a guideline for modeling the carbon cycle of various ecosystem scales and formulates the principle for land-based actions for mitigating the rising atmospheric CO2 concentration. [ABSTRACT FROM AUTHOR]

Aims: Co-limitation of ecosystem productivity by nitrogen (N) and phosphorus (P) is gaining increasing recognition, but how co-limitation through N and P interactions differs among different terrestrial ecosystems remains unclear. Methods: We performed a meta-analysis of 133 independent studies conducted in four natural terrestrial ecosystems to examine the interactive effects of N and P additions on ten plant growth-related variables. Results: Adding N and P individually or in combination significantly increased aboveground biomass (AGB), and the interactions were uniformly synergistic for AGB, and additive for belowground biomass (BGB), but variable for other eight growth-related variables among four different ecosystems. The interaction was synergistic for leaf P and soil NO3-N only in tropical forests, and antagonistic for soil available P (AP) in tropical forests, leaf N in grasslands, root P in wetlands, and leaf P and soil NH4-N in tundra. The interaction for leaf N: P ratios was additive only in tropical forests, and synergistic in the other three ecosystems. Conclusions: Our results highlighted the interactions of N and P additions can promote uptake of both nutrients by plants, and plants tend to maintain the optimal nutrient balance for growth and reproduction through regulating biomass production and tissue nutrient concentrations. [ABSTRACT FROM AUTHOR]

Hand, foot and mouth disease (HFMD) is an infectious disease caused by a variety of enterovirus infections, and the most common types of virus infections are the newenterovirus71 (EV71) and coxsackievirus A group 16 (CoxA16). A small fraction of HFMD will cause further severe HFMD. A rapid and accurate diagnosis biomarker of severe HFMD is important for the timely treatment. In the study, we conducted a clinical biomarker discovery study using iTRAQ combined with MS. Serum proteome alterations in severe HFMD group (n = 32) and health control group (n = 32) were analyzed. 47 proteins were upregulated (fold change > 1.5) between the severe HFMD group and HC group. The identified proteins were classified into different groups according to the molecular function, biology processes, cellular component. During the up-regulated proteins, serum amyloid A (SAA) and human β-actin (ACTB), were confirmed in the serum of the severe HFMD and HC by ELISA assay. SAA and ACTB levels were significantly higher in the sever HFMD patients (P <.01), consistent with iTRAQ-LC-MS/MS analysis. In summary, Our results showed that SAA and human β-actin (ACTB) may be served as a potential biomarker of the clinical diagnosis of severe HFMD. [ABSTRACT FROM AUTHOR]

Plant stoichiometry is critical for the structure and functions of ecosystems. Previous studies on large-scale patterns of plant stoichiometry have focused on single tissues; and the controlling factors have focused on climatic factors or plant functional groups. Here we present results based on an intensive field investigation across China's forest ecosystems, to comprehensively assess the effect of climatic factors, plant functional groups, soil N and P stoichiometry on N and P stoichiometry of different tree tissues. The P concentrations in all tissues were significantly lower when mean annual temperature (MAT) and mean annual precipitation (MAP) were higher, and the N:P ratios in all tissues were significantly higher when MAT and MAP were higher. The N concentrations of branches and trunks were negatively related to MAT and MAP, however, the leaf N concentrations did not change with MAT and MAP. The root N also did not change with MAT, but decreased significantly with MAP. Soil total N had little influence on tree N, however, tree tissue P concentrations significantly increased when soil P increased. The N contents of all tissues were mainly affected by plant functional groups, however, climate factors and soil P content were the main predictors of P and N:P ratios of all tissues. Our results suggest that tree tissue N:P ratios were largely related to climatic factors, and were shaped by soil P rather than soil N in China's forest ecosystems. [ABSTRACT FROM AUTHOR]

Abstract Tropical and subtropical forest ecosystems play an important role in the global carbon regulation. Despite increasing evidence for effects of biodiversity (species diversity, functional diversity and functional dominance), stand structural attributes, stand age and environmental conditions (climate and topography) on tree carbon storage, the relative importance of these drivers at large scale is poorly understood. It is also still unclear whether biodiversity effects on tree carbon storage work through niche complementarity (i.e. increased tree carbon storage due to interspecific resource partitioning) or through the mass-ratio effect (tree carbon storage regulated by dominant traits within communities). Here we analyze tree carbon storage and its drivers using data of 480 plots sampled across subtropical forests in China. We use multiple regression models to test the relative effects of biodiversity, stand structural attributes, stand age and environmental conditions on tree carbon storage, and use a partial least squares path model to test how these variables directly and/or indirectly affect tree carbon storage. Our results show that tree carbon storage is most strongly affected by stand age, followed by climate, biodiversity and stand structural attributes. Stand age and climate had both direct and indirect (through species diversity, functional dominance and stand structural attributes) effects. We find that tree carbon storage correlates with both species diversity and functional dominance after stand age and environmental drivers are accounted for. Our results suggest that niche complementarity and the mass-ratio effect, not necessarily mutually exclusive, both play a role in maintaining ecosystem functioning. Our results further indicate that biodiversity conservation might be an effective way for enhancing tree carbon storage in natural, species-rich forest ecosystems. Graphical abstract Unlabelled Image Highlights • Biodiversity enhances tree carbon storage in subtropical forests. • Niche complementarity and mass-ratio effect both play a role in maintaining ecosystem functioning. • Stand age, stand structure and environmental conditions all affect tree carbon storage. [ABSTRACT FROM AUTHOR]

Abstract Elevated anthropogenic acid deposition has accelerated forest soil acidification in southern China. However, the observed responses to increased acid inputs are quite variable among different forest soils, and the reasons remain unclear. To study the causes for the different responses, soil columns taken from a young pine forest (PF) and an old evergreen broadleaved forest (BF) were applied three levels of acid addition treatments for 60 days. We found that the PF soils were quite acid-sensitive, and the high acid treatment significantly decreased soil pH at 0–20 cm soil layer while significantly increased exchangeable H+ at both 0–20 and 20–40 cm soil layers. Both the low and high acid treatments significantly increased exchangeable Na+ at 0–20 cm soil layer and Ca2+ and Mg2+ at 20–40 cm soil layer. Furthermore, the high acid treatment also significantly increased leaching losses of H+, Ca2+, Mg2+ and Al3+. In contrast, the BF soils were able to buffer both the low and high acid treatments without significantly decreasing soil pH and increasing major exchangeable cations including Al3+ and their leaching losses. The significant differences in soil organic matter content were found to be responsible for these different responses, as a result of significantly positive correlation between cation exchange capacity (CEC) and organic carbon in both forest soils. The BF soils had higher organic matter than the PF soils, therefore a greater CEC for consuming H+ and a stronger capacity for binding cations. Our results explained why the PF soil pH decreased from 4.3 to 3.8, while the BF soil pH did not change significantly over the last 16 years, and highlighted the important roles of soil organic matter in acid buffering and retaining of major cations, especially for Al3+ in the very acidic forest soils in southern China. Highlights • Aluminum dominates acid buffering processes in pine and broadleaved forest soils (pH < 4.2) in southern China. • Acid treatments decrease soil pH and increase leaching losses of metal cations from pine forest soil. • Broadleaved forest soil has a stronger acid buffering capacity because of its higher organic matter content. • Soil organic matter is a major contributor to cation exchange capacity and adsorption of Al3+ in acidic forest soil. [ABSTRACT FROM AUTHOR]

Evapotranspiration (ET) is one of the most important fluxes in terrestrial ecosystems that regulate atmosphere–hydrosphere–biosphere interactions. Several studies have suggested that global ET has significantly increased in the past several decades, and that such increase has exhibited big spatial variability, but there are few detailed studies on the spatio-temporal change in ET over China. Here, we developed a high-resolution data-oriented monthly ET product in China between 1982 and 2015 by integrating remote-sensing and the eddy covariance technique observed ET data in a machine learning approach (model tree ensemble, MTE). We showed that the mean annual ET over China is 552 ± 14 mm yr −1 , which is comparable to the estimate from a MTE-derived product based on water balance, but is larger than that from both previous MTE-derived global product and process-based land surface models. ET in China significantly increased with a rate of 10.7 mm yr −1 per decade over the past 30 years ( p  < 0.05). The largest increases in ET (>60 mm yr −1 per decade) occurred in the eastern periphery of Sichuan, southern Taiwan, and central China, which was attributed to the increases in temperature and solar radiation, as well as the enhanced vegetation productivity. About 22% of the area showed a decreasing trend in ET, mainly in parts of southeastern, southwestern, and northeastern China. The regional decrease in ET was likely due to decreasing precipitation and/or vegetation browning. Although our finding of the significant increase in China’s ET at the country scale is supported by five different ET products, there are still less agreement on the change in ET at the regional scale among different ET products. [ABSTRACT FROM AUTHOR]

Accurate assessment of the strength of China’s terrestrial ecosystem carbon sink is key to understanding its regional carbon budget. However, large uncertainties in current carbon sink estimations still exist, which hinder the prediction of future climate change trajectories. In this study, we generated a high-resolution (1 km × 1 km) dataset of China’s net ecosystem productivity (NEP) in the last decade via a model tree ensemble approach combined with data from 46 flux sites in China and neighboring regions. The upscaling also included detailed information on nitrogen (N) deposition and forest age that have often been neglected in previous studies. The performance of MTE algorithm in simulating NEP at the site level is relatively high for both training (R 2  = 0.81, RMSE = 0.73 gC m −2  day −1 ) and validation datasets (R 2  = 0.76, RMSE = 0.81 gC m −2  day −1 ). Our data-driven estimation showed that roughly 70% of the area is a carbon sink, and the largest carbon sinks are found in the southeast and southwest monsoon regions. The total annual NEP in China in the last decade was 1.18 ± 0.05 Pg C yr −1 , which is similar to the results found by another foundational global-scale study. Yet, the two studies significantly differ in the spatial distribution of carbon sink density. The seasonality of China’s NEP is characterized by region-specific kurtosis and skewness in most areas. Furthermore, ecosystem carbon use efficiency (CUE), defined as the annual NEP/GPP ratio, also showed high spatial variation. For example, the Xiaoxing’anling and Changbai Mountains in northeastern China, the eastern edge of the Tibetan Plateau, and bordering areas of the southeast and southwest monsoon regions have a larger CUE than the rest of China. On average, China’s terrestrial ecosystem CUE is approximately 0.17. Our data-driven NEP and CUE estimates provide a new tool for assessing China’s carbon dioxide flux. Our study also highlights the necessity to incorporate more environmental variables related to vegetation growth and more data derived from flux sites into NEP upscaling to reduce uncertainties in carbon budget estimations. [ABSTRACT FROM AUTHOR]

It has been recognized that the formation and subsequent sequestration of soil organic carbon (SOC) during forest succession are primarily driven by soil microorganisms. However, the time-integrated microbial influence on long term SOC accumulation remains unknown. In a subtropical forest succession including three stages of early coniferous forest, middle mixed species forest and climax broad-leaved forest, we investigated changes in soil amino sugars, a biomarker of microbial residues, along a successional gradient to evaluate contributions of fungal and bacterial residues to SOC accumulation over time. Both the concentrations and stocks of SOC and amino sugars increased with forest succession in the 0–40 cm soil depth, suggesting a close association of microbial proliferation-mortality processes with the sequestration of SOC. In the early successional stage, the contribution of microbial residue-carbon to SOC was low due to the decomposition resistance of needle leaf litter. The later invasion of broad-leaved trees increased the contribution of microbial residues to SOC formation, but the accumulation of amino sugars was more rapid than SOC from early to middle stage, possibly implying that both the production and retention of microbial residues were the essential prerequisite for SOC sequestration. Given the preferences of bacteria to available substrate while the advantage of fungi in using the more recalcitrant part, the proportion of fungal residue-carbon in SOC was significantly larger in the middle stage (mixed forest) while bacterial residues were more prone to accumulate in SOC in the climax stage (broad-leaved forest). The sequestration of SOC along the subtropical forest succession possibly underwent a first stage of accumulation of fungal residues followed by the preferential accumulation of less recalcitrant bacterial residues. [ABSTRACT FROM AUTHOR]

Estimates of atmospheric evaporative demand have been widely required for a variety of hydrological analyses, with potential evapotranspiration (PET) being an important measure representing evaporative demand of actual vegetated surfaces under given metrological conditions. In this study, we assessed the ability of various PET models in capturing long-term (typically 2003–2011) dynamics of evaporative demand at eight ecosystems across various biomes and climatic regimes in China. Prior to assessing PET dynamics, we first examined the reasonability of fourteen PET models in representing the magnitudes of evaporative demand using eddy-covariance actual evapotranspiration (AET) as an indicator. Results showed that the robustness of the fourteen PET models differed somewhat across the sites, and only three PET models could produce reasonable magnitudes of evaporative demand (i.e., PET ≥ AET on average) for all eight sites, including the: (i) Penman; (ii) Priestly-Taylor and (iii) Linacre models. Then, we assessed the ability of these three PET models in capturing dynamics of evaporative demand by comparing the annual and seasonal trends in PET against the equivalent trends in AET and precipitation ( P ) for particular sites. Results indicated that nearly all the three PET models could faithfully reproduce the dynamics in evaporative demand for the energy-limited conditions at both annual and seasonal scales, while only the Penman and Linacre models could represent dynamics in evaporative demand for the water-limited conditions. However, the Linacre model was unable to reproduce the seasonal switches between water- and energy-limited states for some sites. Our findings demonstrated that the choice of PET models would be essential for the evaporative demand analyses and other related hydrological analyses at different temporal and spatial scales. [ABSTRACT FROM AUTHOR]

The Community Land Model (CLM) is an advanced process-based land surface model that simulates carbon, nitrogen, water vapor and energy exchanges between terrestrial ecosystems and the atmosphere at various spatial and temporal scales. We use observed carbon and water fluxes from five representative Chinese Terrestrial Ecosystem Flux Research Network (ChinaFLUX) eddy covariance tower sites to systematically evaluate the new version CLM4.5 and old version CLM4.0, and to generate insights that may inform future model developments. CLM4.5 underestimates the annual carbon sink at three forest sites and one alpine grassland site but overestimates the carbon sink of a semi-arid grassland site. The annual carbon sink underestimation for the deciduous-dominated forest site results from underestimated daytime carbon sequestration during summer and overestimated nighttime carbon emission during spring and autumn. Compared to CLM4.0, the bias of annual gross primary production (GPP) is reduced by 24% and 28% in CLM4.5 at two subtropical forest sites. However, CLM4.5 still presents a large positive bias in annual GPP. The improvement in net ecosystem exchange (NEE) is limited, although soil respiration bias decreases by 16%–43% at three forest sites. CLM4.5 simulates lower soil water content in the dry season than CLM4.0 at two grassland sites. Drier soils produce a significant drop in the leaf area index and in GPP and an increase in respiration for CLM4.5. The new fire parameterization approach in CLM4.5 causes excessive burning at the Changbaishan forest site, resulting in an unexpected underestimation of NEE, vegetation carbon, and soil organic carbon by 46%, 95%, and 87%, respectively. Overall, our study reveals significant improvements achieved by CLM4.5 compared to CLM4.0, and suggests further developments on the parameterization of seasonal GPP and respiration, which will require a more effective representation of seasonal water conditions and the partitioning of net radiation between sensible and heat fluxes. [ABSTRACT FROM AUTHOR]

Elevated anthropogenic acid deposition can significantly affect forest ecosystem functioning by changing soil pH, nutrient balance, and chemical leaching and so on. These effects generally differ among different forests, and the dominant mechanisms for those observed responses often vary, depending on climate, soil conditions and vegetation types. Using soil monoliths (0–40 cm) from pine forest (pioneer), coniferous and broadleaved mixed forest (transitional) and broadleaved forest (mature) in southern China, we conducted a leaching experiment with acid treatments at different pH levels (control: pH ≈ 4.5; pH = 3.5; pH = 2.5). We found that pH 3.5 treatment significantly reduced dissolved organic carbon (DOC) concentrations in leachate from the pioneer forest soil. pH 2.5 treatment significantly increased concentrations of NO 3 − , SO 4 2 − , Ca 2 + , Mg 2 + , Al 3 + , Fe 3 + and DOC in leachate from the pioneer forest soil, and also concentrations of NO 3 − , SO 4 2 − , Mg 2 + , Al 3 + , Fe 3 + and DOC in leachate from the transitional forest soil. All acid treatments had no significant effects on concentrations of these chemicals in leachate from the mature forest soil. The responses can be explained by the changes in soil pH, acid neutralizing capacity (ANC) and concentrations of Al and Fe. Our results showed that acid buffering capacity of the pioneer or transitional forest soil was lower than that of the mature forest soil. Therefore preserving mature forests in southern China is important for reducing the adverse impacts of high acid deposition on stream water quality at present and into the future. [ABSTRACT FROM AUTHOR]