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In this paper, a novel high-directivity microstrip coupler based on reflective resistors is presented. The proposed coupler consists of three pairs of coupled-line sections and one pair of resistors. Generally, the coupling degree can be controlled by the coupled-lines, while the resistors are employed to adjust the amplitude of the reflected signal to cancel out the leakage signal. The mechanism of high directivity is derived and the S-parameters are presented. To verify the design concept, a 20 dB microstrip coupler operating at 2 GHz is processed and measured. The measured results indicate that the return loss of input and output ports is more than 28.5 dB with a typical insert loss of 0.3 dB, while that of coupled and isolated ports is more than 15 dB. And the directivity is more than 20 dB with a maximum 53.1 dB at 2.01 GHz in a fractional bandwidth of 22.5%.

Abstract Key message The forest canopy gaps, formed by natural or anthropogenic factors, have been found to reduce soil carbon content and increase nutrient availability. The magnitudes of these effects have been observed to increase with gap age and size, and are largely influenced by changes in temperature, precipitation, and solar radiation. Context Local studies have illustrated the influence of canopy gaps on the spatial heterogeneity of soil carbon and nutrients, playing a pivotal role in driving forest regeneration and succession. Nevertheless, it remains largely unknown whether the response of soil carbon and nutrient content to gap formation is consistent across forest ecosystems at global scale. Aims The aim of this paper is to assess the homogeneity of the observed responses of soil carbon and nutrients following gap formation among a wide array of forest ecosystems and climatic regions. Methods We performed a meta-analysis synthesizing 2127 pairwise observations from 52 published articles to quantify the changes in in soil physical, chemical, and microbial variables resulting from gap creation in natural forests and plantations spanning tropical to boreal regions. Results Canopy gaps resulted in significant decrease of soil organic carbon (C org) and microbial carbon (C mic). The concentrations of ammonium (NH4 +), nitrate (NO3 −), and available phosphorus (available P) increased following gap creation. These changes mainly occurred in the growing season and in the mineral soil layer, becoming more pronounced with increasing gap age and size. The change in C org was negatively regulated by mean annual precipitation, and was associated with the changes in Nt and N mic . The change in NH4 + was positively regulated by mean annual temperature, and was associated with the changes in available P and oxidoreductases (Ox-EEAs). The model explaining the change in soil carbon content exhibited a higher explanatory power than the one accounting for changes in soil nutrient availability. Conclusion The results indicated that forest canopy gaps resulted in a reduction in soil carbon content and an increase in nutrient availability. These findings contribute to a better understanding of the role of small-scale disturbances as drivers of forest ecosystem succession.

An Al-7Si-1.5Cu-Mg alloy was synthesized through the modification of a commercial A356 alloy with the inclusion of alloying elements. This alloy underwent a treatment regime comprising solid solution, cryogenic treatment, and ageing. The results indicate that cryogenic treatment increased nucleation rate of precipitates, which increases the number of precipitates and reduces their sizes, ultimately improving the mechanical properties and reduce secondary dendrite arm spacing of the alloy. Under the optimal treatment conditions (solid solution at 520 °C for 10 hours, followed by deep cooling for 48 hours, and ageing at 160 °C for 10 hours), the secondary dendrite arm spacing of the alloy was reduced by approximately 37,5 %, exhibiting hardness of 102,8 HV and plasticity of 4,2 %.

A clear understanding of customer needs is key to the success of new product development and customer-centric product design. Online reviews, particularly initial reviews, are commonly used as effective sources for mining customer requirements. Although customers may post truer and more objective supplementary reviews after a period of product use, such reviews are often overlooked when identifying customer requirements for product design improvement. In this study, we proposed a framework for identifying customer requirements by combining initial and supplementary reviews based on text mining. We categorized the identified customer needs into five product attribute categories using the Kano model. Two case studies were conducted in the laptop and cell phone industries to demonstrate the effectiveness of our method. Thus, dynamic customer requirements and satisfaction can be accurately mined and captured when considering supplementary reviews. In practice, the appropriate use of supplementary reviews may provide valuable guidance for product design and development strategies.

Abstract Background Three-North Afforestation Program (TNAP) in China is the largest ecological restoration project on Earth (ongoing from 1978 to 2050), harboring a huge area of newly planted forests, which provides a wealth of goods and ecosystem services that benefit society at levels ranging from region to East Asia. This project-induced carbon (C) sink has been expected to be large, but its size and location remain uncertain. Results In this study, we investigated the changes in the C stocks of biomass, soil C and the C accumulation benefited from the ecological effects in the project areas from 1978 to 2017 within the Three-North regions (4.069 × 106 km2), and evaluated its project-induced C sequestration. Using a combination of remote sensing images, field observations and national forest inventory data, we estimated a total ecosystem sink of 47.06 Tg C per year (1 Tg = 1012 g) increased by the TNAP implementation. Importantly, we first found that the C sink via the ecological effects of this project could contribute to a high proportion up to 15.94%, indicating a critical role of ecological effects in shaping the distribution of C stocks in the protective forests. This finding suggests that it is necessary to explicitly consider carbon sequestration benefited from the ecological effects when estimating C sink and parameterizing C models of the restoration projects in China and globally. Conclusions Our results update the estimates of C pools in the world's largest ecological restoration project area, demonstrating that this project has substantially contributed to mitigating the climate change.

The nearby radio galaxy M87 is a very high-energy (VHE) gamma-ray emitter established by observations with ground-based gamma-ray detectors. Here we report the long-term monitoring of M87 from 2021 to 2024 with the Large High Altitude Air Shower Observatory (LHAASO). M87 has been detected by LHAASO with a statistical significance ∼ 9 σ . The observed energy spectrum extends to 20 TeV, with a possible hardening at ∼20 TeV and then a clear softening at higher energies. Assuming that the intrinsic spectrum is described by a single power law up to 20 TeV, a tight upper bound on the extragalactic background light intensity is obtained. A strong VHE flare lasting 8 days, with a rise time of ${\tau }_{r}^{\mathrm{rise}}=1.05\pm 0.49$ days and decay time of ${\tau }_{d}^{\mathrm{decay}}=2.17\pm 0.58$ days, was found in early 2022. A possible GeV flare is seen also in Fermi Large Area Telescope data during the VHE flare period. The variability time as short as 1 day seen in the LHAASO data suggests a compact emission region with a size of ∼3 × 10 ^15 δ cm ( δ being the Doppler factor of the emitting region), corresponding to a few Schwarzschild radii of the central supermassive black hole in M87. The continuous monitoring of the source reveals a duty cycle of ∼1% for VHE flares with a flux above 10 ^−11 erg cm ^−2 s ^−1 .

The first source catalog of the Large High Altitude Air Shower Observatory (LHAASO) reported the detection of a very high energy gamma-ray source, 1LHAASO J1219+2915. This Letter presents a further detailed study of the spectral and temporal behavior of this pointlike source. The best-fit position of the TeV source (R.A. = 185.°05 ± 0.°04, decl. = 29.°25 ± 0.°03) is compatible with NGC 4278 within ∼0.°03. Variation analysis shows an indication of variability on a timescale of a few months in the TeV band, which is consistent with low-frequency observations. Based on these observations, we report the detection of TeV γ -ray emissions from this low-luminosity active galactic nucleus. The observation by LHAASO's Water Cherenkov Detector Array during the active period has a significance level of 8.8 σ with a best-fit photon spectral index Γ = 2.56 ± 0.14 and a flux f _1–10 TeV = (7.0 ± 1.1 _sta ± 0.35 _syst ) × 10 ^−13 photons cm ^−2 s ^−1 , or approximately 5% of the Crab Nebula. The discovery of VHE gamma-ray emission from NGC 4278 indicates that compact, weak radio jets can efficiently accelerate particles and emit TeV photons.

Global climate change can affect tree growth and carbon sink function by influencing plant carbohydrate synthesis and utilization, while elevation can be used as an ideal setting under natural conditions to simulate climate change effects. The effect of elevation on tree growth may depend on organ type. However, the allocation patterns of nonstructural and structural carbohydrates (NSCs and SCs, respectively) in different tree organs and their response to elevation remain unclear. We selected four dominant tree species, Schima superba, Castanopsis eyrei, Castanopsis fargesii and Michelia maudiae, along an elevation gradient from 609 to 1,207 ​m in subtropical evergreen broad-leaved forests and analyzed leaf, trunk, and fine root NSCs, carbon (C), nitrogen (N) and phosphorus (P) concentrations and the relative abundance of SCs. Leaf NSCs increased initially and then decreased, and trunk NSCs increased with increasing elevation. However, root NSCs decreased with increasing elevation. The relative abundance of SCs in leaves and trunks decreased, while the relative abundance of root SCs increased with increasing elevation. No significant correlations between SCs and NSCs in leaves were detected, while there were negative correlations between SCs and NSCs in trunks, roots, and all organs. Hierarchical partitioning analysis indicated that plant C/N and C/P were the main predictors of changes in SCs and NSCs. Our results suggest that tree organs have divergent responses to elevation and that increasing elevation will inhibit the aboveground part growth and enhance the root growth of trees. A tradeoff between the C distribution used for growth and storage was confirmed along the elevation gradient, which is mainly manifested in the “sink” organs of NSCs. Our results provide insight into tree growth in the context of global climate change scenarios in subtropical forest ecosystems.

In order to promote the rapid development of the meat sheep industry, a three-way crossbred combination experiment was carried out with Australian White, Dorper, and Charollais sheep as terminal male parents and the elite F1 hybrids of Australian White × Small-tailed Han (Han), Dorper × Han, and Charollais × Han as female parents, which was based on the screening of a two-way crossbred combination in meat sheep. The growth performance of six groups of three-way crossbred combinations and Han lambs was measured and analyzed, and the effect of a polymorphism in the CLPG gene on the growth performance of three-way crossbred lambs was also studied. The results showed that under the same rearing conditions, weight at 3 and 6 months of age and average daily gain from birth to 3 months and from 3 to 6 months of age were all the largest for Australian × (Charollais × Han) crossbred lambs. They were significantly or extremely significant different from the other three-way crossbred combinations and Han lambs (P<0.05, P<0.01). The body height, body length, chest girth, and cannon bone circumference at 3 months of age and body length, chest girth, and cannon bone circumference at 6 months of age were also the largest for Australian × (Charollais × Han) crossbred lambs. Among them, body length, chest girth, and cannon bone circumference at 3 months of age were significantly different from the other three-way crossbred combinations and Han lambs (P<0.05), and body length, chest girth, and cannon bone circumference at 6 months of age were significantly or extremely significant different from the other three-way crossbred combinations and Han lambs (P<0.05, P<0.01). The potential genetic effects of the CLPG gene on the growth performance indicators of three-way crossbred lambs showed that a mutation site (g.232C > T) of this gene had two genotypes: CC and CT. Among them, the data of body weights and body sizes from CT genotype individuals at birth, 3 months old, and 6 months old were significantly higher than those of CC genotype individuals, and some indicators showed significant or extremely significant differences (P<0.05, P<0.01), suggesting that higher growth performance was observed in individuals with T alleles. To sum up, the crossbred combination of Australian × (Charollais × Han) could be suggested as the optimal choice. The T allele of the CLPG gene showed potential advantages in the performance of meat production in meat sheep. Based on the current results, we recommend that the offspring of Australian × (Charollais × Han) with the T allele should be preferentially utilized for meat sheep production.

In order to control the desertification, large-scale afforestation programs have been attempted worldwide. Among them, China initiated the world’s largest afforestation program, Three-North Afforestation Program (TNAP, 1978–2050), in which the afforestation in sandy land has been questioned during the first 40 years. In fact, the contribution of the TNAP to vegetation establishment and its effectiveness in desertification control still remain unclear, which limited the further construction of the program. To answer the questions, we detected the dynamics of vegetation distribution (forest, shrubland, and grassland) and desertification status (slight, moderate, severe, and extremely severe) during 1978–2017 in the sandy land (45.5 million ha), by visual interpretation of 5-period remote sensing images with validation based on 3,100 sample plots from field surveys and 15,175 sample plots from the National Forest Resource Inventory. Vegetation degradation was identified by analysis combining the trends of net primary productivity and precipitation use efficiency. By Geographical Detector model, the driving forces of vegetation degradation (climate change, human activities, vegetation type, and sandy land type) were ranked and the contributions of the influential factors (climate change, human activities, and vegetation dynamics) to desertification changes were estimated. The results showed that for the 40 years, vegetation coverage increased by 0.5%, with increasing 113.8% and 338.8% of forest and shrubland, but decreasing 9.0% of grassland. Desertification area had little change while the overall intensity decreased. The TNAP contributed to desertification dynamics by 10.3%, which is lower than expected. Vegetation type was the dominant factor of vegetation degradation in general. Forest is less suitable for afforestation in sandy land than shrubland and grassland because of its lower stand establishment rate, higher degradation rate, and less contribution to desertification control. Thus, adjusting vegetation type to match local conditions (e.g., use shrub-land, grassland, and native species) and improving the vegetation resistance (e.g., transform monoculture forests into mixed forests, and make proper proportion for forest, shrubland, and grassland) was suggested. Our study provided specific and feasible strategies for further planning and implementation of TNAP, and references for vegetation restoration of sandy lands worldwide.

Halophytes play a crucial role in the ecological restoration of saline and alkaline land and hold promising benefits to food security in China. Although a variety of aspects of halophytes have been extensively addressed, there is still a lack of overall understanding of the leaf nitrogen (N) and phosphorus (P) stoichiometric characteristics, especially at a national scale. We compiled a national dataset of 311 observations from 113 sampling sites across China to explore the changing trends and influencing factors on leaf N and P concentrations, and N:P ratio of halophytes. The results showed that leaf N concentration decreased significantly with increasing latitude (LAT), which was mainly driven by the mean annual temperature (MAT) and mean annual precipitation (MAP). The leaf P concentration increased remarkably with increasing longitude (LON), which was induced by the variation in soil total P (TP) content. The leaf N:P ratio increased as LAT increased and LON decreased, which was potentially regulated by the MAT, MAP, and soil TP content. The scaling exponents of the N-P relationship differed significantly among halophyte types and were 0.40, 0.87, and 1.39 for euhalophyte, pseudohalophyte, and recretohalophyte, respectively. The leaf N concentration exhibited significant differences among ecosystem types and halophyte types, whereas the leaf P concentration and N:P ratio remained relatively stable. In summary, the leaf N concentration and N-P scaling exponent might be the classification criteria for halophyte types from the perspective of plant nutrient resource allocation. Moreover, this study characterized the spatial distribution and allocation strategy of leaf N and P stoichiometry in halophytes by data integration analysis, providing the basic information for nutrient management in the processes of the future domestication and introduction of halophytes.

Recently, the Tibetan Plateau (TP) has experienced dramatic climate change, which influence atmospheric and hydrological cycles. The understanding of surface water dynamics is essential to further investigate the water balance and the hydrologic cycle in this region. In this study, we used all available Landsat Surface Reflectance imagery that generated Modified Normalized Difference Water Index (MNDWI) overlapped the TP in time-series for 1996–2019. We detected the annual changes in surface water using the LandTrendr algorithm on the Google Earth Engine (GEE), and examined impact factors on surface water area dynamics. During 1996–2019, the area of 17,065 km2 had changed from land to water body and 3511 km2 had changed from water to land in the entire TP. The drivers of surface water change are spatially heterogeneous. Precipitation is a main cause of surface water variability in the central, northern and eastern parts of the TP. Meanwhile, temperature is the dominant factor affecting the western and southern parts of the TP. Our results proved that LandTrendr could be applied to monitor surface water changes over larger spatial and temporal scales. In conclusion, our study focus on understanding the process of climate change and the hydrological cycle across the TP.

We present the first catalog of very-high-energy and ultra-high-energy gamma-ray sources detected by the Large High Altitude Air Shower Observatory. The catalog was compiled using 508 days of data collected by the Water Cherenkov Detector Array from 2021 March to 2022 September and 933 days of data recorded by the Kilometer Squared Array from 2020 January to 2022 September. This catalog represents the main result from the most sensitive large coverage gamma-ray survey of the sky above 1 TeV, covering decl. from −20° to 80°. In total, the catalog contains 90 sources with an extended size smaller than 2° and a significance of detection at >5 σ . Based on our source association criteria, 32 new TeV sources are proposed in this study. Among the 90 sources, 43 sources are detected with ultra-high energy ( E > 100 TeV) emission at >4 σ significance level. We provide the position, extension, and spectral characteristics of all the sources in this catalog.

Device-to-Device (D2D) communication is a potential technology to improve the spectral and energy efficiency (EE) of communication networks. In this paper, we study energy-efficient power allocation (PA) schemes in uplink distributed antenna system (DAS) with device-to-device underlay communication. Our goal is to maximize the total EE of all D2D pairs while guaranteeing the data rate and transmit power requirements of the cellular user and D2D links. To solve this non-convex constrained optimization problem, we propose an energy-efficient near-optimal PA algorithm based on the concave-convex procedure and fractional programming theory. This near-optimal algorithm can achieve the EE performance close to the optimal exhaustive search. To reduce the complexity, we furthermore present an efficient sub-optimal algorithm with the antenna selection method which can obtain the closed-form power allocation expressions. Simulation results demonstrate the significant EE performance of our proposed PA schemes.

Cloud Forests (CFs) are characterized by their persistent foggy environment, in which fog can save two times the amount of precipitation in the dry season and increase water storage by 10% in the rainy season. CFs play an important role in ecosystems as high biodiversity and abundant endemic species live within CFs. However, CFs are sensitive to environmental changes, especially in current global climate warming conditions. Therefore, a typical cloud forest in Taiwan, Shei-Pa National park, was chosen as the study area. Specifically, the Normalized Difference Vegetation Index (NDVI) with meteorological factors including rainfall, average temperature, maximum temperature, and minimum temperature were obtained to assess the overall CFs trend from 2001 to 2017. Moreover, the Long Short-Term Memory neural network model (LSTM) was implemented to predict the future vegetation status. Preliminary results have shown that vegetation condition in Shei-Pa National park was getting better; rainfall, average temperature, and minimum temperature represented an upward trend while maximum temperature showed a downward trend. Furthermore, the LSTM- maximum temperature model displayed the highest prediction power with the MAPE index of 4.84%. The results provide a valuable reference for forest resource conservation and future climate adaptation strategies in Taiwan.

Abstract The detection of low-energy deposition in the range of sub-eV through ionization using germanium (Ge) with a bandgap of $$\sim $$ ∼ 0.7 eV requires internal amplification of the charge signal. This can be achieved through high electric field that accelerates charge carriers, which can then generate more charge carriers. The minimum electric field required to generate internal charge amplification is derived for different temperatures. We report the development of a planar point contact Ge detector in terms of its fabrication and the measurements of its leakage current and capacitance as a function of applied bias voltage. With the determination of the measured depletion voltage, the field distribution is calculated using GeFiCa, which predicts that the required electric field for internal charge amplification can be achieved in proximity to the point contact. The energy response to an Am-241 source is characterized and discussed. We conclude that such a detector with internal charge amplification can be used to search for low-mass dark matter.

Soil and climatic conditions are known to have close associations with plant morphological and stoichiometric traits at a regional scale along latitudinal gradients; however, how latitude drives biotic and abiotic factors affecting plant nutrient acquisition to accommodate environmental nutrient deficiency remains unclear. We quantified soil, root, leaf, and leaf litter nitrogen (N) and phosphorus (P) concentrations to determine the potentially limiting nutrient and the simultaneous responses of root capture and leaf resorption to nutrient deficiency in seven Quercus acutissima forests across the North–South Transect of Eastern China. The results showed that the mean leaf and root N:P ratios in Q. acutissima were 21.58 and 20.23, respectively, which markedly exceeded the P limitation threshold of 16 for terrestrial plants. The mean leaf litter N and P were 10.63 mg/g and 0.51 mg/g, respectively, indicating that P resorption proficiency was relatively higher than N resorption proficiency. N displayed higher stoichiometric homeostasis than P in the leaf. The leaf and root N:P ratios showed a quadratic variation that first decreased and then increased as latitude increased, whereas the phosphorus resorption efficiency and root-soil accumulation factor of P displayed the opposite trend. Partial least square path modeling (PLS-PM) analysis demonstrated that root nutrient capture and leaf nutrient resorption were regulated by different influential factors. Overall, these findings provide new insights into plant strategies to adapt to environmental nutrient deficiency, as well as the scientific basis for predicting the spatial and temporal patterns of nutrient acquisition in the context of climate change.

Abstract Background Granivore-mediated seed dispersal is susceptible to changes in seed availability and silvicultural management, which alters synzoochorous interactions in the antagonism-mutualism continuum and affects the seed dispersal effectiveness (SDE), and eventually, the plant recruitment. We conducted a whole-year study of seed addition to quantify the granivores-Korean pine (Pinus koraiensis) synzoochorous interactions and the SDE in the same secondary forests with two treatments. Both treatments had seed source limitations: one was caused by the disappearance of Korean pine due to the historical disturbance, the other by pinecone harvesting in Korean pine plantations adjacent to the secondary forests. Thinning with different intensities (control, 25%, and 50%) were also performed to further explore the synzoochorous interactions and SDE in response to silvicultural management in the second type of forests. Results Source limitation increased the proportion of pre- and post-dispersal seed predation, and made the granivores-Korean pine interaction shift more towards antagonism, with the estimated SDE of 2.31 and 3.60, respectively, for the secondary forests without and with Korean pine. Thinning with different intensities did not alleviate the reactions towards antagonism but altered SDE; granivores occurrence decreased, but the proportion of pre- and post-dispersal seed predation increased, resulting in a fivefold decreased seedling recruitment in 25% thinning (the lowest SDE of 0.26). Conclusion The source limitation coupling thinning biased the synzoochorous interactions more towards antagonism and significantly lowered granivore-mediated SDE, which limited the successful recruitment of Korean pine in secondary forests. Forest managers should control pinecone harvesting, protect the synzoochorous interaction, and take into account masting event for Korean pine regeneration in the future.

BackgroundPinus massoniana is an important timber species with high ecological and economic value in southern China and a pioneer species for the reforestation of barren mountains. The structure and function of the existing Masson pine ecosystem have been seriously affected by worsening habitats under current climate change. Its suitable habitat is likely to change greatly in the near future.MethodsTo estimate the potential geographic distribution of P. massoniana and its response to climate change, the Maxent model was selected to simulate the potentially suitable habitat and corresponding changes in the distribution pattern of P. massoniana under current and future climate scenarios (SSP1-2.6, SSP2-4.5, and SSP5-8.5) with two periods (2050s and 2090s).ResultsUnder current climate conditions, the total suitable habitat area of P. massoniana was 2.08 × 106 km2, including 0.76 × 106 km2 of highly suitable habitat, concentrated mainly in Jiangxi and Zhejiang, central and southeastern Hunan, northern Fujian, central and western Chongqing, southern Anhui, central and surrounding areas of Guangdong, central and eastern Guangxi, and northern Taiwan. The areas of moderately suitable habitat and poorly suitable habitat were 0.87 × 106 km2 and 0.45 × 106 km2, respectively. Temperature and precipitation appear to be the most important predictors: precipitation of the driest month (14.7–215.6 mm), minimum temperature of the coldest month (−3.5–13.8°C), annual temperature range (8.1–32.9°C), and mean temperature of the warmest quarter (23.6–34.7°C). P. massoniana are predicted to expand their potential distribution under future climate change: by the end of this century, their total suitable habitat area increased 0.26 × 106 km2 (10.61%) and 0.45 × 106 km2 (17.05%) under the most moderate (SSP1-2.6) and severe (SSP5-8.5) warming scenarios, respectively, by mainly extending northward.ConclusionUnder the different future climate scenarios, the total suitable habitat area of P. massoniana increased by mainly extending northward. Overall, our study clarifies the potential habitat distribution of P. massoniana and provides a critical empirical reference for future P. massoniana conservation and planting practices.

Abstract Classical laws of friction suggest that friction force is proportional to the normal load and independent of the nominal contact area. As a great improvement in this subject, it is now widely accepted that friction force is proportional to the real contact area, and much work has been conducted based on this hypothesis. In present study, this hypothesis will be carefully revisited by measuring the friction force and real contact area in-site and real-time at both normal loading and unloading stages. Our experiments reveal that the linear relation always holds between friction force and normal load. However, for the relation between friction force and real contact area, the linearity holds only at the loading stage while fails at the unloading stage. This study may improve our understanding of the origin of friction.

Acute and extreme weather events can cause considerable damage to the tissues of trees, including stem death and branch or leaf distortion, which may limit their survival and reproduction. In January 2016, a rare cold spell impacted the coastal forests of subtropical China. Using post-hoc assessments, we evaluated the morphological and physiological response of Chinese tallow (Triadica sebifera L.) to the extreme cold spell in two distinct ecoregions, one (Xiangshan, China) representing the cold spell impacted zone and the other (Taizhou, China) representing the non-affected zone. To determine if the extreme cold events impacted the vigor of Chinese tallow, we assessed differences in growth rate, leaf characteristics, and leaf gas exchange. As age may affect tree morphological and physiological response to stress, we grouped subject trees into three distinct cohorts, namely, seedlings (1–2 years old), young-aged (5–6 years old), and middle-aged (10–12 years old). Our results suggest that although tree height and diameter did not differ, leaf area expansion and leaf mass were reduced in the impacted zone. In seedling and young-aged trees, the cold spell significantly reduced leaf net photosynthetic (An), transpiration rates (Tr), stomatal conductance (Gs) and water use efficiency (WUE) while leaf intercellular CO2 concentration (Ci), vapor pressure deficit (Vpd), and intercellular CO2 pressure (Ci-Pa) increased. In contrast, the middle-aged group was less responsive to the cold spell. Across all cohorts, the event did not affect leaf temperature (Tleaf), but the activity of superoxide dismutase (SOD) and peroxidase (POD) decreased. We also detected increases of leaf malondialdehyde (MDA) and free proline (Pro) contents in young-aged and middle-aged groups. Hence, the extreme cold spell caused remarkable negative effects on the morphological and physiological traits of Chinese tallow. Redundancy analysis revealed that the cold spell also impacted the subsequent recovery process of damaged Chinese tallow by reducing the ability of leaf to utilize microenvironmental resources (radiation, air humidity, and CO2) for gas exchange. Results from this study are important to strengthen our understanding of Chinese tallow responding to extreme cold stress within its native range, also be helpful to predict the distributions of Chinese tallow in its invasive range where it has devastating impacts to coastal ecosystems in the southeast US.

Abstract Background To restore secondary forests (major forest resources worldwide), it is essential to accelerate the natural regeneration of dominant trees by altering micro-environments. Forest gaps are products of various disturbances, ranging from natural storms or wildfires to anthropogenic events like logging and slashing-and-burning, and sprouts of most tree species with non-structural carbohydrates (NSCs) storage can regenerate from stumps after gap formation. However, how the stump sprouts with diverse NSCs storages and stump sizes (i.e., diameters) adapt to various micro-environments of within-gap positions remains unclear. Therefore in this study, we monitored the stump sprout regeneration (density, survival, and growth) and NSCs concentrations of three dominant tree species with different shade tolerances and varying stump diameters at five within-gap positions for the first two consecutive years after gap formation. Results Stump diameter was positively correlated with sprout density, growth, and survival of all three tree species, but insignificantly related with sprout NSCs concentrations at the early stage after gap formation. The effect of within-gap position on sprout NSCs concentrations was different among species. After an environmental adaptation of two growing seasons, the north of gap (higher light availability and lower soil moisture habitat) was the least conducive for shade-intolerant Quercus mongolica to accumulate leaf NSCs, and the east of gap (shadier and drier habitat) was conducive to increasing the leaf NSCs concentrations of shade-tolerant Tilia mandshurica. Conclusions Within-gap position significantly affected leaf NSCs concentrations of all three tree species, but most of the sprout growth, survival, and stem NSCs concentrations were independent of the various within-gap positions. Besides stump diameter, the NSCs stored in stump and root systems and the interspecific differences in shade tolerance also contributed more in sprout regeneration at the early stage (2 years) of gap formation. A prolonged monitoring (> 10 years) is needed to further examine the long-term effects of stump diameter and within-gap position on sprout regeneration. All of these findings could be applied to gap-based silviculture by promoting sprout regeneration of dominant tree species with different shade tolerances, which would help accelerate the restoration of temperate secondary forests.

Drought stress is one of the major environmental factors that limit maize yield in agriculture. However, few studies have analyzed how proteins respond to different degrees of drought at the proteome level. In this study, physiological characteristics and comparative tandem mass tag proteomics were used to analyze the responses of maize seedlings to mild and severe drought stresses in pot experiments. A total of 104 and 464 proteins were differentially expressed under mild and severe drought, respectively, but only 30 proteins were overlapped. Further Gene Ontology enrichment analysis showed maize can adapt to mild drought by activating antioxidant system and photorespiration. Under severe drought stress, photosystem and protein synthesis-related proteins were downregulated indicating severe drought damaged the photosynthetic apparatus. The plant biomass under drought stress was also reduced sharply compared to control. Taken together, our study provides insights into proteomic information of maize leaves under increasing drought stress.

Abstract We statistically investigate the spectral scalings of magnetic fluctuations at the upstream and downstream regions near the Venusian bow shock and perform a differentiation by shock geometry. Based on the Venus Express data, 115 quasi-parallel ( $$Q_{\parallel }$$ Q ‖ ) bow shock crossings and 303 quasi-perpendicular ( $$Q_{ \bot }$$ Q ⊥ ) bow shock crossings are selected. The statistical results suggest that the bow shock tends to modify the upstream spectra flatter to 1/f noise in the magnetohydrodynamics (MHD) regime and steeper to turbulence in the kinetic regime after the magnetic fluctuations crossing the bow shock, and this modification for the $$Q_{\parallel }$$ Q ‖ and $$Q_{ \bot }$$ Q ⊥ bow shocks is basically consistent. However, the upstream spectral scalings are associated with the shock geometry. The changes of the spectral scalings of magnetic fluctuations near the $$Q_{\parallel }$$ Q ‖ bow shocks are not as significant as near the $$Q_{ \bot }$$ Q ⊥ bow shock crossings. That might result from the fluctuations generated by the backstreaming ions which can escape across the $$Q_{\parallel }$$ Q ‖ bow shock into the foreshock. Our results suggest that the energy cascade and dissipation near Venus can be modified by the Venusian bow shock, and the $$Q_{\parallel }$$ Q ‖ bow shock plays an important role on the energy injection and dissipation in the solar wind interaction with Venus. The large dispersion of spectral scalings indicates that this fluctuation environment is complicated, and the shock geometry is not the only key factor in the fluctuations across the Venusian bow shock. Other possible factors in the shock modification to the upstream fluctuations will be explored in future.

By studying charge trapping in germanium detectors operating at temperatures below 10 K, we demonstrate for the first time that the formation of cluster dipole states from residual impurities is responsible for charge trapping. Two planar detectors with different impurity levels and types are used in this study. When drifting the localized charge carriers created by α particles from the top surface across a detector at a lower bias voltage, significant charge trapping is observed when compared to operating at a higher bias voltage. The amount of charge trapping shows a strong dependence on the type of charge carriers. Electrons are trapped more than holes in a p-type detector, while holes are trapped more than electrons in an n-type detector. When both electrons and holes are drifted simultaneously using the widespread charge carriers created by γ rays inside the detector, the amount of charge trapping shows no dependence on the polarity of bias voltage.

The plant nutrient acquisition strategies are diverse, such as root nutrient acquisition and leaf nutrient resorption, playing important roles in driving soil processes, vegetation performance as well as ecosystem nutrient cycling. However, it is still in a debate whether there is a synergy or tradeoff between above- and below-ground nutrient acquisition strategy under nitrogen (N) and phosphorus (P) addition, or with stand age. Herein, this study investigated the responses of root-soil accumulation factor (RSAF) and leaf nutrient resorption efficiency (NuRE) to long-term N and P fertilization, and further explored the trade-off between them in Metasequoia glyptostroboides plantations with different stand age. Results showed that under N fertilization in young plantations, leaf N resorption efficiency (NRE) increased, and root-soil accumulation factor for P (RSAF-P) decreased. For young forests under P fertilization, the NRE increased whereas RSAF-P decreased. For middle-aged forests under P fertilization, the NRE and leaf P resorption efficiency (PRE) increased and the RSAF-P decreased. Under P fertilization in young and middle-aged plantations, PRE had a significant positive correlation with RSAF-P. Under N fertilization in young plantations, NRE was significantly positive correlated with root-soil accumulation factor for N (RSAF-N). The covariance-based structural equation modeling (CB-SEM) analysis indicated that stand age had positive effects on PRE whether under N or P fertilization, as well as on RSAF-P under N fertilization, whereas had no effects on the NRE or RSAF-N. Overall, our results can shed light on the nutrient acquisition strategies of M. glyptostroboides plantations under future environmental changes and the results could be applied to the nutrient management practices.

Abstract For the first time, electrical conduction mechanisms in the disordered material system is experimentally studied for p-type amorphous germanium (a-Ge) used for high-purity Ge detector contacts. The localization length and the hopping parameters in a-Ge are determined using the surface leakage current measured from three high-purity planar Ge detectors. The temperature dependent hopping distance and hopping energy are obtained for a-Ge fabricated as the electrical contact materials for high-purity Ge planar detectors. As a result, we find that the hopping energy in a-Ge increases as temperature increases while the hopping distance in a-Ge decreases as temperature increases. The localization length of a-Ge is on the order of $$2.13^{-0.05}_{+0.07}\mathrm{{A}}^\circ $$ 2 . 13 + 0.07 - 0.05 A ∘ to $$5.07^{-0.83}_{+2.58}\mathrm{{A}}^\circ $$ 5 . 07 + 2.58 - 0.83 A ∘ , depending on the density of states near the Fermi energy level within bandgap. Using these parameters, we predict that the surface leakage current from a Ge detector with a-Ge contacts can be much smaller than one yocto amp (yA) at helium temperature, suitable for rare-event physics searches.

Abstract For the first time, planar high-purity germanium detectors with thin amorphous germanium contacts were successfully operated directly in liquid nitrogen and liquid argon in a cryostat at the Max-Planck-Institut für Physics in Munich. The detectors were fabricated at the Lawrence Berkeley National Laboratory and the University of South Dakota, using crystals grown at the University of South Dakota. They survived long-distance transportation and multiple thermal cycles in both cryogenic liquids and showed reasonable leakage currents and spectroscopic performance. Also discussed are the pros and cons of using thin amorphous semiconductor materials as an alternative contact technology in large-scale germanium experiments searching for physics beyond the Standard Model.

Abstract Germanium (Ge) detectors with ability of measuring a single electron–hole (e–h) pair are needed in searching for light dark matter (LDM) down to the MeV scale. We investigate the feasibility of Ge detectors with amorphous-Ge (a-Ge) contacts to achieve the sensitivity of measuring a single e-h pair, which requires extremely low leakage current. Three Ge detectors with a-Ge contacts are used to study the charge barrier height for blocking electrons and holes. Using the measured bulk leakage current and the Döhler–Brodsky model, we obtain the values for charge barrier height and the density of localized energy states near the Fermi energy level for the top and bottom contacts, respectively. We predict that the bulk leakage current is extremely small and can be neglected at helium temperature ($$\sim $$ ∼ 4 K). Thus, Ge detectors with a-Ge contacts possess the potential to measure a single e–h pair for detecting LDM particles.

Surface water system is an important part of global ecosystem, and the changes in surface water may lead to disasters, such as drought, waterlog, and water-borne diseases. The rapid development of remote sensing technology has supplied better strategies for water bodies extraction and further monitoring. In this study, AdaBoost and Random Forest (RF), two typical algorithms in integrated learning, were applied to extract water bodies in Chaozhou area (mainly located in Guangzhou Province, China) based on GF-1 data, and the Decision Tree (DT) was used for comparative tests to comprehensively evaluate the performance of classification algorithms listed above for surface water body extraction. The results showed that: (1) Compared with visual interpretation, AdaBoost performed better than RF in the extraction of several typical water bodies, such as rivers, lakes and ponds Moreover, the water extraction results of the strong classifiers using AdaBoost or RF were better than the weak basic classifiers. (2) For the quantitative accuracy statistics, the overall accuracy (96.5%) and kappa coefficient (93%) using AdaBoost exceeded those using RF (5.3% and 10.6%), respectively. The classification time of AdaBoost increased by 403 seconds and 918 seconds relative to RF and DT methods. However, in terms of visual interpretation, quantitative statistical accuracy and classification time, AdaBoost algorithm was more suitable for the water body extraction. (3) For the sample proportion comparison experiment of AdaBoost, four sampling proportions (0.1%, 0.2%, 1% and 2%) were chosen and 0.1% sampling proportion reached the optimum classification accuracy (93.9%) and kappa coefficient (87.8%).