Subjects: Biology >> Botany >> Applied botany submitted time 2024-05-07 Cooperative journals: 《广西植物》
Abstract： Seedling is the most important stage during the life history of plant and plays a critical role in the forest regeneration. We studied the species composition seasonal dynamics and spatial distribution of tree seedlings in the 20 hm 2 Ailaosha n forest dynamics plot . The forest dynamics plot was built in a mid mountain moist evergreen broad leaved forest in the Ailaoshan. Within the 20 hm 2 plot, we established 450 seedling quadrats of size 1 m × 1 m . We investigated the species composition, seas onal recruitment, seasonal mortality and spatial distribution of tree seedlings for four years ( from 2019 to 2022). The results were as follows: 1 We recorded a total of 2 928 seedlings of 58 species belonging to 42 genera and 26 families. There were 817 recruits of 47 species and 1 181 dead seedlings of 50 species. (2) The i mportance val u e s of tree seedlings varied among different tree species across years . Symplocos ramosissima and Machilus bombycina were t he dominant species, with importan ce values con sistently in the top 2 in four years while the importan ce value of the pioneer species Viburnum cyclindricum decline d continuously (3) W e didn't find significant differences in species richness, average species richness in a quadrat, species diversity S hannon Wiener index, Simpson index) index), abundance, recruits, recruitment rate, mortality and mortality rate of tree seedlings between different seasons. 4 The majority of species exhibited restricted distribution within the plot, wh ile only a few species di splayed a broader distribution across the plot. Topography was found to determine the distribution and diversity of tree seedlings with higher species richness, density and diversity (Shannon Wiener index and Simpson index) in the flat topography compared to the ridge and valley of the plot . T hese findings suggest that we don't find significant differences in community composition, recruitment and mortality of tree seedlings between different seasons. Topography influences the spatial distribution and diver sity of tree seedlings. The present study reveals the dynamics of recruitment and mortality of tree seedlings and provide the theoretical basis for biodiversity conservation and forest management.
Subjects: Geosciences >> Geography submitted time 2024-04-29 Cooperative journals: 《干旱区研究》
Abstract： As an important energy production and supply base in China, Xinjiang plays a pivotal role in the deli#2;cate balance between economic development and carbon emissions. Ensuring a harmonious coordination between these factors is essential to achieve sustainable economic growth and meet goals related to energy conservation and emission reduction. This paper measures and analyzes the spatiotemporal characteristics of energy consumption carbon emissions in Xinjiang from 2000 to 2020 using spatial autocorrelation based on the data obtained from Xinjiang Statistical Yearbook. Results indicate that the total carbon emission intensity from energy consump#2;tion in Xinjiang shows an increasing trend every year during the study period. Nevertheless, the overall trend reveals a reduction in the intensity of carbon emissions. The spatial distribution of carbon emission intensity shows that the eastern slope of Tianshan Mountain has a high carbon emission intensity, whereas the northern edge of Junggar, the northern slope of Tianshan Mountain, and the northern slope of Kunlun Mountain has a low carbon emission intensity. These regions exhibit evident clustering characteristics. Considering global warming and carbon emission reduction, Xinjiang must work toward achieving the goals of“carbon peak and“carbon neutrality”while promoting high-quality socioeconomic development in the area through the implementation of a multienergy, complementary green energy network
Subjects: Physics >> Nuclear Physics submitted time 2024-02-20
Longxiang Liu
Kang Sun
Han Yi
Fei Lu
Hongwei Wang
Gongtao Fan
Xiguang Cao
Yue Zhang
Suyalatu Zhang
Dexin Wang
Xinxiang Li
Yuxuang Yang
Pan Kuang
Xinrong Hu
Zirui Hao
Sheng Jin
Kaijie Chen
Wei Jiang
Ruirui Fan
Qiang Li
Abstract： The angle-differential cross sections of neutron-induced d production from carbon were measured at neutron energies 33.9 MeV at China Spallation Neutron Source (CSNS) Back-n white neutron source. By employing the ΔE-E telescopes of the Light-charged Particle Detector Array (LPDA) system at 24.5° to 155.5° in the laboratory system, the angle-differential cross sections of the 12C(n,d)x reactions were measured.
The experimental results are in good agreement with the previous ones.The present work can provide a reference to the data library considering the lack of experimental data.
Subjects: Astronomy >> Astrophysical processes submitted time 2023-11-24 Cooperative journals: 《天文研究与技术》
Abstract： The Chinese Space Station Telescope (CSST), which is expected to be launched in 2025, will mainly be used for large-scale multicolor imaging and slitless surveys. Before launch, it is necessary to use ground-based telescopes to conduct ground tests on the optical imaging system, detectors, and equipment of the space telescope for long-term operational stability. This dissertation designs a slitless spectral ground test for the 80 centimeter telescope at Xinglong Observation Observatory. By utilizing the strong absorption and emission line characteristics of A-type stars, B-type stars, and the Wolf-Rayet star HD4004, the dispersion equation is fitted and found to have spatial distribution characteristics. We performed quadratic surface fitting on the zero order spectral position information and dispersion equation coefficients of 53 pieces of HR3173 data, and used this curve to calibrate the wavelength of HR718 data within the zero order image position range of HR3173. The average radial velocity accuracy obtained was 51 km/ s.
Subjects: Astronomy >> Astrophysical processes submitted time 2023-11-24 Cooperative journals: 《天文研究与技术》
Abstract： In astronomical observation, the long-slit spectrometer is a kind of spectral observation equipment commonly used. The long-slit spectral mode of the Beijing Faint Object Spectrograph and Camera (BFOSC) mounted on the 2.16 m telescope of the Xinglong Observatory, National Astronomical Observatories, Chinese Academy of Sciences, is widely used, but it is not equipped with a specific data processing software. After observation, users usually run IRAF software interactively to obtain the final data product. This paper introduces an automatic data processing software for BFOSC long slit spectrum. It includes bias and flat-field correction, background subtraction, spectrum extraction and wavelength calibration. We describe the processing method and the flow of the program, and present the results of processing with the observed data, and compare them with the IRAF results. Our software realizes automatic operation on the basis of completing all the necessary steps of spectrum processing, and adopts the optimal extraction method, which automatically deducts most cosmic rays and ensures the high precision of output results.
Subjects: Astronomy >> Astrophysical processes submitted time 2023-11-24 Cooperative journals: 《天文研究与技术》
Abstract： The GCRF (Gaia Celestial Reference Frame) based on Gaia astrometric data has systematic differences from the ICRF (International Celestial Reference Frame) based on VLBI (Very Long Baseline Interferometry). An external independent evaluation of the data from Gaia is required to link optical and radio reference frame. Celestial bodies with both optical and radio radiation are generally used to link the two frames, quasars are used at the dark end (magnitude G≥15), and radio stars are used at the bright end (G≤13). It is very difficult to apply for the ordinary VLBI observations, so we try to focus on some geodesic observations that can use phase reference mode to observe radio stars in geodesic observations. In order to test the feasibility of this kind of observation, we use piggy-back phase referencing mode in geodetic observation of IVS (The International VLBI Service for Geodesy and Astrometry) and LBA (Large Baseline Array), and select Del Lib and HR 1099 as the targets. Our observations have obtained the VLBI images, flux densities and single￣epoch coordinates of these two radio stars, and the coordinate accuracy is higher than that of the previous work; at the same time, we also combine the data of the previous work to fit parallax and proper motion of the two radio stars. Our results are consistent with the results of the previous VLBI work and Gaia′s, and some of the accuracy is higher. Our work verify the feasibility of observing radio stars with piggy-back phase referencing mode in geodetic observation, and lay a certain foundation for the subsequent enrichment of VLBI astrometric samples of radio stars and linking of optical and radio reference frames.
Subjects: Astronomy >> Astrophysical processes submitted time 2023-11-17 Cooperative journals: 《天文研究与技术》
Abstract： In order to complete the monitor of ultra-broadband spectrum for solar radio burst，Yunnan Observatories have designed and developed 4 solar radio spectrometers with the frequency range of 15-80 MHz，100-750 MHz，600-4 200 MHz and 4-15 GHz，which are called decametric, metric, decimetric and resolution centimetric solar radio spectrometer, respectively. For the decametric solar radio spectrometer, the spectral resolution and temporal resolution have reached 7. 6 kHz and 1 ms, respectively. For metric and decametric, the spectral resolution and temporal resolution have reached 9. 5 kHz and 10 ms, respectively. For the centimetric spectrometer, the spectral and temporal resolution have reached 76 kHz and 10 ms, respectively. Each spectrometer includes antenna system, receiver and digital spectrometer. In order to obtain a spectrum with ultra-high spectral resolution, the maximum word length of FFT is 262 144, which cannot be achieved by one-time FFT in FPGA, the parallel FFT algorithm is need. For the large word length of FFT, the data need to be transformed into a FFT with two small word length by doing a row decomposition and then parallel processing. In this paper, the algorithm is studied and simulated by using Matlab, then is applied to digital spectrometer. The test results of the digital spectrometer are good consistency with the simulation, indicating the successful application of the algorithm on the digital spectrometer. This paper introduces the composition of solar radio spectrometer and the method of implementing ultra-high resolution based on FPGA.
Subjects: Astronomy >> Astrophysical processes submitted time 2023-10-23 Cooperative journals: 《天文研究与技术》
Abstract： Film thickness uniformity is an important indicator for the preparation of high-performance optical films. In order to further improve the uniformity of the film thickness of the 2.4 m primary mirror reflective film, an optimization scheme for the film thickness uniformity of the large-aperture telescope coating is designed. Based on the cosine distribution law followed by vacuum thermal evaporation, combined with the geometry of ZZ3200 vacuum coater and the actual needs of telescope coating, a film thickness calculation program is written to simulate the theoretical distribution of film thickness. The film thickness optimization design method and optimization results are given. Method 1: Add a correction mask at a suitable position inside the evaporation source, the results show that the radius of curvature of the mask is installed within 3 mm, and the Peak to Valley value of film thickness inhomogeneity decreases from 15% to 4% without mask, this method has certain universality, but the installation position of the mask should be accurately controlled; Method 2: Combined with the circular hole structure in the middle of the reflection primary mirror, the double ring evaporation source is designed, and the results show that when the center distance between the inner and outer ring evaporation sources is 10 cm and 130 cm, respectively, and the number of evaporation sources in the outer ring is 12 times that of the inner ring, the PV value of film thickness uniformity is 1.85%, which is designed for the mirror with a round hole in the center, and is suitable for most reflective astronomical telescope coatings.
Subjects: Astronomy >> Astrophysical processes submitted time 2023-10-20 Cooperative journals: 《天文研究与技术》
Abstract： In order to explore the differences in the applications of Astrometry.net and SCAMP in astrometric calibration as well as the differences in the calibration results obtained by running them in different processes, we first introduce the working principles of the two suits of software, and then do astrometric calibration to 100 images from the ZTF survey in 4 difference processes, taking Gaia DR2 catalog as the reference catalog. The calibration results including those given by ZTF itself are compared in terms of total time consuming, catalog matching, and coordinate RMS deviation. The results show that Astrometry.net can quickly calculate rough linear calibration results, while SCAMP can quickly perform distortion correction based on the former. The combined calibration process averagely takes only 1 second, and the average right ascension and declination RMS deviations are less than 70 milliarcseconds, which is better than the calibration result only using Astrometry.net. Therefore, using Astrometry. net and SCAMP in combination can achieve faster and more accurate astrometric calibration, which may be applied to data reduction of time-domain projects nowadays.
Subjects: Astronomy >> Astrophysical processes submitted time 2023-10-18 Cooperative journals: 《天文研究与技术》
Abstract： As an important basis for predicting solar activity, the McIntosh classification of sunspots is used by more and more international institutions and astronomical institutes because some categories are closely related to flare eruption. With the rapid increase in the amount of data, automatic McIntosh classification of sunspots has become an urgent need. Using the 720s-SHARP series data products provided by SDO/ HMI and SRS files from NOAA as images and labels for McIntosh classification, this paper first augmented valid samples of a complete solar cycle (time span of 12 years) and cleaned data to establish the sunspot database newSharp on the basis of the Sharp database with only 7-year data. Secondly, in view of the characteristics of sunspot images, a series of preprocessing operations such as data allocation by active region number were taken, and proved its rationality and necessity. Finally, four classical classification neural network models in CNN were used to compare Sharp and newSharp for McIntosh classification experiments. The results show that compared with Sharp, newSharp not only has a significant increase in the amount of data, but also has better weighted F1 score of most categories by augmenting valid samples and cleaning invalid samples. Besides, the weighted F1 score of categories with a small number from newSharp even has achieved a breakthrough of 0. Over all, the weighted F1 score of McIntosh-p improved the most, which greatly verifies the effectiveness of establishing a complete and reliable database and proves the rationality of using scientific and reasonable experimental methods. Thus it is able to better automatedly realize the end-to-end McIntosh classification tasks of sunspot images that are actually observed.
Subjects: Geosciences >> Geography submitted time 2023-05-30 Cooperative journals: 《干旱区研究》
Abstract： Abstract：The changes in soil loss, runoff, and sediment load in the headwaters of the Yangtze River and their correlation were studied based on the data of daily precipitation at 12 stations, and annual runoff and sediment at Zhimenda station in the headwaters of this river from 1980 to 2020. (1) The annual soil erosion modulus in the source area showed a significantly increasing trend (P<0.05), and the average annual soil erosion modulus was 4.71 t·hm-2·a-1. The erosion intensity and higher grades of erosion were mainly distributed in the southeast of the headwaters of the Yangtze River. (2) The runoff increased significantly (P<0.05), however, there was an abrupt change in 2004 when the suspended sediment concentrate and sediment load showed no significant change. (3) Precipitation had a significant positive effect on runoff and soil loss at 70% and 52.9%, respectively. Both runoff and soil loss showed direct positive effects on the sediment load. Precipitation, runoff, and soil loss explained 72.5% of the variation in sediment load. During this period, changes in precipitation had significant effects on soil loss and sediment in the headwaters of the Yangtze River. The results can provide a scientific basis for the research and evaluation of the effects of implementing ecological engineering in the headwaters of the Yangtze River.
Subjects: Biology >> Botany submitted time 2023-05-30 Cooperative journals: 《干旱区研究》
Abstract： The release of high- quality protoplasts from plant tissues is a prerequisite for the establishment of other technical systems such as protein subcellular localization, transient expression analysis, and protein-protein interactions. To quickly explore the special functional genes of the C3-C4 intermediate plant Salsola laricifolia, it is essential to establish a simple and efficient method for preparing leaf protoplasts. In this study, the euphylla of axenic tissue culture seedlings of S. laricifolia was used as material to analyze the effects of different concentration ratios of cellulase and isolated enzymes and osmotic pressure on protoplast isolation. The results showed that the true leaves of sterile tissue culture seedlings with a seedling age of 25 days were used for enzymatic hydrolysis in enzymatic hydrolysis solution of 2% cellulase + 0.5% isolated enzyme R-10 + 0.6 mol·L-1 mannitol at 25 °C for 2 h, and W5 The solution was purified at a speed of 800 rpm·min-1, the yield of protoplasts could reach 1.21 × 106, and the viability was 85%. Using the obtained protoplast of S. laricifolia as a receptor, the pBI121-SaNADP-ME4-GFP plasmid vector was successfully transformed by the PEG transformation method, and it was detected that SaNADP- ME4 was located in the chloroplast. In this study, an efficient system for preparing protoplasts from the leaves of S. laricifolia was established, which lays the foundation for mining the special gene functions of this species.
Subjects: Biology >> Ecology submitted time 2023-05-30 Cooperative journals: 《干旱区研究》
Abstract： Many studies on grassland ecosystem degradation have been performed using vegetation coverage orproductivity indexes for evaluation. However, it is difficult to comprehensively evaluate different degrees ofgrassland degradation using a single evaluation index. Taking Bayinbuluk grassland in the Xinjiang TianshanMountains as a research object, a remote sensing method for evaluating grassland degradation based onstandardized processing sub- index coupling was proposed. The grassland vegetation coverage, average grasslayer height, and total grass yield were selected to determine the weight of the three indexes by principalcomponent analysis. The Min-Max standardized method was introduced to construct the grassland degradationindex (GDI). Finally, the degree of degradation of Bayinbuluk grassland in the Xinjiang Tianshan Mountains wasdetermined through Landsat image inversion and reasonable classification of the rate of change of grasslanddegradation index from 1986 to 2021. The results showed that GDIg has the best correlation with NDVI. In 2021,the proportion of undegraded area of Bayinbuluk grassland relative to the total area was 60.51%. The degree ofdegradation of different grassland types showed clear differences. The spatial distribution showed a trend of basinto mountain degradation. The GDIrs model could be applied to other years through the radiation registrationmethod. The degree of degradation of Bayinbuluk grassland significantly improved from 2000 to 2009 andslightly fluctuated from 2009 to 2021. The results of this research provide robust data support and a theoreticalbasis for guiding evaluation of the degree of degradation of Bayinbuluk grassland and protecting the grasslandecosystem.
Subjects: Geosciences >> Geography submitted time 2023-05-30 Cooperative journals: 《干旱区研究》
Abstract： The Wuding River Basin is the key area for the implementation of the grain for green program on the Loess Plateau. Exploring the spatial differentiation mechanism of land cover and the characteristics of variation of related water-carbon variables is essential for supporting water and soil resources conservation and planning, along with serving the construction of regional ecological civilization. Here we used the linear tendency method, Mann-Kendall trend test, Pettitt test, and geodetector to analyze the spatiotemporal characteristics and the factors driving the spatial differentiation of land cover in Wudinghe River Basin. In addition, from the perspective of land- water- carbon coupling, we analyzed the characteristics of variation of total primary productivity (GPP), actual evapotranspiration (ET), and water use efficiency (WUE). Three main results were as follows: (i) The total grassland, forest, and construction land increased significantly, while the cropland and barren land decreased significantly during 1990-2019. The area of forest and grassland increased mainly in the lower reaches of the basin and along Wuding River. (ii) Population density, precipitation, and temperature have a significant impact on the spatial pattern of land cover. On the whole, the influence of socioeconomic factors is greater than that of natural factors, but the influence of natural factors represented by precipitation and temperature is increasing. (iii) There is a good correlation between the variation of water- carbon variables and land cover change. Spatially, GPP, ET, and WUE are relatively high in the southeastern part of the basin where cropland, forest, and grassland are the main cover, while they are lower in the northwestern part of the basin where grassland and barren land are the main cover. In terms of time, GPP, ET, and WUE all showed increasing trends during 2001-2019. GPP and WUE increased significantly in most parts of the basin, while ET increased significantly mainly in its middle and lower reaches. In conclusion, under the implementation of the grain for green program and climate change, the forest and grass in Wudinghe River Basin have been restored and the ecology has been improved.
Subjects: Geosciences >> Atmospheric Sciences submitted time 2023-03-15 Cooperative journals: 《干旱区地理》
Abstract： As the main carrier of alpine freshwater ecosystems, alpine lakes are currently experiencing rapid climate change that has profound and complex effects on their ecosystems. In this study, we systematically analyze the effects of altitude-dependent warming on the thermal properties, dissolved oxygen stratification, and biological processes of alpine lakes in the context of climate change, describe the adaptation measures of alpine aquatic organisms and changes in underwater radiation characteristics in the context of radiation enhancement, and reveal the effects of precipitation changes on the cross-ecosystem material subsidies and biogeochemical cycles in alpine lakes, as well as the mechanism of the impact of precipitation changes on these cross-ecosystem material subsidies and biogeochemical cycles in mountain lakes. In the future research, we must improve the integrated response experiments of lake habitats under the changes of multiple climate factors, strengthen the systematic monitoring and integration of the whole elements of alpine lake ecosystems, and change the research type (i.e., static and qualitative research to process, dynamic, and quantitative research) to enhance knowledge on the response mechanism of alpine lake ecosystems to global climate change.
Subjects: Geosciences >> Hydrology submitted time 2023-03-14 Cooperative journals: 《干旱区地理》
Abstract： In arid areas，snowmelt is the main source of water resource formation. Therefore, the formation, transformation and utilization of snow resources are important research topics on the development and utilization of water resources in Xinjiang, China. Further, hydrological model is a key to determine the formation and transformation of water resources. This study uses the field experimental area of Tianshan Snow Station, Chinese Academy of Sciences, as the experimental area. The meteorological data and snowmelt amount were adopted as the independent and dependent variables. A snowmelt model based on temperature change is studied, and a singlefactor simple model is calibrated and validated. Simultaneously, the variation law of snowmelt in the experimental area for many years and the response process of snowmelt to temperature are analyzed. The results indicate that snowmelt still occurs in winter in certain low- temperature ranges. In the study area of Tianshan Mountains, the critical value of daily average temperature of snowmelt is approximately -7 ℃. When the temperature is lower than -7 ℃, snowmelt is basically suspended, reflecting the characteristics of snowmelt in arid areas. In terms of the model, a single factor simple snowmelt model based on temperature exhibits good performance in simulating snowmelt in mountainous areas. During the calibration period (2016—2020), the correlation parameters of Bias, MAE, RMSE, NSE and R2 between the observed and simulated snowmelt values were -0.037, 0.367, 0.482, 0.870, and 0.876 respectively. The values of validation period were -0.210, 0.292, 0.577, 0.845, and 0.811, respectively. The simulation results and correlation coefficients during the validation period indicate that the simulated value of the model has good consistency with the measured value. The advantage is that the amount of snowmelt in the basin can be estimated through the available meteorological data. The results provide a relatively simple algorithm for snowmelt calculation in arid areas and a simple and effective snowmelt submodule for a hydrological model. This study has an important reference value for understanding the change law of snowmelt and the simulation and prediction of snowmelt runoff in subsequent studies
Subjects: Biology >> Ecology submitted time 2023-03-13 Cooperative journals: 《干旱区研究》
Abstract： The understanding of the evolution process of barchan dune and its movement rate is an important prerequisite for wind prevention and sand fixation and ecological construction in Minqin oasis. Based on field measurement and high- resolution remote sensing image analysis, The study discusses the relationship between the morphological parameters of barchan dune and its movement rate in the upwind edge of Minqin oasis. The results show that: (1) The aspect ratio of the dunes remains a constant value of 16 in 16 years. (2) The average annual moving distance of the tall dune is less than 3 m, which is a medium moving speed. The shape of the tall dune is basically unchanged, and the change is obvious only at the baseline, ridge line, and wing Angle of the windward slope. Low dunes move fast, with an average annual distance of more than 10 m, which is an extremely fast-moving speed. (3) The downwind velocity of the dune is inversely proportional to its width, and the proportionality constant is 718.52 m2 ·a-1. In this area, the barchan dune is dominated by fast-moving speed, which is greater than 5 m·a-1, accounting for 52.63%. (4) During the process of sand erosion on the windward slope and deposition on the leeward slope, large dunes maintain stable morphology and move slowly. Small dunes change dramatically and move rapidly, and the dunes tend to shrink in development.
Subjects: Biology >> Botany submitted time 2023-03-13 Cooperative journals: 《干旱区研究》
Abstract： Leaves and roots respond to drought stress through morphological, physiological, and biomass accumulation changes. Alhagi sparsifolia is the dominant plant in the desert- oasis transition zone of Cele. We analyzed the characteristics of growth and physiological changes in leaves and roots of 1-year-old A. sparsifolia seedlings through a pot experiment. Results revealed the adaptive strategy of A. sparsifolia to drought stress. We simulated three water conditions (CK is well- watered: 70%-75% field capacity (FC); W1 is mild stress: 50%- 55% FC; W2 is severe stress: 25%-30% FC). The results show the following: (1) Drought significantly inhibited the growth of the aboveground and underground tissues of A. sparsifolia. The main manifestations are: leaf area, root length, root surface area, root tissue density, and soluble sugar content of leaves and roots decreased significantly under stress (P < 0.05). The leaf tissue density, leaf dry matter content, specific root length, proline and malondialdehyde contents of leaf and root increased. (2) In the early growth stage, the aboveground biomass of A. sparsifolia under all treatments was relatively high (root-shoot ratios under CK, W1, and W2 were 0.43 ± 0.14, 0.59 ± 0.1, and 0.83 ± 0.83), while in the late growth stage, the below-ground biomass under all treatments was relatively high. The root-shoot ratio was the highest under severe stress (3.12 ± 0.32). The results indicate that A. sparsifolia enhanced the investment of resources underground in the late growth stage, and the resource allocation characteristic is more obvious under severe drought stress. (3) Pearson-correlation analysis showed that there was a significant tradeoff between core traits related to leaf morphology and root physiology in A. sparsifolia (P < 0.05). Meanwhile, the leaf and root had synergistic changes in physiological metabolism. The results preliminary indicate the adaptive characteristics and A. sparsifolia seedlings under drought exhibit high dry matter storage, defense capacity, and low water consumption. A. sparsifolia can coordinate the resource allocation relationship between leaves and roots. At the same time, with drought stress time increased, the adaptive strategy of slow investment and conservative growth of A. sparsifolia was gradually formed. The results provide a reference for the restoration and management of desert vegetation in this region.
Subjects: Astronomy >> Astrophysical processes submitted time 2023-03-13 Cooperative journals: 《天文研究与技术》
Abstract： Continuously rotating waveplates as the polarization modulator is an important candidate polarimeter configuration for many solar telescopes to measure the solar magnetic field. It is widely adopted in many ground-based or space-based solar telescopes for the solar magnetic field measurement. In this paper, we present the derivation and formula of the Fourier demodulation in the context of continuously rotating waveplates. We further testify the formula correctness by using the synthetic FeI Stokes profiles, which are produced by the RH radiative transfer code with a given atmosphere model. In addition, we calculate the effect of the home-position errors, the positioning errors of the waveplate rotation and the time difference between the waveplate slot time and the detector frame time on the demodulated results, by using two kinds of demodulation methods, i.e., the demodulation matrix and the Fourier analysis. The main findings are: (1) The new Fourier analysis can provide more accurate results than the simple one adopted by the step-wise modulation. Similar results are obtained when we do the relative error estimation using these two demodulation methods. (2) Considering the relative errors due to the home-position angle error, we find the demodulated linear polarization are almost the same using these two methods. However, in the case of circular polarization, the demodulation based on the demodulation matrix is more reliable. Whatever which method is applied, it is shown that the home-position angle error has the same effect on both the circular and linear polarization. The relative error of 10-3 requires the home-position angle accuracy within ten arc seconds. (3) Calculating the relative error caused by the position error of the waveplate rotation, we find the demodulation results are almost equal using these two methods. Both of them show that the position error has more influence on the linear polarization. Furthermore, the requirements of the position accuracy are much higher (ten of arc seconds) than that in the case of step-wise modulation (0.1 degree) in order to achieve the relative error of 10-3. (4) It is crucial to precisely match the detector frame time and the waveplate rotation slot time. We investigate the relative error due to the difference between them and find that the time difference (∆) can cause cross-talk between the linear polarization signals. It has more prominent effect on the linear polarization than on the circular polarization. The time difference as a percent of the waveplate slot time (∆/T) is required to be smaller than 1% if the relative error is smaller than 10-3 for the linear polarization.
Subjects: Biology >> Botany submitted time 2023-01-30 Cooperative journals: 《广西植物》
Abstract：
Wild plants are an important part of the natural ecological system, and China is one of the countries with the most abundant wild plant species. It is of great significance to study the distribution characteristics, protection status and of potential distribution areas of National Key Protected Wild Plants for supporting and formulating biodiversity conservation strategies. In this study, we built an occurrence database containing 1 032 species (belonging to 315 genera, 129 families) of National Key Protected Wild Plants, then used the top 5% richness algorithm to identify hotspots and evaluate the conservation effectiveness and gaps of current nature reserves. Furthermore, we used maximum entropy (MaxEnt) model to predict the potential distribution and range shifts of National Key Protected Wild Plants. The results were as follows: (1) The areas with the highest species richness of the National Key Protected Wild Plants mainly confined to south and southwest of China, especially central Sichuan, southern and southeastern Yunnan, northern Guangxi, northern Guangdong and Hainan. (2) The conservation effectiveness of hotspot grid cells showed that 171 (85.50 %) hotspots are efficient protection (including 80.5 % of total species) and 29 hotspots (14.50 %) are not effectively protected (including 51.2 % of total species). (3) By comparing the potential distribution of National Key Protected Wild Plants under current and future climate scenarios, we found that potential distribution would expand to southeast of Xizang, southwestern Guangxi, southern Guangdong, and southern Fujian in the future, while those around Sichuan Basin, southern Yunnan and southern Guizhou would shrink. Therefore, it is necessary to strengthen the dynamic monitoring of biodiversity and pay continuous attention to the impact of climate change on National Key Protected Wild Plants in the region. Based on the analysis results of hotspot grids, conservation effectiveness and potential distribution areas identified in this study, strong data support and reference can be provided for the identification of national priority protected areas for National Key Protected Wild Plants diversity and the formulation of conservation policies.
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