Genetic diversity and population structure of a protected species: Polygala tenuifolia Willd.

Polygala tenuifolia Willd. is an important protected species used in traditional Chinese medicine. In the present study, amplified fragment length polymorphism (AFLP) markers were employed to characterize the genetic diversity in wild and cultivated P. tenuifolia populations. Twelve primer combinations of AFLP produced 310 unambiguous and repetitious bands. Among these bands, 261 (84.2%) were polymorphic. The genetic diversity was high at the species level: percentage of polymorphic loci (PPL)=84.2%, Nei's gene diversity (h)=0.3296 and Shannon's information index (I)=0.4822. Between the two populations, the genetic differentiation of 0.1250 was low and the gene flow was relatively high, at 3.4989. The wild population (PPL=81.9%, h=0.3154, I=0.4635) showed a higher genetic diversity level than the cultivated population (PPL=63.9%, h=0.2507, I=0.3688). The results suggest that the major factors threatening the persistence of P. tenuifolia resources are ecological and human factors rather than genetic. These results will assist with the design of conservation and management programs, such as in natural habitat conservation, setting the excavation time interval for resource regeneration and the substitution of cultivated for wild plants.

[Analysis on Impact Factors of Thermal Polarized Radiation Characteristics of the Soil].

As an important content of the nature, soil has great influence on the formation of ecological system and human life. Therefore, the study of soil's polarized thermal radiation characteristics has great practical significance. There have been few reports about the study of the polarized radiation characteristics of the soil in 2π space. The results showed that the polarized brightness temperature performed nonlinearly as the change of detection angles between 0° to 80°. However, polarized brightness temperature increased greatly when the detection angle changed from 60° to 80°. It also changed under different azimuth angles. The polarized brightness temperature increased as the growth of the azimuth angles in the range of 0° to 240°, but its tendency was opposite in the range between 240° and 320°. The channels and polarized angles both influenced the polarized brightness temperature. Their amplitudes of fluctuation of their own curves were gentle and the temperatures of different agrotype were various. The order was Meadow Soil>Leached Chernozem>Chernozem>Aeolian Soil. These results provide significant foundation to the study about the basic theory of thermal infrared polarization remote sensing.

[An Identification Study on Field-Derived Spectra of Grassland Combustibles and Soil Based on Fractal Theory].

Grassland fire disaster is an important influence factor to grassland ecological system in China. Therefore, it is crucial to study on the monitoring, prediction and management of grassland fire. Remote Sensing (RS) provides detailed data and saves a lot of manpower, material resources and financial resources on the research of grassland fire. However, it is difficult to identify the grassland fuel and soil with Remote Sensing. In this paper, we introduced fractal into the spectral analyses of the field-derived spectra (FDS) of grassland fuel and soil to solve the problem above. The study area laid on the Westward of Changling, Jinlin province, China. Study subjects included soil and dominant species: Leymus chinensis, Reed, Chloris virgate, Kalimeris integrifolia and Artemisia mongolica. FDS of study subjects were measured with ASD FS3 and continuums of FDS were calculated by Matlab 2010. Meanwhile, Box-counting values of FDS and continuums were calculated by Matlab 2010. According to the spectral and continuum analysis, it is difficult to identify soil, Leymus chinensis, Reed, Chloris virgate, and Artemisia mongolica because of the similar spectral curves. However, the Artemisia mongolica can be identified for the strong reflection. For typical fractal characteristics of FDS and continuum, clustering analyses of study subjects were done according to box-counting values of FDS and continuum. The results of clustering analyses show that Box-counting values of FDS and continuum are important indexes to identify the study subjects. This study provides a new thought to identity the grassland combustibles and soil with Remote Sensing.

[Research on the Thermal Infrared Polarization Properties of Fresh Snow].

Snow can directly affect the surface energy balance and climate change and has a significant impact on human life and production. It is therefore of great significance to study the fresh snow emission spectroscopy properties by using the thermal infrared Polarization technique. This can provide a basis for quantitative thermal infrared remote sensing monitoring of snow as well as a deeper understanding of global warming and appropriate countermeasures. This paper focuses on the investigation of the thermal infrared polarization properties of the fresh snow. The results show that the thermal emissive polarization properties of fresh snow depend significantly on the wavelengths (channels) and view angles used to measure them. Four channels are considered in this study, their spectral response ranges are 8-14 microm for channel 1 (CH1), 11.5-12.5 microm for channel 2 (CH2), 10.3-11.5 microm for channel 3 (CH) and 8.2-9.2 microm for channel 4 (CH4). The snow polarized radiance (L) and its polarized brightness temperature (T) manifest as L(CH1) >L(CH3) > L(CH4) > L(CH2) and T(CH4) > T(CH1) > T(CH2) > TCH3, respectively, while the degree of polarization (P) manifests as P0 > P30 > P40 > P20 > P0 > P50 where the subscript of P denotes the view angle. The maximum of both L and T occurs at the view angle of 50 degree and polarization angle of 90 degree while their minimum appears at the view angle of 30 degree and polarization angle of 75 degree for each channel. In addition, the results show that: CH3 is more appropriate for better investigation of the emissive polarization properties of snow. Linear relationship is found between the fresh snow polarized T and the polarization angle with the coefficient of determination larger than 0.77 for all four channels. The polarized brightness temperature of the fresh snow is found to be increased about 0.003 K per polarization angle within 0-135 degree. The degree of polarization of snow is almost independent of the channels we used (CH1 to CH4). The snow emissive polarization is isotropic and the relative azimuth view angle has no significant impact on the snow emissive polarization properties. The impact of the polarization angle may be neglected if the investigation of the relative azimuth view angle on the fresh snow thermal emissive polarization is conducted. The difference of the fresh snow emissive polarization properties mainly comes from the snow surface roughness and structure.

[Study of Retrieving the Sandy Surface Roughness Land Based on the Bidirectional Reflectance Model].

In the semiarid area, the structural nature of sandy land is changed due to wind erosion. Furthermore, assessing the changes in the composition and surface roughness in several spatial and temporal scales is significant for the wind erosion model calculations. As a noninvasive approach, remote sensing can be used to improve the study of sandy surface in time and space. In order to characterize the surface structure using the reflectance of sandy land, we analysis the effects of the changes of sandy surface structure on the bidirectional reflectance distribution basing on the multi-angular and hyperspectral measurements in the field; the measured sandy land samples are taken from nature, but the surface structures are artificial: one type is the direction of sand furrows is parallel to the incident direction, the other is the direction of sand furrows is perpendicular to the incident direction. At the same time, we analyzed the effects of surface structure on the bidirectional reflectance factor of sand land and we also retrieve the sandy surface roughness using the reflectance model parameter. The results suggest that both types of sand furrows will influence the distribution of reflectance of sandy land surface, for example, the backward scattering of sandy land increased when the direction of sand furrows is perpendicular to the incident direction, and the range of backward scattering of sandy land expended when the direction of sand furrows is parallel to the incident direction. When we compared the measured reflectance with the modeled results basing on the reflectance model, it is found that the reflectance model can be used to simulate the reflectance property of sandy land surface and prove that the parameter of model is useful for retrieving the surface roughness. This research not only presents the sample for quantifying the structural information of sandy land by the reflectance measurements, but also shows valuable reference for the research of intrinsic optical property of sandy land and the reversion of the texture of sandy land. In other words, this paper can also help the scientists understand the effect of the structural information on the optical properties of sandy land.

[Analysis of related factors of slope plant hyperspectral remote sensing].

In the present paper, the slope gradient, aspect, detection zenith angle and plant types were analyzed. In order to strengthen the theoretical discussion, the research was under laboratory condition, and modeled uniform slope for slope plant. Through experiments we found that these factors indeed have influence on plant hyperspectral remote sensing. When choosing slope gradient as the variate, the blade reflection first increases and then decreases as the slope gradient changes from 0° to 36°; When keeping other factors constant, and only detection zenith angle increasing from 0° to 60°, the spectral characteristic of slope plants do not change significantly in visible light band, but decreases gradually in near infrared band; With only slope aspect changing, when the dome meets the light direction, the blade reflectance gets maximum, and when the dome meets the backlit direction, the blade reflectance gets minimum, furthermore, setting the line of vertical intersection of incidence plane and the dome as an axis, the reflectance on the axis's both sides shows symmetric distribution; In addition, spectral curves of different plant types have a lot differences between each other, which means that the plant types also affect hyperspectral remote sensing results of slope plants. This research breaks through the limitations of the traditional vertical remote sensing data collection and uses the multi-angle and hyperspectral information to analyze spectral characteristics of slope plants. So this research has theoretical significance to the development of quantitative remote sensing, and has application value to the plant remote sensing monitoring.

[Study on the thermal radiation polarization characteristics of ice].

As an important parameter of the global energy balance, climate, hydrological and ecological model, ice directly affects the energy balance of the earth-atmosphere system, weather and climate. It is of great significance to use the thermal infrared polarization technology to study ice thermal radiation. For the ice monitoring and the impact of global climate change on the ice, studies on ice thermal radiation polarization characteristics were conducted based on the wavelength, detection angle and azimuth angle. The results show that the wavelength has an obvious impact on the ice thermal radiation polarization properties. The polarized radiance of four bands shows that L(CH1) > L(CH3) > L(CH4) > L(CH2) while the polarization brightness temperature shows that T(CH4) > T(CH1) > TCH2 > TCH3. It's better to use the brightness temperature of the third channel than the radiance to study the thermal radiation polarization. The detection angle affects the ice thermal radiation polarization characteristics greatly and there are some differences between the polarization angles. The brightness temperature of ice is the lowest in the detection angle of 10 degrees and the polarization angle of 30 degrees, which are non-accidental factors. These was closely related to ice physical and chemical properties. The degree of ice polarization performance shows that P0 < P40

[Autotoxicity of aqueous extracts from plant of cultivated Astragalus membranaceus var. mongholicus].

OBJECTIVE: To exploring the relationship between continuous cropping obstacle and autotoxicity of Astragalus membranaceus var. mongholicus, autotoxic effect of plant aqueous extract were determined. METHODS: Distilled water (CK), aqueous extract of plant, including root, stem and leaf (12.5, 25, 50 and 100 mg/mL respectively)were applied to testing their effect on early growth of Astragalus membranaceus var. mongholicus. Specifically, seed germination rate, germination index, emergence rate, elongation of radical and embryo, and seedling vigor index were determined. RESULTS: The aqueous extract of root, stem, and leaf at 25 mg/mL significantly inhibited the seed germination and seedling growth of Astragalus membranaceus var. mongholicus, and this inhibitory effect generally increased with the increase of the concentration of aqueous extracts. To the comprehensive allelopathic effect, the extracts from Astragalus membranaceus var. mongholicus stem were more inhibitory than those from leaf and root. The germination index and seedling vigor index were more sensitive to extract than other determined parameters. CONCLUSION: Aqueous extracts from Astragalus membranaceus var. mongholicus plant gave inhibitory effects on Astragalus. membranaceus var. mongholicus germination and seedling growth, and this inhibitory effect generally increased with the increases of aqueous extract concentration at a certain ranges. In conclusion, there is an autotoxicity in continuous cropping of Astragalus membranaceus var. mongholicus.

[Study on quality assessment of Polygalae Radix based on HPLC-DAD fingerprint].

OBJECTIVE: To establish an HPLC fingerprint to evaluate the quality of Polygalae Radix, root xylem, and those collected in different growth ages or harvest time. METHOD: Separation was performed at 30 °C on a Kromasil C18 column (4.6 mm x 250 mm, 5 µm); the mobile phases was acetonitrile and 0.05% H3PO4 water in the gradient elution; the flow rate was set at 1.0 mL · min(-1) and the detection wavelength at 314 nm; the quality discriminant analyses were accomplished by means of similarity analysis, cluster analysis, principal component analysis and neural network model. RESULT: In 26 batches of Polygalae Radix, 24 batches fingerprint similarities were above 0.8. In 5 different growth or harvest time batches, 4 batches were above 0.8; in 8 batches root xylem samples, the similarities were all above 0.875. The similarity analysis was in accord with the quality discriminant analysis of cluster analysis, principal component analysis and neural network model. CONCLUSION: Fingerprint combined with chemical pattern recognition technique can effectively evaluate the quality of Polygalae Radix. The active substance species are all similar in cultivated, wild, different growth or harvest time Polygalae Radix and polygala root xylem, but the chromatography peak areas are different. The effective material contents are similar between wild and cultivated Polygalae Radix, but each chromatographic peak area of the root xylem is much smaller than that of Polygalae Radix. The chemical substance accumulation mainly depends on harvest month, but little growth time in Polygalae Radix.

[The research of the relationship between snow properties and the bidirectional polarized reflectance from snow surface].

In the context of remote sensing, the reflectance of snow is a key factor for accurate inversion for snow properties, such as snow grain size, albedo, because of it is influenced by the change of snow properties. The polarized reflectance is a general phenomenon during the reflected progress in natural incident light In this paper, based on the correct measurements for the multiple-angle reflected property of snow field in visible and near infrared wavelength (from 350 to 2,500 nm), the influence of snow grain size and wet snow on the bidirectional polarized property of snow was measured and analyzed. Combining the results measured in the field and previous conclusions confirms that the relation between polarization and snow grain size is obvious in infrared wavelength (at about 1,500 nm), which means the degree of polarization increasing with an increase of snow grain size in the forward scattering direction, it is because the strong absorption of ice near 1,500 nm leads to the single scattering light contributes to the reflection information obtained by the sensor; in other word, the larger grain size, the more absorption accompanying the larger polarization in forward scattering direction; we can illustrate that the change from dry snow to wet snow also influences the polarization property of snow, because of the water on the surface of snow particle adheres the adjacent particles, that means the wet snow grain size is larger than the dry snow grain size. Therefore, combining the multiple-angle polarization with reflectance will provide solid method and theoretical basis for inversion of snow properties.

[Study on the response to the soil moisture polarized spectrum under visible-near infrared band].

Moisture is one of the important parameters in soil polarized spectrum. It has great significance in soil remote sensing band selection and image interpretation; it also provides the information for soil investigation and analysis on physical and chemical properties. In the present paper we tested and analyzed the soil polarized spectrum with different moisture in 350-2 500 nm wavelength range to study on the relationship between soil polarized spectral data and moisture, to determine the spectral response and changes in soil moisture, to establish models between spectral data and soil moisture and select the best forecast model. The results show that the accuracy of the polarized derivative spectra model is higher than the polarized spectral model and absorbance model. All the models showed a water content threshold, and found that it is a certain regularity that critical value of soil moisture in different polarization is near 30%.

[Study on the nonlinear characteristics of the mixed pixel's reflectance in hyperspectral space].

Under the experimental condition of the 50 degree incidence zenith angle and 45 degree detection azimuth, 24 groups of reflectance spectral of the mixed pixel of lotus and water body acquired using the reflex platform and FieldSpec 3 Hi-Res portable spectrum instrument. The hyperspectral space was built based on the reflectance character. The relationship between similarity and the index of lotus area ratio was analyzed using the linear, logarithm and quadratic curve fitting, and the goodness of fitting is 63.6%, 76.2% and 82.9% respectively. According to the real relationship of the mixed pixel spectral vector and the reference spectral, the best fitting model has nonlinear characteristics. The idea that the mixed pixel may have the critical value was proposed on the base of the analysis. The research result will help understand the mixed pixel further, and provide a new direction for unmixing the mixed pixel.

[Analysis of the polarization properties of snow in a different melting state].

Nowdays, under the circumstance of global warming, the traditional study of solid-state snow can not meet the current needs. The present paper involves qualitative analysis of the polarization reflectance spectrum of snow in a different melting state. Special attention is paid to the investigation of the relationship among polarization angles, azimuth angles, the light incidence zenith angles, the detection zenith angles and the different types of snowmelt. It turns out that all these factors have certain influences on the polarization reflectance spectrum of different types of snowmelt. At the waveband of the visible light, the polarization reflectance of snowmelt is the largest at 90 degrees, and the smallest at 0 degrees. The wider the detection angles and the incidence angles, the larger the polarization reflectance. Anomalies (unusual phenomena), different from other spectra, occur when the polarization reflectance spectrum of snowmelt is observed at different azimuth angles. The characteristics of polarization spectra at some certain wavebands play an important role in determining the water content of snowmelt, and meanwhile with the increase of which, the polarization reflectance will go down obviously. These rules have laid a solid foundation for the quantitative analysis of snowmelt properties by using polarization spectrum in the future and are also of great importance in fresh water management as well as monitoring natural disasters such as the spring flood.

[Studies of the thermal radiation multi-angle polarization properties of snow].

This paper, catering to the need of the study of remote sensing for thermal radiation polarization properties of ground features, detects the thermal radiation multi-angle polarization properties of snow, and makes analysis of effects of four factors, i. e. detecting zenith angle, detecting azimuth angle, bands and polarizing angle, on the thermal radiation properties of snow. The results show that the radiance and brightness temperature of snow increases with the detecting zenith angle. When the detecting zenith angle is greater than 30 degrees, the growth accelerated, and the effect of detecting zenith angle on the brightness temperature of snow is more significant than that of the radiance; the changes in detecting azimuth angle have some effect on the radiance and brightness temperature of snow, and have much influence on the brightness temperature than that of the radiance; the radiance and brightness temperature of snow is significantly affected by the changes in bands, and the effect on the radiance is more significant; the changes in polarizing angle have some effect on the radiance and brightness temperature of the snow, and have much influence on its brightness temperature. The results of the study provide new ideas and methods for the application of remote sensing technology to carrying out the thermal infrared quantitative study of snow, and have important theoretical significance and potential applications.

[Study on the thermal infrared polarization characteristics of the grassland withered plants].

With the development of remote sensing technology, it is important to study on the thermal infrared polarization characteristics of the land surface objects. In order to explore the thermal infrared polarization characteristics of the grassland withered plants, the samples of the grassland withered plants were measured indoor according to the thermal infrared polarized detection mechanism, using thermal infrared radiometer. The results showed that the thermal infrared polarized radiance and brightness temperature have increased with the viewing angle and have increased first and then decreased with the azimuth and polarized state. Chloris virgata's brightness temperature decreased first and then increased at 180 degrees azimuth, which is an exceptional case. These reflect that the thermal infrared polarization characteristics are related to the materials' roughness, the detecting direction, the internal structure and its emission ability, and this research laid the foundation for other quantitative studies.

[Effect of spectral resolution on black soil organic matter content predicting model based on laboratory reflectance].

Laboratory reflectance of Black soil samples was re-sampled with different spectral resolution, and the correlation between soil organic matter (OM) and reflectance, spectral variables was analyzed to study the effect of spectral resolution on black soil OM predicting model. The results are as follows: the spectral response range of black soil OM is between 445 and 1 380 nm, high OM content shades the spectral effect of other soil properties. The precision of black soil OM predicting models increases and decreases with spectral resolution, and the maximum accuracy is at 50 nm, which is wider than hyperspectral resolution, and narrower than the bandwidth of multispectral sensors; with the derivative of logarithmic reflectance reciprocal as input variables, the optimal black soil organic matter predicting model shows high accuracy, with R2 = 0.799 and RMSE = 0.439; the results can provide the academic and technical support for soil organic matter remote sensing reversing and quick instrument developing.

[Studies of the thermal radiation characteristics of urban typical surface features].

The use of thermal infrared technology to monitor the land surface temperature has received mature development, and the acceleration of urbanization makes the urban heat effect emerge, thus, studies of the thermal radiation characteristics of urban typical surface features make great significance for the analysis of the causes and distribution of the thermal phenomenon. Based on the study of ground measured data of Baoding city, we have found that, the feature types, the observation time and wall orientations are principal factors that exert an influence on the thermal radiation brightness temperature of urban typical surface features. The results show that different types of surface features will significantly affect the brightness temperature, but "different things with the same spectrum" still exists; the observation time has direct impact on the intensity of thermal radiation and to a large extent on the brightness temperature difference of each channel; the brightness temperature of different wall orientations are also different, and the difference changes with the change in observation time. Studies of thermal radiation characteristics of urban typical surface features have theoretical and practical significance, providing basis for thermal infrared remote sensing to monitor the urban heat effect.

[Effects of leaf hair on leaf reflectance and hyperspectral vegetation indices].

Many hyperspectral vegetation indices have been used to estimate the biochemical contents such as pigment content, nondestructively. These reflectance indices are influenced by leaf hair, and the existence of the leaf hair affects the performance of the indices on the estimation of the biochemical contents. The present research studied the possible effects of the leaf hair on the reflectance of the same leaf before and after removal of leaf hair. The authors found that dehairing had decreased the reflectance between wavelength 400 and 1 000 nm, and the decrease depends on the wavelength. The changes of 39 hyperspectral indices before and after the hair removal were compared. The results revealed that some indices that only use visible wavebands or the near infrared wavebands such as CTR1: R695/R420, D740/D720, WBI: R900/R970, R860/(R550 x R708) and REP (Red-edge position) were not affected much by the dehairing process and are thought relatively robust to estimate the biochemical contents.

[Study on the reflected and hyperspectral mixed-pixel character of aquatic plants and water].

A study on the reflected and hyperspectral mixed-pixel of aquatic plants and water was given by using a orthogonal experimental design with three factors and two levels. The results of F test suggest that for the single factors, the band and the area ratio of mixed-pixel on the reflected and hyperspectral mixed-pixel of the reflection effects are particularly significant, however, the detector angle had no significant effect under these experimental conditions; For the interaction, the band and the area ratio of mixed-pixel, the detector and the area ratio of mixed-pixel, the effects of these two interactions on the reflected and hyperspectral mixed-pixel are also particularly significant, This study did quantitative analysis of the factors affecting the reflected and hyperspectral mixed-pixel character and their interaction, and provided a new method for the indepth study of mixed-pixel.

[Quantitative analysis of the polarized reflection factor of influence of oil film on water surface and their interaction].

In order to extract more reflection characteristic information of oil film on water surface by using remote sensing technology, the authors measured and analyzed the multi-angle hyperspectral polarized reflection information of oil film based on the traditional remote sensing researches. The authors used polarization as the indicator of quantitative study, adopted a three-factor-three-level orthogonal test to analyze the incident angle, oil film thickness, band, and the influence of oil film on water surface from their interaction between each other. The results of variance analysis of this orthogonal test show that: the three factors and their interaction between each other all have an influence on the polarization of oil film; the interaction between incident angle and thickness of oil slick, and the interaction between band and thickness of oil slick both show a significant impact on polarization. That is to say, the research on oil film by using hyperspectral multi-angle polarized reflectance needs both the influence on polarization from each factor and their interaction.