Exploring the response differences of leaf physiology parameters to enhanced nitrogen deposition between saplings and trees is vital for predicting the variations of terrestrial ecosystem structure and function under ...Exploring the response differences of leaf physiology parameters to enhanced nitrogen deposition between saplings and trees is vital for predicting the variations of terrestrial ecosystem structure and function under future global climate change. In this study, the ecophysiological parameters of saplings and trees of Fraxinus mandshurica Rupr. were measured at different levels of nitrogen addition in a temperate forest. The results show that ecophysiological parameters maximum net photosynthetic rate(Pmax), apparent quantum efficiency(a), dark respiration(Rd), light saturation point(Lsp), photosynthetic nitrogen use efficiency(PNUE),specific leaf area(SLA)and stomatal conductance under saturated light intensity(Gsmax) were higher in saplings than in trees. These physiological parameters and not Nleaf(leaf nitrogen content)led to relatively lower Pmaxand Rdin trees. For both saplings and trees, low and median nitrogen addition(23 and 46 kg ha-1a-1) resulted in significant increases in Pmax, Rd, Lsp, Chl, PNUE, SLA and Gsmax. These parameters tended to decline under high additions of nitrogen(69 kg ha-1a-1),whereas Nleaf was always enhanced with increasing nitrogen. Variations in Pmax and Rd with increasing nitrogen were attributed to variations in the strongly related parameters of, Lsp, Chl, PNUE, SLA and Gsmax. Overall, the response sensitivity of physiological parameters to enhanced nitrogen levels was lower in trees compared with saplings.展开更多
Species-habitat association analysis is useful to detect spatial arrangement of individual plants, to discover rules about the distribution of species and to generate hypotheses about the possible underlying process c...Species-habitat association analysis is useful to detect spatial arrangement of individual plants, to discover rules about the distribution of species and to generate hypotheses about the possible underlying process controlling observed structures. Quantifying methods were used to classify habitats in terms of topographical variables in a mixed temperate broad-leaved Korean pine forest of the Changbai mountains in northeastern China. All of the 625 20 m × 20 m quadrats of the plot could be unambiguously assigned to one of three habitat categories （low-plateau, high-plateau and slope）. Torus-translation tests were used to estimate species-habitat associations. Many species are clearly distributed in a biased fashion with respect to habitats. Fifteen （55.6%） out of 27 species showed strong positive or negative association with specific habitats. We compared species-habitat associations at the sapling and adult stages. Adjusted density values indicated few species exhibit extremely strong habitat associations. Only 9 out of 26 species had adjusted densities 〉 3 in the habitat for which they had strong positive affinity. Few species show the same associations at the small tree and large tree stages. Only 3 out of 22 occurring associations with a specific habitat appeared to have a consistent habitat association at the two stages. These results suggest that species-habitat associations exist in the 25-ha plot of the temperate forest of the Chang- bai mountains. Owing to limitations in our statistical methodology, we partly underestimated associations by ignoring rare species. Regeneration niches can contribute to co-existence, but regeneration niches due to habitat associations play a limited role in species co-existence, since most species show a similar trend in habitat associations at the sapling and adult stages. We should pay more attention to shifts in habitat associations, i.e. niche shifts at different stages of existence.展开更多
The demand of grape in Bangladesh is fulfilled through import from foreign countries. The fruits of local cultivars of grapes are sour and seeded. Development of seedless grape varieties having increased sweetness, hi...The demand of grape in Bangladesh is fulfilled through import from foreign countries. The fruits of local cultivars of grapes are sour and seeded. Development of seedless grape varieties having increased sweetness, higher yield with better nutritional quality is necessary to reduce the import dependency. The present research activities are the part of a grape improvement project. A pot experiment was conducted at the Bangladesh Institute of Nuclear Agriculture (BINA), Mymensingh, during June to November 2011 to determine the suitable gamma irradiation doses on growth, leaf area and biochemical characters of grape saplings. Three vegetative bud stages viz. bud initiation stage, 4-leaf stage and 8-leaf stage, and four doses of gamma irradiation viz. 0, 5, 10, and 15 Gy were used as treatments. The experiment was laid out in a Randomized Complete Block Design with four replications. Different irradiation doses and vegetative bud stages showed significant variations in respect of plant growth characters, leaf area, soluble protein and total sugar content. Interaction effects also had significant variations on most of the parameters studied. Higher doses of gamma irradiation had showed detrimental effect on grape saplings. Generally, increased in irradiation doses showed decreased and detrimental effects on most of the parameters under study. Maximum numbers and length of roots, total dry matter, leaf area and chlorophyll-a and chlorophyll-b content were found at 5 Gy irradiation dose. Total soluble protein and sugar content of leaf were found maximum at no irradiation and 15 Gy, respectively. Higher number of roots and length, total dry matter, leaf area, chlorophyll-a, and b and soluble protein content of leaf were observed at bud initiation stage while 8-leaf stage showed maximum total sugar of leaf. In the combined effect of gamma irradiation and vegetative bud stages, all parameters showed best results in 5 Gy with bud initiation stage except total sugar content of leaf.展开更多
Nonstructural carbon(NSC),which represents the relationship between the carbon source and carbon sink,is an important factor that reflects the functions and performance of a tree.However,little is known regarding the ...Nonstructural carbon(NSC),which represents the relationship between the carbon source and carbon sink,is an important factor that reflects the functions and performance of a tree.However,little is known regarding the timeseries responses of NSC storage in evergreen species to different nitrogen(N)fertilization regimes.This study,which was based on a pot experiment,examined the response of the NSC(soluble sugars and starch storage to different N addition intensities[light N addition(LN):6.5 g N m^(-2)a^(-1);moderate N addition(MN):13.0 g N m^(-2)a^(-1);and heavy N addition(HN):26.0 g N m^(-2)a^(-1))]in saplings of the evergreen species Podocarpus macrophyllus.Our results showed that the net photosynthetic rate(P_(n))under MN was significantly higher than that under LN,but was comparable to that under HN.Moreover,saplings subject to MN had a significant higher leaf biomass than that to LN and HN.These results indicated that the C supply via photosynthesis under MN was greater than that under LN and HN.The NSCs reserve under MN was considerable with that under LN,which suggested that saplings in MN group consumed higher and stored lower properties of NSCs than those in LN group.However,saplings under HN stored higher properties of NSCs than those under MN considering that no difference in NSCs pools was found between the two treatments.The leaf N concentrations were found in the increasing sequence of LN<MN<HN,whilst the leaf chlorophyll concentration under HN was obviously lower than that under MN.The growth rate under MN was higher than that under LN and HN.We concluded that the NSCs allocation between con-sumption and reserve in P.macrophyllus saplings depended on soil N availability,and an excessive N addition to soil favors the storage rather than the consumption of NSCs by plants.展开更多
The height growth of Korean pine plantation was investigated for different ages of saplings in Benxi city of the eastern Liaoning, China. The sapling and seedling age were determined by branch annuals. Results show th...The height growth of Korean pine plantation was investigated for different ages of saplings in Benxi city of the eastern Liaoning, China. The sapling and seedling age were determined by branch annuals. Results show that the mean height of third- to eight-year Korean pines ranges from 13.31 cm to 111.73 cm and only 19.4% of the saplings reached the height above 130 cm. The height （Y） of eight-year-old Korean pine increases linearly with the increment of ground stem （x） （Y=3.1x＋35.15）. The relation between height and age can be described by an exponential equation. The second year after planting of the Korean pine is considered as the key period of Korean pine growth really adapting to the local environment; plantation management should be strengthened in this year. The Korean pine seedlings need two years to adapt to the local environment, thus early care and management should be taken in the second year.展开更多
The reasonable tree and population structure parameters of various cylindrical pear orchards were studied.The results showed that for 3-year-old ‘Xinli No.7’,the tree height was 3.48 m,and the trunk height was 63 cm...The reasonable tree and population structure parameters of various cylindrical pear orchards were studied.The results showed that for 3-year-old ‘Xinli No.7’,the tree height was 3.48 m,and the trunk height was 63 cm;there were 63 branches per plant,which was equivalent to 19 971 branches per 667 m^2;the leaf area index was 1.62.For the 3-year-old ‘Xueqing’,the tree height was 3.03 m,and the trunk height was 74 cm;the number of branches per plant was 57,which was equivalent to 18 069 branches per 667 m^2;the leaf area index was 1.73.The cylindrical trees of the two varieties had the following characteristics: the canopy structure was tight;the branches were equally distributed,and the number of medium branches and short branches accounted for more than 60% of the total number of branches of the whole plant.展开更多
[ Objective] This study aimed to investigate the effects of different water and fertilizer combinations on apple saplings. [ Method] ＇ Tianhong 2＇ Fuji /SH40/Malus robusta Rehd. was used as the experimental material...[ Objective] This study aimed to investigate the effects of different water and fertilizer combinations on apple saplings. [ Method] ＇ Tianhong 2＇ Fuji /SH40/Malus robusta Rehd. was used as the experimental material to analyze the effects of different irrigation modes and combinations of basal fertilizer and dressing fertilizer on tree structure, leaf parameters and photosynthesis of apple saplings. [ Result] The results showed that different water and fertilizer combinations ex- hibited varying effects on tree structure, leaf parameters and photosynthesis of apple saplings. To be specific, applying 432 000 kg/hm2 basal fertilizer, 480 kg/hm2 urea and 915 kg/hmz organic fertilizer ＋ 0 ＋ 915 kg/hm2 organic fertilizer as dressing fertilizer, and 1% urea as leaf fertilizer was conducive to promoting growth of branches and leaves, increasing leaf thickness, individual leaf area and SPAD, and improving photosynthesis of apple saplings under half root irrigation and whole root irrigation conditions. In addition, the effects were more significant under whole root irrigation conditions. [ Conclusion] Selecting the appropriate water and fertilizer combination is conducive to the growth of apple saplings.展开更多
The regeneration of Tetracentron sinense Oliv.is poor in the understory and in open areas due to the charac-teristics of natural regeneration of the species on forest edges and in gaps.It is unclear whether different ...The regeneration of Tetracentron sinense Oliv.is poor in the understory and in open areas due to the charac-teristics of natural regeneration of the species on forest edges and in gaps.It is unclear whether different light intensities in various habitats affect eco-physiological characteristics of saplings and their natural regeneration.In this study,the light intensity in T.sinense habitats was simulated by artificial shading(L1:100%NS(natural sunlight)in the open;L2:50%NS in a forest gap or edge;L3:10%NS in understory)to investigate differences in morphology,leaf structure,physiology,and photosynthesis of 2-year-old sap-lings,and to analyze the mechanism of light intensity on sapling establishment.Significant differences were observed in morphology(including leaf area,and specific leaf area)under different light intensities.Compared to L1 and L3,chloroplast structure in L2 was intact.With increasing time,superoxide dismutase(SOD)and catalase(CAT)activities in L2 became gradually higher than under the other light intensities,while malondialdehyde(MDA)content was opposite.Shading decreased osmoregulation substance contents of leaves but increased chlorophyll.The results suggest that light intensities significantly affect the eco-physiological characteristics of T.sinense saplings and they would respond most favorably at intermediate levels of light by optimizing eco-physiological characteristics.Therefore,50%natural sunlight should be created to promote saplings establishment and population recovery of T.sinense during in situ conservation,including sowing mature seeds in forest edges or gaps and providing appropriate shade protection for seedlings and saplings in the open.展开更多
The growth of Nyssa yunnanensis saplings in Guanping area was monitored in 2011, 2013 and 2015. The results showed that the average basal diameter growth rate during 2013-2015 was higher than that during 2011-2013, an...The growth of Nyssa yunnanensis saplings in Guanping area was monitored in 2011, 2013 and 2015. The results showed that the average basal diameter growth rate during 2013-2015 was higher than that during 2011-2013, and that during 2009-2011 was lowest; the average height growth rates in the durations of 2011-2013 and 2013-2015 were basically the same, and that during 2009-2011 was relatively slow; the growth of diameter at breast height（DBH） in the duration of 2013-2015 was significantly higher than that in the duration of 2011-2013. Comprehensive and better nature-returning work, as well as long-term and stable funding, is required for the protection of Nyssa yunnanensis.展开更多
Background:Trees and forests in drylands help mitigate the challenges through provision of economic products and vital environmental services such as habitat for biodiversity,prevention of erosion and desertification,...Background:Trees and forests in drylands help mitigate the challenges through provision of economic products and vital environmental services such as habitat for biodiversity,prevention of erosion and desertification,regulation of water,microclimate,and soil fertility.The condition and changes in dry forests can be assessed by using ecological indicators able to quantify spatial and temporal changes in vegetation.One of the ways to determine the condition of the forest is to study the dominant tree species and its regeneration.Our study aimed to assess whether the abundance of Prosopis flexuosa saplings is affected by environmental and biological factors.Results:To evaluate the first variables we used data from remote sensing such as satellite images and Aster Global Digital Model(GDEM).The second set of variables was about exotic and native ungulates and we used feces of these animals and camera traps to take data.We found that sapling abundance related positively to sandy substrates and negatively to Wetness Index.On the other hand,in relation to biological variables,the abundance of saplings was positively affected by density of adult trees and by number of seeds dispersed by equines,but space use by Lama guanicoe had a negative relationship with saplings.This research shows that P.flexuosa saplings are benefited from sandy substrates and the conditions around adult trees.In addition to this,we found that exotic ungulates in low densities have neutral(i.e.cattle)or positive(i.e.equines)effects on sapling abundance.Conclusions:Based on these findings,we conclude that regeneration of the population of P.flexuosa in our study area has no major problems.In addition,we corroborated that the presence of exotic and domestic ungulates in low densities does not have deleterious consequences for saplings of the dominant tree,P.flexuosa.展开更多
This study focuses on determining the second-order irregular wave loads in the time domain without using the Inverse Fast Fourier Transform(IFFT).Considering the substantial displacement effects that Floating Offshore...This study focuses on determining the second-order irregular wave loads in the time domain without using the Inverse Fast Fourier Transform(IFFT).Considering the substantial displacement effects that Floating Offshore Wind Turbine(FOWT)support structures undergo when subjected to wave loads,the time-domain wave method is more suitable,while the frequency-domain method requiring IFFT cannot be used for moving bodies.Nonetheless,the computational challenges posed by the considerable computer time requirements of the time-domain wave method remain a significant obstacle.Thus,the paper incorporates various numerical schemes,including parallel computing and extrapolation of wave forces during specific time steps to improve overall efficiency.Despite the effectiveness of these schemes,the computational difficulties associated with the time-domain wave method persist.This study then proposes an innovative approach utilizing different randomnumbers in distinct segments,significantly reducing the computation of second-order wave loads.This random number interpolation ensures a smooth curve transition between two segments,emphasizingminimizing errors near the end of the first segment.Numerical analyses demonstrate substantial decreases in total computer time for FOWT structural analyses while maintaining consistent steel design results.The proposed method is uncomplicated,requiring only a simple subprogram modification in a conventional wave load computer program.展开更多
Traditionally, airborne time-domain electromagnetic （ATEM） data are inverted to derive the earth model by iteration. However, the data are often highly correlated among channels and consequently cause ill-posed and ...Traditionally, airborne time-domain electromagnetic （ATEM） data are inverted to derive the earth model by iteration. However, the data are often highly correlated among channels and consequently cause ill-posed and over-determined problems in the inversion. The correlation complicates the mapping relation between the ATEM data and the earth parameters and thus increases the inversion complexity. To obviate this, we adopt principal component analysis to transform ATEM data into orthogonal principal components （PCs） to reduce the correlations and the data dimensionality and simultaneously suppress the unrelated noise. In this paper, we use an artificial neural network （ANN） to approach the PCs mapping relation with the earth model parameters, avoiding the calculation of Jacobian derivatives. The PC-based ANN algorithm is applied to synthetic data for layered models compared with data-based ANN for airborne time-domain electromagnetic inversion. The results demonstrate the PC-based ANN advantages of simpler network structure, less training steps, and better inversion results over data-based ANN, especially for contaminated data. Furthermore, the PC-based ANN algorithm effectiveness is examined by the inversion of the pseudo 2D model and comparison with data-based ANN and Zhody＇s methods. The results indicate that PC-based ANN inversion can achieve a better agreement with the true model and also proved that PC-based ANN is feasible to invert large ATEM datasets.展开更多
An electromagnetic field is generated through the accelerating movement of two equal but opposite charges of a single dipole. An electromagnetic field can also be generated by a time-varying infinitesimal point charge...An electromagnetic field is generated through the accelerating movement of two equal but opposite charges of a single dipole. An electromagnetic field can also be generated by a time-varying infinitesimal point charge. In this study, a comparison between the electromagnetic fields of an infinitesimal point charge and a dipole has been presented. First, the time-domain potential function of a point source in a 3D conductive medium is derived. Then the electric and magnetic fields in a 3D homogeneous lossless space are derived via the relation between the potential and field. The field differences between the infinitesimal point charge and the dipole in the step-off time, far-source, and near-source zones are analyzed, and the accuracy of the solutions from these sources is investigated. It is also shown that the field of the infinitesimal point charge in the near-source zone is different from that of the dipole, whereas the far-source zone fields of these two sources are identical. The comparison of real and simulated data shows that the infinitesimal point charge represents the real source better than the divole source.展开更多
To effectively minimize the electromagnetic field response in the total field solution, we propose a numerical modeling method for the two-dimensional （2D） time- domain transient electromagnetic secondary field of t...To effectively minimize the electromagnetic field response in the total field solution, we propose a numerical modeling method for the two-dimensional （2D） time- domain transient electromagnetic secondary field of the line source based on the DuFort- Frankel finite-difference method. In the proposed method, we included the treatment of the earth-air boundary conductivity, calculated the normalized partial derivative of the induced electromotive force （Emf）, and determined the forward time step. By extending upward the earth-air interface to the air grid nodes and the zero-value boundary conditions, not only we have a method that is more efficient but also simpler than the total field solution. We computed and analyzed the homogeneous half-space model and the fiat layered model with high precision--the maximum relative error is less than 0.01% between our method and the analytical method--and the solution speed is roughly three times faster than the total-field solution. Lastly, we used the model of a thin body embedded in a homogeneous half-space at different delay times to depict the downward and upward spreading characteristics of the induced eddy current, and the physical interaction processes between the electromagnetic field and the underground low-resistivity body.展开更多
Electrically anisotropic strata are abundant in nature, so their study can help our data interpretation and our understanding of the processes of geodynamics. However, current data processing generally assumes isotrop...Electrically anisotropic strata are abundant in nature, so their study can help our data interpretation and our understanding of the processes of geodynamics. However, current data processing generally assumes isotropic conditions when surveying anisotropic structures, which may cause discrepancies between reality and electromagnetic data interpretation. Moreover, the anisotropic interpretation of the time-domain airborne electromagnetic （TDAEM） method is still confined to one dimensional （1D） cases, and the corresponding three-dimensional （3D） numerical simulations are still in development. In this study, we expanded the 3D TDAEM modeling of arbitrarily anisotropic media. First, through coordinate rotation of isotropic conductivity, we obtained the conductivity tensor of an arbitrary anisotropic rock. Next, we incorporated this into Maxwell＇s equations, using a regular hexahedral grid of vector finite elements to subdivide the solution area. A direct solver software package provided the solution for the sparse linear equations that resulted. Analytical solutions were used to verify the accuracy and feasibility of the algorithm. The proven model was then applied to analyze the effects of arbitrary anisotropy in 3D TDAEM via the distribution of responses and amplitude changes, which revealed that different anisotropy situations strongly affected the responses of TDAEM.展开更多
A 1D finite element method in time domain is developed in this paper and applied to calculate in-plane wave motions of free field exited by SV or P wave oblique incidence in an elastic layered half-space. First, the l...A 1D finite element method in time domain is developed in this paper and applied to calculate in-plane wave motions of free field exited by SV or P wave oblique incidence in an elastic layered half-space. First, the layered half-space is discretized on the basis of the propagation characteristic of elastic wave according to the Snell law. Then, the finite element method with lumped mass and the central difference method are incorporated to establish 2D wave motion equations, which can be transformed into 1D equations by discretization principle and explicit finite element method. By solving the 1D equations, the displacements of nodes in any vertical line can be obtained, and the wave motions in layered half-space are finally determined based on the characteristic of traveling wave. Both the theoretical analysis and the numerical results demonstrate that the proposed method has high accuracy and good stability.展开更多
Copper sulfate pentahydrate is investigated by terahertz time-domain spectroscopy. It is shown that the terahertz absorption coefficients are correlated with the particle size of the samples, as well as the heating ra...Copper sulfate pentahydrate is investigated by terahertz time-domain spectroscopy. It is shown that the terahertz absorption coefficients are correlated with the particle size of the samples, as well as the heating rates of the ambient temperature. Furthermore, the water molecules of copper sulfate pentahydrate can be quantitatively characterized due to the high sensitivity of the terahertz wave to water molecules. Based on such results, the status of water incorporated in mineral opal is also characterized using terahertz time-domain spectroscopy. It indicates that terahertz technology can be considered as an efficient method to detect the dehydration of minerals.展开更多
A time-domain method is applied to simulate nonlinear wave diffraction around a surface piercing 3-D arbitrary body. The method involves the application of Taylor series expansions and the use of perturbation procedur...A time-domain method is applied to simulate nonlinear wave diffraction around a surface piercing 3-D arbitrary body. The method involves the application of Taylor series expansions and the use of perturbation procedure to establish the corresponding boundary value problems with respect to a time-independent fluid domain. A boundary element method based on B-spline expansion is used to calculate the wave field at each time step, and the free surface boundary condition is satisfied to the second order of wave steepness by a numerical integration in time. An artificial damping layer is adopted on the free surface for the removal of wave reflection from the outer boundary. As an illustration, the method is used to compute the second-order wave forces and run-up on a surface-piercing circular cylinder. The present method is found to be accurate, computationally efficient, and numerically stable.展开更多
The path loss analysis model based on 5 rays in vacancy indoor environment is proposed. The relationship between multipath overlapping and the path loss is analyzed mathematically. Time-domain technique is introduced ...The path loss analysis model based on 5 rays in vacancy indoor environment is proposed. The relationship between multipath overlapping and the path loss is analyzed mathematically. Time-domain technique is introduced to compute reflection coefficient in a very short time interval. A 5 rays path loss calculation method, which is satisfactory accurate, is developed. 5 typical environments are involved to analyze and generalize the common path loss characteristics in vacancy indoor environment. The simulation result shows that the path loss can be characterized as 3 zones with different path loss exponent as distance between transmitter and receiver increasing.展开更多
We report a broadband terahertz time-domain spectroscopy(THz-TDS)which enables twenty vibrational modes of adenosine nucleoside to be resolved in a wide frequency range of 1-20 THz.The observed spectroscopic features ...We report a broadband terahertz time-domain spectroscopy(THz-TDS)which enables twenty vibrational modes of adenosine nucleoside to be resolved in a wide frequency range of 1-20 THz.The observed spectroscopic features of adenosine are in good agreement with the published spectra obtained using Fourier transform infrared spectroscopy(FTIR)and Raman spectroscopy.This much extended bandwidth leads to enhanced material characterization capability as it provides spectroscopic information on both intra-and inter-molecular vibrations.In addition,we also report a low-cost frequency modulation continuous wave(FMCW)imaging system which has a fast measurement speed of 40000 waveforms per second.Cross-sectional imaging capability through cardboard has also been demonstrated using its excellent penetration capability at a frequency range of 76-81 GHz.We anticipate that the integration of these two complementary imaging technologies would be highly desirable for many real-world applications because it provides both spectroscopic discrimination and penetration capabilities in a single instrument.展开更多
基金funded by the National Key Research and Development Program of China(2016YFC0400206-04,2017YFC0505304)the National Natural Science Foundation of China(51309016)+1 种基金Central Public-interest Scientific Institution Basal Research Fund(CKSF2016007/TB)Changjiang River Scientific Research Institute Innovation Team(CKSF2017064/NS)
文摘Exploring the response differences of leaf physiology parameters to enhanced nitrogen deposition between saplings and trees is vital for predicting the variations of terrestrial ecosystem structure and function under future global climate change. In this study, the ecophysiological parameters of saplings and trees of Fraxinus mandshurica Rupr. were measured at different levels of nitrogen addition in a temperate forest. The results show that ecophysiological parameters maximum net photosynthetic rate(Pmax), apparent quantum efficiency(a), dark respiration(Rd), light saturation point(Lsp), photosynthetic nitrogen use efficiency(PNUE),specific leaf area(SLA)and stomatal conductance under saturated light intensity(Gsmax) were higher in saplings than in trees. These physiological parameters and not Nleaf(leaf nitrogen content)led to relatively lower Pmaxand Rdin trees. For both saplings and trees, low and median nitrogen addition(23 and 46 kg ha-1a-1) resulted in significant increases in Pmax, Rd, Lsp, Chl, PNUE, SLA and Gsmax. These parameters tended to decline under high additions of nitrogen(69 kg ha-1a-1),whereas Nleaf was always enhanced with increasing nitrogen. Variations in Pmax and Rd with increasing nitrogen were attributed to variations in the strongly related parameters of, Lsp, Chl, PNUE, SLA and Gsmax. Overall, the response sensitivity of physiological parameters to enhanced nitrogen levels was lower in trees compared with saplings.
基金supported by the National Natural Science Foundation of China (Grant Nos. 30570306, 30870400 and 40971286)the Public Benefit Research Foun- dation of State Forestry Administration, China (No. 201104040)
文摘Species-habitat association analysis is useful to detect spatial arrangement of individual plants, to discover rules about the distribution of species and to generate hypotheses about the possible underlying process controlling observed structures. Quantifying methods were used to classify habitats in terms of topographical variables in a mixed temperate broad-leaved Korean pine forest of the Changbai mountains in northeastern China. All of the 625 20 m × 20 m quadrats of the plot could be unambiguously assigned to one of three habitat categories （low-plateau, high-plateau and slope）. Torus-translation tests were used to estimate species-habitat associations. Many species are clearly distributed in a biased fashion with respect to habitats. Fifteen （55.6%） out of 27 species showed strong positive or negative association with specific habitats. We compared species-habitat associations at the sapling and adult stages. Adjusted density values indicated few species exhibit extremely strong habitat associations. Only 9 out of 26 species had adjusted densities 〉 3 in the habitat for which they had strong positive affinity. Few species show the same associations at the small tree and large tree stages. Only 3 out of 22 occurring associations with a specific habitat appeared to have a consistent habitat association at the two stages. These results suggest that species-habitat associations exist in the 25-ha plot of the temperate forest of the Chang- bai mountains. Owing to limitations in our statistical methodology, we partly underestimated associations by ignoring rare species. Regeneration niches can contribute to co-existence, but regeneration niches due to habitat associations play a limited role in species co-existence, since most species show a similar trend in habitat associations at the sapling and adult stages. We should pay more attention to shifts in habitat associations, i.e. niche shifts at different stages of existence.
文摘The demand of grape in Bangladesh is fulfilled through import from foreign countries. The fruits of local cultivars of grapes are sour and seeded. Development of seedless grape varieties having increased sweetness, higher yield with better nutritional quality is necessary to reduce the import dependency. The present research activities are the part of a grape improvement project. A pot experiment was conducted at the Bangladesh Institute of Nuclear Agriculture (BINA), Mymensingh, during June to November 2011 to determine the suitable gamma irradiation doses on growth, leaf area and biochemical characters of grape saplings. Three vegetative bud stages viz. bud initiation stage, 4-leaf stage and 8-leaf stage, and four doses of gamma irradiation viz. 0, 5, 10, and 15 Gy were used as treatments. The experiment was laid out in a Randomized Complete Block Design with four replications. Different irradiation doses and vegetative bud stages showed significant variations in respect of plant growth characters, leaf area, soluble protein and total sugar content. Interaction effects also had significant variations on most of the parameters studied. Higher doses of gamma irradiation had showed detrimental effect on grape saplings. Generally, increased in irradiation doses showed decreased and detrimental effects on most of the parameters under study. Maximum numbers and length of roots, total dry matter, leaf area and chlorophyll-a and chlorophyll-b content were found at 5 Gy irradiation dose. Total soluble protein and sugar content of leaf were found maximum at no irradiation and 15 Gy, respectively. Higher number of roots and length, total dry matter, leaf area, chlorophyll-a, and b and soluble protein content of leaf were observed at bud initiation stage while 8-leaf stage showed maximum total sugar of leaf. In the combined effect of gamma irradiation and vegetative bud stages, all parameters showed best results in 5 Gy with bud initiation stage except total sugar content of leaf.
基金supported by the National Natural Science Foundation of China(Grant No.31560061)。
文摘Nonstructural carbon(NSC),which represents the relationship between the carbon source and carbon sink,is an important factor that reflects the functions and performance of a tree.However,little is known regarding the timeseries responses of NSC storage in evergreen species to different nitrogen(N)fertilization regimes.This study,which was based on a pot experiment,examined the response of the NSC(soluble sugars and starch storage to different N addition intensities[light N addition(LN):6.5 g N m^(-2)a^(-1);moderate N addition(MN):13.0 g N m^(-2)a^(-1);and heavy N addition(HN):26.0 g N m^(-2)a^(-1))]in saplings of the evergreen species Podocarpus macrophyllus.Our results showed that the net photosynthetic rate(P_(n))under MN was significantly higher than that under LN,but was comparable to that under HN.Moreover,saplings subject to MN had a significant higher leaf biomass than that to LN and HN.These results indicated that the C supply via photosynthesis under MN was greater than that under LN and HN.The NSCs reserve under MN was considerable with that under LN,which suggested that saplings in MN group consumed higher and stored lower properties of NSCs than those in LN group.However,saplings under HN stored higher properties of NSCs than those under MN considering that no difference in NSCs pools was found between the two treatments.The leaf N concentrations were found in the increasing sequence of LN<MN<HN,whilst the leaf chlorophyll concentration under HN was obviously lower than that under MN.The growth rate under MN was higher than that under LN and HN.We concluded that the NSCs allocation between con-sumption and reserve in P.macrophyllus saplings depended on soil N availability,and an excessive N addition to soil favors the storage rather than the consumption of NSCs by plants.
文摘The height growth of Korean pine plantation was investigated for different ages of saplings in Benxi city of the eastern Liaoning, China. The sapling and seedling age were determined by branch annuals. Results show that the mean height of third- to eight-year Korean pines ranges from 13.31 cm to 111.73 cm and only 19.4% of the saplings reached the height above 130 cm. The height （Y） of eight-year-old Korean pine increases linearly with the increment of ground stem （x） （Y=3.1x＋35.15）. The relation between height and age can be described by an exponential equation. The second year after planting of the Korean pine is considered as the key period of Korean pine growth really adapting to the local environment; plantation management should be strengthened in this year. The Korean pine seedlings need two years to adapt to the local environment, thus early care and management should be taken in the second year.
基金Supported by Special Project for Construction of National Pear Industry Technology System(CARS-28-36)National Natural Science Foundation of China(31601708)+2 种基金Agricultural Science and Technology Innovation Project of Shandong Academy of Agricultural Sciences(CXGC2018F03)Agricultural Seed Improvement Project of Shandong Province,China(2016LZGC034)Major Science and Technology Innovation Project of Shandong Province,China(2018CXGC0208)
文摘The reasonable tree and population structure parameters of various cylindrical pear orchards were studied.The results showed that for 3-year-old ‘Xinli No.7’,the tree height was 3.48 m,and the trunk height was 63 cm;there were 63 branches per plant,which was equivalent to 19 971 branches per 667 m^2;the leaf area index was 1.62.For the 3-year-old ‘Xueqing’,the tree height was 3.03 m,and the trunk height was 74 cm;the number of branches per plant was 57,which was equivalent to 18 069 branches per 667 m^2;the leaf area index was 1.73.The cylindrical trees of the two varieties had the following characteristics: the canopy structure was tight;the branches were equally distributed,and the number of medium branches and short branches accounted for more than 60% of the total number of branches of the whole plant.
基金Supported by National Modern Agricultural(Apple)Industry Technology System of China(CARS-28)
文摘[ Objective] This study aimed to investigate the effects of different water and fertilizer combinations on apple saplings. [ Method] ＇ Tianhong 2＇ Fuji /SH40/Malus robusta Rehd. was used as the experimental material to analyze the effects of different irrigation modes and combinations of basal fertilizer and dressing fertilizer on tree structure, leaf parameters and photosynthesis of apple saplings. [ Result] The results showed that different water and fertilizer combinations ex- hibited varying effects on tree structure, leaf parameters and photosynthesis of apple saplings. To be specific, applying 432 000 kg/hm2 basal fertilizer, 480 kg/hm2 urea and 915 kg/hmz organic fertilizer ＋ 0 ＋ 915 kg/hm2 organic fertilizer as dressing fertilizer, and 1% urea as leaf fertilizer was conducive to promoting growth of branches and leaves, increasing leaf thickness, individual leaf area and SPAD, and improving photosynthesis of apple saplings under half root irrigation and whole root irrigation conditions. In addition, the effects were more significant under whole root irrigation conditions. [ Conclusion] Selecting the appropriate water and fertilizer combination is conducive to the growth of apple saplings.
基金funded by the National Natural Science Foundation of China (No.32070371)the Innovation Team Funds of China West Normal University (No.KCXTD2022-4)+1 种基金the fund of Sichuan Meigu Dafegnding National Nature Reserve (No.mgdfd2022-13)Sichuan Micang Mountain National Nature Reserve (No.N5108212022000043)。
文摘The regeneration of Tetracentron sinense Oliv.is poor in the understory and in open areas due to the charac-teristics of natural regeneration of the species on forest edges and in gaps.It is unclear whether different light intensities in various habitats affect eco-physiological characteristics of saplings and their natural regeneration.In this study,the light intensity in T.sinense habitats was simulated by artificial shading(L1:100%NS(natural sunlight)in the open;L2:50%NS in a forest gap or edge;L3:10%NS in understory)to investigate differences in morphology,leaf structure,physiology,and photosynthesis of 2-year-old sap-lings,and to analyze the mechanism of light intensity on sapling establishment.Significant differences were observed in morphology(including leaf area,and specific leaf area)under different light intensities.Compared to L1 and L3,chloroplast structure in L2 was intact.With increasing time,superoxide dismutase(SOD)and catalase(CAT)activities in L2 became gradually higher than under the other light intensities,while malondialdehyde(MDA)content was opposite.Shading decreased osmoregulation substance contents of leaves but increased chlorophyll.The results suggest that light intensities significantly affect the eco-physiological characteristics of T.sinense saplings and they would respond most favorably at intermediate levels of light by optimizing eco-physiological characteristics.Therefore,50%natural sunlight should be created to promote saplings establishment and population recovery of T.sinense during in situ conservation,including sowing mature seeds in forest edges or gaps and providing appropriate shade protection for seedlings and saplings in the open.
基金Supported by Garnier Plant Protection Fund of Landscape Conservation Center(56317)~~
文摘The growth of Nyssa yunnanensis saplings in Guanping area was monitored in 2011, 2013 and 2015. The results showed that the average basal diameter growth rate during 2013-2015 was higher than that during 2011-2013, and that during 2009-2011 was lowest; the average height growth rates in the durations of 2011-2013 and 2013-2015 were basically the same, and that during 2009-2011 was relatively slow; the growth of diameter at breast height（DBH） in the duration of 2013-2015 was significantly higher than that in the duration of 2011-2013. Comprehensive and better nature-returning work, as well as long-term and stable funding, is required for the protection of Nyssa yunnanensis.
基金supported by“The chica,the retamo,and the algarrobo:umbrella species for the conservation of the Native Forest of the Ischigualasto Provincial Park and nearby zones.Biological interactions,effects of human activities and their mitigation”,Plan for the Conservation of Native Forests Law 26.331.
文摘Background:Trees and forests in drylands help mitigate the challenges through provision of economic products and vital environmental services such as habitat for biodiversity,prevention of erosion and desertification,regulation of water,microclimate,and soil fertility.The condition and changes in dry forests can be assessed by using ecological indicators able to quantify spatial and temporal changes in vegetation.One of the ways to determine the condition of the forest is to study the dominant tree species and its regeneration.Our study aimed to assess whether the abundance of Prosopis flexuosa saplings is affected by environmental and biological factors.Results:To evaluate the first variables we used data from remote sensing such as satellite images and Aster Global Digital Model(GDEM).The second set of variables was about exotic and native ungulates and we used feces of these animals and camera traps to take data.We found that sapling abundance related positively to sandy substrates and negatively to Wetness Index.On the other hand,in relation to biological variables,the abundance of saplings was positively affected by density of adult trees and by number of seeds dispersed by equines,but space use by Lama guanicoe had a negative relationship with saplings.This research shows that P.flexuosa saplings are benefited from sandy substrates and the conditions around adult trees.In addition to this,we found that exotic ungulates in low densities have neutral(i.e.cattle)or positive(i.e.equines)effects on sapling abundance.Conclusions:Based on these findings,we conclude that regeneration of the population of P.flexuosa in our study area has no major problems.In addition,we corroborated that the presence of exotic and domestic ungulates in low densities does not have deleterious consequences for saplings of the dominant tree,P.flexuosa.
基金funded by National Science and Technology Council,grant number NSTC 113-2223-E-006-014.
文摘This study focuses on determining the second-order irregular wave loads in the time domain without using the Inverse Fast Fourier Transform(IFFT).Considering the substantial displacement effects that Floating Offshore Wind Turbine(FOWT)support structures undergo when subjected to wave loads,the time-domain wave method is more suitable,while the frequency-domain method requiring IFFT cannot be used for moving bodies.Nonetheless,the computational challenges posed by the considerable computer time requirements of the time-domain wave method remain a significant obstacle.Thus,the paper incorporates various numerical schemes,including parallel computing and extrapolation of wave forces during specific time steps to improve overall efficiency.Despite the effectiveness of these schemes,the computational difficulties associated with the time-domain wave method persist.This study then proposes an innovative approach utilizing different randomnumbers in distinct segments,significantly reducing the computation of second-order wave loads.This random number interpolation ensures a smooth curve transition between two segments,emphasizingminimizing errors near the end of the first segment.Numerical analyses demonstrate substantial decreases in total computer time for FOWT structural analyses while maintaining consistent steel design results.The proposed method is uncomplicated,requiring only a simple subprogram modification in a conventional wave load computer program.
基金supported by the National Natural Science Foundation of China (Grant No. 40974039)High-Tech Research and Development Program of China (Grant No.2006AA06205)Leading Strategic Project of Science and Technology, Chinese Academy of Sciences (XDA08020500)
文摘Traditionally, airborne time-domain electromagnetic （ATEM） data are inverted to derive the earth model by iteration. However, the data are often highly correlated among channels and consequently cause ill-posed and over-determined problems in the inversion. The correlation complicates the mapping relation between the ATEM data and the earth parameters and thus increases the inversion complexity. To obviate this, we adopt principal component analysis to transform ATEM data into orthogonal principal components （PCs） to reduce the correlations and the data dimensionality and simultaneously suppress the unrelated noise. In this paper, we use an artificial neural network （ANN） to approach the PCs mapping relation with the earth model parameters, avoiding the calculation of Jacobian derivatives. The PC-based ANN algorithm is applied to synthetic data for layered models compared with data-based ANN for airborne time-domain electromagnetic inversion. The results demonstrate the PC-based ANN advantages of simpler network structure, less training steps, and better inversion results over data-based ANN, especially for contaminated data. Furthermore, the PC-based ANN algorithm effectiveness is examined by the inversion of the pseudo 2D model and comparison with data-based ANN and Zhody＇s methods. The results indicate that PC-based ANN inversion can achieve a better agreement with the true model and also proved that PC-based ANN is feasible to invert large ATEM datasets.
基金supported by Chinese National Programs for Fundamental Research and Development(No.2012CB416605)the National Natural Science Foundation of China(No.41174090)Development Project of National Key Scientific Equipment(No.ZDYZ2012-1-05-04)
文摘An electromagnetic field is generated through the accelerating movement of two equal but opposite charges of a single dipole. An electromagnetic field can also be generated by a time-varying infinitesimal point charge. In this study, a comparison between the electromagnetic fields of an infinitesimal point charge and a dipole has been presented. First, the time-domain potential function of a point source in a 3D conductive medium is derived. Then the electric and magnetic fields in a 3D homogeneous lossless space are derived via the relation between the potential and field. The field differences between the infinitesimal point charge and the dipole in the step-off time, far-source, and near-source zones are analyzed, and the accuracy of the solutions from these sources is investigated. It is also shown that the field of the infinitesimal point charge in the near-source zone is different from that of the dipole, whereas the far-source zone fields of these two sources are identical. The comparison of real and simulated data shows that the infinitesimal point charge represents the real source better than the divole source.
基金supported by the National High Technology Research and Development Program (863 Program)(2009AA06Z108)
文摘To effectively minimize the electromagnetic field response in the total field solution, we propose a numerical modeling method for the two-dimensional （2D） time- domain transient electromagnetic secondary field of the line source based on the DuFort- Frankel finite-difference method. In the proposed method, we included the treatment of the earth-air boundary conductivity, calculated the normalized partial derivative of the induced electromotive force （Emf）, and determined the forward time step. By extending upward the earth-air interface to the air grid nodes and the zero-value boundary conditions, not only we have a method that is more efficient but also simpler than the total field solution. We computed and analyzed the homogeneous half-space model and the fiat layered model with high precision--the maximum relative error is less than 0.01% between our method and the analytical method--and the solution speed is roughly three times faster than the total-field solution. Lastly, we used the model of a thin body embedded in a homogeneous half-space at different delay times to depict the downward and upward spreading characteristics of the induced eddy current, and the physical interaction processes between the electromagnetic field and the underground low-resistivity body.
基金financially supported by National Nonprofit institute Research Grant of IGGE(Nos.AS2017J06,AS2017Y04,and AS2016J10)Survey on coastal area for airborne magnetic method of UNV in Jiangsu(No.DD20160151-03)+3 种基金Key National Research Project of China(No.2017YFC0601900)Key Program of National Natural Science Foundation of China(No.41530320)Natural Science Foundation(No.41274121)China Natural Science Foundation for Young Scientists(No.41404093)
文摘Electrically anisotropic strata are abundant in nature, so their study can help our data interpretation and our understanding of the processes of geodynamics. However, current data processing generally assumes isotropic conditions when surveying anisotropic structures, which may cause discrepancies between reality and electromagnetic data interpretation. Moreover, the anisotropic interpretation of the time-domain airborne electromagnetic （TDAEM） method is still confined to one dimensional （1D） cases, and the corresponding three-dimensional （3D） numerical simulations are still in development. In this study, we expanded the 3D TDAEM modeling of arbitrarily anisotropic media. First, through coordinate rotation of isotropic conductivity, we obtained the conductivity tensor of an arbitrary anisotropic rock. Next, we incorporated this into Maxwell＇s equations, using a regular hexahedral grid of vector finite elements to subdivide the solution area. A direct solver software package provided the solution for the sparse linear equations that resulted. Analytical solutions were used to verify the accuracy and feasibility of the algorithm. The proven model was then applied to analyze the effects of arbitrary anisotropy in 3D TDAEM via the distribution of responses and amplitude changes, which revealed that different anisotropy situations strongly affected the responses of TDAEM.
基金the National Natural Science Foundation of China(50478014)the National 973 Program(2007CB714200)the Beijing Natural Science Foundation(8061003).
文摘A 1D finite element method in time domain is developed in this paper and applied to calculate in-plane wave motions of free field exited by SV or P wave oblique incidence in an elastic layered half-space. First, the layered half-space is discretized on the basis of the propagation characteristic of elastic wave according to the Snell law. Then, the finite element method with lumped mass and the central difference method are incorporated to establish 2D wave motion equations, which can be transformed into 1D equations by discretization principle and explicit finite element method. By solving the 1D equations, the displacements of nodes in any vertical line can be obtained, and the wave motions in layered half-space are finally determined based on the characteristic of traveling wave. Both the theoretical analysis and the numerical results demonstrate that the proposed method has high accuracy and good stability.
基金Project supported by the National Natural Science Foundation of China(Grant No.61805214)the Fundamental Research Funds for the Central Universities,China(Grant No.2652017142)
文摘Copper sulfate pentahydrate is investigated by terahertz time-domain spectroscopy. It is shown that the terahertz absorption coefficients are correlated with the particle size of the samples, as well as the heating rates of the ambient temperature. Furthermore, the water molecules of copper sulfate pentahydrate can be quantitatively characterized due to the high sensitivity of the terahertz wave to water molecules. Based on such results, the status of water incorporated in mineral opal is also characterized using terahertz time-domain spectroscopy. It indicates that terahertz technology can be considered as an efficient method to detect the dehydration of minerals.
基金The project was financially supported by the National Natural Science Foundation of China under the Grant No. 19732004 the National Science Fund for Distinguished Young Scholars under the Grant No. 50029002
文摘A time-domain method is applied to simulate nonlinear wave diffraction around a surface piercing 3-D arbitrary body. The method involves the application of Taylor series expansions and the use of perturbation procedure to establish the corresponding boundary value problems with respect to a time-independent fluid domain. A boundary element method based on B-spline expansion is used to calculate the wave field at each time step, and the free surface boundary condition is satisfied to the second order of wave steepness by a numerical integration in time. An artificial damping layer is adopted on the free surface for the removal of wave reflection from the outer boundary. As an illustration, the method is used to compute the second-order wave forces and run-up on a surface-piercing circular cylinder. The present method is found to be accurate, computationally efficient, and numerically stable.
基金This project was supported by the key programof the Nationed Natural Science Foundation of China (60432040)
文摘The path loss analysis model based on 5 rays in vacancy indoor environment is proposed. The relationship between multipath overlapping and the path loss is analyzed mathematically. Time-domain technique is introduced to compute reflection coefficient in a very short time interval. A 5 rays path loss calculation method, which is satisfactory accurate, is developed. 5 typical environments are involved to analyze and generalize the common path loss characteristics in vacancy indoor environment. The simulation result shows that the path loss can be characterized as 3 zones with different path loss exponent as distance between transmitter and receiver increasing.
基金Project supported by the Royal Society and Natural Science Foundation of China(NSFC)International Exchanges Cost Share(IEC\NSFC\181415).
文摘We report a broadband terahertz time-domain spectroscopy(THz-TDS)which enables twenty vibrational modes of adenosine nucleoside to be resolved in a wide frequency range of 1-20 THz.The observed spectroscopic features of adenosine are in good agreement with the published spectra obtained using Fourier transform infrared spectroscopy(FTIR)and Raman spectroscopy.This much extended bandwidth leads to enhanced material characterization capability as it provides spectroscopic information on both intra-and inter-molecular vibrations.In addition,we also report a low-cost frequency modulation continuous wave(FMCW)imaging system which has a fast measurement speed of 40000 waveforms per second.Cross-sectional imaging capability through cardboard has also been demonstrated using its excellent penetration capability at a frequency range of 76-81 GHz.We anticipate that the integration of these two complementary imaging technologies would be highly desirable for many real-world applications because it provides both spectroscopic discrimination and penetration capabilities in a single instrument.
