Forest resource conservation has been widely accepted as a key to sustain the local and regional economic development. The forest edges are affected by anthropogenic activities including deforestation, forest fragment...Forest resource conservation has been widely accepted as a key to sustain the local and regional economic development. The forest edges are affected by anthropogenic activities including deforestation, forest fragmentation, selective logging, extraction of non-timber forest products, collection of medicinal plants, recreations, hydroelectric pro- jects and its associated developmental activities, which alter the biodiver- sity. The present study intends to evaluate the edge effect on vegetation structure and species compositions in the tropical forest ecosystems at Periyar Wildlife Sanctuary in the Western Ghats. High species richness （number of species） and Shannon＇s diversity indices were observed in the site IlI （completely undisturbed forest） compared to site I （adjacent to the village/edge of the forest, which is next to the teal（ plantation, severely disturbed forest） and site II （in between the undisturbed forest and mod- erately disturbed forest） while density of tree species showed greater value in site II. Single species such as Tectona grandis （IVI of 80） and Terminaliapaniculata （IVI of 112） were the dominant tree species in site I and site II, respectively, whereas, in site III Terminalia bellirica, Bishofia javanica and Syzgium gardneri shared the dominance. Perturba- tion leads to alien plant invasion particularly Lantana camara, Eupato- rium odoratum and Ageratum conizoides. Site II is at forest transition level because the site is dominated by both natural species as well as plantation species such as Tectona grandis. This site seems to be a buffer zone on natural forest and plantations. Further studies are required to analyse the real patterns of regeneration and dynamic change due to human impact by long term monitoring with the establishment of perma- nent plots.展开更多
Background:Urban remnant forests are embedded in urban areas and are threatened directly and indirectly by urbanization.The direct effects(e.g.,loss of area)have been well studied.However,knowledge about the indirect ...Background:Urban remnant forests are embedded in urban areas and are threatened directly and indirectly by urbanization.The direct effects(e.g.,loss of area)have been well studied.However,knowledge about the indirect influence of urbanization through edge effects on the biodiversity in remnant forests is limited.Methods:In this study,we surveyed woody plant species in 72 plots in nine remnant forest patches in Guiyang,China.We examined the influences of urbanization and edge effects on the species diversity and composition of woody plants in remnant forests.We compared alpha diversities and quantified compositional dissimilarities in interior and edge sites at different levels of urbanization.We also measured the niche width of the recorded plant species and assessed whether high levels of urbanization and edge effects increased the number of generalist species.Results and conclusions:The Shannon index,the Simpson index and the Pielou index of adult trees were lowest in the edge habitat under high levels of urbanization.Significant differences in the Shannon index and the Simpson index of sapling/seedling were detected between interior and edge sites under low urbanization.The edge effects on the species composition of adult trees were intensified by high levels of urbanization.Woody plant species with wide niche widths were more abundant at edge sites under high levels of urbanization.Therefore,we recommend that urban expansion surrounding remnant patches should be strictly controlled to alleviate edge effects on biodiversity.展开更多
Researches and analyses were carried on the mechanism of forest edge effect by the classification of its types in forest ecosystem. Two kinds of practical models were put forward to extricate forestry from 'Two Cr...Researches and analyses were carried on the mechanism of forest edge effect by the classification of its types in forest ecosystem. Two kinds of practical models were put forward to extricate forestry from 'Two Crisises' and increase the utilization efficiency of solar energy and the net primary productivity on unit area by combination forest edge effect theory with forestry production. 1. Cultivating fast growth and rich yield plantation directionally in optimal community structure by use of forest edge effect theory. 2. Establishing artificial-natural compound forest community by openning up effect belts in natural secondary forest.展开更多
The first principles density-functional theoretical calculations of U adatom adsorption and diffusion on a planar graphene and quasi-one-dimensional graphene nanoribbons（GNRs） are performed. An energetic preference ...The first principles density-functional theoretical calculations of U adatom adsorption and diffusion on a planar graphene and quasi-one-dimensional graphene nanoribbons（GNRs） are performed. An energetic preference is found for U adatom diffusing to the hollow sites of both graphene and GNRs surface. A number of U distinctive diffusion paths either perpendicular or parallel to the ribbon growth direction are examined. The edge effects are evidenced by the calculated energy barriers of U adatom diffusion on armchair and zigzag nanoribbons surfaces. The calculation results indicate that the diffusion of U adatom from the inner site toward the edge site is a feasible process, particularly in zigzagGNR. It is viable to control the initial morphology of nuclear carbon material to retard the diffusion and concentration of nuclides.展开更多
Ab initio density functional theory calculations are carried out to predict the electronic properties and relative stability of gallium sulfide nanoribbons(Ga2S2-NRs) with either zigzag- or armchair-terminated edges. ...Ab initio density functional theory calculations are carried out to predict the electronic properties and relative stability of gallium sulfide nanoribbons(Ga2S2-NRs) with either zigzag- or armchair-terminated edges. It is found that the electronic properties of the nanoribbons are very sensitive to the edge structure. The zigzag nanoribbons(Ga2S2-ZNRs)are ferromagnetic(FM) metallic with spin-polarized edge states regardless of the H-passivation, whereas the bare armchair ones(Ga2S2-ANRs) are semiconducting with an indirect band gap. This band gap exhibits an oscillation behavior as the width increases and finally converges to a constant value. Similar behavior is also found in H-saturated Ga2S2-ANRs,although the band gap converges to a larger value. The relative stabilities of the bare ANRs and ZNRs are investigated by calculating their binding energies. It is found that for a similar width the ANRs are more stable than the ZNRs, and both are more stable than some Ga2S2nanoclusters with stable configurations.展开更多
Helical edge states are the hallmark of the quantum spin Hall insulator. Recently, several experiments have observed transport signatures contributed by trivial edge states, making it difficult to distinguish between ...Helical edge states are the hallmark of the quantum spin Hall insulator. Recently, several experiments have observed transport signatures contributed by trivial edge states, making it difficult to distinguish between the topologically trivial and nontrivial phases. Here, we show that helical edge states can be identified by the randomgate-voltage induced Φ_(0)/2-period oscillation of the averaged electron return probability in the interferometer constructed by the edge states. The random gate voltage can highlight the Φ_(0)/2-period Al'tshuler–Aronov–Spivak oscillation proportional to sin^(2)(2πΦ/Φ_(0)) by quenching the Φ_(0)-period Aharonov–Bohm oscillation. It is found that the helical spin texture induced π Berry phase is key to such weak antilocalization behavior with zero return probability at Φ = 0. In contrast, the oscillation for the trivial edge states may exhibit either weak localization or antilocalization depending on the strength of the spin-orbit coupling, which has finite return probability at Φ = 0. Our results provide an effective way for the identification of the helical edge states. The predicted signature is stabilized by the time-reversal symmetry so that it is robust against disorder and does not require any fine adjustment of system.展开更多
Background:Shifts in forest phenological events serve as strong indicators of climate change.However,the sensitivity of phenology events to climate change in relation to forest origins has received limited attention.M...Background:Shifts in forest phenological events serve as strong indicators of climate change.However,the sensitivity of phenology events to climate change in relation to forest origins has received limited attention.Moreover,it is unknown whether forest phenology changes with the proximity to forest edge.Methods:This study examined the green-up dates,dormancy dates,time-integrated NDVI(LiNDVI,a measure of vegetation productivity in growing season),and their sensitivities to climatic factors along the gradients of distance(i.e.proximity)to forest edge(0–2 km)in China's natural forests(NF)and planted forests(PF).For the analysis,field-surveyed data were integrated with Moderate Resolution Imaging Spectroradiometer(MODIS)NDVI from 2000 to 2022.Results:Our results reveal that PF had earlier green-up dates,later dormancy dates,and higher LiNDVI than NF.However,green-up sensitivities to temperature were higher at the edges of NF,whereas no such pattern was observed in PF.Conversely,the sensitivity of dormancy dates remains relatively stable from the inner to the edge of both NF and PF,except for a quadratic change in dormancy date sensitivity to precipitation found in NF.Additionally,we found that the green-up sensitivity to temperature increased with decreasing proximity to edge in NF evergreen forests,while it showed the opposite trend in PF evergreen forests.Furthermore,we observed that the precipitation impact on green-up dates shifts from postponing to advancing from the inner to the edge of NF,whereas precipitation dominantly postpones PF's green-up dates regardless of the proximity to edge.The LiNDVI exhibits higher sensitivity to precipitation at the edge areas,a phenomenon observed in NF but not in PF.Conclusions:These results suggest that the responses of forests to climate change vary with the distance to the edge.With increasing edge forests,which results from fragmentation caused by global changes,we anticipate that desynchronized phenological events along the distance to the edge could alter biogeochemical cycles and reshape ecosystem services such as energy flows,pollination duration,and the tourism industry.Therefore,we advocate for further investigations of edge effects to improve ecosystem modelling,enhance forest stability,and promote sustainable tourism.展开更多
Optical properties of metallic edge-like structures known as knife-edges are a topic of interest and possess potential applications in enhanced Raman scattering, optical trapping, etc. In this work, we investigate the...Optical properties of metallic edge-like structures known as knife-edges are a topic of interest and possess potential applications in enhanced Raman scattering, optical trapping, etc. In this work, we investigate the near-field optical polar- ization response at the edge of a triangular gold nanosheet, which is synthesized by a wet chemical method. A homemade scanning near-field optical microscope （SNOM） in collection mode is adopted, which is able to accurately locate its probe at the edge during experiments. An uncoated straight fiber probe is used in the SNOM, because it s611 preserves the prop- erty of light polarization though it has the depolarization to some extent. By comparing near-field intensities at the edge and glass substrate, detected in different polarization directions of incident light, the edge-induced depolarization is found, which is supported by the finite differential time domain （FDTD） simulated results. The depolarized phenomenon in the near-field is similar to that in the far-field.展开更多
In a general plane-parallel electrode system the edge of the electrode will undermine the uniformity of the dielectric barrier discharge （DBD） because of the influence of the distorted electrical field. In this pape...In a general plane-parallel electrode system the edge of the electrode will undermine the uniformity of the dielectric barrier discharge （DBD） because of the influence of the distorted electrical field. In this paper, the influence of the non-uniform electrical field on the edge effect of DBDs in a short-gap is investigated. We present some o.f the experimental results of DBDs produced by three kinds of convex-spherical electrodes. The results show that there is a dark area （the homogeneous discharge） in the central region of the electrode and a bright halo （the filamentary discharge） in the outer peripheral region, and the radius of the dark region is determined by the electrode geometry. The calculated results of the transverse （radial） field component distribution on the surface of the electrodes show that the edge effect does not come from the electrode edge, but the transverse field. The discharge has enough space to be fully developed and then format the filamentary discharge in the outer peripheral region because the streamer of the filamentary discharge is driven to move along the direction of the longer path by the transverse field. Thus, the homogeneous discharge （the Townsend DBD or a glow DBD） could not be produced in this area.展开更多
Habitat loss and fragmentation have been associated with the decline of endangered species. In 1987, a catastrophic fire in the northern Great Hing＇an Mountains of China, where the main habitat of sables （Martes zib...Habitat loss and fragmentation have been associated with the decline of endangered species. In 1987, a catastrophic fire in the northern Great Hing＇an Mountains of China, where the main habitat of sables （Martes zibellina） is located, aggravated the loss and fragmentation of the forest landscape. Due to restricted distribution and low population density, sables were listed in the national first-grade protected species in China. The objective of this paper was to identify to what extent the habitat of sables had been restored 13 years after the fire. Based on the behavioral data, which came from field survey information by radio-tracking, GPS （Global Positioning System） and forest inventory data, suitability habitat maps were derived using the Ecological Niche Suitability Model （ENSM）. In addition, the habitat structure was analyzed with selected landscape indices. Although forest cover mostly had been restored by 2000, the results indicated that, compared to the pre-fire situation, the areas of suitable habitat had been reduced significantly, especially those of less suitable, marginally suitable and moderately suitable designation. Fragmentation was aggravated, and suitable patches were found to be further isolated with the exception of those in most suitable areas. The ratio of the patch perimeter to area in unsuitable, moderately suitable and suitable areas decreased, while the ratios within other suitability types increased. Moreover, the percentage of soft boundaries decreased slightly, which can influence the redistribution of sables. The results above indicated that the suitable habitat had deteriorated, and the restoration of the sables＇ habitat remained to be done.展开更多
Understanding the sea surface scattering process is very important in the development of models to detect the target above or under the surface. In this paper, both the analytical and the numerical methods applied in ...Understanding the sea surface scattering process is very important in the development of models to detect the target above or under the surface. In this paper, both the analytical and the numerical methods applied in sea surface scattering are summarized. Some important problems concerned in this field are discussed. For numerical study, edge effect brings artificial nonrealistic scattering and therefore must be suppressed. Different edge treatment methods are compared in this paper. Scattering of breaking wave surface at very low grazing angle always needs more attentions than other scattering problems. Some numerical results show the existence of the special phenomena at very low grazing angle, for example, the ＂sea spikes＂ and the Doppler splitting.展开更多
A new method for increasing the productivity of larch plantation was pointed out by applying the edge effect in production in this paper. For the radiation of sunlight is identical in the same unit area of the same la...A new method for increasing the productivity of larch plantation was pointed out by applying the edge effect in production in this paper. For the radiation of sunlight is identical in the same unit area of the same latitude, we could not increase the productivity by changing the total radiation, but we can change the property of the floor by setting up effect be1ts and develop the structure of community and the photosynthetic system. In the end, significant benefits on productivity and biological, ecological effects were showed by 30 years experiments.展开更多
According to the characteristics of comb-drive structures, the electrical potential field is analyzed; the model based on comer capacitor is presented and solved with the capacitance characteristic formula of nonlinea...According to the characteristics of comb-drive structures, the electrical potential field is analyzed; the model based on comer capacitor is presented and solved with the capacitance characteristic formula of nonlinear capacitor. Compared with the results of finite element method simulation, the model based on comer capacitor is more accurate than the models based on infinite parallel plate capacitor and parallel plate capacitor with edge effects.展开更多
文摘Forest resource conservation has been widely accepted as a key to sustain the local and regional economic development. The forest edges are affected by anthropogenic activities including deforestation, forest fragmentation, selective logging, extraction of non-timber forest products, collection of medicinal plants, recreations, hydroelectric pro- jects and its associated developmental activities, which alter the biodiver- sity. The present study intends to evaluate the edge effect on vegetation structure and species compositions in the tropical forest ecosystems at Periyar Wildlife Sanctuary in the Western Ghats. High species richness （number of species） and Shannon＇s diversity indices were observed in the site IlI （completely undisturbed forest） compared to site I （adjacent to the village/edge of the forest, which is next to the teal（ plantation, severely disturbed forest） and site II （in between the undisturbed forest and mod- erately disturbed forest） while density of tree species showed greater value in site II. Single species such as Tectona grandis （IVI of 80） and Terminaliapaniculata （IVI of 112） were the dominant tree species in site I and site II, respectively, whereas, in site III Terminalia bellirica, Bishofia javanica and Syzgium gardneri shared the dominance. Perturba- tion leads to alien plant invasion particularly Lantana camara, Eupato- rium odoratum and Ageratum conizoides. Site II is at forest transition level because the site is dominated by both natural species as well as plantation species such as Tectona grandis. This site seems to be a buffer zone on natural forest and plantations. Further studies are required to analyse the real patterns of regeneration and dynamic change due to human impact by long term monitoring with the establishment of perma- nent plots.
基金funded by the Guizhou Science and Technology Department under Grant(QKHLHZ[2016]7447)the first-class discipline construction project of Guizhou Province under Grant(GNYL[2017]007).
文摘Background:Urban remnant forests are embedded in urban areas and are threatened directly and indirectly by urbanization.The direct effects(e.g.,loss of area)have been well studied.However,knowledge about the indirect influence of urbanization through edge effects on the biodiversity in remnant forests is limited.Methods:In this study,we surveyed woody plant species in 72 plots in nine remnant forest patches in Guiyang,China.We examined the influences of urbanization and edge effects on the species diversity and composition of woody plants in remnant forests.We compared alpha diversities and quantified compositional dissimilarities in interior and edge sites at different levels of urbanization.We also measured the niche width of the recorded plant species and assessed whether high levels of urbanization and edge effects increased the number of generalist species.Results and conclusions:The Shannon index,the Simpson index and the Pielou index of adult trees were lowest in the edge habitat under high levels of urbanization.Significant differences in the Shannon index and the Simpson index of sapling/seedling were detected between interior and edge sites under low urbanization.The edge effects on the species composition of adult trees were intensified by high levels of urbanization.Woody plant species with wide niche widths were more abundant at edge sites under high levels of urbanization.Therefore,we recommend that urban expansion surrounding remnant patches should be strictly controlled to alleviate edge effects on biodiversity.
文摘Researches and analyses were carried on the mechanism of forest edge effect by the classification of its types in forest ecosystem. Two kinds of practical models were put forward to extricate forestry from 'Two Crisises' and increase the utilization efficiency of solar energy and the net primary productivity on unit area by combination forest edge effect theory with forestry production. 1. Cultivating fast growth and rich yield plantation directionally in optimal community structure by use of forest edge effect theory. 2. Establishing artificial-natural compound forest community by openning up effect belts in natural secondary forest.
基金supported by the International S&T Cooperation Program of China(Grant No.2014DFG60230)the National Natural Science Foundation of China(Grant Nos.91326105,21306220,and 21501189)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA02040104)
文摘The first principles density-functional theoretical calculations of U adatom adsorption and diffusion on a planar graphene and quasi-one-dimensional graphene nanoribbons（GNRs） are performed. An energetic preference is found for U adatom diffusing to the hollow sites of both graphene and GNRs surface. A number of U distinctive diffusion paths either perpendicular or parallel to the ribbon growth direction are examined. The edge effects are evidenced by the calculated energy barriers of U adatom diffusion on armchair and zigzag nanoribbons surfaces. The calculation results indicate that the diffusion of U adatom from the inner site toward the edge site is a feasible process, particularly in zigzagGNR. It is viable to control the initial morphology of nuclear carbon material to retard the diffusion and concentration of nuclides.
基金supported by the National Natural Science Foundation of China(Grant Nos.11174220 and 11374226)the Key Scientific Research Project of the Henan Institutions of Higher Learning(Grant No.16A140009)+1 种基金the Program for Innovative Research Team of Henan Polytechnic University(Grant Nos.T2015-3 and T2016-2)the Doctoral Foundation of Henan Polytechnic University(Grant No.B2015-46)
文摘Ab initio density functional theory calculations are carried out to predict the electronic properties and relative stability of gallium sulfide nanoribbons(Ga2S2-NRs) with either zigzag- or armchair-terminated edges. It is found that the electronic properties of the nanoribbons are very sensitive to the edge structure. The zigzag nanoribbons(Ga2S2-ZNRs)are ferromagnetic(FM) metallic with spin-polarized edge states regardless of the H-passivation, whereas the bare armchair ones(Ga2S2-ANRs) are semiconducting with an indirect band gap. This band gap exhibits an oscillation behavior as the width increases and finally converges to a constant value. Similar behavior is also found in H-saturated Ga2S2-ANRs,although the band gap converges to a larger value. The relative stabilities of the bare ANRs and ZNRs are investigated by calculating their binding energies. It is found that for a similar width the ANRs are more stable than the ZNRs, and both are more stable than some Ga2S2nanoclusters with stable configurations.
基金Supported by the National Natural Science Foundation of China (Grant Nos. 12074172, 11674160, and 11974168)the Startup Grant at Nanjing University+1 种基金the State Key Program for Basic Researches of China (Grant No. 2017YFA0303203)the Excellent Programme at Nanjing University。
文摘Helical edge states are the hallmark of the quantum spin Hall insulator. Recently, several experiments have observed transport signatures contributed by trivial edge states, making it difficult to distinguish between the topologically trivial and nontrivial phases. Here, we show that helical edge states can be identified by the randomgate-voltage induced Φ_(0)/2-period oscillation of the averaged electron return probability in the interferometer constructed by the edge states. The random gate voltage can highlight the Φ_(0)/2-period Al'tshuler–Aronov–Spivak oscillation proportional to sin^(2)(2πΦ/Φ_(0)) by quenching the Φ_(0)-period Aharonov–Bohm oscillation. It is found that the helical spin texture induced π Berry phase is key to such weak antilocalization behavior with zero return probability at Φ = 0. In contrast, the oscillation for the trivial edge states may exhibit either weak localization or antilocalization depending on the strength of the spin-orbit coupling, which has finite return probability at Φ = 0. Our results provide an effective way for the identification of the helical edge states. The predicted signature is stabilized by the time-reversal symmetry so that it is robust against disorder and does not require any fine adjustment of system.
基金supported by National Science Foundation of China(Nos.32001166,32371663)the Forestry Peak Discipline Construction Project of Fujian Agriculture and Forestry University,China(No.72202200205).
文摘Background:Shifts in forest phenological events serve as strong indicators of climate change.However,the sensitivity of phenology events to climate change in relation to forest origins has received limited attention.Moreover,it is unknown whether forest phenology changes with the proximity to forest edge.Methods:This study examined the green-up dates,dormancy dates,time-integrated NDVI(LiNDVI,a measure of vegetation productivity in growing season),and their sensitivities to climatic factors along the gradients of distance(i.e.proximity)to forest edge(0–2 km)in China's natural forests(NF)and planted forests(PF).For the analysis,field-surveyed data were integrated with Moderate Resolution Imaging Spectroradiometer(MODIS)NDVI from 2000 to 2022.Results:Our results reveal that PF had earlier green-up dates,later dormancy dates,and higher LiNDVI than NF.However,green-up sensitivities to temperature were higher at the edges of NF,whereas no such pattern was observed in PF.Conversely,the sensitivity of dormancy dates remains relatively stable from the inner to the edge of both NF and PF,except for a quadratic change in dormancy date sensitivity to precipitation found in NF.Additionally,we found that the green-up sensitivity to temperature increased with decreasing proximity to edge in NF evergreen forests,while it showed the opposite trend in PF evergreen forests.Furthermore,we observed that the precipitation impact on green-up dates shifts from postponing to advancing from the inner to the edge of NF,whereas precipitation dominantly postpones PF's green-up dates regardless of the proximity to edge.The LiNDVI exhibits higher sensitivity to precipitation at the edge areas,a phenomenon observed in NF but not in PF.Conclusions:These results suggest that the responses of forests to climate change vary with the distance to the edge.With increasing edge forests,which results from fragmentation caused by global changes,we anticipate that desynchronized phenological events along the distance to the edge could alter biogeochemical cycles and reshape ecosystem services such as energy flows,pollination duration,and the tourism industry.Therefore,we advocate for further investigations of edge effects to improve ecosystem modelling,enhance forest stability,and promote sustainable tourism.
基金Project supported by the National Key Basic Research Program of China(Grant No.2013CB934004)the Fundamental Research Funds for the Central Universities,China(Grant No.YWF-13-D2-XX-14)
文摘Optical properties of metallic edge-like structures known as knife-edges are a topic of interest and possess potential applications in enhanced Raman scattering, optical trapping, etc. In this work, we investigate the near-field optical polar- ization response at the edge of a triangular gold nanosheet, which is synthesized by a wet chemical method. A homemade scanning near-field optical microscope （SNOM） in collection mode is adopted, which is able to accurately locate its probe at the edge during experiments. An uncoated straight fiber probe is used in the SNOM, because it s611 preserves the prop- erty of light polarization though it has the depolarization to some extent. By comparing near-field intensities at the edge and glass substrate, detected in different polarization directions of incident light, the edge-induced depolarization is found, which is supported by the finite differential time domain （FDTD） simulated results. The depolarized phenomenon in the near-field is similar to that in the far-field.
基金supported by National Natural Science Foundation of China(No.51177059)
文摘In a general plane-parallel electrode system the edge of the electrode will undermine the uniformity of the dielectric barrier discharge （DBD） because of the influence of the distorted electrical field. In this paper, the influence of the non-uniform electrical field on the edge effect of DBDs in a short-gap is investigated. We present some o.f the experimental results of DBDs produced by three kinds of convex-spherical electrodes. The results show that there is a dark area （the homogeneous discharge） in the central region of the electrode and a bright halo （the filamentary discharge） in the outer peripheral region, and the radius of the dark region is determined by the electrode geometry. The calculated results of the transverse （radial） field component distribution on the surface of the electrodes show that the edge effect does not come from the electrode edge, but the transverse field. The discharge has enough space to be fully developed and then format the filamentary discharge in the outer peripheral region because the streamer of the filamentary discharge is driven to move along the direction of the longer path by the transverse field. Thus, the homogeneous discharge （the Townsend DBD or a glow DBD） could not be produced in this area.
基金Foundation project： This paper was supported by the Natural Science Foundation of China （No. 30270225, 40331008）
文摘Habitat loss and fragmentation have been associated with the decline of endangered species. In 1987, a catastrophic fire in the northern Great Hing＇an Mountains of China, where the main habitat of sables （Martes zibellina） is located, aggravated the loss and fragmentation of the forest landscape. Due to restricted distribution and low population density, sables were listed in the national first-grade protected species in China. The objective of this paper was to identify to what extent the habitat of sables had been restored 13 years after the fire. Based on the behavioral data, which came from field survey information by radio-tracking, GPS （Global Positioning System） and forest inventory data, suitability habitat maps were derived using the Ecological Niche Suitability Model （ENSM）. In addition, the habitat structure was analyzed with selected landscape indices. Although forest cover mostly had been restored by 2000, the results indicated that, compared to the pre-fire situation, the areas of suitable habitat had been reduced significantly, especially those of less suitable, marginally suitable and moderately suitable designation. Fragmentation was aggravated, and suitable patches were found to be further isolated with the exception of those in most suitable areas. The ratio of the patch perimeter to area in unsuitable, moderately suitable and suitable areas decreased, while the ratios within other suitability types increased. Moreover, the percentage of soft boundaries decreased slightly, which can influence the redistribution of sables. The results above indicated that the suitable habitat had deteriorated, and the restoration of the sables＇ habitat remained to be done.
文摘Understanding the sea surface scattering process is very important in the development of models to detect the target above or under the surface. In this paper, both the analytical and the numerical methods applied in sea surface scattering are summarized. Some important problems concerned in this field are discussed. For numerical study, edge effect brings artificial nonrealistic scattering and therefore must be suppressed. Different edge treatment methods are compared in this paper. Scattering of breaking wave surface at very low grazing angle always needs more attentions than other scattering problems. Some numerical results show the existence of the special phenomena at very low grazing angle, for example, the ＂sea spikes＂ and the Doppler splitting.
文摘A new method for increasing the productivity of larch plantation was pointed out by applying the edge effect in production in this paper. For the radiation of sunlight is identical in the same unit area of the same latitude, we could not increase the productivity by changing the total radiation, but we can change the property of the floor by setting up effect be1ts and develop the structure of community and the photosynthetic system. In the end, significant benefits on productivity and biological, ecological effects were showed by 30 years experiments.
基金Sponsored by the Ministerial Level Foundation(A2220060040)
文摘According to the characteristics of comb-drive structures, the electrical potential field is analyzed; the model based on comer capacitor is presented and solved with the capacitance characteristic formula of nonlinear capacitor. Compared with the results of finite element method simulation, the model based on comer capacitor is more accurate than the models based on infinite parallel plate capacitor and parallel plate capacitor with edge effects.
