In order to research the population distribution pattern of endangered species Toona ciliata Roem., the sampling quadrats of 5 mx5 m and 3 m×3 m in size, accurate to 1 mxl m, were established in 2 newly-found onl...In order to research the population distribution pattern of endangered species Toona ciliata Roem., the sampling quadrats of 5 mx5 m and 3 m×3 m in size, accurate to 1 mxl m, were established in 2 newly-found only existing T. cili- ata Roem. communities （T1 and T2） with contiguous grid quadrate method, in the Nanhe River valley, Gucheng County. By X2 test, t-test of distribution coefficient Cx method, and F test of Morisita pattern index Iδ whether the distribution patterns of the T. ciliata Roem. populations conformed to Poisson distribution were checked. The results indicated that, population T1 was in Poisson distribution under 5 m×5 m and 3 m×3 m in size by Cx and 16 methods, but in clumped distribution pattern un- der 5 m×5 m in size by the Chi-square test; however, the population was in Pois- son distribution under the dimension of 3 m×3 m. Population T2 under human dis- turbance had higher population density, indicating clumped distribution under 3 above-mentioned tests. If Chi-square test is satisfied, a distribution pattern is in Poisson distribution, and size and quantity of sampling quadrats should be given pri- ority to; and if df is greater, both theoretical values and observed values tend to- wards normal distribution more probably, and the test of distribution pattern, there- fore will be more dependable.展开更多
The positive and negative terrains(P-N terrains) widely distributed across China's Loess Plateau constitute the dual structure characteristic of loess landforms. Analysis of loess P-N terrains at the watershed sca...The positive and negative terrains(P-N terrains) widely distributed across China's Loess Plateau constitute the dual structure characteristic of loess landforms. Analysis of loess P-N terrains at the watershed scale can serve to elucidate the structural characteristics and spatial patterns of P-N terrains, which benefits a better understanding of watershed evolution and suitable scales for loess landform research. The Two-Term Local Quadrat Variance Analysis(TTLQV) is calculated as the average of the square of the difference between the block totals of all possible adjacent pairs of block size, which can be used to detect both the scale and the intensity of landscape patches(e.g., plant/animal communities and gully networks). In this study, we determined the latitudinal and longitudinal spatial scale of P-N terrain patterns within 104 uniformly distributed watersheds in our target soil and water conservation region. The results showed that TTLQV is very effective for examining the scale of P-N terrain patterns. There were apparently three types of P-N terrain pattern in latitudinal direction(i.e., Loess Tableland type, Loess Hill type, and Transitional Form between Sand and Loess type), whereas there were both lower and higher values for P-N terrain pattern scales in all loess landforms in the longitudinal direction. The P-N terrain pattern alsoclearly presented anisotropy, suggesting that gully networks in the main direction were well-developed while others were relatively undeveloped. In addition, the relationships between the first scales and controlling factors(i.e., gully density, nibble degree, watershed area, mean watershed slope, NDVI, precipitation, loess thickness, and loess landforms) revealed that the first scales are primarily controlled by watershed area and loess landforms. This may indicate that the current spatial pattern of P-N terrains is characterized by internal force. In selecting suitable study areas in China' Loess Plateau, it is crucial to understand four control variables: the spatial scale of the P-N terrain pattern, the watershed area, the main direction of the watershed, and the loess landforms.展开更多
Fieldwork along several segments of the Altyn Tagh Fault,between 85 and 95°E,confirms that it ranks as one of the most active faults of Asia.In the East,near Aksay,the active fault trace offsets numerous stream c...Fieldwork along several segments of the Altyn Tagh Fault,between 85 and 95°E,confirms that it ranks as one of the most active faults of Asia.In the East,near Aksay,the active fault trace offsets numerous stream channels,terrace risers and fans tens to hundreds of meters. 14 C dating of organic remains and charcoal within terrace gravels indicates that most of the terraces were emplaced after the beginning of the Holocene,implying a left\|slip rate of about 2cm/a.Large mole tracks attest to the occurrence of great earthquakes.Even larger mole tracks are found north of Lenghu,within the Altun Shan push\|up,a 6000 m high range in a restraining bend of the fault,now sliced by its most active strand.North of Huatougou,at the transition between another push\|up mountain and a recent pull\|apart basin,a spectacular sequence of five flat\|floored,hanging channels,beheaded by the fault from a unique source in the mountain,have been horizontally displaced by up to 1250m.Cosmogenic dating of the abandonment of these channels and of nearby offset terrace risers confirms the slip\|rate at Aksay.Several km to the west,pressure ridges exceeding 10m in height across a large young fan,imply the repeat of several great earthquakes in a relatively short time span.展开更多
sing the natural limestone samples taken from the field with dimension of 500 mm×500 mm×1 000 mm, the D-D (dilatancy-diffusion) seismogeny pattern was modeled under the condition of water injection, which ob...sing the natural limestone samples taken from the field with dimension of 500 mm×500 mm×1 000 mm, the D-D (dilatancy-diffusion) seismogeny pattern was modeled under the condition of water injection, which observes the time-space evolutionary features about the relative physics fields of the loaded samples from deformation, formation of microcracks to the occurrence of main rupture. The results of observed apparent resistivity show: ① The process of the deformation from microcrack to main rupture on the loaded rock sample could be characterized by the precursory spatial-temporal changes in the observation of apparent resistivity; ② The precursory temporal changes of observation in apparent resistivity could be divided into several stages, and its spatial distribution shows the difference in different parts of the rock sample; ③ Before the main rupture of the rock sample the obvious ″tendency anomaly′ and ′short-term anomaly″ were observed, and some of them could be likely considered as the ″impending earthquake ″anomaly precursor of apparent resistivity. The changes and distribution features of apparent resistivity show that they are intrinsically related to the dilatancy phenomenon of the loaded rock sample. Finally, this paper discusses the mechanism of resistivity change of loaded rock sample theoretically.展开更多
Climate sequences can be applied to defining sensitive climate zones, and then the mining of spatio-temporal teleconnection patterns is useful for learning from the past and preparing for the future. However, scale-de...Climate sequences can be applied to defining sensitive climate zones, and then the mining of spatio-temporal teleconnection patterns is useful for learning from the past and preparing for the future. However, scale-dependency in this kind of pattern is still not well handled by existing work. Therefore, in this study, the multi-scale regionalization is embedded into the spatio-temporal teleconnection pattern mining between anomalous sea and land climatic events. A modified scale-space clustering algorithm is first developed to group climate sequences into multi-scale climate zones. Then, scale variance analysis method is employed to identify climate zones at characteristic scales, indicating the main characteristics of geographical phenomena. Finally, by using the climate zones identified at characteristic scales, a time association rule mining algorithm based on sliding time windows is employed to discover spatio-temporal teleconnection patterns. Experiments on sea surface temperature, sea level pressure, land precipitation and land temperature datasets show that many patterns obtained by the multi-scale approach are coincident with prior knowledge, indicating that this method is effective and reasonable. In addition, some unknown teleconnection patterns discovered from the multi-scale approach can be further used to guide the prediction of land climate.展开更多
快速城市化与气候变化的共同胁迫使得高密度城市面临多重生态风险,包括城市热岛、洪涝灾害与空气污染等,这些生态问题不仅影响城市生态系统的稳定性,同时威胁人类福祉。因此,亟需对全球高密度城市的生态问题与应对策略开展研究。以Web o...快速城市化与气候变化的共同胁迫使得高密度城市面临多重生态风险,包括城市热岛、洪涝灾害与空气污染等,这些生态问题不仅影响城市生态系统的稳定性,同时威胁人类福祉。因此,亟需对全球高密度城市的生态问题与应对策略开展研究。以Web of Science和Scopus为文献检索数据源,通过系统性分析258篇文献揭示全球高密度城市生态问题的研究特征。首先,对全球高密度城市关键生态问题的数量分布与地理空间分布特征进行分析;其次,对三大生态问题的影响因素与尺度差异进行讨论,并提出城区与场地尺度下生态问题的应对策略;最后,研究表明城市三维形态、立体生态空间是未来生态问题的重点。研究结论表明:(1)亚洲地区对高密度城市生态问题关注度最高,城市热岛是全球高密度城市研究的热点问题;(2)景观格局特征与建成环境特征是城市热岛与洪涝的重要影响因素,生物物理特征与建成环境特征是空气污染的重要影响因素;(3)优化城市景观构成与空间配置可缓解高密度城市生态问题。研究结果为高密度城市开展生态研究与应对生态风险提供了重要启发。展开更多
基金Supported by Public Welfare Research Project of Science and Technology Agency of Hubei Province(402012DBA40001)~~
文摘In order to research the population distribution pattern of endangered species Toona ciliata Roem., the sampling quadrats of 5 mx5 m and 3 m×3 m in size, accurate to 1 mxl m, were established in 2 newly-found only existing T. cili- ata Roem. communities （T1 and T2） with contiguous grid quadrate method, in the Nanhe River valley, Gucheng County. By X2 test, t-test of distribution coefficient Cx method, and F test of Morisita pattern index Iδ whether the distribution patterns of the T. ciliata Roem. populations conformed to Poisson distribution were checked. The results indicated that, population T1 was in Poisson distribution under 5 m×5 m and 3 m×3 m in size by Cx and 16 methods, but in clumped distribution pattern un- der 5 m×5 m in size by the Chi-square test; however, the population was in Pois- son distribution under the dimension of 3 m×3 m. Population T2 under human dis- turbance had higher population density, indicating clumped distribution under 3 above-mentioned tests. If Chi-square test is satisfied, a distribution pattern is in Poisson distribution, and size and quantity of sampling quadrats should be given pri- ority to; and if df is greater, both theoretical values and observed values tend to- wards normal distribution more probably, and the test of distribution pattern, there- fore will be more dependable.
基金supported by the National Natural Science Foundation of China (NO. 41201464, 41371424)the Fundamental Research Funds for the Central Universities of China (GK201703042)
文摘The positive and negative terrains(P-N terrains) widely distributed across China's Loess Plateau constitute the dual structure characteristic of loess landforms. Analysis of loess P-N terrains at the watershed scale can serve to elucidate the structural characteristics and spatial patterns of P-N terrains, which benefits a better understanding of watershed evolution and suitable scales for loess landform research. The Two-Term Local Quadrat Variance Analysis(TTLQV) is calculated as the average of the square of the difference between the block totals of all possible adjacent pairs of block size, which can be used to detect both the scale and the intensity of landscape patches(e.g., plant/animal communities and gully networks). In this study, we determined the latitudinal and longitudinal spatial scale of P-N terrain patterns within 104 uniformly distributed watersheds in our target soil and water conservation region. The results showed that TTLQV is very effective for examining the scale of P-N terrain patterns. There were apparently three types of P-N terrain pattern in latitudinal direction(i.e., Loess Tableland type, Loess Hill type, and Transitional Form between Sand and Loess type), whereas there were both lower and higher values for P-N terrain pattern scales in all loess landforms in the longitudinal direction. The P-N terrain pattern alsoclearly presented anisotropy, suggesting that gully networks in the main direction were well-developed while others were relatively undeveloped. In addition, the relationships between the first scales and controlling factors(i.e., gully density, nibble degree, watershed area, mean watershed slope, NDVI, precipitation, loess thickness, and loess landforms) revealed that the first scales are primarily controlled by watershed area and loess landforms. This may indicate that the current spatial pattern of P-N terrains is characterized by internal force. In selecting suitable study areas in China' Loess Plateau, it is crucial to understand four control variables: the spatial scale of the P-N terrain pattern, the watershed area, the main direction of the watershed, and the loess landforms.
文摘Fieldwork along several segments of the Altyn Tagh Fault,between 85 and 95°E,confirms that it ranks as one of the most active faults of Asia.In the East,near Aksay,the active fault trace offsets numerous stream channels,terrace risers and fans tens to hundreds of meters. 14 C dating of organic remains and charcoal within terrace gravels indicates that most of the terraces were emplaced after the beginning of the Holocene,implying a left\|slip rate of about 2cm/a.Large mole tracks attest to the occurrence of great earthquakes.Even larger mole tracks are found north of Lenghu,within the Altun Shan push\|up,a 6000 m high range in a restraining bend of the fault,now sliced by its most active strand.North of Huatougou,at the transition between another push\|up mountain and a recent pull\|apart basin,a spectacular sequence of five flat\|floored,hanging channels,beheaded by the fault from a unique source in the mountain,have been horizontally displaced by up to 1250m.Cosmogenic dating of the abandonment of these channels and of nearby offset terrace risers confirms the slip\|rate at Aksay.Several km to the west,pressure ridges exceeding 10m in height across a large young fan,imply the repeat of several great earthquakes in a relatively short time span.
文摘sing the natural limestone samples taken from the field with dimension of 500 mm×500 mm×1 000 mm, the D-D (dilatancy-diffusion) seismogeny pattern was modeled under the condition of water injection, which observes the time-space evolutionary features about the relative physics fields of the loaded samples from deformation, formation of microcracks to the occurrence of main rupture. The results of observed apparent resistivity show: ① The process of the deformation from microcrack to main rupture on the loaded rock sample could be characterized by the precursory spatial-temporal changes in the observation of apparent resistivity; ② The precursory temporal changes of observation in apparent resistivity could be divided into several stages, and its spatial distribution shows the difference in different parts of the rock sample; ③ Before the main rupture of the rock sample the obvious ″tendency anomaly′ and ′short-term anomaly″ were observed, and some of them could be likely considered as the ″impending earthquake ″anomaly precursor of apparent resistivity. The changes and distribution features of apparent resistivity show that they are intrinsically related to the dilatancy phenomenon of the loaded rock sample. Finally, this paper discusses the mechanism of resistivity change of loaded rock sample theoretically.
基金Projects(41601424,41171351)supported by the National Natural Science Foundation of ChinaProject(2012CB719906)supported by the National Basic Research Program of China(973 Program)+2 种基金Project(14JJ1007)supported by the Hunan Natural Science Fund for Distinguished Young Scholars,ChinaProject(2017M610486)supported by the China Postdoctoral Science FoundationProjects(2017YFB0503700,2017YFB0503601)supported by the National Key Research and Development Foundation of China
文摘Climate sequences can be applied to defining sensitive climate zones, and then the mining of spatio-temporal teleconnection patterns is useful for learning from the past and preparing for the future. However, scale-dependency in this kind of pattern is still not well handled by existing work. Therefore, in this study, the multi-scale regionalization is embedded into the spatio-temporal teleconnection pattern mining between anomalous sea and land climatic events. A modified scale-space clustering algorithm is first developed to group climate sequences into multi-scale climate zones. Then, scale variance analysis method is employed to identify climate zones at characteristic scales, indicating the main characteristics of geographical phenomena. Finally, by using the climate zones identified at characteristic scales, a time association rule mining algorithm based on sliding time windows is employed to discover spatio-temporal teleconnection patterns. Experiments on sea surface temperature, sea level pressure, land precipitation and land temperature datasets show that many patterns obtained by the multi-scale approach are coincident with prior knowledge, indicating that this method is effective and reasonable. In addition, some unknown teleconnection patterns discovered from the multi-scale approach can be further used to guide the prediction of land climate.
文摘快速城市化与气候变化的共同胁迫使得高密度城市面临多重生态风险,包括城市热岛、洪涝灾害与空气污染等,这些生态问题不仅影响城市生态系统的稳定性,同时威胁人类福祉。因此,亟需对全球高密度城市的生态问题与应对策略开展研究。以Web of Science和Scopus为文献检索数据源,通过系统性分析258篇文献揭示全球高密度城市生态问题的研究特征。首先,对全球高密度城市关键生态问题的数量分布与地理空间分布特征进行分析;其次,对三大生态问题的影响因素与尺度差异进行讨论,并提出城区与场地尺度下生态问题的应对策略;最后,研究表明城市三维形态、立体生态空间是未来生态问题的重点。研究结论表明:(1)亚洲地区对高密度城市生态问题关注度最高,城市热岛是全球高密度城市研究的热点问题;(2)景观格局特征与建成环境特征是城市热岛与洪涝的重要影响因素,生物物理特征与建成环境特征是空气污染的重要影响因素;(3)优化城市景观构成与空间配置可缓解高密度城市生态问题。研究结果为高密度城市开展生态研究与应对生态风险提供了重要启发。
