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Drivers of spatial structure in thinned forests

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Forest Ecosystems 2024年第2期11卷 202-213页

作者： Zichun Wang Yaoxiang Li Guangyu Wang Zheyu Zhang Ya Chen Xiaoli Liu Rundong Peng College of Mechanical and Electrical Engineering Northeast Forestry UniversityHarbin150040China Department of Forest Resources Management University of British ColumbiaVancouverCanada

Background:As is widely known,an increasing number of forest areas were managed to preserve and enhance the health of forest ecosystems.However,previous research on forest management has often overlooked the importance of structure-based.Aims:Our objectives were to define the direction of structure-based forest management.Subsequently,we investigated the relationships between forest structure and the regeneration,growth,and mortality of trees under different thinning treatments.Ultimately,the drivers of forest structural change were explored.Methods:On the basis of 92 sites selected from northeastern China,with different recovery time (from 1 to 15years) and different thinning intensities (0–59.9%) since the last thinning.Principal component analysis (PCA)identified relationships among factors determining forest spatial structure.The structural equation model (SEM)was used to analyze the driving factors behind the changes in forest spatial structure after thinning.Results:Light thinning (0–20%trees removed) promoted forest regeneration,and heavy thinning (over 35% of trees removed) facilitated forest growth.However,only moderate thinning (20%–35%trees removed) created a reasonable spatial structure.While dead trees were clustered,and they were hardly affected by thinning intensity.Additionally,thinning intensity,recovery time,and altitude indirectly improve the spatial structure of the forest by influencing diameter at breast height (DBH) and canopy area.Conclusion:Creating larger DBH and canopy area through thinning will promote the formation of complex forest structures,which cultivates healthy and stable forests.

关键词： Thinning Natural secondary forest spatial structure Dynamic changes Growth factors Structural equation modeling

spatial structural characteristics of the Deda ancient landslide in the eastern Tibetan Plateau:Insights from Audio-frequency Magnetotellurics and the Microtremor Survey Method

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China Geology 2024年第2期7卷 188-202页

作者： Zhen-dong Qiu Chang-bao Guo Yi-ying Zhang Zhi-hua Yang Rui-an Wu Yi-qiu Yan Wen-kai Chen Feng Jin Institute of Geomechanics Chinese Academy of Geological SciencesBeijing 100081China Faculty of Engineering China University of GeosciencesWuhan 430074China Key Laboratory of Active Tectonics and Geological Safety Ministry of Natural ResourcesBeijing 100081China Research Center of Neotectonism and Crustal Stability China Geological SurveyBeijing 100081China China Water Resources Beifang Investigation Design and Research Co.Ltd.Tianjin 300222China

It is of crucial importance to investigate the spatial structures of ancient landslides in the eastern Tibetan Plateau’s alpine canyons as they could provide valuable insights into the evolutionary history of the landslides and indicate the potential for future reactivation.This study examines the Deda ancient landslide,situated in the Chalong-ranbu fault zone,where creep deformation suggests a complex underground structure.By integrating remote sensing,field surveys,Audio-frequency Magnetotellurics(AMT),and Microtremor Survey Method(MSM)techniques,along with engineering geological drilling for validation,to uncover the landslide’s spatial feature s.The research indicates that a fault is developed in the upper part of the Deda ancient landslide,and the gully divides it into Deda landslide accumulation zoneⅠand Deda landslide accumulation zoneⅡin space.The distinctive geological characteristics detectable by MSM in the shallow subsurface and by AMT in deeper layers.The findings include the identification of two sliding zones in the Deda I landslide,the shallow sliding zone(DD-I-S1)depth is approximately 20 m,and the deep sliding zone(DD-I-S2)depth is 36.2-49.9 m.The sliding zone(DD-Ⅱ-S1)depth of the DedaⅡlandslide is 37.6-43.1 m.A novel MSM-based method for sliding zone identification is proposed,achieving less than 5%discrepancy in depth determination when compared with drilling data.These results provide a valuable reference for the spatial structural analysis of large-deepseated landslides in geologically complex regions like the eastern Tibetan Plateau.

关键词： Ancient landslide Remote sensing Audio-frequency Magnetotellurics(AMT) Microtremor Survey Method(MSM) Geological drilling engineering spatial structure Tibetan Plateau Geological hazard survey engineering

spatial structure and seasonal changes of nekton assemblages in the Taiwan Strait

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Acta Oceanologica Sinica 2016年第6期35卷 59-67页

作者： SONG Puqing LIN Longshan LI Yuan ZHONG Zhihui The Third Institute of Oceanography State Oceanic Administration

The Taiwan Strait is a transition zone between the East China Sea and the South China Sea with unique hydrology and a geographical environment that creates special marine community features.To analyze the spatial structure and seasonal changes of the nekton assemblages in the Taiwan Strait,seasonal experimental trawl surveys were conducted during 2006-2007.The results showed that there were two assemblages in the area with different sets of species,and the average similarity within each group varies between 39.38% and 74.20%.By using multivariate statistical analysis and analyzing the distribution of dominant species,we found that the structures of the assemblages had obvious seasonal variation.The middle region from the Putian transect to the Xiamen transect could be considered a mixing area for the two assemblages.The analysis of the relationship between species assemblages and environmental factors indicated that temperature was the most important factor affecting the community structure in cold seasons,and 22.5°C and 17°C could be considered dividing lines for spring and winter,respectively.In warm seasons,the most important factor was water depth,but the relationship with depth was not as significant,with a correlation between 0.264 and 0.399.The seasonal changes of nekton assemblages basically reflected the dynamic currents in the Taiwan Strait.The south coastal assemblage extended to nearly the entire area of the Taiwan Strait along with a strong and intense warm current that shrinks in spring and winter when the southward intrusion of the cold Zhejiang-Fujian coastal current becomes stronger.The impact of shortterm and long-term environmental changes,such as extreme weather,global warming and human activity on nekton assemblages,had been recognized but need further research.Our study on nekton assemblages could be used as a baseline for measuring future changes.

关键词： nekton assemblages species composition spatial structure transition zone Taiwan Strait

spatial structure,Hierarchy and Formation Mechanisms of Scientific Collaboration Networks:Evidence of the Belt and Road Regions

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Chinese Geographical Science 2020年第6期30卷 959-975页

作者： GU Weinan LIU Hui Institute o f Geographic Sciences and Natural Resources Research Chinese Academy of SciencesBeijing 100101China Key Laboratory of Regional Sustainable Development Modelings Chinese Academy of Sciences Beijing 100101China College of Resource and Environment University of Chinese Academy of SciencesBeijing 100049China

Scientific collaboration has become an important part of the people-to-people exchanges in the Belt and Road initiative,and remarkable progress has been made since 2013.Taking the 65 countries along the Belt and Road(BRI countries)as the research areas and using collaborated Web of Science(WOS)core collection papers to construct an international scientific collaboration matrix,the paper explores the spatial structure,hierarchy and formation mechanisms of scientific collaboration networks of 65 countries along the Belt and Road.The results show that:1)Beyond the Belt and Road regions(BRI regions),Central&Eastern Europe,China and West Asia&North Africa have formed a situation in which they all have the most external links with other countries beyond BRI regions.China has the dominant role over other BRI countries in generating scientific links.The overall spatial structure has changed to a skeleton structure consisting of many dense regions,such as Europe,North America,East Asia and Oceania.2)Within the Belt and Road regions,Central&Eastern Europe has become the largest collaboration partner with other sub-regions in BRI countries.The spatial structure of scientific collaboration networks has transformed from the‘dual core’composed of China and the Central&Eastern Europe region,to the‘multi-polarization’composed of‘one zone and multi-points’.3)The hierarchical structure of scientific collaboration networks presents a typical‘core-periphery’structure,and changes from‘single core’to‘double cores’.4)Among the formation mechanisms of scientific collaboration networks,scientific research strength and social proximity play the most important roles,while geographical distance gradually weakens the hindrance to scientific collaboration.

关键词： scientific collaboration networks spatial structure hierarchy formation mechanisms the Belt and Road regions

spatial structure of a Bose-Einstein condensate in a combined trap

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Communications in Theoretical Physics 2023年第3期75卷 105-113页

作者： Fei Li Zhijian He Wenwu Li Department of Physics Hunan First Normal UniversityChangsha 410205China Department of Science Hunan First Normal UniversityChangsha 410205China

We study the spatial structure of a Bose-Einstein condensate(BEC)with a space-dependent s-wave scattering length in a combined trap.There exists a space-dependent nonlinear atomic current in the system.The atomic current has an important influence on the spatial structure of the BEC.Research findings reveal that a large chemical potential can effectively suppress the chaotic spatial structure in the BEC system.Due to the large chemical potential,a strong atomic current is necessary to make the system lose its periodic spatial structure and lead the system into a chaotic spatial structure.But when the atomic current intensity exceeds a critical value,the chaotic spatial structure of the BEC will be completely eliminated and the system will always be kept in a series of single-periodic states as the atomic current becomes stronger.For a very weak atomic current,the spatial structure of the BEC is very sensitive to the intensity of the atomic current and a very small change of the intensity can dramatically change the spatial structure of the BEC.The effects of the combined trap parameters on the spatial structure of BECs are also discussed.

关键词： Bose-Einstein condensates atomic current spatial structure chaos

spatial structure of valley economic development in the mountainous areas in Beijing

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Journal of Geographical Sciences 2011年第2期21卷 331-345页

作者： ZHANG Yifeng JIA Dameng ZHANG Hongye TAN Jie SONG Siyu SUN Ruifeng Institute of Geographic Sciences and Natural Resources Research CAS Beijing 100101 China Graduate University of Chinese Academy of Sciences Beijing 100049 China

Valley economy is a new mode in mountainous area development that is defined by various characters of valley development, and is a distinguishing economical geographic pattern for mountainous area development. The special spatial coupling relations in the distribution of different mountainous elements in valleys are new subjects for the mountain development studies, and such studies are meaningful both for researches and practices. Based on the long term researches on mountainous area development and following a brief exploration into the connotations and the spatial organizing process of valley economy, the authors analyzed the present situations of the development of valley economy in Beijing＇s mountainous areas, studied the characteristics and the impacts of the spatial structural changes of the valley economy in Beijing＇s mountainous areas, and finally proposed a rational arrangement of the spatial structure of the valley economy in Beijing＇s mountainous areas. It is considered in this study that valley economy plays an important role in the development and functional transformation in Beijing＇s mountainous areas in the new epoch. Firstly, valley economy is not outlined by the administrative boundaries, and it connects most of the villages in the mountainous areas roughly along the major transportation lines. Therefore, valley economy can exert positive influence on the development in the mountainous areas, at least in the aspects such as the rearrangement of industrial structure in the mountainous areas and the coordinated development of rural and urban areas. In addition, it is found that the valley economy in Beijing＇s mountainous areas is evolved in a spatial organizing stage of secondary concentration, which is characterized by resource-saving, ecological protection and industrial optimization. Therefore, the development of valley economy will be helpful to the coordination between ecological protection and economic development in the mountainous areas, and will promote the integrated development of the

关键词： the mountainous areas in Beijing valley economy mountainous area development spatial structure

通过空间结构及网络稳健性理解协同发展--以京津冀地区为例

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Journal of Geographical Sciences 2024年第5期34卷 1007-1036页

作者：王浩张校源张晓宇刘若文宁晓刚 Chinese Academy of Surveying and Mapping Beijing 100036China School of Information Engineering China University of GeosciencesBeijing 100083China College of Land Science and Technology China Agricultural UniversityBeijing 100193China

In the context of accelerated globalization,intercity factor flows are becoming in-creasingly dependent on a reasonable and orderly spatial structure.Therefore,an in-depth study of the optimization and adjustment of spatial structure is essential for coordinated de-velopment.This study quantitatively evaluated urban development levels and introduced network analysis methods to analyse the spatial structure and robustness of development.The results indicated the following:(1)The urban development level in the Beijing-Tianjin-Hebei(BTH)region increased in all dimensions,and the transmission efficiency significantly improved.(2)The spatial structure of the BTH region has been relatively stable,as illustrated by the main pattern of the spatial distribution of central cities,with a trend towards contiguous development.(3)The ranking of network robustness is environment>society>economy,and the core network and key nodes are primarily located within the radiation of the three central cities of Beijing,Tianjin,and Shijiazhuang.(4)The coordinated development of the BTH re-gion is effective but still needs to be optimized and adjusted,and the strategic significance of edge cities has not been completely exploited.This study aims to provide an emerging ana-lytical perspective for optimizing regional spatial structure and promoting regional coordinated development.

关键词： urban network spatial structure network robustness coordinated development Beijing-Tianjin-Hebei(BTH)region

Geometric spatial structure of traditional Tibetan settlements of Degger County, China： A case study of four villages

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Frontiers of Architectural Research 2018年第3期7卷 304-316页

作者： Yingzi Zhang Suolang Baimu Jing Tong Wenshuang Wang School of Architecture and Design Southwest Jiaotong University Chengdu PR China Engineering College of Tibet University Lhasa PR China Beijing Tsinghua Tongheng Urban Planning & Design Institute Sichuan Branch Chengdu PR China

This study investigates the characteristics of spatial elements and structure in a multi-cultural traditional settlement in Degger County, Sichuan Province, in the Tibetan area of China. This study aims to clarify the geometric spatial representation of traditional settlements. The geometric features of their settlement plans are compared using mathematical analysis after examining the spatial arrangement of four typical settlements. Results indicate that the settlement structure has strong centrality. The spatial structure characteristics and proposed spatial models of traditional settlements in this area are discussed to aim for the results to contribute to new village planning and preserve a traditional settlement heritage.

关键词： Traditional settLe-ment spatial structure MathematicalanaLysis Tibet

Roughness height of submerged vegetation in flow based on spatial structure

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Journal of Hydrodynamics 2018年第4期30卷 754-757页

作者：王伟杰彭文启槐文信渠晓东董飞冯健 State Key Laboratory of Simulation and Regulation of Water Cycle in River Basin China Institute of Water Resources and Hydropower Research Department of Water Environment China Institute of Water Resources and Hydropower Research State Key Laboratory of Water Resources and Hydropower Engineering Science Wuhan University

The classic hydraulic resistance formulas, such as those in the Darcy–Weisbach methods, perform well in the hydraulic design with the characteristic roughness height ks smaller than the flow depth, which can be linked with the momentum roughness height based on the turbulent boundary-layer theory with the log-law formulation. However, when the roughness scale is of the same order as the flow depth, the traditional log-law formulation cannot provide satisfactory results because the flow structure is complicated and the vortices in different layers are dominated by various principles, such as the Karman streets near the channel bed, the mixing layer near the vegetation top, and a canonical turbulent boundary layer above the vegetation layer. Thus, the distribution of the streamwise velocity in the vegetated flow is a combination of the velocity profile linked with the dominant vortex and shows significant differences as compared with the traditional log-law distribution. This paper proposes a new characteristic roughness height of vegetation kv by linking vegetation attributes, especially the characteristics of the cross section in the flow within the vegetation. The power law resistance formula is derived based on a large amount of experimental data. Results show that the new formula is applicable to shallow flows with vegetation.

关键词： Vegetation resistance friction factor roughness height spatial structure