Accurate acquisition of forest spatial competition and tree 3D structural phenotype parameters is crucial for exploring tree-environment interactions.However,due to the occlusion between tree crowns,current UAV-based ...Accurate acquisition of forest spatial competition and tree 3D structural phenotype parameters is crucial for exploring tree-environment interactions.However,due to the occlusion between tree crowns,current UAV-based and ground-based LiDAR struggles to capture complete crown information in dense stands,making parameter extraction challenging such as maximum crown width height(HMCW).This study proposes a canopy spatial relationship-based method for constructing forest spatial structure units and employs five ensemble learning techniques to train 11 machine learning model combinations.By coupling spatial competition with phenotype parameters,the study identifies the optimal fitting model for HMCW of Chinese fir.The results demonstrate that the constructed spatial structure units align closely with existing research while addressing issues of incorrectly selected or omitted neighboring trees.Among the 10,191 trained HMCW models,the Bagging model integrating XGBoost,Random Forest(RF),Support Vector Regression(SVR),Gradient Boosting(GB),and Ridge exhibited the best performance.Compared to the best single model(RF),the Bagging model achieved improved accuracy(R^(2)=0.8346,representing a 1.6%improvement;RMSE=1.4042,reduced by 6.66%;EVS=0.8389;MAE=0.9129;MAPE=0.0508;and MedAE=0.5076,with corresponding improvements of 1.63%,1.49%,0.1%,and 7.06%,respectively).This study provides a viable solution for modeling HMCW in all species with similar structural characteristics and offers a method for extracting other hard-to-measure parameters.The refined spatial structure units better link 3D structural phenotypes with environmental factors.This approach aids in canopy morphology simulation and forest management research.展开更多
Intervening opportunity is an important factor in spatial interaction, and has very important impacts on tourist destination development in a region. There are few literatures on this topic in tourist researches, and ...Intervening opportunity is an important factor in spatial interaction, and has very important impacts on tourist destination development in a region. There are few literatures on this topic in tourist researches, and especially in China fewer tourist researchers pay attention to intervening opportunity theory. This article, taking Lin’an as a case study, aims to introduce intervening opportunity theory in tourist destination development by the comprehensive ana-lysis of some data including literatures, Internet information, longitudinal data and some tourist surveys. Both qualitative and quantitative methods are all used in this research. Firstly, the authors expatiate upon the definition of intervening opportunity, by reviewing the literatures in detail, take Lin’an of Zhejiang Province as a case study, and then analyze some necessary factors of intervening opportunity, such as regional tourist demands and supplies, tourist attractions, spatial distance and transportation, tourist images and costs, regional competition and cooperation in tourist destinations. Finally the impacts of intervening opportunity on Lin’an tourist development are analyzed in detail. The results show that intervening opportunity do not occur everywhere, and there must be some critical factors, and intervening opportunity surely plays important roles in tourist destination development. The tourist development in Lin’an is attributed to intervening opportunity of the spatial location between Hangzhou and Huangshan that are two famous tourist cities in China, and the occurrence of intervening opportunities in Lin’an is the integration of some external and internal factors.展开更多
The distributions of two ubiquitous fouling cheilostome bryozoans,Cryptosula pallasiana(Moll,1803)and W atersipora sp.,on a ship moored for almost six years in Qingdao Bay show diff erences with respect to illuminatio...The distributions of two ubiquitous fouling cheilostome bryozoans,Cryptosula pallasiana(Moll,1803)and W atersipora sp.,on a ship moored for almost six years in Qingdao Bay show diff erences with respect to illumination,C ryptosula being dominant on the side of the ship which was exposed to the sun and Watersipora dominating on the other side which was in shadow for most of the time.Competitive interactions for substrate space were nearly always won by Watersipora,which succeeded in overgrowing the edges of C ryptosula colonies regardless of the side of the ship.Reasons for the superiority of W atersipora in spatial competition with Cryptosula could include faster growth rate and the stronger feeding currents created by the larger lophophores of Watersipora.展开更多
Aims Within a habitat of multiple plant species,increased resource availabilities and altered species abundances following disturbances create opportunities for exotic species to successfully establish and subsequentl...Aims Within a habitat of multiple plant species,increased resource availabilities and altered species abundances following disturbances create opportunities for exotic species to successfully establish and subsequently naturalize into its non-native environment.Such post-disturbance changes in abiotic and biotic environments may also promote a naturalized exotic species(or invading species)to become invasive through rapid colonization of the habitat sites by reducing the extent and size of resident plant species.By combining species life history traits with that of the disturbance-induced changes in habitat characteristics,we aimed to determine those interacting factors and associated mechanism allowing an exotic invasion to start off.Methods We used a modified version of the classic competition–colonization(CC)model which was formulated first by Hastings(1980)and studied later by Tilman(1994)to explain spatial coexistence of multiple species.Within this model framework,recruitment-limited spatial competition has explicitly been linked with interspecific resource competition without altering the basic assumptions and structure of the original CC model.Important findings The model results showed that at a constant rate of resource supply,invading species can stably coexist with native species via trade-offs between species competitive ability and colonizing ability.On the other hand,the model predicted that with a fluctuating resource condition,invading species can successfully invade a habitat following continuous reductions in the size and extent of native species.Whether or not invading species holds competitive superiority over the native species for limiting resource,we showed that there exists a range of variation in available resource that allows an exotic invasion to start off in post-disturbance habitat.The associated disturbance-induced mechanism promoting invading species to become invasive has been identified.It states that occurrences of disturbances such as fire or clear-cutting influence variation in resource availability,and in addition open up many vacant microsites;given these disturbance-induced changes,invading species with a higher rate of propagule production and with a higher survival rate of adults particularly in low-resource condition recruits microsites at faster rate relative to native competitor species,and with a given range of variation in resource availabilities,it maintains continued expansions following reductions in size and extent of native species.Moreover,we identified those interacting factors and their specific roles that drive this mechanism.These factors include propagule supply,variable resource level and vacant microsite availability.Increased availability of vacant microsites following disturbances creates an opportunity for rapid colonization.Given this opportunity,higher number of propagules supplied by the invading species enhances the rate of colonization success,whereas the resource variation within a range of given thresholds maintains enhanced colonization rate of the invading species while it depresses native competitor species.Owing to the each factor’s invasion regulatory ability,controlling one or all of them may have strong negative impact on the occurrence of exotic invasion.展开更多
基金funded by Fundamental Research Funds of CAF(CAFYBB2023PA003)Science and Technology Innovation 2030-Major Projects(2023ZD0406103)National Natural Science Foundation of China(32271877).
文摘Accurate acquisition of forest spatial competition and tree 3D structural phenotype parameters is crucial for exploring tree-environment interactions.However,due to the occlusion between tree crowns,current UAV-based and ground-based LiDAR struggles to capture complete crown information in dense stands,making parameter extraction challenging such as maximum crown width height(HMCW).This study proposes a canopy spatial relationship-based method for constructing forest spatial structure units and employs five ensemble learning techniques to train 11 machine learning model combinations.By coupling spatial competition with phenotype parameters,the study identifies the optimal fitting model for HMCW of Chinese fir.The results demonstrate that the constructed spatial structure units align closely with existing research while addressing issues of incorrectly selected or omitted neighboring trees.Among the 10,191 trained HMCW models,the Bagging model integrating XGBoost,Random Forest(RF),Support Vector Regression(SVR),Gradient Boosting(GB),and Ridge exhibited the best performance.Compared to the best single model(RF),the Bagging model achieved improved accuracy(R^(2)=0.8346,representing a 1.6%improvement;RMSE=1.4042,reduced by 6.66%;EVS=0.8389;MAE=0.9129;MAPE=0.0508;and MedAE=0.5076,with corresponding improvements of 1.63%,1.49%,0.1%,and 7.06%,respectively).This study provides a viable solution for modeling HMCW in all species with similar structural characteristics and offers a method for extracting other hard-to-measure parameters.The refined spatial structure units better link 3D structural phenotypes with environmental factors.This approach aids in canopy morphology simulation and forest management research.
基金U nderthe auspicesofthe N ationalN aturalScience Foundation ofChina (N o.40171027)
文摘Intervening opportunity is an important factor in spatial interaction, and has very important impacts on tourist destination development in a region. There are few literatures on this topic in tourist researches, and especially in China fewer tourist researchers pay attention to intervening opportunity theory. This article, taking Lin’an as a case study, aims to introduce intervening opportunity theory in tourist destination development by the comprehensive ana-lysis of some data including literatures, Internet information, longitudinal data and some tourist surveys. Both qualitative and quantitative methods are all used in this research. Firstly, the authors expatiate upon the definition of intervening opportunity, by reviewing the literatures in detail, take Lin’an of Zhejiang Province as a case study, and then analyze some necessary factors of intervening opportunity, such as regional tourist demands and supplies, tourist attractions, spatial distance and transportation, tourist images and costs, regional competition and cooperation in tourist destinations. Finally the impacts of intervening opportunity on Lin’an tourist development are analyzed in detail. The results show that intervening opportunity do not occur everywhere, and there must be some critical factors, and intervening opportunity surely plays important roles in tourist destination development. The tourist development in Lin’an is attributed to intervening opportunity of the spatial location between Hangzhou and Huangshan that are two famous tourist cities in China, and the occurrence of intervening opportunities in Lin’an is the integration of some external and internal factors.
基金Supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(Nos.XDA11020303,XDA11020305)the Chinese Academy of Sciences President’s International Fellowship Initiative(No.2015VEA009)the Project of Knowledge Innovation Project of Chinese Academy of Sciences(No.KSCX2-EW-Z-8)
文摘The distributions of two ubiquitous fouling cheilostome bryozoans,Cryptosula pallasiana(Moll,1803)and W atersipora sp.,on a ship moored for almost six years in Qingdao Bay show diff erences with respect to illumination,C ryptosula being dominant on the side of the ship which was exposed to the sun and Watersipora dominating on the other side which was in shadow for most of the time.Competitive interactions for substrate space were nearly always won by Watersipora,which succeeded in overgrowing the edges of C ryptosula colonies regardless of the side of the ship.Reasons for the superiority of W atersipora in spatial competition with Cryptosula could include faster growth rate and the stronger feeding currents created by the larger lophophores of Watersipora.
基金US National Science Foundation’s Biocomplexity Program(DEB-0421530)Long Term Ecological Research Program(Sevilleta)(DEB-0620482)and the University of California Agricultural Experiment Station。
文摘Aims Within a habitat of multiple plant species,increased resource availabilities and altered species abundances following disturbances create opportunities for exotic species to successfully establish and subsequently naturalize into its non-native environment.Such post-disturbance changes in abiotic and biotic environments may also promote a naturalized exotic species(or invading species)to become invasive through rapid colonization of the habitat sites by reducing the extent and size of resident plant species.By combining species life history traits with that of the disturbance-induced changes in habitat characteristics,we aimed to determine those interacting factors and associated mechanism allowing an exotic invasion to start off.Methods We used a modified version of the classic competition–colonization(CC)model which was formulated first by Hastings(1980)and studied later by Tilman(1994)to explain spatial coexistence of multiple species.Within this model framework,recruitment-limited spatial competition has explicitly been linked with interspecific resource competition without altering the basic assumptions and structure of the original CC model.Important findings The model results showed that at a constant rate of resource supply,invading species can stably coexist with native species via trade-offs between species competitive ability and colonizing ability.On the other hand,the model predicted that with a fluctuating resource condition,invading species can successfully invade a habitat following continuous reductions in the size and extent of native species.Whether or not invading species holds competitive superiority over the native species for limiting resource,we showed that there exists a range of variation in available resource that allows an exotic invasion to start off in post-disturbance habitat.The associated disturbance-induced mechanism promoting invading species to become invasive has been identified.It states that occurrences of disturbances such as fire or clear-cutting influence variation in resource availability,and in addition open up many vacant microsites;given these disturbance-induced changes,invading species with a higher rate of propagule production and with a higher survival rate of adults particularly in low-resource condition recruits microsites at faster rate relative to native competitor species,and with a given range of variation in resource availabilities,it maintains continued expansions following reductions in size and extent of native species.Moreover,we identified those interacting factors and their specific roles that drive this mechanism.These factors include propagule supply,variable resource level and vacant microsite availability.Increased availability of vacant microsites following disturbances creates an opportunity for rapid colonization.Given this opportunity,higher number of propagules supplied by the invading species enhances the rate of colonization success,whereas the resource variation within a range of given thresholds maintains enhanced colonization rate of the invading species while it depresses native competitor species.Owing to the each factor’s invasion regulatory ability,controlling one or all of them may have strong negative impact on the occurrence of exotic invasion.
