For decades, Africa has undergone many crisis, affecting economy, climate, food, politics as well as society with irreparable consequences on the environment. The protection of the latter, being one of the cornerstone...For decades, Africa has undergone many crisis, affecting economy, climate, food, politics as well as society with irreparable consequences on the environment. The protection of the latter, being one of the cornerstones of sustainable development, is only possible if it＇s based on a reliable and rigorous diagnosis and inventory. This study suggests a method to characterize natural resources, in particular agricultural ones, by showing their landscape context. In this perspective and in the absence of any pre-existing mapping, as it is often the case in Africa, this work provides a simple and reproducible approach that merely uses Landsat Thematic Mapper （TM） （free） images, with the only constraint of the cross-checking of several images at different times of the plant cycle.展开更多
Many ecosystems extend across national or political boundaries. The consistent and effective protection of these ecosystems in transboundary areas(ETAs) is an important global research focus. Previous research on the ...Many ecosystems extend across national or political boundaries. The consistent and effective protection of these ecosystems in transboundary areas(ETAs) is an important global research focus. Previous research on the protection of such areas can be categorized into seven themes: 1) ecological conservation of a single ETA; 2) investigation of the effects of a single conservation measure on a specific ETA; 3) determination of species-level effects due to ETA conservation; 4) comparison of the same protection measures between different ETAs; 5) introduction of a single conservation measure to a specific ETA; 6) understanding the relationship between conservation and sustainable development; and 7) generalization across multiple ETA conservation cases. The protection of ETAs involves various considerations, including funding support, demand and will for collaboration, community and public participation, historical and cultural factors, political backgrounds, uniqueness of biological resources, formulation of laws and regulations, founding of specialized administrative departments, non-governmental organizations, and fairness. Here, we briefly explain the research themes and considerations related to ETA conservation. The most important finding is that most major research themes do not focus on the challenges of ETA conservation. We use two nature reserves located between China and North Korea as examples to identify specific ways to improve ETA conservation on Changbai Mountains. The efficiency of ETA administration still remains low. The study of ETA conservation should focus on concrete regional information and aim to improve existing measures through the accumulation of experience.展开更多
In this paper, a nonautonomous stochastic food-chain system with functional response and impulsive perturbations is studied. By using Ito＇s formula, exponential martingale inequality, differential inequality and othe...In this paper, a nonautonomous stochastic food-chain system with functional response and impulsive perturbations is studied. By using Ito＇s formula, exponential martingale inequality, differential inequality and other mathematical skills, some sufficient conditions for the extinction, nonpersistence in the mean, persistence in the mean, and stochastic permanence of the system are established. Furthermore, some asymptotic properties of the solutions are also investigated. Finally, a series of numerical examples are presented to support the theoretical results, and effects of different intensities of white noises perturbations and impulsive effects are discussed by the simu｜ations.展开更多
In this paper, we consider a nonautonomous competitive model with dispersion and a finite number of discrete delays. The system, which consists of two Lotka-Volterra patches, has two competitors: one can disperse betw...In this paper, we consider a nonautonomous competitive model with dispersion and a finite number of discrete delays. The system, which consists of two Lotka-Volterra patches, has two competitors: one can disperse between the two patches, but the other is confined to one patch and cannot disperse. Our purpose is to demonstrate that the dispersion rates have no effect on the uniform persistence of the solutions of the system. Furthermore, we establish the conditions under which the system admits a positive periodic solution which attracts all solutions.展开更多
In the real world, quite a few infectious diseases like schistosomiasis spread seasonally. In this paper, a nonautonomous schistosomiasis system is established, in which the saturation incidence rate and the coefficie...In the real world, quite a few infectious diseases like schistosomiasis spread seasonally. In this paper, a nonautonomous schistosomiasis system is established, in which the saturation incidence rate and the coefficients varying with time are taken into account. The long-time behavior of the model is studied. Under quite weak assumptions, sufficient conditions for the permanence and extinction of infectious population of disease are obtained. Finally, numerical simulations illustrate the validity of our results.展开更多
文摘For decades, Africa has undergone many crisis, affecting economy, climate, food, politics as well as society with irreparable consequences on the environment. The protection of the latter, being one of the cornerstones of sustainable development, is only possible if it＇s based on a reliable and rigorous diagnosis and inventory. This study suggests a method to characterize natural resources, in particular agricultural ones, by showing their landscape context. In this perspective and in the absence of any pre-existing mapping, as it is often the case in Africa, this work provides a simple and reproducible approach that merely uses Landsat Thematic Mapper （TM） （free） images, with the only constraint of the cross-checking of several images at different times of the plant cycle.
基金National Science and Technology Support Program(No.2012BAC10B01)Sci-technology Project of Yunnan Province(No.2012CA013)
文摘Many ecosystems extend across national or political boundaries. The consistent and effective protection of these ecosystems in transboundary areas(ETAs) is an important global research focus. Previous research on the protection of such areas can be categorized into seven themes: 1) ecological conservation of a single ETA; 2) investigation of the effects of a single conservation measure on a specific ETA; 3) determination of species-level effects due to ETA conservation; 4) comparison of the same protection measures between different ETAs; 5) introduction of a single conservation measure to a specific ETA; 6) understanding the relationship between conservation and sustainable development; and 7) generalization across multiple ETA conservation cases. The protection of ETAs involves various considerations, including funding support, demand and will for collaboration, community and public participation, historical and cultural factors, political backgrounds, uniqueness of biological resources, formulation of laws and regulations, founding of specialized administrative departments, non-governmental organizations, and fairness. Here, we briefly explain the research themes and considerations related to ETA conservation. The most important finding is that most major research themes do not focus on the challenges of ETA conservation. We use two nature reserves located between China and North Korea as examples to identify specific ways to improve ETA conservation on Changbai Mountains. The efficiency of ETA administration still remains low. The study of ETA conservation should focus on concrete regional information and aim to improve existing measures through the accumulation of experience.
基金Acknowledgments The authors would like to thank the editors and the anonymous referees for their helpful suggestions and comments which led to the improvement of our original manuscript. This work is supported by the National Natural Science Foundation of China （11372294 and 11261017）, Scientific Research Fund of Sichuan Provincial Education Department （14ZB0115 and 15ZB0113）, Zhejiang Provincial Natural Science Foundation （LQ13A010023） and Doctorial Research Fund of Southwest University of Science and Technology （15zx7138）.
文摘In this paper, a nonautonomous stochastic food-chain system with functional response and impulsive perturbations is studied. By using Ito＇s formula, exponential martingale inequality, differential inequality and other mathematical skills, some sufficient conditions for the extinction, nonpersistence in the mean, persistence in the mean, and stochastic permanence of the system are established. Furthermore, some asymptotic properties of the solutions are also investigated. Finally, a series of numerical examples are presented to support the theoretical results, and effects of different intensities of white noises perturbations and impulsive effects are discussed by the simu｜ations.
基金This research is supported by the National Natural Science Foundation of China the Natural Science Foundation of Henan Province.
文摘In this paper, we consider a nonautonomous competitive model with dispersion and a finite number of discrete delays. The system, which consists of two Lotka-Volterra patches, has two competitors: one can disperse between the two patches, but the other is confined to one patch and cannot disperse. Our purpose is to demonstrate that the dispersion rates have no effect on the uniform persistence of the solutions of the system. Furthermore, we establish the conditions under which the system admits a positive periodic solution which attracts all solutions.
基金Special thanks to the anonymous referees who have given us very useful suggestions. The research has been supported by the Natural Science Foundation of China （11261004）, the National Key Technologies R＆D Program of China （2009BAI78B01） and the Science and Technology Plan Projects of Jiangxi Provincial Education Department （GJJ14665, GJJ14673）.
文摘In the real world, quite a few infectious diseases like schistosomiasis spread seasonally. In this paper, a nonautonomous schistosomiasis system is established, in which the saturation incidence rate and the coefficients varying with time are taken into account. The long-time behavior of the model is studied. Under quite weak assumptions, sufficient conditions for the permanence and extinction of infectious population of disease are obtained. Finally, numerical simulations illustrate the validity of our results.
