The parasitic plant dwarf mistletoe(Arceuthobium) is currently one of the most threatening infestations of coniferous forests worldwide,especially in Eurasia and North America,but its population dynamics in relation t...The parasitic plant dwarf mistletoe(Arceuthobium) is currently one of the most threatening infestations of coniferous forests worldwide,especially in Eurasia and North America,but its population dynamics in relation to one of its hosts(spruce) remain unclear.Here,toward understanding the population dynamics,differential equations were used to construct a life history model for the two populations,and two relatively independent subsystems,host and parasite,were generated from their symbiotic relationships.A suspected-infection model was used to couple them.The resulting models were used to analyze structural changes in the forest.When each infected spruce was assumed to support 1000 parasite shoots,the spruce population first increased rapidly,then slows.When 2000 parasite shoots were assumed,the forest declined dramatically,slipping to zero in the 10 th year,and the spruce seedlings were unable to regenerate.Parasite shoot population curves transformed from exponential J-shapes to logistic S-shapes,reaching population limitations as germination rates changed.These results provide important clues to understanding developmental trends of the present parasite population and will assist in reconstructing invasion histories.展开更多
We study the synchronization dynamics in a system of multiple interacting populations of phase oscillators. Using the dimensionality-reduction technique of Ott and Antonsen, we explore different types of synchronizati...We study the synchronization dynamics in a system of multiple interacting populations of phase oscillators. Using the dimensionality-reduction technique of Ott and Antonsen, we explore different types of synchronization dynamics when the incoherent state becomes unstable. We find that the inter-population coupling is crucial to the synchronization. When the intra-population interaction is repulsive, the local synchronization can still be maintained through the inter-population coupling. For attractive inter-population coupling, the local order parameters in different populations are of in-phase while the local synchronization are of anti-phase for repulsive inter-population coupling.展开更多
Despite the ecological and economic importance of Acacia senegal, little is known about the effects of anthropogenic disturbances on its natural regeneration patterns and population structure. We investigated the effe...Despite the ecological and economic importance of Acacia senegal, little is known about the effects of anthropogenic disturbances on its natural regeneration patterns and population structure. We investigated the effects of these factors within the Lake Baringo woodland ecosystem. Data was collected from 60 plots of 20 m × 20 m systematically distributed in four A. senegal-dominated populations within the Lake Baringo woodland. Sample populations spanned a degradation gradient measured by a population disturbance index (PDI). Trees were measured for diameter at breast height (DBH) and categorized by growth stages: seedling, sapling and adult tree. Higher seedling and sapling densities were recorded in lightly than heavily disturbed populations, but only sapling density was significantly different between the two disturbance levels (P = 0.02). Lightly disturbed populations revealed a reversed J-shape size-class distribution (SCD) indicative of stable structure unlike the heavily disturbed populations. The quotient and permutation indices indicated unstable populations with episodic recruitment and mortality. Our study reveals that natural regeneration and population structure of A. senegal were affected majorly by selective harvesting and heavy browsing. Suitable management strategies to control livestock grazing and illegal tree harvesting within the woodland is required to promote conservation of the species genetic resources展开更多
A modified model, a set of rate equations based on time-dependent correlation function, is used to study vibrational relaxation dynamics in transient grating spectroscopy. The dephasing, the population dynamics, and t...A modified model, a set of rate equations based on time-dependent correlation function, is used to study vibrational relaxation dynamics in transient grating spectroscopy. The dephasing, the population dynamics, and the vibrational coherence concerning two vibrational states are observed respectively in organic dye IR780 perchlorate molecules doped polyvinyl alcohol matrix. The result shows that in addition to the information concerning system-environment interaction and vibrational coherence, the vibrational energy transfer can be described by this modified model.展开更多
The basic objects of investigation in this article are nonlinear impulsive dif- ferential equations. The impulsive moments coincide with the moments of meeting of the integral curve and some of the so-called barrier c...The basic objects of investigation in this article are nonlinear impulsive dif- ferential equations. The impulsive moments coincide with the moments of meeting of the integral curve and some of the so-called barrier curves. For such type of equations, suf- ficient conditions are found under which the solutions are continuously dependent on the perturbations with respect to the initial conditions and barrier curves. The results are applied to a mathematical model of population dynamics.展开更多
The endangered giant panda (Ailuropoda melanoleuca) is endemic to th e mountains of Sichuan, Gansu and Shaanxi Provinces in China. The species had nu mbered over 2000 animals in early 1970s, but declined to no more th...The endangered giant panda (Ailuropoda melanoleuca) is endemic to th e mountains of Sichuan, Gansu and Shaanxi Provinces in China. The species had nu mbered over 2000 animals in early 1970s, but declined to no more than 1,000 anim als fragmented into perhaps 32 subpopulations in late 1990s as the result of num erous detrimental forces such as habitat shrinking, poaching and bamboo flowerin g. The mass flowering and followed die-off of bamboo played key roles in the dec lination of panda population in the past three decades. It trigged the starvatio n and following high mortality of giant pandas in 1970s over Min Mountains and i n 1980s across Qionglai Mountains in Sichuan Province. The situation of survivor ship is made worse by the fact that the panda habitat is fragmented into many sm all 'islands', each containing only a few pandas. Such small, isolated panda pop ulations are rendered even more vulnerable to extinction form threats such as ha bitat degradation, natural disaster, disease, and the deleterious effects of inb reeding. So restoring the panda habitat and reintroduction pandas to their histo rical habitat might be an important issue for protecting the giant panda in wild .展开更多
基金supported by the National Key Research and Development Program (2017 YFD0600105)。
文摘The parasitic plant dwarf mistletoe(Arceuthobium) is currently one of the most threatening infestations of coniferous forests worldwide,especially in Eurasia and North America,but its population dynamics in relation to one of its hosts(spruce) remain unclear.Here,toward understanding the population dynamics,differential equations were used to construct a life history model for the two populations,and two relatively independent subsystems,host and parasite,were generated from their symbiotic relationships.A suspected-infection model was used to couple them.The resulting models were used to analyze structural changes in the forest.When each infected spruce was assumed to support 1000 parasite shoots,the spruce population first increased rapidly,then slows.When 2000 parasite shoots were assumed,the forest declined dramatically,slipping to zero in the 10 th year,and the spruce seedlings were unable to regenerate.Parasite shoot population curves transformed from exponential J-shapes to logistic S-shapes,reaching population limitations as germination rates changed.These results provide important clues to understanding developmental trends of the present parasite population and will assist in reconstructing invasion histories.
文摘We study the synchronization dynamics in a system of multiple interacting populations of phase oscillators. Using the dimensionality-reduction technique of Ott and Antonsen, we explore different types of synchronization dynamics when the incoherent state becomes unstable. We find that the inter-population coupling is crucial to the synchronization. When the intra-population interaction is repulsive, the local synchronization can still be maintained through the inter-population coupling. For attractive inter-population coupling, the local order parameters in different populations are of in-phase while the local synchronization are of anti-phase for repulsive inter-population coupling.
基金supported by Kenya Forestry Research Institute(KEFRI/FBEM 2014_2015/2.3)International Foundation for Science(IFS D5452-1)
文摘Despite the ecological and economic importance of Acacia senegal, little is known about the effects of anthropogenic disturbances on its natural regeneration patterns and population structure. We investigated the effects of these factors within the Lake Baringo woodland ecosystem. Data was collected from 60 plots of 20 m × 20 m systematically distributed in four A. senegal-dominated populations within the Lake Baringo woodland. Sample populations spanned a degradation gradient measured by a population disturbance index (PDI). Trees were measured for diameter at breast height (DBH) and categorized by growth stages: seedling, sapling and adult tree. Higher seedling and sapling densities were recorded in lightly than heavily disturbed populations, but only sapling density was significantly different between the two disturbance levels (P = 0.02). Lightly disturbed populations revealed a reversed J-shape size-class distribution (SCD) indicative of stable structure unlike the heavily disturbed populations. The quotient and permutation indices indicated unstable populations with episodic recruitment and mortality. Our study reveals that natural regeneration and population structure of A. senegal were affected majorly by selective harvesting and heavy browsing. Suitable management strategies to control livestock grazing and illegal tree harvesting within the woodland is required to promote conservation of the species genetic resources
基金supported by the Defense Industrial Technology Development Program of China (Grant No. B1520110002)the PreResearch Foundation of PLA General Armament Department, China (Grant No. 9104C6709101106)the National Natural Science Foundation of China (Grant Nos. 20973050 and 20573028)
文摘A modified model, a set of rate equations based on time-dependent correlation function, is used to study vibrational relaxation dynamics in transient grating spectroscopy. The dephasing, the population dynamics, and the vibrational coherence concerning two vibrational states are observed respectively in organic dye IR780 perchlorate molecules doped polyvinyl alcohol matrix. The result shows that in addition to the information concerning system-environment interaction and vibrational coherence, the vibrational energy transfer can be described by this modified model.
文摘The basic objects of investigation in this article are nonlinear impulsive dif- ferential equations. The impulsive moments coincide with the moments of meeting of the integral curve and some of the so-called barrier curves. For such type of equations, suf- ficient conditions are found under which the solutions are continuously dependent on the perturbations with respect to the initial conditions and barrier curves. The results are applied to a mathematical model of population dynamics.
文摘The endangered giant panda (Ailuropoda melanoleuca) is endemic to th e mountains of Sichuan, Gansu and Shaanxi Provinces in China. The species had nu mbered over 2000 animals in early 1970s, but declined to no more than 1,000 anim als fragmented into perhaps 32 subpopulations in late 1990s as the result of num erous detrimental forces such as habitat shrinking, poaching and bamboo flowerin g. The mass flowering and followed die-off of bamboo played key roles in the dec lination of panda population in the past three decades. It trigged the starvatio n and following high mortality of giant pandas in 1970s over Min Mountains and i n 1980s across Qionglai Mountains in Sichuan Province. The situation of survivor ship is made worse by the fact that the panda habitat is fragmented into many sm all 'islands', each containing only a few pandas. Such small, isolated panda pop ulations are rendered even more vulnerable to extinction form threats such as ha bitat degradation, natural disaster, disease, and the deleterious effects of inb reeding. So restoring the panda habitat and reintroduction pandas to their histo rical habitat might be an important issue for protecting the giant panda in wild .
