The study has examined the tempo-spatial patterns of cultivated land use change in Jiangsu province. A principal component analysis （PCA） of 18 selected indicators of cultivated land use during the period 1970-2010 ...The study has examined the tempo-spatial patterns of cultivated land use change in Jiangsu province. A principal component analysis （PCA） of 18 selected indicators of cultivated land use during the period 1970-2010 identified 2 main pat- terns of change in planting productivity and economic efficiency. A major shift from production-centered pattern to profit-oriented one occurred in 1984, the time of grain yield surplus and the mitigation of population pressure. In response to the impending Opened Market System, there was a notable tendency of higher efficiency and less productivity since 1997, as well as remarkable regional disparity of cultivated land use change spatially. It revealed a relative decrease in grain cropping share, crop- ping scale and cultivation intensity in South Jiangsu, especially in Tai-Lake region, and the reverse in North Jiangsu. Some suggestions for the future were finally dis- cussed from the above findings.展开更多
Issues of scale and aggregation become important when large range of space and time scales is considered in landscape models.However,identifying appropriate levels of aggregation to accurately represent the processes ...Issues of scale and aggregation become important when large range of space and time scales is considered in landscape models.However,identifying appropriate levels of aggregation to accurately represent the processes and components of ecological systems is challenging.A raster-based spatially explicit forest landscape model,LANDIS,was used to study the effects of spatial aggregation on simulated spatial pattern and ecological process in Youhao Forest Bureau of the Small Khingan Mountain in Northeastern China.The model was tested over 500 simulation years with systematically increased levels of spatial aggregation.The results show that spatial aggregation significantly influences the simulation of fire disturbance,species abundance,and spatial pattern.Simulated fire regime was relatively insensitive to grain size between 30.m and 270.m in the region.Spatial aggregation from 300.m to 480.m dramatically decreased fire return interval(FRI) and increased mean fire size.Generally,species abundance and its aggregation index(AI) remained higher level over simulation years at the fine-grained level of spatial aggregation than at coarser grains.In addition,the simulated forest dynamics was more realistic at finer grains.These results suggest that appropriate levels of spatial aggregation for the model should not be larger than 270m.展开更多
Aims Ecological strategies related to the adaptation of plants to environmental stress have long been studied by ecologists,but few studies have systematically revealed the ecological process of plant adaptation to he...Aims Ecological strategies related to the adaptation of plants to environmental stress have long been studied by ecologists,but few studies have systematically revealed the ecological process of plant adaptation to herbivores as a whole.Methods In this study,Stipa breviflora,the dominant species in the desert steppe of Inner Mongolia,was used to analyse its reproductive individual characteristics and seed traits as well as the soil seed bank and spatial patterns under heavy-grazing and no-grazing treatments.Important Findings The results showed that the number of reproductive branches positively affected the number of vegetative branches.The analysis of the soil seed bank showed that the density of S.breviflora seeds beneath reproductive S.breviflora individuals was significantly higher than that in bare land.The seed density was also significantly negatively correlated with the seed characteristics and the soil seed bank in bare land.The spatial distribution of S.breviflora was aggregated under heavy grazing.Our results suggest that under heavy grazing,reproductive activity plays a key role in resource allocation.Stipa breviflora evolved the ecological strategy of nearby diffusion by regulating the morphological characteristics of the seeds,which promotes a positive spatial correlation between the juvenile and adult populations at a small scale,thus leading to the formation of‘safe islands’.展开更多
This paper deals with the stability analysis to a three-species food chain model with crossdiffusion, the results of which show that there is no Turing instability but crossdiffusion makes the model instability possib...This paper deals with the stability analysis to a three-species food chain model with crossdiffusion, the results of which show that there is no Turing instability but crossdiffusion makes the model instability possible. We then show that the spatial patterns are spotted patterns by using numerical simulations. In order to understand why the spatial patterns happen, the existence of the nonhomogeneous steady states is investigated. Finally, using the Leray-Schauder theory, we demonstrate that cross-diffusion creates nonhomogeneous stationary patterns.展开更多
基金Supported by A Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)~~
文摘The study has examined the tempo-spatial patterns of cultivated land use change in Jiangsu province. A principal component analysis （PCA） of 18 selected indicators of cultivated land use during the period 1970-2010 identified 2 main pat- terns of change in planting productivity and economic efficiency. A major shift from production-centered pattern to profit-oriented one occurred in 1984, the time of grain yield surplus and the mitigation of population pressure. In response to the impending Opened Market System, there was a notable tendency of higher efficiency and less productivity since 1997, as well as remarkable regional disparity of cultivated land use change spatially. It revealed a relative decrease in grain cropping share, crop- ping scale and cultivation intensity in South Jiangsu, especially in Tai-Lake region, and the reverse in North Jiangsu. Some suggestions for the future were finally dis- cussed from the above findings.
基金Supported by National Natural Science Foundation of China (No.30870441,40331008)the Project of Chinese Academy of Sciences (No.KSCX2-SW-133)
文摘Issues of scale and aggregation become important when large range of space and time scales is considered in landscape models.However,identifying appropriate levels of aggregation to accurately represent the processes and components of ecological systems is challenging.A raster-based spatially explicit forest landscape model,LANDIS,was used to study the effects of spatial aggregation on simulated spatial pattern and ecological process in Youhao Forest Bureau of the Small Khingan Mountain in Northeastern China.The model was tested over 500 simulation years with systematically increased levels of spatial aggregation.The results show that spatial aggregation significantly influences the simulation of fire disturbance,species abundance,and spatial pattern.Simulated fire regime was relatively insensitive to grain size between 30.m and 270.m in the region.Spatial aggregation from 300.m to 480.m dramatically decreased fire return interval(FRI) and increased mean fire size.Generally,species abundance and its aggregation index(AI) remained higher level over simulation years at the fine-grained level of spatial aggregation than at coarser grains.In addition,the simulated forest dynamics was more realistic at finer grains.These results suggest that appropriate levels of spatial aggregation for the model should not be larger than 270m.
基金supported by the Qinghai Provincial Key R&D Program in Qinghai Province(2019-SF-145)the Platform of the Adaptive Management of the Alpine Grassland-livestock System(2020-ZJ-T07)+1 种基金the Natural Science Foundation for Young Scientists of Qinghai Province(2018-ZJ-939Q)the National Natural Science Foundation of China(31460126,3177131141).
文摘Aims Ecological strategies related to the adaptation of plants to environmental stress have long been studied by ecologists,but few studies have systematically revealed the ecological process of plant adaptation to herbivores as a whole.Methods In this study,Stipa breviflora,the dominant species in the desert steppe of Inner Mongolia,was used to analyse its reproductive individual characteristics and seed traits as well as the soil seed bank and spatial patterns under heavy-grazing and no-grazing treatments.Important Findings The results showed that the number of reproductive branches positively affected the number of vegetative branches.The analysis of the soil seed bank showed that the density of S.breviflora seeds beneath reproductive S.breviflora individuals was significantly higher than that in bare land.The seed density was also significantly negatively correlated with the seed characteristics and the soil seed bank in bare land.The spatial distribution of S.breviflora was aggregated under heavy grazing.Our results suggest that under heavy grazing,reproductive activity plays a key role in resource allocation.Stipa breviflora evolved the ecological strategy of nearby diffusion by regulating the morphological characteristics of the seeds,which promotes a positive spatial correlation between the juvenile and adult populations at a small scale,thus leading to the formation of‘safe islands’.
文摘This paper deals with the stability analysis to a three-species food chain model with crossdiffusion, the results of which show that there is no Turing instability but crossdiffusion makes the model instability possible. We then show that the spatial patterns are spotted patterns by using numerical simulations. In order to understand why the spatial patterns happen, the existence of the nonhomogeneous steady states is investigated. Finally, using the Leray-Schauder theory, we demonstrate that cross-diffusion creates nonhomogeneous stationary patterns.
