Search results for " Population dynamics"
showing 5 items of 35 documents
Variation of post-dispersal weed seed predation according to weed species, space and time
2008
International audience; Post-dispersal seed predation is an important source of mortality in plant populations. If this phenomenon is better known in tropical and woody systems, information is lacking for weeds in French agrosystems. In this paper, we evaluated seed predation variability in an organic wheat field by conducting experiments on weed seed preference and on spatial and temporal variation in predation rates. Weed seed predation preferences followed a species rank: Viola arvensis = Stellaria media > Alopecurus myosuroides = Chenopodium album > Sinapis arvensis = Anagallis arvensis = Galium aparine > > Plastic globules (for control), with weekly mean predation rates between 19 and …
Progress towards sustainable agriculture – Drivers of change
2021
Sustainable Development Goal (SDG) 2 calls for global action to “end hunger, achieve food security and improved nutrition, and promote sustainable agriculture”. Meeting this challenge requires global partnerships to support more productive, nutritious and equitable food systems, while helping to conserve environmental resources and reduce the greenhouse gas (GHG) emissions responsible for global climate change. The Food and Agriculture Organization of the United Nations (FAO) offers a global vision for a more sustainable agriculture that encompasses economic, social and environmental dimensions of food and agriculture systems. This technical study examines the key factors driving changes in…
Age-Structured Human Population Dynamics
2006
ABSTRACT A von Foerster-McKendrick model to study age-structured human population dynamics is presented in this paper. Forecasts of population density (population per age unit) depending on ages are possible using this model. The model consists of a quasi-linear first order partial differential equation for the dynamics of population density per age-unit (except for the zero-age), a boundary condition for the births flow at zero-age, and an initial condition for the population density at the initial instant. A general solution independent of the particular human-system under study is obtained based on some hypotheses about the mathematical structure of its input variables. The model has bee…
Time evolution of non-lethal infectious diseases: a semi-continuous approach.
2005
A model describing the dynamics related to the spreading of non-lethal infectious diseases in a fixed-size population is proposed. The model consists of a non-linear delay-differential equation describing the time evolution of the increment in the number of infectious individuals and depends upon a limited number of parameters. Predictions are in good qualitative agreement with data on influenza.
CHECK-LIST DEGLI UCCELLI DELLA R.N.O. “SALINE DI TRAPANI E PACECO” CON LISTA COMMENTATA DEI NON PASSERIFORMES
2018
Update of the checklist of the birds of the Nature Reserve “Saline di Trapani e Paceco” (Sicily). The present work provides an update to the checklist of birds of the “Saline di Trapani e Paceco” published nine years ago by IENTILE (2008). The overall number of bird species increased from 209 to the current value of 229. The present work also includes a quantitative estimate of the breeding and wintering species. A table, detailing the number of individuals of each species present for each month of the year at the Saline di Trapani and Paceco, is included. This work aims at underscoring the importance of the Saline as an Important Bird Area (IBA), as a key area for the migration pathways of…