Habitat fragmentation is a leading cause of extinction, with effects that may be particularly pronounced in tropical ecosystems. However, little is known regarding the demographic mechanisms underlying changes in abundance in fragmented landscapes. Using six years of demographic data collected from .6600 individuals of the Amazonian understory herb Heliconia acuminata, we calculated population ...

The effects of natural or experimental environmental perturbations on populations can be diverse, simultaneously affecting several life history variables. Populationlevel responses to such influences frequently are measured as changes in projected population growth rate (l). Sensitivity and elasticity analyses can be used to quantify the potential influence of small changes in different life hi...

development, reproduction and life table parameters of tetranychus urticae koch were determined on leaves of peach (g. h. hale cultivar) at different temperatures, ranging from 13 to 33°c under laboratory conditions. no development was observed at 13°c. egg-to-adult developmental time decreased gradually from 17 to 27°c and increased at higher temperatures (27 to 33°c). an average of 136.43 deg...

the beet armyworm (spodoptera exigua hübner) is an important pest of many agricultural crops all over the world. most of the sugar beet growing regions in iran are infested. in this study, the acute lethal effects of pyriproxyfen, spinosad, and indoxacarb as well as sublethal effects of pyriproxyfen on the 1st instar s. exigua were assessed by leaf dip bioassay method. mortality was recorded 48...

the life table parameters of schizaphis graminum (rondani) (hemiptera: aphididae) on four commercial cultivars of wheat (kohdasht, pastor, tajan and zagros) were determined in laboratory conditions. fertility life table were constructed using age-specific survivorship (lx) and age-specific fecundity (mx) and subsequently analyzed using jackknife method and anova. there were significant differen...

effects of four pesticides (imidacloprid, dichlorvos, pymetrozine and abamectin) were evaluated on life table parameters of orius albidipennis (reuter). pesticides were used at the concentrations recommended by the manufacturers. the bioassays were carried out using drum-cell method, in a growth chamber at 27 â± 1âºc, r.h. of 65 â± 5% and 16 h photo phase. the net reproductive rate (r0) value f...

the tomato fruit borer, helicoverpa armigera (hã¼bner), is a destructive insect pest of many host crops in iran and worldwide. the effect of different tomato cultivars (sun 6108 f1, rio grande ug, korral, ch falat, hed rio grande and cal jn3) was studied on life table parameters of h. armigera under laboratory (25 â± 1 â°c, 65 â± 5% rh and a photoperiod of 16: 8 (l: d) hours), and on the activi...

due to the limitations of the “life table method” the exponential model was used to estimate the iud termination and retention rate among 1,390 women. since the conditional probability of iud termination during the first month of insertion is considerably higher than the subsequent months, data relating to the first 30 days was considered separately. furthermore a constant termination rate was ...

The lowering of the groundwater table causes the area above the water table to become unsaturated and capillary phenomena to appear in this zone. This means that the bearing capacity of shallow footings will be influenced by capillary stress or matric suction. In this research, the effect of groundwater table lowering on the bearing capacity of a shallow square model footing on dense sand has b...