Wild oat is a problematic weed species that requires new managementtechniques in the face of herbicide resistance; harvest weed-seed control(HWSC) may be an option. Wild oat demographic information was collected inlong-term, rotational field studies in Lacombe, AB, Canada, in 2006 and2007, and a periodic matrix model was parameterized using managementextremes (no IPM, no herbicide to high IPM, and full herbicide). Populationgrowth rates were calculated for each treatment and year. Prospective(elasticity) and retrospective (LTRE) analyses were conducted alongside arearrangement of the model equation in which population growth rates weredesignated and the required proportion of newly shed seed survival thatgives that growth rate was solved for. All populations had λ > 1 orincreasing populations. Elasticity analyses indicated that λ was most-highlyelastic to the overwinter seedbank (Esw = 1), followed by seedling survival, fecundity, and survival ofnewly shed seed (0.63 to 0.86 across treatments). The latter may be themost-accessible vital rate for management of herbicide resistantpopulations. LTRE exposed the stochasticity of wild oat population growthrates between years and their ability to take advantage of lapses incontrol. Decreasing the proportion of newly shed seeds(snew) that survives was the most-effective and available controlstrategy until reduced to 0.1 to 0.3 when the summer seedbank becomes morecritical. When averaged across treatments, > 80% of newly shed seed mustbe eliminated to stop the population from growing, resulting in a stablepopulation, but not a decline. Because of preharvest shattering, HWSC willlikely not be effective enough alone to cause wild oat populations todecline. New management techniques for wild oat control that can be used incombination with HWSC and integrated weed management strategies areneeded.

Weed seeds initiate most weed invasions of arable fields, yet there is relatively little information on the value of managing weed seed banks. Matrix population models were used to examine the relative importance of managing weed seed banks, in relation to other life stages, for four model weed species with varying life histories. Simulations for giant foxtail and common lambsquarters, summer annual weeds of arable fields; garlic mustard, an obligate biennial invasive weed of temperate forests; and Canada thistle, a perennial weed of pastures and arable fields, were run under conditions of varying population density and efficacy of seedling control. The models were subjected to elasticity analysis to determine what happened to weed populations when different life stages were targeted. Losses from the dormant seed bank were most important for summer annual weeds, of intermediate importance for biennial weeds, and of low importance for perennial weeds. More effort is needed to develop weed seed-bank management techniques for summer annual weed species as part of integrated weed management systems.

Demographic comparisons between wild and restored populations of at-risk plant species can reveal key management strategies for effective conservation, but few such studies exist. This paper evaluates the potential restoration success of Alyxia stellata, a Hawaiian vine. Stage-structured matrix projection models that compared long-term and transient dynamics of wild versus restored A. stellata populations, and restored populations under different levels of canopy cover, were built from demographic data collected over a four year period. Stochastic models of wild populations projected stable or slightly declining long-term growth rates depending on frequency of dry years. Projected long-term population growth rates of restored populations were significantly higher in closed than open canopy conditions, but indicated population decline under both conditions. Life table response experiments illustrated that lower survival rates, especially of small adults and juveniles, contributed to diminished population growth rates in restored populations. Transient analyses for restored populations projected short-term decline occurring even faster than predicted by asymptotic dynamics. Restored populations will not be viable over the long term under conditions commonly found in restoration projects and interventions will likely be necessary. This study illustrates how the combination of long-term population modelling and transient analyses can be effective in providing relevant information for plant demographers and restoration practitioners to promote self-sustaining native populations, including under future climates.

Epiphytes are one of the most ubiquitous elements of tropical forest canopies, including seasonally dry tropical forests. Given the temporal variation in weather conditions in the latter, epiphyte populations may be subject to wide temporal variation in seedling recruitment, reproductive success, vegetative propagation and mortality rate. In this study, we use a 3-y demographic data set for Tillandsia brachycaulos to project its long-term population dynamics through the use of average and periodic matrices, as well as stochastic simulations. The results show that demographic behaviour varied over the 3 years of study, apparently in relation to rainfall. The first 2 years yielded a low λ value (0.79 and 0.80 – although only the former was significantly lower than unity), while the third year resulted in a λ = 1.08 (not significantly different from 1.0). When incorporating this demographic variation in an average matrix, a periodic matrix and stochastic simulations, the resulting overall λ was below unity in all three cases. The projections of the stochastic simulations suggest that the population would be able to persist in the long run only if the frequency of “good” years (defined here as those with an August rainfall above 200 mm) was above 0.6, which appears unlikely given that global warming might result in a lower frequency of rainy years in tropical dry forests.