1. Plant Ecology - Chapter 8 Plant Life Histories

2. r strategist Unstable environment, density independent K strategist Stable environment, density dependent Small size of organismLarge size of organism Much energy for reproductionLittle energy for reproduction Many offspring producedFew offspring produced Early maturityLate maturity (often after parental care) Short life expectancyLong life expectancy SemelparousIteroparous Type III survivorship curveType I or II survivorship curve Life History Strategies

3. Grime’s Triangular Model

6. Dealing with Variation “Hedging their bets” to maximize fitness in a varying environment Spread reproduction more evenly among years Increase seed dispersal area Increase dispersal time via seed banks

7. Dealing with Variation When should seeds germinate? Controlled by temperature, light, moisture, others Can plants evolve predictable germination? - depends on predictability of environment Fire?

8. Dealing with Variation Masting - large and erratic variation among years in the size of the seed crop produced Synchronized among plants within the population

9. Dealing with Variation Often explained as a response to avoid seed predators Overwhelm abilities of predators to eat all the seed - some survive to germinate

10. Dealing with Variation May actually be adaptation in wind- pollinated plants to reduce pollen limitations Many plants are pollen-limited, and increasing pollen densities increases pollination efficiency

11. Dealing with Variation Synchrony achieved by low reproduction one year (bad weather, low pollen), low resource expenditures, greater likelihood of more reproduction next year

12. Plant Phenology Timing of growth and reproduction within a year Much variation among species, populations, individuals Constrained mostly by temperature, moisture

13. Vegetative Phenology Forest floor plants in temperate regions grow, flower before tree leaf expansion Get sunlight before canopy closes, but much colder than trees experience for their growth, flowering

14. Vegetative Phenology Plants use temperature (degree-days) and photoperiod to determine phenologies Photoperiod prevents growth during mid- winter warm periods

15. Vegetative Phenology In warmer climates, moisture is major controller of vegetative phenology Grow leaves, lose leaves in response to changes in moisture

16. Reproductive Phenology Flowering regulated by many abiotic factors: temperature, light availability, moisture Belief that moisture limitation and related stressors induce flowering not fully supported: not in annuals, weak in perennials

17. Reproductive Phenology: biotic factors Biotic factors can influence reproductive phenology, especially pollinators Pollen-limited, animal- pollinated plants may be strongly controlled

18. Reproductive Phenology: biotic factors Two structuring forces possible: Competition for pollinators may lead to temporal separation of flowering, or Similar phenologies may attract more pollinators than separate flowering Little evidence for either

19. Reproductive Phenology: biotic factors Fruit or seed eaters more likely to be affected by plant phenology than to affect it Crowding by neighbors delays flowering, may select for faster growth or earlier flowering

20. Reproductive & Vegetative Phenologies: linked? Link generally weak, especially for longer- lived plants like forest trees Plants can store products of photosynthesis at one time and use them at another Temperate trees flower when leafless