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Primary thesis objectives

Linking spatial and temporal patterns in resource availability, individual performance, & population dynamics. Primary thesis objectives. Determine how much individual detail is needed in models of population dynamics.

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Primary thesis objectives

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  1. Linking spatial and temporal patterns in resource availability, individual performance, & population dynamics.

  2. Primary thesis objectives • Determine how much individual detail is needed in models of population dynamics. • Relate explicitly spatial and temporal variation in resource abundance to individual “success”.

  3. Red Squirrel (Tamiasciuris hudsonicus) For today…. • Population level dynamics of red squirrels in Kluane valley • Temporal/spatial variation in resource abundance and territory sizes

  4. Population dynamics

  5. 1. Population dynamics: • Holistic approach assumes: • Habitat is homogeneous • All individuals are identical • Reductionist approach assumes: • individual level of detail is important Go with Holistic View - for now

  6. 60 m Midden locations

  7. KL SU 60 m

  8. Female densities

  9. Population models • 4 competing models • Density independent: Nt+1 = Nt•ea • Density dependent: Nt+1 = Nt•ea+bNt • Delayed density dependent: Nt+1 = Nt•ea+bNt+cNt-1 • Response Surface model: Nt+1 = Nt•ea+bNt+cNt-1+dNt2+eNt-12+fNtNt-1 • AICc used to compare model fit to data

  10. Population models: AICc results

  11. Population models: Density dependence?? SU

  12. What about food?? KL

  13. Population summary • Food and density effects appear to differ between these ‘populations’ • KL - Density independent/Density dependent • SU - Density dependent • Habitat quality too???

  14. Why are they different? • Different birth rates, survival patterns? • λ-contribution analysis (λ=er) • which life-history characteristic best-tracks changes in population growth-rate? • begin to tease apart what life-history is related to changes in the population growth rate (ie. fecundity, survival) • also, investigate spatial variation in this “key-factor” within each population, and relate to territory ‘quality’

  15. CONESAND TERRITORY SIZE

  16. 3m Annual cone production • White spruce - a masting species • Cone index - count top 3m of tree • Cone calibration - count all cones!! Actual cone range: 1 - 2774 y=1.185*x r2=0.996

  17. * * * * * 350 300 250 200 Spruce Cones 150 100 50 0 1988 1990 1992 1994 1996 1998 2000

  18. * * * * *

  19. Territory size Methods: - individual squirrels visually observed - territorial behaviours & locations noted - 100 % MCP 60 m 1994 and 2001

  20. * * * * * Temporal patterns

  21. * * * * * Temporal patterns

  22. Linking food availability to reproductive output

  23. * * * * * ANOVA P > 0.05 NS Number of offspring per female per year.

  24. * * * * * ANOVA P < 0.001 Number of squirrels weaned per female per year.

  25. * * * * * ANOVA P < 0.001 Number of squirrels born surviving to one year.

  26. Territory Size - temporal summary • Territory size decreases after a mast year, otherwise • size appears mostly constant • No significant effect of resource fluctuations on litter size, BUT significant effect on juvenile survival to weaning, 1-yr

  27. Recall: assumption of spatial homogeneity IS IT?

  28. Spatial vegetation patterns • Vegetation transects every 60m • - 3 transects 1200, 2400, 3600 • - each transect 4m x 25m • Kriged surfaces based on transects (10m2 cell size) • - ws density • - ws density >5cm dbh, alive • - bark beetle killed trees • - aspen • - willow

  29. 60 m Total white spruce density

  30. 60 m Midden placement (total ws den)

  31. 60 m White spruce (>5cm dbh, alive) density

  32. 60 m Bark beetle killed spruce density

  33. 60 m Aspen density

  34. 60 m Willow density

  35. Spatial patterns in territory size

  36. 60 m White spruce (>5cm dbh, alive) density and August 2002territories

  37. 60 m White spruce (>5cm dbh, alive) density,Juneand Augustterritories

  38. 84 166 110 399 123 579 248 170 293 70 175 101 139 429 120 57 119 95 310 143 286 40 58 122 41 652 28 700 1034 400 735 258 333 579 90 60 m Number of white spruce (>5cm dbh) and Augustterritories

  39. Spatial patterns in cone production • IS IT SPATIALLY HOMOGENEOUS??? • Additional cone count trees established in 2002 • Modelling cone production • - independent variables: dbh, density of surrounding trees, dbh of surrounding trees, location (r2 = 0.38) • plus.. slope, aspect, height, basal light class (r2 = 0.60)

  40. Cone Production 2002

  41. Cone Production 2003

  42. Change in June territory size 2002-03 p<0.05

  43. Goal - to map variation in habitat quality c c c c c c = +

  44. Continuing Objectives • Continue to develop cone production models • Link spatial and temporal cone availabity and territory size to territory quality & “success” • Investigate individual contributions to overall population dynamics

  45. Long-Term Food Add Thoughts • What happens to territory size when under constant high food conditions? • Will females maintain high reproductive output under high food? • What’s the key factor for recruitment? • (What is the effect of lack of cues for increased cone production?)

  46. Summer 2002 – field methods 1. Territory mapping

  47. Population growth rate

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