Disturbance mosaics (treefall gaps, hurricanes, fires)

1. Disturbance mosaics (treefall gaps, hurricanes, fires) • Patchy, recurrent disturbance • environment states vary demographically • environment states change over time • Dynamics includes demographic and environment transitions

2. Concepts • Structured populations • Mosaic of environmental states • Each environmental state = one population projection matrix • Entire heterogeneous landscape = set of matrices

3. Many different ways to link together... • arithmetic average • products of matrices (a fixed sequence) • Megamatrix • Stochastic sequence

4. Megamatrix • Environment-by-stage classes • Matrix size = no. of environments x no. stages • Environmental transition matrix • Aggregates over all patches of a given environment at each time step

5. Environment transition matrix

6. Environmental characteristics from a matrix? • Sequence of types of environments • Temporal autocorrelation • Relative abundance of types of environments in the sequence over time reaches an equilibrium

7. What happens here next? • Start green • 50% chance of going to Red • 50% chance of going to Blue • Start red • 50% chance of going to Green • 50% chance of staying Red • Start blue • 100% probability of going to Green

8. Try it… • Start red.

9. What happens here long term?

10. Environment transition phenology census census time t t+1 late change early change

11. Megamatrix: early change

12. Megamatrix: late change

13. New sensitivity questions • Environment by life history stage classification • Does the same life-history event in different environments differ in elasticity values? • Elasticities (can be summed) • By environment • By stage across all environments • By stage within environments • …

14. What’s next? • Cumulative pop growth • Stochastic sequences • Stochastic elasticities • Age from stage