Ecological Archives A016-005-A3

Charles D. Canham and María Uriarte. 2006. Analysis of neighborhood dynamics of forest ecosystems using likelihood methods and modeling. Ecological Applications 16:62–73.

Appendix C. Estimated parameters for dispersal functions using different neighborhood search distances and functional forms of the dispersal kernel.

We estimated parameters for dispersal functions using different neighborhood search distances and functional forms of the dispersal kernel for a hypothetical data set generated from 1-km2 area of source trees and 200 1-m2 quadrats distributed in two transects through a central 1-ha portion of the source area. Simulated seed rain was generated as a Poisson process, with a lognormal dispersal function ("Logn") and parameter values given in Table C1. The "Theoretical" curve is the true, underlying lognormal dispersal function (see Appendix A) used to generate the hypothetical data set. The exponential function ("Exp") allowed both B and in Eq. 3 to vary. The "2Dt" curve was estimated using the dispersal function presented by Clark et al. (1999).  The three sets of estimated parameters for the lognormal function used neighborhood radii of 25, 50, and 100 m, respectively. We also used a 100-m radius and examined the fit to the underlying lognormal data if an exponential or 2Dt function was used.

TABLE C1. Estimated parameters for dispersal functions using different neighborhood search distances and functional forms of the dispersal kernel.

             
 

Theoretical

Logn - 25 m

Logn - 50 m

Logn - 100 m

Exp - 100 m

2Dt  - 100 m

Search Radius

 

25

50

100

100

100

No. quadrats

 

200

200

200

200

200

Log-likelihood

 

-528.8

-493.6

-492.5

-500.3

-499.1

r2

 

0.8283

0.8377

0.8394

0.8194

0.8214

Normalizer

1941.4

3043.2

2539.6

2180.9

2199.4

0

A

500

1449.5

487.3

462.8

411.5

426.2

2

1.6

2.2

2.1

2.2

2.2

B

10

15.3

11.6

11.5

40.3

1458.1

0.6

0.50

0.59

0.56

1.70

2.27

† The u parameter for the 2Dt model of Clark et al. (1999).

‡ The p parameter for the 2Dt model of Clark et al. (1999).

 

LITERATURE CITED

Clark, J. S., M. Silman, R. Kern, E. Macklin, and J. HilleRisLambers. 1999. Seed dispersal near and far: patterns across temperate and tropical forests. Ecology 80:1475–1494.



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