Ecological Archives E094-200-A1

Li-Wan Chang, David Zelený, Ching-Feng Li, Shau-Ting Chiu, Chang-Fu Hsieh. 2013. Better environmental data may reverse conclusions about niche- and dispersal-based processes in community assembly. Ecology 94:2145–2151. http://dx.doi.org/10.1890/12-2053.1

Appendix A. Comparison of environmental data for the Lienhuachih forest plot with those used by De Cáceres et al. (2012).

All four topographical variables in our study (elevation, convexity, slope, and aspect) are derived from the dataset of measured elevation of grid corners, calculated in the same way as in Legendre et al. (2009) and De Cáceres et al. (2012). Elevation, convexity, and slope are calculated according to Valencia et al. (2004). Elevation of the target cell is calculated as a mean elevation of its four corners. Convexity is calculated as elevation of target cell minus mean elevation of surrounding eight cells. Convexity of marginal cells should be calculated as elevation of the cell midpoint minus the mean of the elevation of its four corners; however, the midpoint elevation is not available (midpoint elevation cannot equal to the elevation of the cell, which is calculated as mean elevation of four corners, because the convexity of all marginal cells would become zero), and must be approximated by krigging (Valencia et al. 2004). De Cáceres et al. (2012) did not offer further details about how the problem of marginal cells was dealt with, so the reason for the differences in convexity (Table A1) may be caused by the difference in the krigging method used. Slope was calculated as the mean angular deviation from the horizontal of each of the four triangular planes formed by connecting three of its corners (Harms et al. 2001). Aspect was calculated following the formula in De Cáceres et al. (2012, Appendix S2), and this calculated aspect was found to be similar to the real aspect measured in the field (not shown here). However, the mean and standard deviation values for sin (aspect) and cos (aspect), respectively, which were used as easterness and northerness, are different from those referred by De Cáceres et al. (2012, Table S2 in Appendix S1). The reason for this difference remains unclear.

Literature cited

De Cáceres M., P. Legendre, R. Valencia, M. Cao, L.-W. Chang, G. Chuyong, R. Condit, Z. Hao, C.-F. Hsieh, S. Hubbell, D. Kenfack, K. Ma, X. Mi, N.S. Noor, A. R. Kassim, H. Ren, S.-H. Su, I.-F. Sun, D. Thomas, W. Ye, and F. He. 2012. The variation of tree beta diversity across a global network of forest plots. Global Ecology and Biogeography, 21:1191–1202.

Harms, K. E., R. Condit, S. P. Hubbell, and R. B. Foster. 2001. Habitat associations of trees and shrubs in a 50-ha neotropical forest plot. Journal of Ecology 89:947–959.

Legendre P., X. Mi, H. Ren, K. Ma, M. Yu, I.-F. Sun, and F. He. 2009. Partitioning beta diversity in a subtropical broad-leaved forest of China. Ecology 90:663–674.

Valencia, R., R. B. Foster, G. Villa, R. Condit, J.-C. Svenning, C. Hernández, K. Romoleroux, E. Losos, E. Magård, and H. Balslev. 2004. Tree species distributions and local habitat variation in the Amazon: large forest plot in eastern Ecuador. Journal of Ecology 92:214–229.

 

Table A1. Comparison of topographical variables (their mean values and variances) reported by De Cáceres et al. (2012, Table S2 in Appendix S1) and those used in our study.

 

This study

De Cáceres et al. (2012)

Year of the census

2008

2008

Number of species in the plot

144

145

Percentage of rare species

75%

75%

Number of individuals

203316

203313

Tree density (ind/m²)

0.81

0.81

Elevation (m) – mean

764

764

Elevation (m) – s.d.

35.9

35.9

Convexity – mean

-0.108

-0.257

Convexity – s.d.

3.83

7.54

Slope (°) – mean

33.4

33.4

Slope (°) – s.d.

8.53

8.69

EW aspect – mean

0.22

0.14

EW aspect – s.d.

0.67

0.73

NS aspect – mean

-0.08

-0.11

NS aspect – s.d.

0.71

0.66


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