Ecological Archives E094-262-A4

David M. Newbery, Peter Stoll. 2013. Relaxation of species-specific neighborhood effects in Bornean rain forest under climatic perturbation. Ecology 94:2838–2851. http://dx.doi.org/10.1890/13-0366.1

Appendix D.Effects of including dead neighbors and correcting for gbh measurement errors.

Table D1. Regression models for the effects of larger conspecific neighbors (CON), inclusive of dead neighbors, on absolute stem growth rate (agr) in two periods (P1: 1986–1996, P2: 1996–2007) using 18 overstory species at Danum. CON-effect size was the dependent variable and plot basal area (BA) the independent variable.

 

P1: adj. R² = 57.0%

 

P2: adj. R²= 11.2%

 

Estimate

SE

t16

P

 

Estimate

SE

t16

P

Intercept

-0.14

0.03

-4.6

0.003

 

-0.07

0.03

-2.1

0.048

BA

-0.27

0.06

-4.9

0.002

 

-0.11

0.06

-1.8

0.095

Compared to the neighborhood models that exclude dead trees (i.e., living at the start but dying during the period, Table 2 in the main text), the adjusted R² of the regression is slightly decreased (from 58.1 to 57.0% ) in P1 and slightly increased (from 7.6 to 11.2%) in P2. The P values of intercept and slope remain very similar.

 

Table D2. Correcting for possible gbh measurement errors on large trees in P1

Of 437 trees in P1 with gbh86 ≥ 100 cm, agr86-96 was more than 2-fold agr86-07 for 38, and for 19 of the latter gbh86 was > 5% smaller than the mean of gbh96, gbh01 and gbh07 (mgbh96-07) (eight trees with 25–46% differences). Neighborhood analyses were rerun with mgbh96-07 substituting  these likely erroneous values of gbh86. [There were no differences > 5% larger than mgbh96-07 in P1. In P2, there was just one isolated gbh96-value that was smaller than expected, but this was left uncorrected.]

 

P1: adj. R² = 58.9%

 

Estimate

SE

t16

P

Intercept

-0.17

0.03

-5.2

0.0001

BA

-0.31

0.06

-5.0

0.0001

Mean ± SE difference in CON-effect, original – corrected, was 0.0022 ± 0.0016 (n = 18 species). Adj. R² increased slightly from 58.1 to 58.9%. Estimates and P values were almost identical.


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