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Table 3 Results of GAMs applied to inventory data from the USA

From: Tree species richness enhances stand productivity while stand structure can have opposite effects, based on forest inventory data from Germany and the United States of America

   USA
Term Intercept a Std. error Sig. R-sq. (adj)
QI/QII f 1 (Lon × Lat) 6.22 0.00 *** 0.90
f 2 (Precip × Temp) ***
f 3 (R × CVd) ***
f 4 (SDI × dq) ***
QIII f 1 (Lon × Lat) 0.44 0.00 *** 0.37
f 2 (Precip × Temp) ***
f 3 (SDI × R) ***
  1. Lon longitude, Lat latitude, Precip annual precipitation, Temp mean annual temperature, R species richness, CVd coefficient of variation of diameter, SDI stand density index, dq quadratic mean diameter (cm). Sig. Significance values: 0 ‘***’, 0.001 ‘**’, 0.01 ‘*’, 0.05