Agreement of included predictors, and the signs of
their coeficients, with the expectations based on other
studies (Section 4.2) corroborates model Eq. (1). As
expected, increased rainfall is associated with
increased site index; calcium and clay contents has
a negative relation to site index; and surplus water has
a negative coeficient in accordance with well known
problems of Douglas-®r planted in excessively wet
soil conditions.