New Zealand Journal of Forestry Science 42 (2012) 81-89

Abstract

Data from a nationwide set of permanent sample plots and interpolated climate and nutrition surfaces were used to develop multiple regression models describing Sequoia sempervirens (D.Don) mean top height at age forty (referred to as Site Index) and volume mean annual increment at age forty for a stocking of 400 stems ha-1 (referred to as 400 Index). The final Site Index model explained 82% of the variance in the data using mean annual daily air temperature and mean summer vapour pressure deficit, with the variables accounting for 71 and 11% of the variance, respectively. The final 400 Index model accounted for 76% of the variance in the data. Independent model variables for the 400 Index include mean spring air temperature, subsoil acid soluble phosphorus, and mean summer vapour pressure deficit, with these variables respectively accounting for 55, 16 and 5% of the variance in the data. A one-at-a-time validation procedure indicated both final models were relatively unbiased and accurate. For Site Index, partial response curves show a positive linear relationship with mean annual daily air temperature and a downward facing parabolic relationship with summer vapour pressure deficit that reached an optimum Site Index at 0.53 kPa. Partial response curves show a positive relationship between 400 Index and mean spring air temperature, and acid soluble phosphorus, and a negative linear relationship with summer vapour pressure deficit. Maps illustrating the spatial variation in 400 Index and Site Index for S. sempervirens across New Zealand are provided