Accordingly, equations for predicting tree development for these two species had been fitted for all four growth simulators. Open-grown tree relationships and maximum density relationships for these species have

been published ( Kramer et al., 1970, Stiefvater, 1982, Thren, 1986, Lässig, 1991, Stampfer, 1995 and Hasenauer, 1997) and various spacing trials have been conducted for these SCR7 species ( Burger, 1936, Abetz, 1976, Erteld, 1979, Bergel, 1982, Abetz and Unfried, 1983, Abetz and Feinauer, 1987, Röhle, 1995, Mäkinen and Isomäki, 2004 and Mäkinen et al., 2005). These two species provide an interesting comparison, because Scots pine is light demanding while Norway spruce is more tolerant of shade. To simulate open-grown tree behaviour, we simulated planting 1 tree per hectare with a dbh of 10 cm on a good, average, and poor site. These three sites were defined by using the best, average, and worst site index at the age of 100 years according to the yield tables “Fichte Hochgebirge” and “Kiefer

Litschau” (Marschall, 1992). This corresponded to site indices of 38 m, 26 m, and 14 m for spruce, and site indices of 30 m, 22 m, and 14 m for pine. For growth models that do not explicitly take a site index, we selected corresponding site parameters and re-ran the model until it yielded the desired site index. A maximum deviation of the desired site index of ±0.1 m was tolerated. To obtain initial height values for the SB203580 clinical trial 10 cm dbh tree, height values for the open-grown trees were calculated using the open-grown tree relationships of Stampfer (1995). This resulted in a tree height of 6.4 m for spruce and 5.6 m for pine. We selected the study on open-grown trees by Stampfer (1995) because dimensional relationships for open-grown trees were available for both Norway spruce and Scots pine, both young and old trees were included in the

dataset, and the original data used to fit the relationship was available. Initial values that would have been obtained from other open-grown tree studies are comparable and ranged from 4.2 to 6.6 m (Kramer et al., 1970, Stiefvater, 1982, Lässig, 1991 and Hasenauer, 1997) for spruce, and 6.0 m for pine Diflunisal (Thren, 1986). For Moses and BWIN, the initial age was obtained by solving the top-height site-index equations for age. For the growth models Prognaus and Silva, which do not rely on yield tables, the age at the beginning of the simulation was assumed to be 15, 23, and 45 years for spruce and 12, 19, and 33 years for pine to correspond to good, average, and poor sites, respectively. This represents an average value for age of different yield tables. We then simulated open-grown tree growth until a dbh of 80 cm for spruce and 60 cm for pine was reached on all sites. From the simulation output we obtained the relationship between dbh and height:diameter ratio at all sites. Then we calculated the dbh, height, and crown ratio at an age of 100 years.