Hydraulic architecture of Scots pine

Abstract

The hydraulic architecture of plants is controlled by internal and external variables like, inter alia, species (Huber, 1928; Zimmermann, 1978; Yang and Tyree, 1993), genotype (Neufeld et al., 1992), competition (Sellin, 1993), site fertility (Espinosa-Banclari et al., 1987; Long and Smith, 1989), stand management (Pothier and Margolis, 1988), climate (Whitehead et al., 1984; Mencuc-cini and Grace, 1995), and air pollution (Happla et al., 1986a,b; 1987a,b; Gruber, 1995). In the 1980s, concern about the decline of forests due to air pollution was widespread in the industrialised countries. Only rarely, though, have parameters of hydraulic architecture been included in studies on the causes of forest damage related to air pollution. Some investigations have focused on the relationship between crown transparency, then understood to be an indicator of tree vigour, and heartwood formation. In Scots pine, a lower sapwood/heartwood ratio was sometimes associated with high crown transparency (Happla and co-workers (1986a,b; 1987a,b), but see Bauch et al. (1986) and Bues and Schulz (1988)).