“
“Leaf area as photosynthetically active area is one of

the main drivers for tree growth and thus an important tree characteristic for tree growth studies. For silvicultural purposes trees have to be considered as parts of stands, and individual tree growth has to be investigated in relation to stand structure. Thus, O’Hara (1988) PCI-32765 concentration used the area for individual trees as a measure of site occupancy. Leaf area in relation to stand parameters, e.g., ground area potentially available (APA), which could be named as individual tree leaf area index, but also leaf area in relation to stemwood increment which is described as growth efficiency (Waring, 1983) are important research issues. However, leaf area is hard to determine precisely and non-destructively. For leaf area index determination of stands various optical instruments like LAI-2000 (Li-Cor) or SunScan (Delta-T) are available. But these instruments are limited by the complexity of the canopy structure and improvement in accuracy is still needed (Moser et al., 1995, Chen et al., 1997, Pokorny and Marek, 2000 and Pokorny et al., 2004). Another

way to determine stand leaf area index is to use the individual tree leaf area. Hence, different approaches to estimate individual tree leaf area in an indirect way were and are investigated. Such investigations aim at strong relations of leaf area to other tree characteristics. Based on the pipe model of Shinozaki et al. (1964), BEZ235 in vitro which supposed that a given leaf area is supplied ifenprodil with water from a respective quantity of conducting pipes, mainly sapwood area (e.g., Waring et al., 1982, Bancalari et al., 1987 and Meadows and Hodges, 2002), early sapwood area (Eckmüllner and Sterba, 2000), and diameter at breast height (e.g., Gholz et al., 1979 and Baldwin, 1989) are used as estimators for leaf area or leaf biomass. A few studies deal with estimating leaf area with allometric functions based on different other

tree characteristics (e.g., Pereira et al., 1997 and Kenefic and Seymore, 1999). The majority of studies dealing with indirect leaf area estimation describe sapwood area as the most accurate estimator for leaf area (e.g., Long et al., 1981, O’Hara and Valappil, 1995 and Meadows and Hodges, 2002). But to get continuously information about leaf area and related characteristics, e.g., growth efficiency, and their development over time, the determination via sapwood area is not feasible, because from the same trees cores cannot be taken every 5 or 10 years over a long term. Additionally, it is well known that the relationship between leaf area and sapwood area, even within species, is not constant. Differences could be shown between sites, crown classes, stand density, and age (Long et al.