As substrate and energy resources in plants are limited, there is a need for plants for a well balanced trade-off, which allows growth but does not exclude defense mechanisms. This is addressed by the “Growth-Differentiation-Balance Theory” (GDB; Loomis 1953; Lorio 1988) as accentuated by Herms and Mattson (1992) and adapted by Matyssek et al. (2002, 2005). However, this theory suffers from substantial deficits in the understanding of mechanisms that underlie the balance between resource sequestration (as mediated through the plant’s competitiveness related to growth) and retention (as a result of defence). Therefore since 1998 an integrative research center, entitled “Growth and Parasite Defense–Competition for Resources in Economic Plants from Agronomy and Forestry” (Sonderforschungsbereich 607, SFB 607, funded by the ‘Deutsche Forschungsgemeinschaft’, DFG) has been established in the Munich area (Germany). The mechanistic and ecological perspective of GDB makes understandable that “third-party trade-offs” between further internal (e.g. reserve storage, reproduction) or external resources (e.g. driven through symbionts or other associative soil micro-organisms), may intensely impact on and modulate the principal resource trade-off addressed by GDB between growth and defence (Stitt and Schulze 1994; Heil and Baldwin 2002; Stamp 2003; Matyssek et al. 2005). This integrated view on GDB requires spatiotemporal process scaling that bridges gene regulation, metabolism, whole-plant functionality and resource flux at the stand level, being aware of the intense resource interchange that occurs between plants and their environment at the specific field sites. The scarcity of knowledge about the mechanistic and ecological foundations of GDB (Heil and Baldwin 2002, Stamp 2003) is evident, in particular, in forest trees, as their longevity and dimension pose a particular spatiotemporal challenge on research. Process scaling is to be extended, therefore, across plant-ontogenetic stages and a range of growth conditions, the latter being most distinctively represented by controlled, short-term chamber studies (where most of the currently available evidence is derived from, while being restricted to juvenile trees; e.g., Kolb and Matyssek 2001) versus long-term experimentation understand conditions with adult forest trees (e.g., Matyssek et al. 2007). In view of such challenges, scaling concepts that integrate Plant Soil (2009) 323:1–5 DOI 10.1007/s11104-009-0070-6