Abstract
Light capture is linked to occupation of canopy space by tree crowns, which requires investment of carbon and nutrients. We hypothesize that (i) late-successional trees invest more in casting shade than in occupying space than early-successional trees, and (ii) shade production and crown volume expansion are generally greater in more productive species. For six Central European early-successional (Betula pendula, Pinus sylvestris), mid/late-successional (Quercus petraea, Carpinus betulus), and late-successional tree species (Tilia cordata, Fagus sylvatica), we measured through full-tree harvests (1) crown volume, (2) the costs of canopy space exploration (carbon (C) and nutrients invested to fill crown volume), of space occupation (annual foliage production per volume), and of shade production (foliage needed to reduce light transmittance), and (3) related the costs to aboveground productivity (ANPP). The C and nutrient costs of canopy volume exploration and occupation were independent of the species’ seral stage, but increased with ANPP. In contrast, the cost of shade production decreased from early-to late-successional species, suggesting that the economy of shade production is more decisive for the competitive superiority of late-successional species than the economy of canopy space exploration and occupation.
Highlights
Plants optimize their access to resources through a suite of morphological and physiological adaptations of shoots and roots
The study was conducted in each two mature stands of early-successional Betula pendula and Pinus sylvestris, mid-/late-successional Quercus petraea and Carpinus betulus, and late-successional Tilia cordata, and Fagus sylvatica, which grew on similar soils in the Pleistocene lowlands of north-west and central
Later in stand development, when competitive exclusion becomes a more important process, the economy of shade production seems to be more decisive than the economy of crown space exploration and occupation
Summary
Plants optimize their access to resources through a suite of morphological and physiological adaptations of shoots and roots. One strategy to avoid competition for light is superior height growth and the occupation of crown volume not accessible for other trees. This growth pattern is manifested in tall-growing trees, which can monopolize the light resource [2,3]. Other factors with influence on crown space and the biomass contained in it are mechanical forces exerted by wind and swaying neighbor crowns.
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