Nutrient contents and efficiencies of beech and spruce saplings as influenced by competition and O3/CO2 regime

Abstract

Saplings of Fagus sylvatica and Picea abieswere grown under conditions of intra and interspeciWc competition in a 2-year phytotron study under combinations of ambient and elevated ozone (+O 3 which is 2 £ O 3 , but <150 nl l ¡1 ) as well as carbon dioxide concentrations (+CO 2 which is amb. CO 2 + 300 l CO 2 l ¡1 ) in a full factorial design. Saplings were analysed for various mineral nutrients in diVerent plant organs as well as biomass production and crown development. The study was based on the assumption that nutritional parameters important for growth and competitiveness are aVected by stress defence under limiting nutrient supply. The hypotheses tested were (1) that nutrient uptake-related parameters (a) as well as eYciencies in nutrient use for above-ground competition (b) of beech rather than spruce are impaired by the exposure to elevated O 3 concentrations, (2) that the eYciency in nutrient uptake of spruce is enhanced by elevated CO 2 concentrations in mixed culture, and (3) that the ability to occupy above-ground space at low nutrient cost is co-determinant for the competitive success in mixed culture. Clear nitrogen deWciencies were indicated for both species during the 2-year phytotron study, although foliar nitrogen-biomass relationships were not so close for spruce than for beech. O 3 stress did not impair nutrient uptake-related parameters of beech; thus hypothesis (1a). was not supported. A negative eVect of elevated O 3 (under amb. CO 2 ) on the N and P based eYciencies in above-ground space occupation (i.e. lower crown volume per unit of N or P invested in stems, limbs and foliage) of beech supported hypothesis (1b). It appeared that ozone stress triggered a nutrient demand for stress defence and tolerance at the expense of above-ground competition (trade-oV). Crown volume of beech under O 3 stress was stabilized in monoculture by increased nutrient uptake. In general, the +CO 2 -treatment was able to counteract the impacts of 2 £ O 3 . Elevated CO 2 caused lower N and S concentrations in current-year foliage of both tree species, slightly higher macronutrient amounts in the root biomass of spruce, but did not increase the eYciencies in nutrient uptake of spruce in mixed culture. Therefore hypothesis (2) was not supported. At the end of the experiment spruce turned out to be the stronger competitor in mixed culture as displayed by its higher total shoot biomass and crown volume. The amounts of macronutrients in the above-ground biomass of spruce individuals in mixed culture distinctly exceeded those of beech, which had been strongly reduced by interspeciWc competition. The superior competitiveness of spruce was related to higher N and P-based eYciencies in aboveground space occupation as suggested in hypothesis (3).

Hidden shift of the ionome of plants exposed to elevated CO2 depletes minerals at the base of human nutrition

“… spruce tree No 350 Pfirrmann et al, 1996 Picea abies 'Karst.' spruce tree No 300 Rodenkirchen et al, 2009 Picea abies 'Karst.' spruce tree No 300 Weigt et al, 2011 Picea rubens spruce tree No 350 Shipley et al, 1992 Pinus ponderosa pine tree No 346 USA Walker et al, 2000 Pinus ponderosa 'Laws.'…”

Plant-Mediated Ecosystem Effects of Tropospheric Ozone

“…Under conditions of interspecific competition, P. abies was found to be superior in nitrogen acquisition whereas F. sylvatica in turn appeared to be nitrogen-limited (Grams and Matyssek 2010;Kozovits et al 2005). Effects on nutrient efficiency indicate that processes of stress defence due to O 3 exposure trigger a nutrient demand at the expense of above-ground competition (Rodenkirchen et al 2009). Recently, Grams et al (2012) demonstrated that the more intense the competition between F. sylvatica and P. abies is, the stronger the response to other stressors may be modified.…”

Multiple environmental control of leaf area and its significance for productivity in beech saplings

“…For estimating the dry matter production of the saplings, a reference dry weight of ten randomly chosen saplings was obtained at the first day of the study. Biomass production was calculated as the difference in dry weight at the beginning and at the end of the study by subtracting the mean initial dry weight of the reference plants from the plant's weight at harvest (Cernusak et al 2009, Rodenkirchen et al 2009). …”