engleski

Ecophysiological response of beech seedlings grown under excessive sun conditions and different fertilization treatments

Silver fir dieback of catastrophic proportions, present in Croatia in the past three decades has led to major spread of pure beech on beech-fir sites. The area of beech-fir forests has been reduced and proportion of pure beech forests has increased (Croatian Forests Ltd., Forest management plan 2007), due to natural regeneration of beech on sun-exposed sites. This is in contradiction with recent forestry practices (regeneration under canopy shelter) and known ecological requirements of beech (Fagus sylvatica L.) (sensitivity to sunburn, shade tolerance). To determine the ecophysiological response of beech seedlings to full sunlight conditions, a nursery experiment was established with three fertilization treatments (2, 4 and 6g of Osmocote Exact per 1 liter of substrate) to simulate various soil fertility conditions (poor, adequate and excessive availability of nutrients, simulating nutritionally poor, moderately rich and very rich soils). For every treatment total biomass of seedlings (foliage, stem, roots) has been determined and plant material chemically analysed. Height and root-collar diameter have been measured and roots morphologically analyzed (WinRhizo). Light saturation curves and A-Ci curves have been measured (LI-6400) in controlled environment . Height, diameter and biomass of seedlings increased with fertilizer dose. Concentrations of N, P and K were growing with fertilizer dose, while Ca and Mg concentrations showed negative effects of overfertilization at the highest fertilizer dose. Root length, surface area and number of root tips were highest in the intermediate treatment while roots were least developed at the highest fertilizer dose. In all cases assimilation rates of seedlings corresponded well with leaf mass (r2=0, 59), leaf (r2=0, 44) and root total nitrogen (r2=0, 58) and total leaf phosphorus (r2=0, 45).

Beech; light; fertilization; nutrients; photosynthesis; biomass; leaf; stem; root

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