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Competition between sessile oak (Quercus petraea) and black cherry (Padus serotina) : dynamics of seedlings growth

Robakowski P., Bielinis E.

Polish Journal of Ecology

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2011

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Vol. 59, nr 2

297-306

EN

Competition is an evolutionary mechanism which exerts a selection pressure on living organisms. Forest trees compete for light, water and nutrients, especially at a young age. It was observed that the Quercus petraea and Padus serotina natural regenerations occupied the same site growing under the canopy of Scots pine (Pinus silvestris L.). To simulate the competition between young sessile oaks and black cherries found in forest, a controlled experiment was conducted using one-year-old seedlings of both species. There were eight treatments of different competition intensity. The treatments were established varying the number of potted seedlings and adding fresh cherry leaves to the substrate to enhance allelopathic effects. It was hypothesized that black cherry would reduce the height growth and diameter at root collar of sessile oak seedlings and this inhibitory effect would be magnified by an increasing number of cherry seedlings and/or fresh leaves. Black cherry as an invasive, fast-growing species was presumed to win the growth competition with oak. However, the differences in growth parameters would not only depend on genetic differences between the species, but also on the number of competing seedlings in pots and an allelopathic effect of cherry leaves. During the whole vegetative season, each two weeks, the growth parameters of seedlings (height, height increment and diameter at root collar) were measured. The results did not support the hypothesis that cherry had an inhibitory effect on oak growth, at least after one vegetative season. Contrary, a presence of cherry seedlings enhanced the oak height increment (F = 8.6, P <0.001) which might be due to either the strong interspecific competition for light or, less plausibly, positive allelopathic effect, or an interaction of both. Our results indicated a negative auto-allelopathic effect of cherry seedlings and/or fresh cherry leaves on height of cherry seedlings (F = 47.7, P <0.001). This invader showed a continuous and steep height increment within the whole vegetative season, whereas oak seedlings grew rapidly only in July. When compared the mean initial heights in April with those after the bud set in September, cherry was four fold and oak only two fold higher. A very intensive height increment gives black cherry an advantage over sessile oak at a young age which can disturb the spontaneous conversion of pine stands into a mixed pine-oak forest with a greater share of oak and other native deciduous tree species.

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Ability of silver fir and European beech sapling to acclimate photochemical processes to the light environment under different canopies of trees

Robakowski P., Antczak P.

Polish Journal of Ecology

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2008

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Vol. 56, nr 1

3-16

EN

Ability to acclimate photo-chemical processes by saplings of silver fir (Abies alba Mill.) and European beech (Fagus sylvatica L.) growing in contrasting light environments was investigated using chlorophyll a fluorescence. The leaves of saplings acclimated to irradiance under the open canopy of Larix decidua Mill. showed higher photosynthetic efficiency and more efficient photoprotective mechanism than those under the shade of the denser Picea abies Karst. canopy. Interspecific differences in quantum yield of PS II photochemistry, apparent electron transport rate, non-photochemical quenching and the values of the cardinal points of a light response curves of these parameters resulted from the shade adaptation of leaves and leaf life-span. Acclimation to shade did not increase sensitivity to strong PS II downregulation induced by light patch of low intensity but predisposed both species to photoinhibition caused by high light stress. They were able to efficiently use light patches of low intensity, but after high light stress beech leaves from the Larix stand recovered more dynamically in quantum yield of PS II photo-chemistry than silver fir. It may give an advantage to beech in between-species competition for use of short-lasting and intensive sun patches.

3

Variation in ultrastructure of chloroplasts in needles of silver fir (Abies alba Mill.) saplings growing under the canopies of diverse tree species

Kierzkowski D., Samardakiewicz S., Robakowski P.

Polish Journal of Ecology

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2007

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Vol. 55, nr 4

821-825

EN

Ultrastructural traits of chloroplasts in needles of Abies alba saplings growing under the canopy of Larix decidua Mill. and Picea abies Karst. were studied. An acclimation of chloroplast from the palisade parenchyma to different light conditions created by the principal species of the canopy was assessed using transmission electron microscope and light microscope. A comparison of such chloroplast patterns as: number of chloroplast per palisade parenchyma section unite, chloroplast section surface, number of thylakoids per granum, number of grana per section surface of chloroplast, thylakoids section surface to stroma section surface ratio, number of osmophilic granules, and size of starch granules allowed to determine plasticity of the ultrastructures in response to irradiance level under each canopy. There was, for example, evidence that the number of thylakoids per granum was lower, whereas chloroplast section surface inversely, was higher at greater canopy openness. The investigated patterns of chloroplasts, which reflect their biochemical adaptations, might significantly affect photosynthetic capacity of the young firs. Their variation reflected an ability of Abies alba photosynthetic apparatus to acclimate to canopy shading at the ultrastructural level.

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Variation in structure of needles of silver fir (Abies alba Mill.) saplings groowing under the canopies of diverse tree species

Robakowski P., Samardakiewicz S., Kierzkowski D.

Polish Journal of Ecology

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2004

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Vol. 52, nr 4

563-568

EN

Morphological and anatomical traits of needles of Abies alba saplings growing under the canopies of Picea abies, Fagus sylvatica, Betula pendula, Pinus sylvestris and Larix decidua were studied. An acclimation of the needles to different light conditions created by the principal species of the canopy was assessed using different microscopic methods. Length, width, needle area, stomatal density, parenchyma thickness, resin ducts diameter, central cylinder size and other traits of needles allowed to determine their structural plasticity in response to irradiance level, Leaf mass to area ratio, palisadeparenchyma thickness, diameter of resin ducts increased, whereas width/thickness ratio and needle thickness/parenchyma thickness ratio decreased with increasing canopy openness. Variation in the investigated patterns of the needles reflected their structural plasticity and also an ability of silver fir saplings to acclimate to irradiance under the canopies of diverse tree species.

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Acclimation of silver fir (Abies alba Mill.) seedlings to irradiance conditions under canopies of different tree species in Sudety Mts. (Southern Poland)

Robakowski P., Wyka T.

Polish Journal of Ecology

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2003

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Vol. 51, nr 3

323-337

EN

To determine the influence of tree canopy composition on growth and physiological performance of silver fir (Abies alba Mill.) in Karkonoski National Park (Sudety Mountains, Southern Poland), three-year-old fir seedling were planted in five forest stands dominated by Betula pendula, Fagus sylvatica, Larix decidua, Picea abies or Pinus sylvestris. The stands differed in canopy openness such that young fir plants experienced drastically different light environments. After three years of acclimation to site conditions, length of shoots, seasonal changes in chlorophyll a fluorescence parameters, and the contents of chlorophyll, carotenoids and nutrients in the needles were studied to evaluate the seedling performance. Growth and photosynthetic characteristics of the young seedlings responded strongly to local light conditions. The lengths of leader shoot and twigs of the upper whorl reflected variation in canopy openness during the growing season and were highest under Larix. The potential quantum yield of photosystem II (F[v]/F[m]) showed a strong depression in the spring, especially under the leafless canopies of Betula and Fagus, probably because of the occurrence of low air temperatures. Later in the season F[v]/F[m] showed substantial recovery in all stands. Effective quantum yield FI[psii] measured under actinic light also showed a growing trend throughout the season with the lowest levels noted in the spring, particularly under Fagus and Betula. Fluorescence quenching revealed complex seasonal behaviour with little obvious relationship with stand illumination, except for consistently low value of photochemical quenching, and immediate or high nonphotochemical quenching under the dark Picea canopy, probably reflecting photoprotective acclimation to sunflecks. Although needle chlorophyll content showed no relationship to ambient light, the ratio of carotenoids to chlorophyll was positively linked to canopy openness suggesting the existence of leaf photoprotection that evaded detection by quenching analysis. Nutrient contents in needles depended on site conditions. In the light-transparent Larix stand, the fir needles were strongly depleted in Mg and Ca. Overall, however, all fir plants from experimental plots had much lower needle nutrient content than nursery-raised plants. Needle chlorosis found in Betula and Pinus stands was, however, not caused by macronutrient deficiencies. Considering all variables, conditions most conductive for fir growth and good vigor were found under larch and pine canopies where light penetration was intermediate to high. In contrast, the poorest conditions were found in the Betula stand, where high light penetration in the spring was followed by shading of firs during the growing season.

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Altitudinal trends in needle chlorophyll content and chlorophyll fluorescence of Norway spruce (Picea abies Karst.) seedlings exposed to increased ultraviolet-b radiation

Robakowski P., Modrzyński J.

Polish Journal of Ecology

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2000

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Vol. 48, nr 1

49-62

EN

The main purpose of this study was to determine the relation between the altitude of Norway spruce seed origin and seedling response enhanced UV-B irradiation. There were threeUV-B treatments: high UV-B with a dose of 22.76 kJ m^-2 d^-1 UV-B[BE] (biologically effective dose), low UV-B-5.69kJ m^-2 d^-1 UV-B[BE] and control>> ~ 0 kJ m^-2 d^-1 UV-B[BE]. The plants were exposed to enhanced UV-B during 120 days in the greenhouse. Needle chlorophyll content and chlorophyll fluorescence parameters were investigated. The chlorophyll content in irradiated needles was lower relative to control after 30 days of exposure to UV-B, but it was higher after 70 days. All the measured chlorophyll fluorescence parameters including relative vitality indexes were reduced for needles exposed to an increased UV-B radiation. Generally, the needles' chlorophyll content was increased and chlorophyll fluorescence parameters were decreased with altitude of seed origin. The results suggest that the acclimation to higher altitudes may also consist of an increased chlorophyll production. The alterations in chlorophyll concentration among the seedlings originating from different altitudes showed that response of Norway spruce to an enhanced UV-B irradiation depends on the altitude of origin.

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Impact of ultraviolet-B radiation on two species of forest dwarf shrubs : bilberry (Vaccinium myrtillus L.) and cowberry (Vaccinium vitis-idaea L.)

Robakowski P.

Polish Journal of Ecology

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1999

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Vol. 47, no 1

3-13

EN

Impact of UV-B irradiation on chlorophyll content and chlorophyll fluorescence of two dwarf shrub species: Vaccinium myrtillus L. and Vaccinium vitis-idaea L. was investigated. The plants originating from different latitudes were used. The experiment was carried in the greenhouse. Three variants of ultraviolet-B irradiation were applied = O, lower dose = 11.32 and higher dose = 22.64 kJ m^-2 day^-1 UV-B[BE] (biologically effective dose of UV-B). Measurements of chlorophyll fluorescence and chlorophyll content were carried out. The response of dwarf shrubs to the increased UV-B radiation depended on UV-B dose, species traits and provenance. Vaccinium vitis-idaea was less sensitive to UV-B than Vaccinium myrtillus. The permanent discoloration was observed only on Vaccinium myrtillus leaves. The leaf bud brea of this species was accelerated at high UV-B dose compared to the control. The UV-B radiation influenced its photosynthetic apparatus: the chlorophyll content in leaves was reduced, the maximal and the steady state fluorescence of chlorophyll were diminished. The chlorophyll content in leaves of Vaccinium vitis-idaea did not change significantly but the relative vitality index and the steady state fluorescence were modified under the influence of the radiation.