Experimental evidence from Cantabrian mountain heathlands suggests new recommendations for management of Vaccinium myrtillus L

Background: Management actions in mountain heathlands oriented to increasing the cover of Vaccinium myrtillus promote mowing of Calluna vulgaris to avoid competition. However, such action ignores the fact that plant–plant interactions range from competition to facilitation under different stress conditions.

Aims: To test whether the interactions between these two species are related to competition or facilitation, which would change the perspective for their management in mountain heathlands.

Methods: A total of 40 experimental plots located in a montane heathland (northern Spain) were selected. Calluna or Vaccinium plants were either cut at ground level or not cut, and plots were fertilized with nitrogen or not in a three-factorial design. Vegetative and reproductive shoot mass and length of the current year’s shoots were estimated in two consecutive years for both species. Herbivory on Vaccinium by browsing ungulates was compared in control plots and plots where Calluna had been cut 2 yrs ago.

Results: The two study species co-occurred in 72.4% of the sampled plots, although Calluna was more abundant. Vaccinium growth was greater in plots with Calluna than in plots where Calluna had been cut. Browsing on Vaccinium was also higher in plots were Calluna had been cut, and the effect of fertilization was only significant on the reproductive biomass of Calluna.

Conclusions: Contrary to initial proposals, our results suggest that Vaccinium does not always benefit from the cutting of Calluna in heathlands. Thus, the management of Cantabrian mountain heathlands should consider maintaining Calluna in order to facilitate the growth of Vaccinium.     

Influence of clonal growth on selfing rate in Vaccinium myrtillus L

Clonal growth, which allows the multiplication of flowering shoots of the same genet, can lead to a large floral display and may thus increase the rate of selfing through geitonogamy as a consequence of an increase in the number of successively visited flowers. The aim of the present research was to analyse the combined effect of the diversity and intermingling of clones on the rate of selfing in Vaccinium myrtillus. Four mother plants were selected within patches characterised by contrasting clonal structure (low versus high number and intermingling of clones). The selfing rate was significantly lower for plants situated within patches characterised by a high number of intermingled clones (3%) than for plants situated in patches with a low number of clones (50%). Therefore, for this species suffering from inbreeding depression, an increase in the number or the intermingling of the clones could reduce the rate and the cost of geitonogamy and allow a large floral display to attract pollinators. We also found that the main pollinators, bumblebee queens, presented a foraging behaviour favouring geitonogamy, as their successive visits to flowers were quite short (89% of flights were 40 cm or less).     

Ecophysiological studies on the shrub Vaccinium myrtillus L. taken from a wide altitudinal range

Summary Observations have been made on the gas exchange and morphology of Vaccinium myrtillus taken from altitudes of 200 m, 610 m and 1,100 m along an altitudinal gradient in central Scotland. Under saturating irradiance, optimum temperatures and a range of vapour pressure deficits, photosynthetic rate and stomatal conductance increased with the altitude of origin of the populations. Correlated with these increases was an increase in the adaxial stomatal density with altitude. This response to altitude could be simulated in controlled conditions, by growing plants in a CO₂ concentration below ambient, similar to that expected at altitude.Plant height decreased with altitude, a feature which was maintained in cultivation. Stem rigidity declined with altitude, in a manner which is predicted to limit the reproductive capacity of the population from 1,100 m in high wind speeds.Total leaf nitrogen increased with altitude. The nitrogen economy of the shoot is discussed in terms of nitrogen availability for stems and leaves and its control over maximum rates of photosynthesis, competitive ability and reproductive capacity.     

Vascular plant species richness and rarity across a minerotrophic gradient in wetlands of St. Lawrence County,New York,USA

Thirteen wetlands in St. Lawrence County, NY were sampled to examine the effect of a minerotrophic gradient on vascular plant species richness and rarity. Wetlands ranged from organic soil based poor fens (average conductivity 46.40 microsemens, average Ca 3.55 ppm) to mineral soil based rich fens (average conductivity 342.10 microsemens, Ca 23.00 ppm). Vascular plant species richness was sampled during 1990 in randomly located 1.0 m² quadrats. Specific conductivity, presence or absence of hummocks, and water depth predicted 62% of the variation in richness. Richness increased as conductivity increased until 413 microsemens at which a down trend became obvious. The negative curvilinear relation between conductivity and richness is in accordance with the hump-backed model of Grime but occurs at high rather than intermediate conductivity values. State-listed rare species were found in species-rich wetlands only and had a mean associated richness value of 14.50 species m^-2. This relationship should be taken into consideration when selecting wetlands for protection or managing wetlands for maximum plant diversity.     

Substitution of Vaccinium myrtillus L. for Aronia melanocarpa (Michx.) Elliott in a commercial batch

Abstract

The fruits of Vaccinium myrtillus and Aronia melanocarpa are utilized in pharmaceutical and food preparations as rich sources of anthocyanoside pigments. However, these two drugs should not be considered equivalent because their chemical profiles are different. In this work, we report a case of substitution of V. myrtillus for A. melanocarpa in a commercial batch. The comparative morphological investigation of the two drugs is described.     

Protective effect of bilberry (Vaccinium myrtillus L.) on cisplatin induced ovarian damage in rat

Cisplatin is one of the most effective chemotherapeutic agents but injury may occur at higher doses. The aim of this study was to investigate the effect of bilberry on cisplatin induced toxic effects in rat ovary. Twenty-one female Wistar–Albino rats were utilized to form three groups: In group 1 (control group), each rat received intraperitoneal injection of 1 mL of 0.9 % NaCl saline solution during 10-days. In group 2 (cisplatin group), a single dose of 7.5 mg/kg b.w. cisplatin was given. In group 3 (cisplatin + bilberry group), a single dose of 7.5 mg/kg cisplatin and bilberry at 200 mg/kg b.w. were given for 10 days. Ovaries were surgically removed in all groups and prepared for biochemical and light microscopic investigations at the examination times. Malondialdehyde (MDA) levels and activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and glutathione-S-transferase (GST) of tissue samples were measured. Histopathological damages in cisplatin administrated rats were seen such as severe edema, vascular congestion, hemorrhage and follicular degeneration in the ovary tissue. Moderate pathological alterations were observed in rats treated with bilberry plus cisplatin. Cisplatin administration significantly increased MDA production and decreased SOD, CAT, GPx and GST activities in the ovarian tissue when compared to the control group (p < 0.05). Cisplatin + bilberry administration increased antioxidant enzymes activities and reduced MDA levels. Bilberry administration seems to reduce the cisplatin induced ovarian toxicity thus it alleviates free radical damage. But it dose not protect completely rat ovary tissues.     

Non-interactive fish communities in the coastal streams of North-western France

1. Spatial patterns of freshwater fish species at regional and local scales were investigated to explore the possible role of interspecific interactions in influencing distribution and abundance within communities occupying coastal streams of North-Western France.
2. Nine sites from nine streams situated in the same biogeographical region were sampled annually over the 6-year period from 1990 to 1995.
3. Similar habitats (sites) with richer regional colonization pools exhibited proportionally richer local communities in terms of number of species, total density and total biomass of individuals. Furthermore, no negative relationships were found between density and biomass of each of the most common species and local species richness.
4. Results of dynamic regression models (applied to the above-mentioned species) suggest an absence of strong competition between all pairs of species.
5. The evidence on lack of density compensation for species-poor communities and absence of perceptible interspecific competition between species suggest that the communities studied are non-interactive.
6. Two main explanations can be advanced. First, the local abundance of species in the communities studied could be determined through differential responses to unpredictable environmental changes, rather than through biological interactions. Second, as a result of historical events, the communities studied are reduced in congeneric species which can limit, in turn, the influence of interspecific competition in structuring these communities.
7. These results underline the strong influence of regional processes in shaping local riverine fish communities and minimize the possible influence of species interactions in governing these communities.     

Responses to harvesting intensity in a clonal dwarf shrub,the bilberry (Vaccinium myrtillus L.)

The effects of herbivory were simulated on stands of bilberry (Vaccinium myrtillus L.) in a boreal Empetrum-Myrtillus type forest. Five harvesting intensities were used (0% (A), 25% (B), 50% (C), 100% (D) of the bilberry ramets or all the ramets of all species (E)). Density and biomass of the stands, and growth of the ramets were monitored for five growth seasons, from 1986 to 1990. After damage new ramets emerged rapidly from dormant buds at the base of removed ramets. Between 70 and 97% of the density relative to the control level was regained by the final harvest. However, only between 11 and 64% of the biomass relative to the control level was recovered. Clipping reduced the branch growth, both in the new ramets and in the new parts of the old, unclipped ramets. Severe treatments (D and E) decreased the growth more than did light harvesting (B and C). Survival and fecundity of the ramets were not affected. The result therefore suggested that the bilberry is not able to recover totally from severe herbivory damage between the years of peak rodent population that shows a 3–4 year cycle. Nevertheless, extreme grazing pressure is rare in boreal ecosystems as alternative food is available for herbivores, and predators also limit the herbivore population. Hence the bilberry exhibits moderate tolerance of the usual level of herbivory damage.     

The influence of altitude on the distribution of subterranean organs and humus components in Vaccinium myrtillus carpets

Abstract. Humus profiles were sampled along an altitudinal gradient in the Macot‐La‐Plagne Forest (France, northern Alps) to investigate variation occurring under carpets of Vaccinium myrtillus present within Picea abies forests. The vertical distribution of subterranean organs of V. myrtillus was compared with (1) that of P. abies roots and other accompanying vegetation and (2) other components of humus profiles, in particular humified organic matter mainly consisting of animal faeces. It was shown that V. myrtillus roots were mostly concentrated in mineral horizons, while P. abies roots and V. myrtillus rhizomes occupied litter horizons. This was interpreted in terms of competition for nutrient capture between P. abies and V. myrtillus. The effects of altitude were (1) a change in the vegetation accompanying V. myrtillus in dense V. myrtillus carpets, bryophytes at the montane level being replaced by forbs at the sub‐alpine level and (2) a decrease in the thickness of ecto‐organic horizons. This was interpreted as a shift from a moder system characterized by recalcitrant litter (moss) processed by an active faunal community (stabilized in the form of animal faeces) to a mor system characterized by low animal abundance but with litter of better quality which is easily leached in the absence of prominent faunal activity.     

Study of the Stability Of Vaccinium myrtillus Peroxidase in Reverse Micellar Systems

The stability of a cationic peroxidase isolated and purified from a cell suspension of Vaccinium myrtillus , microencapsulated in reverse micelles of sodium dioctylsulfosuccinate (AOT) was evaluated. By using a central composite design (CCD), some relevant parameters for the enzymatic activity, such as surfactant and water concentration, pH and buffer molarity, were analysed. The response surface curves showed that 50 mM AOT, 500 mM water, 80 mM buffer and pH 7.6 were the best conditions for enzyme stability. The effect of carbohydrates and polyols on enzyme stability was also evaluated. At 20 mM, carbohydrates like arabinose, and trehalose increased the enzymatic stability by a factor of 4.4 and 2.3, respectively, but melezitose had no effect. From the three polyols tested, inositol and sorbitol increased the peroxidase stability by a factor of 3.8 and 1.8, respectively, while mannitol had no effect.     

Trace amounts of nickel in belowground rhizomes of Vaccinium myrtillus L. decrease anthocyanin concentrations in aerial shoots without water stress

Nickel (Ni) may impair plant water balance through detrimental effects on the belowground level. Bilberry (Vaccinium myrtillus L.) plants were grown in a mesic heath forest-type soil and subjected to Ni sulphate (NiSO₄·6H₂O) concentrations of 0, 10, 50, 100 and 500 mg m⁻² during an entire growing season in northern Finland (65°N). Biomass of belowground rhizomes, and tissue water content (TWC) and anthocyanin concentrations of aerial shoots were determined from mature plants in order to study rhizospheric Ni stress, and its possible long-distance effects on aerial shoots. As the major proportion of biomass of bilberry is invested in belowground parts, it was hypothesised that Ni-induced rhizospheric disturbance causes water stress in aerial shoots and increases their anthocyanin concentrations for osmotic regulation. Uptake of Ni from the soil to the rhizome and aerial shoots was measured with X-ray fluorescence spectrometry. Ni concentrations in the soil and rhizome exhibited a dose–response relationship, but the concentrations in the rhizome were about 10-fold lower (<3 mg Ni kg⁻¹) than those in the soil (<30 mg Ni kg⁻¹). Translocation of Ni from the rhizome to aerial shoots did not occur, as Ni concentrations in shoots remained at 1 mg Ni kg⁻¹. Although Ni concentrations in the rhizome were below the threshold values of Ni toxicity (i.e. 10–50 mg Ni kg⁻¹), Ni decreased the rhizome biomass. Anthocyanins decreased in aerial shoots along with the Ni accumulation in the rhizome, while TWC was unaffected. The result suggests that anthocyanins are not involved in osmotic regulation under Ni stress, since anthocyanins in aerial shoots responded to the Ni concentrations in the rhizome despite the lack of water stress.     

Drought tolerance of juvenile and mature leaves of a deciduous dwarf shrub Vaccinium myrtillus L. in a boreal environment

The difference between drought tolerance of juvenile and mature leaves of the winter-deciduous dwarf shrub bilberry (Vaccinium myrtillus L.) from a northern boreal environment was investigated. It was hypothesised that mature leaves are more drought sensitive than juvenile leaves. Bilberry plants were allowed to dry out by excluding irrigation when leaves were at juvenile and mature stages. Tissue water content decreased at both phenological stages, but the response was more pronounced in the mature leaves. Anthocyanin concentrations increased as the tissue water content decreased, and again this occurred to a greater extent in the mature leaves. Chlorophyll concentrations decreased only marginally at the juvenile stage, while the decrease was significant in the mature leaves. Chlorophyll degradation was enhanced by drought stress. Soluble proteins decreased and protein oxidation increased in the mature leaves, and degradation of oxidised proteins increased in the drought-stressed plants. The results suggest that leaves of bilberry are more sensitive to drought stress at the mature stage, and that drought stress accelerates senescence at the mature stage. The significance of the results is that dry periods during the juvenility of leaves are not as detrimental as they may be later in summer. In addition, the strategy of a winter-deciduous plant is obviously to protect its perennial parts from severe drought by accelerated leaf senescence at the mature stage. Therefore, the deciduous life form may provide an excellent adaptation against drought also in northern ecosystems. The role of anthocyanins in photoprotection under drought stress is also discussed.     

Study of the Stability Of Vaccinium myrtillus Peroxidase in Reverse Micellar Systems

The stability of a cationic peroxidase isolated and purified from a cell suspension of Vaccinium myrtillus, microencapsulated in reverse micelles of sodium dioctylsulfosuccinate (AOT) was evaluated. By using a central composite design (CCD), some relevant parameters for the enzymatic activity, such as surfactant and water concentration, pH and buffer molarity, were analysed. The response surface curves showed that 50 mM AOT, 500 mM water, 80 mM buffer and pH 7.6 were the best conditions for enzyme stability. The effect of carbohydrates and polyols on enzyme stability was also evaluated. At 20 mM, carbohydrates like arabinose, and trehalose increased the enzymatic stability by a factor of 4.4 and 2.3, respectively, but melezitose had no effect. From the three polyols tested, inositol and sorbitol increased the peroxidase stability by a factor of 3.8 and 1.8, respectively, while mannitol had no effect.     

Long-Term Effects of Forest Regrowth and Selective Logging on the Seed Bank of Tropical Forests in NE Costa Rica1.

To investigate long-term effects of land use on the soil seed bank, we compared the abundance/density, species richness, life form distribution, and species composition of seeds stored in the soil of four 15–20 yr-old second-growth stands, two old-growth stands, and two previously selectively-logged stands in the Caribbean lowlands of Costa Rica. Surface soil (10 cm deep, 4.7 cm diameter) was collected at 10 m intervals along three 120–160 m long transects in each stand (44–48 soil cores, 22–24 combined seed bank samples per site). Seed density was highest but variable in second-growth stands (8331–14535 seeds/m²), low and homogeneous in old-growth stands (2258–2659 seeds/m²), and intermediate and highly variable in selectively-logged stands (1165–6854 seeds/m²), which also had contrasting logging intensities. Species richness was strongly dependent on seed density, but showed less variation. Life form distribution did not differ statistically among or within land-use categories. In each stand, herbs-forbs, shrubs, and vines dominated the seed bank (> 75% of the species richness and abundance), whereas trees were a minor component (< 20% of the species richness and < 5% of the abundance) and were predominandy early successional. Shrubs and vines were most abundant in second-growth stands where regrowth vegetation was repeatedly cut before abandonment, whereas grasses and sedges were most abundant in the only forest stand that was completely surrounded by pastures. In terms of species composition, old-growth stands were more similar to selectively-logged stands than to second-growth stands, but across stands, selectively-logged forests were most distinct from the other two forest types. An inventory of the standing woody vegetation in each site showed little representation of the woody taxa found in the seed bank. We discuss these results in the context of the main factors that have been postulated to influence the abundance, life form, and species composition of tropical forest seed banks, and explore the role of the latter during intermediate phases of tropical forest succession and regeneration.     

Effects of forest management on understorey vegetation in a Pinus sylvestris L. Plantation in NE Scotland

Summary

This paper reports on a six-year experiment which assessed the effects of crop thinning, fencing, and ground preparation (screefing) on the development of understorey vegetation in a first rotation Pinus sylvestris plantation. Thinning or fencing had no effect on species richness or diversity, but richness increased to a greater degree in screefed plots than in unscreefed controls. Fencing benefited the establishment of Goody era repens colonies. Vegetation was matched against the National Vegetation Classification W18a community (Pinus sylvestris-Hylocomium splendens woodland: Erica cinerea-Goodyera repens sub-community. Pinewoods have relatively species-poor floras in comparison to other native woodland types, and these results indicate the importance of striking a balance between management for ‘general’ biodiversity and the conservation of rare and specialized species assemblages.     

Effect of the canopy of Retama sphaerocarpa on its understorey in a semiarid environment

1. A dense understorey of annual and perennial herbs grow under the canopy of Retama sphaerocarpa shrubs in semiarid environments of south-east Spain, influencing plant productivity and diversity at a regional scale. We investigated the facilitation by the shrub on its understorey in field and laboratory experiments with Barley designed to explore the mechanisms of interaction between both vegetation layers and their spatial variation.
2. There was a gradient of spatial heterogeneity in soil chemical fertility under the shrub canopy, with organic matter and soil nitrogen contents higher at the centre than at the edge of the canopy. Dry mass production of Barley was also higher in soils from intermediate positions, and lower in soils from both the centre and edge of the canopy.
3. In the field, pots sown with Barley placed near the centre, at an intermediate position and at the edge of the canopy of Retama shrubs showed significant differences in productivity, suggesting a mulching effect of the canopy that also affects seedling establishment.
4. Micro-climatic measurements showed significant differences in total radiation reaching the soil, mean air and soil temperatures and maximum temperature among different positions in the understorey, increasing radially from the centre to the edge of the canopy.
5. These results and field observations suggest that the optimal association of climatic factors under the canopy would combine with a high soil fertility mediated by litter decomposition to increase biomass production mid-way between the centre and the edge of the canopy. Overstorey and understorey thus interact to increase nutrient retention locally, which benefits both the shrub and the herb layer.     

Response patterns of Vaccinium myrtillus and V. vitis-idaea along nutrient gradients in boreal forest

Abstract. The relationships between biomass of dwarf shrub species and nutrient gradients of forest soils was studied under field conditions in boreal forests. The biomass-response curves of Vaccinium myrtillus and V. vitis-idaea were fitted against soil nutrient gradients using Generalized Linear Models (GLM). Ecological niches of Vaccinium myrtillus and V. vitis-idaea were evaluated, and effects of nitrogen addition (manipulation of the nutrient gradient) on response function were tested. The Vaccinium species showed statistically significant Gaussian responses along soil nitrogen, phosphorus and calcium gradients, but not along other gradients (K and Mg). Furthermore, manipulation of the nitrogen gradient seemed to have a minor effect on response functions, i.e. addition of nitrogen did not change ecological niches of these species. Ecological optima of V. myrtillus and V. vitis-idaea on the nutrient gradients were about the same. This study suggests that differences in dominance between Vaccinium myrtillus and V. vitis-idaea in boreal forest is not determined by nutrient gradients, but may rather be explained by light conditions and/or moisture availability.