Tree Form of Juniper (Juniperus communis L.) in the Forests of the Vologda Region

Common juniper (Juniperus communis L.) is one of the most widespread undergrowth species in the forests of Russia. It has not only important silvicultural significance but is also widely used in economic activities. Numerous works of Russian and foreign authors are devoted to its study. The article shows the results of geobotanical and forest inventory studies of a unique area of pine plantation in the Kirillovskiy district of the Vologda region. In the second understorey of which tree-form common juniper grows. The stand was classified as high-density (relative fullness – 0.85) and low quality (quality class – V–IV). The total stock of trunk wood on the site is 280 m3/ha, including the stock of juniper wood – 28 m3/ha. The average diameter of juniper trunks is 14 cm, the average height is 11 m and the age is 180 yrs. This is several times higher than its usual parameters in other forests. A significant number of specimens of juniper (50 pcs/ha) are in the stage of drying out or have already died and represent dead wood of different years. The number of small and medium-sized juniper undergrowth is 1.5 ths pcs/ha or 62.5 % of the growing. Undergrowth of European spruce, downy birch and black alder is also found. The existing undergrowth is assessed as promising, but Scots pine undergrowth is missing. The ground cover is dominated by green and sphagnum mosses as well as shrubs of the Ericaceae and Vacciniaceae families. The study of such objects, extremely rare not only in the north of the European part of Russia, but also everywhere, is of great practical importance. It is also important for understanding the biology of the only representative of the Cupressaceae family that naturally grows here. The tree-form juniper in the pine plantation has survived and reached a size not typical for this species due to the inaccessibility of the site, the lack of fires and forest felling. Such forest areas should be identified, protected, and subjected to stationary research. For citation: Evdokimov I.V., Dobrynin A.P., Armeeva N.A. Tree Form of Juniper (Juniperus communis L.) in the Forests of the Vologda Region. Lesnoy Zhurnal [Russian Forestry Journal], 2021, no. 5, pp. 201–209. DOI: 10.37482/0536-1036-2021-5-201-209

Longevity and germination of Juniperus communis L. pollen after storage

Pollen storage belongs among the most important activities associated with pollen handling. It overcomes the differences in pollen shedding and ovule receptivity during controlled pollination experiments. It is especially important for species like common juniper (Juniperus communis L.) with an extremely low quality of seeds due to pollination failure. Additionally, it is a substantial part of germplasm preservation programmes in pollen banks. In the present paper, the effect of short-term storage of pollen was studied using pollen samples from five shrubs in an in vitro germination test. Two temperature regimes were tested. The pollen viability of freshly collected pollen varied considerably between individual shrubs, exhibiting 67.3–88.6% germination rate and 248.0–367.3 µm of pollen tubes. Storage at + 4 °C for four months was accompanied by a profound decline in pollen viability. The germination percentage was reduced to 49.2–75.2% and the pollen tube length to 32.5–69.0%, depending on individual shrubs. The corresponding decline in pollen viability characteristics during storage at − 20 °C was only negligible in two of the tested shrubs. In the remaining three shrub samples, an increase in germination percentage was observed. Pollen tube growth responded more sensitively to freezing, but, on average, the decrease in length was lower than that at + 4 °C. The rate of reduction in pollen tube length varied between 11.5 and 45.4%. Cytological events accompanying in vitro germination of freezer-stored pollen exhibited some delay in releasing the exine from pollen grains during the early stages of germination as compared with freshly collected pollen. In conclusion, short-term storage of the common juniper pollen in a freezer is better for the preservation of its viability than storage at + 4 °C.

Cavitation fatigue in conifers: a study on eight European species

After drought-induced embolism and repair, tree xylem may be weakened against future drought events (cavitation fatigue). Since there are few data on cavitation fatigue in conifers available, we quantified vulnerability curves (VCs) after embolism/repair cycles on eight European conifer species. We induced 50 and 100% loss of conductivity (LC) with a cavitron, and analysed VCs. Embolism repair was obtained by vacuum infiltration. All species demonstrated complete embolism repair and a lack of any cavitation fatigue after 50% LC. After 100% LC, European larch (Larix decidua), stone pine (Pinus cembra), Norway spruce (Picea abies) and silver fir (Abies alba) remained unaffected, while mountain pine (Pinus mugo), yew (Taxus baccata) and common juniper (Juniperus communis) exhibited 0.4 to 0.9 MPa higher vulnerability to embolism. A small cavitation fatigue observed in Scots pine (Pinus sylvestris) was probably biased by incomplete embolism repair, as indicated by a correlation of vulnerability shifts and conductivity restoration. Our data demonstrate that cavitation fatigue in conifers is species-specific and depends on the intensity of preceding LC. The lack of fatigue effects after moderate LC, and relevant effects in only three species after high LC, indicate that conifers are relatively resistant against cavitation fatigue. This is remarkable considering the complex and delicate conifer pit architecture and may be important considering climate change projections.

Biofilm Degradation of Nontuberculous Mycobacteria Formed on Stainless Steel Following Treatment with Immortelle (Helichrysum italicum) and Common Juniper (Juniperus communis) Essential Oils

Nontuberculous mycobacteria, like other opportunistic premise plumbing pathogens, produce resistant biofilms on various surfaces in the plumbing system including pipes, tanks, and fittings. Since standard methods of water disinfection are ineffective in eradicating biofilms, research into new agents is necessary. Essential oils (EOs) have great potential as anti-biofilm agents. Therefore, the purpose of this research was to investigate the potential anti-biofilm effect of common juniper (Juniperus communis) and immortelle (Helichrysum italicum) EOs. Minimum inhibitory concentrations (MIC), minimum bactericidal concentrations (MBC), and minimum effective concentrations of EOs on Mycobacterium avium, M. intracellulare, and M. gordonae were tested. Additionally, biofilms on the surface of a stainless steel disc were treated with single or mixed concentration of EOs, in order to investigate their degeneration via the bacterial count and confocal laser scanning microscopy (CLSM). H. italicum EO showed the strongest biofilm degradation ability against all Mycobacteria strains that were tested. The strongest effect in the biofilm degradation after the single or mixed applications of EOs was observed against M. gordonae, followed by M. avium. The most resistant was the M. intracellulare biofilm. Synergistic combinations of J. communis and H. italicum EOs therefore seem to be an effective substance in biofilm degradation for use in small water systems such as baths or hot tubs.

Effects of heathland management on seedling recruitment of common juniper (Juniperus communis)

Background and aims – Common juniper (Juniperus communis L.) is one of the most widespread woody species on the planet. Over recent decades, however, common juniper populations are decreasing in size and number in different regions. Lack of recruitment, caused by extremely low seed viability and the absence of suitable microsites for recruitment, is the key reason for this decline. For successful germination, the seeds need gaps in the existing vegetation and a soil with a relatively high base saturation. The aim of this study was therefore to assess how management actions such as sod cutting, rotavation and liming (alone or in various combinations) influence soil characteristics, seed germination and seedling survival of common juniper.Methods – We installed a sowing experiment across 104 1-m2 plots in four different sites in Belgium and the Netherlands using treatments with different combinations of fencing, sod cutting, rotavation, litter addition and liming. We determined how these treatments affected soil characteristics and how they influenced seed germination and seedling survival.Key results and conclusions – Across the whole experiment, germination rates of juniper seeds were very low (almost always < 1%). Our results confirm that bare ground promotes the germination of juniper seeds. Secondly, higher silt and lutum (clay) proportions in the soil and higher soil organic matter content seemed to have a positive impact on recruitment, possibly due to drought reduction. Management actions that negatively affect those soil characteristics, such as deep sod cutting, should thus be avoided in heathlands on sandy soils. Our results reveal a complex relationship between seedling recruitment success, soil conditions and management of common juniper populations. Overall, combinations of fencing, (superficial) sod cutting and liming or rotavation were most successful.