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7P/Pons–Winnecke is a near-Earth short-period comet of a moderate activity level. In this paper, we present the analysis of observations performed during a favorable apparition of the comet in 2021, indicating its status as a transitional ageing comet. The sublimation starts when the comet is close to the Sun, at a distance of RON = 1.76 ± 0.1 AU, and continues for ~13 months, which is apparently caused by residual reserves of water ice. The dust production rate of the comet is not high even at perihelion (<150 kg/s), and the 1.4-percent active portion of the nucleus area is sufficient to provide this mass loss. The photometric age of the comet is PAGE = 54.4 comet years; being combined with a light curve amplitude of ASEC(1;1) = 5.5m, this age corresponds to the state of a transitional middle-aged comet. [ABSTRACT FROM AUTHOR]

The problem of interpretation of a photometric light curve and the use of the Lomb–Scargle periodogram to determine the rotation period of fast-rotating artificial Earth satellites (AESs) when they are observed with a slow read-out CCD camera are described. A method for solving this problem is given. It is proposed, if there is a priori information about the AES rotation period, to use the Lomb–Scargle periodogram in a narrowed frequency range; in the absence of a priori information, the problem is solved by using trail photometry. Comparison of results obtained with different telescopes equipped with different slow read-out CCD cameras with results independently obtained with other telescopes equipped with fast read-out CCD cameras clearly demonstrates the effectiveness of the method in both cases. The limitations in the applicability of the method application and possible ways to improve its accuracy are also considered. [ABSTRACT FROM AUTHOR]

The effect of site preparation (mixed mounding and removal of the humus layer) under a shelterwood of mixed boreal forest along a forest interior-edge gradient on Norway spruce (Picea abies) seedlings was studied two years after planting. Mounds had a positive effect on root development, ectomycorrhiza formation and the absorption of nitrogen (N) and phosphorus (P) in the seedlings, and augmented their survival, growth and biomass. Humus removal had an adverse effect on the root biomass and ectomycorrhiza formation. A decreased soil fertility after the removal of humus led to a low N and P content in the seedlings. Two years after planting, humus removal had not affected the growth of the seedlings, but reduced their biomass. The influence of the forest edge, compared to the interior plot, was mostly associated with a decrease in the stand density, reduced amount of litter and increased light availability for the seedlings. [ABSTRACT FROM AUTHOR]

In the present paper, the results of the research of biometric parameters and functional peculiarities of photosynthetic apparatus of Stellaria humifusa in West Spitsbergen are discussed. The study showed that the largest proportion of the mat is composed of a brown layer of dead leaves covering the assimilative organs (about 70%). Green leaves and shoots accounted for about 20%, whereas generative organs - for about 10% of the mat mass. The values of the maximum photochemical quantum yield of PS II (FV/FM) in all the studied plants were lower than the optimal values (0.83), which suggests that the plants are exposed to stress factors. The low values of chlorophyll and carotenoid content and relatively high values of the light-harvesting complex (70-80%), the sharp decrease in the quantum yield of PS II (ΦPSII) entailed by a marginal increase in PPFD indicative of a sufficiently high of photochemical activity within the range of low and medium values of light. It also suggests that Stellaria humifusa is well-adapted to the shaded conditions created in the mat. Besides, a considerable decrease the maximum fluorescence yield of a light-adapted leaf (FM') at increasing PPFD was observed, which suggests that Stellaria humifusa has a well-developed mechanism of energy dissipation via the non-photochemical (NPQ) pathway. The rapid development of NPQ gives reason to assume that, under high light conditions, non-photochemical quenching is likely to serve as the main mechanism for preventing the photodamage of the photosynthetic apparatus. Thus, it was shown that the photosynthetic apparatus of Stellaria humifusa works efficiently under the conditions created in the mat, and the thick layer of dead leaves covering the assimilative organs, on the one hand, protects them from excessive light, and on the other hand, absorbs thermal energy, which raises temperature of the local habitat. [ABSTRACT FROM AUTHOR]

At present, chlorophyll meters are widely used for a quick and nondestructive estimate of chlorophyll (Chl) contents in plant leaves. Chl meters allow to estimate the Chl content in relative units - the Chl index (CI). However, using such meters, one can face a problem of converting CI into absolute values of the pigment content and comparing data acquired with different devices and for different plant species. Many Chl meters ( SPAD-502, CL-01, CCM-200) demonstrated a high degree of correlation between the CI and the absolute pigment content. A number of formulas have been deduced for different plant species to convert the CI into the absolute value of the photosynthetic pigment content. However, such data have not been yet acquired for the atLEAF+ Chl meter. The purpose of the present study was to assess the applicability of the atLEAF+ Chl meter for estimating the Chl content. A significant species-specific exponential relationships between the atLEAF value (corresponding to CI) and extractable Chl a, Chl b, Chl ( a+ b) for Calamus dioicus and Cleistanthus sp. were shown. The correlations between the atLEAF values and the content of Chl a, Chl b, and Chl ( a+ b) per unit of leaf area was stronger than that per unit of dry leaf mass. The atLEAF value- Chl b correlation was weaker than that of atLEAF value-Chl a and atLEAF value-Chl ( a+ b) correlations. The influence of light conditions (Chl a/ b ratio) on the atLEAF value has been also shown. The obtained results indicated that the atLEAF+ Chl meter is a cheap and convenient tool for a quick nondestructive estimate of the Chl content, if properly calibrated, and can be used for this purpose along with other Chl meters. [ABSTRACT FROM AUTHOR]

In forests, a significant proportion of the carbon fixed by trees during photosynthesis is transported belowground along the conducting phloem, so variations in phloem anatomy can lead to variations in transport capacity. Phloem conductance at tree level (Ktree) is also affected by tree height. Both the phloem anatomy and the tree size change during ontogeny, and also differ under different environmental conditions. The goal of our work was to identify the main drivers of variation in Ktree in Scots pine trees growing in natural boreal forests. We conducted a phloem anatomical study and calculated Ktree in trees of three age groups growing in different climatic conditions along a latitudinal gradient from south to north. We found that Ktree was maintained at the same level in actively growing pine trees (25–80-years-old) but increased in old-aged trees (180–190-years-old), possibly reflecting the shift in source-sink relationships of aboveground and belowground parts of trees. Trees of the same age group growing in different climatic conditions demonstrated similar values of Ktree due to coordinated changes in the phloem anatomy and the tree height. In general, the negative influence of tree height on Ktree is offset by the positive influence of phloem width (or trunk diameter) and sieve cell diameter. The exception was young trees growing in the transition zone of the northern taiga subzone to the tundra, where Ktree was the highest in its age group and even exceeded Ktree of middle-aged trees. [ABSTRACT FROM AUTHOR]

Background and aims: Clear-cut logging currently is a key factor transforming forest communities in many boreal regions. The dynamics of biogeochemical processes taking place in clear-cuts makes them a good model for studying the response of plants to changes in environmental conditions. This study aimed to assess the response of nutrient, carbon and water exchange parameters in coniferous and deciduous plants after clear-cut forest harvesting. Methods: The effects of environmental factors on the functional traits of regrowing trees in Scots pine (Pinus sylvestris L.), silver birch (Betula pendula Roth), aspen (Populus tremula L.) and grey alder (Alnus incana (L.) Moench) were analysed during four growing seasons (2016–2019) in a clear-cut site and under the canopy of an undisturbed bilberry-type pine forest in the middle taiga of Karelia, Northwest Russia. Results: Unidirectional changes were observed in the specific nutrient content, specific leaf area, biological macronutrient absorption capacity, stomatal conductance, and rates of photosynthesis and transpiration in the different tree species along a gradient of environmental factors. In most cases, the nutrient concentrations and N:P:K ratio were consistent in all species as environmental conditions changed. Species-specific responses were observed for the N:P:K and K:Ca:Mg ratios, photosynthetic water use and nitrogen use efficiency. Contrasting environmental conditions in the clear-cut and under forest canopy most significantly affect plant capacity to absorb nitrogen. Conclusions: Variation in functional traits in the coniferous and deciduous species reflects their specific resource-use strategies in a heterogeneous environment and, hence, indicates the different adaptation potentials for various plant species. [ABSTRACT FROM AUTHOR]

The results of a study of the short gamma-ray burst GRB 231115A in the X-ray and gamma-ray ranges are presented, based on data from the INTEGRAL and Fermi space observatories. The source of the burst is localized by the IBIS/ISGRI telescope of INTEGRAL observatory with an accuracy of , it is located in the Cigar Galaxy (M 82). Early follow-up observations of the burst localization region were carried out in the optical range with the 36-cm telescope of the ISON-Kitab observatory and the 70-cm telescope AS-32 of the Abastumani Astrophysical Observatory. The optical emission has not been detected. The proximity of the host galaxy ( Mpc) significantly limits energetics of the event ( erg) and allows us to interpret the burst as a giant flare of a previously unknown soft gamma repeater (SGR) which is an extreme manifestation of the activity of a highly magnetized neutron star (magnetar). This conclusion is confirmed by the energy spectrum atypically hard for cosmological gamma-ray bursts, as well as the absence of optical afterglow and gravitational wave signal, which should have been detected in the LIGO/Virgo/KAGRA experiments if the burst was caused by a merger of binary neutron stars. The location of the burst in the and diagrams also suggests that GRB 231115A was a magnetar giant flare. This is the first well-localized giant flare of an extragalactic SGR. [ABSTRACT FROM AUTHOR]

We present the results of our analysis of multiwavelength observations for the long gamma-ray burst GRB 200829A. The burst redshift has been determined photometrically at the afterglow phase. In gamma rays the event is one of the brightest (in isotropic equivalent), erg. The multicolor light curve of the GRB 200829A afterglow is characterized by chromatic behavior and the presence of a plateau gradually transitioning into a power-law decay that can also be interpreted as a quasi-synchronous inhomogeneity (flare). We assume that the presence of a chromatic inhomogeneity in the early afterglow is consistent with the model of a structured jet. [ABSTRACT FROM AUTHOR]

We report observations of colour in the inner coma of Comet C/2013 UQ4 (Catalina) with the broad-band B and R filters. We find significant temporal variations of the colour slope, ranging from -12.67 ± 8.16% per 0.1 µm to 35.09 ± 11.70% per 0.1 µm. It is significant that the comet changes colour from red to blue over a period of only 2 d. Such dispersion cannot be characterized with an average colour slope. We also observe Comet C/2013 UQ4 (Catalina) in infrared using Spitzer and find no significant CO/CO2 gaseous species in its coma. Therefore, we classify Comet C/2013 UQ4 (Catalina) as a dust-rich comet and attribute the measured colour slope to its dust. We analyse the colour slope using the model of agglomerated debris particles and conclude that the C/2013 UQ4 coma was chemically heterogeneous, consisting of at least two components. The first component producing the bluest colour is consistent with Mg-rich silicates. There are three different options for the second component producing the reddest colour. This colour is consistent with either Mg-Fe silicates, kerogen type II or organic matter processed with a low dose of ultraviolet radiation. [ABSTRACT FROM AUTHOR]

We present new photometric observations for twelve asteroids ((122) Gerda, (152) Atala, (260) Huberta, (665) Sabine, (692) Hippodamia, (723) Hammonia, (745) Mauritia, (768) Struveana, (863) Benkoela, (1113) Katja, (1175) Margo (2057) Rosemary) from the outer part of the main belt aimed to obtain the magnitude-phase curves and to verify geometric albedo and taxonomic class based on their magnitude-phase behaviors. The measured magnitude-phase relations confirm previously determined composition types of (260) Huberta (C-type), (692) Hippodamia (S-type) and (1175) Margo (S-type). Asteroids (665) Sabine and (768) Struveana previously classified as X-type show phase-curve behavior typical for moderate-albedo asteroids and may belong to the M-type. The phase-curve of (723) Hammonia is typical for the S-type which contradicts the previously determined C-type. We confirmed the moderate-albedo of asteroids (122) Gerda and (152) Atala, but their phase-curves are different from typical for the S-type and may indicate more rare compositional types. Based on magnitude-phase behaviors and V-R colors, (2057) Rosemary most probably belongs to M-type, while asteroids (745) Mauritia and (1113) Katja belong to S-complex. The phase curve of the A-type asteroid (863) Benkoela does not cover the opposition effect range and further observations are needed to understand typical features of the phase-curves of A-type asteroids in comparison with other types. We have also determined lightcurve amplitudes of the observed asteroids and obtained new or improved values of the rotation periods for most of them. • New photometric observations for twelve outer belt asteroids were performed and the magnitude-phase curves were obtained. • We made estimations of geometric albedo and composition type of the observed asteroids using their magnitude-phase curves. • Most part of moderate albedo asteroids from our set have surface properties different from typical for the S-type and may indicate more rare compositional types. • Part of moderatealbedo asteroids from our set have properties different from S-type and may indicate more rare types. [ABSTRACT FROM AUTHOR]