Victor L. Mironov

Despite the increasing body of knowledge concerning the influence of the lunar cycle on various components of the biosphere, how living organisms respond to environmental factors across this cycle remains unclear. Recent evidence that cryptochromes are involved in the perception of both magnetic fields and moonlight suggests a potential mechanistic link, whereby plant sensitivity to the geomagnetic field may vary with lunar phase. Here, we test the hypothesis that geomagnetic sensitivity of plant growth is modulated during the lunar cycle. Growth dynamics of Sphagnum riparium were analysed using a long‐term field dataset obtained from Karelian mires (Russia). Monitoring was conducted at 2‐day intervals over 10 full growing seasons, yielding 1795 growth rate estimates derived from measurements of 245860 shoots. Although no significant relationship between growth rate and the geomagnetic K _p index was detected across the full dataset, phase‐resolved analysis revealed a different pattern. Near both the full moon and the new moon, the growth response to geomagnetic variations became significant and exhibited a characteristic flip–flop pattern, with a positive response preceding the lunar phase and a negative response immediately following it. These responses were confined to narrow time windows. The results support the hypothesis of lunar modulation of geomagnetic sensitivity in plants and demonstrate that this sensitivity is temporally gated within specific phases of the lunar cycle. The emergence of a half‐lunar (~14.8‐day) periodicity in geomagnetic response, absent in the growth rate itself, suggests that this mechanism may function as a regulatory layer synchronizing plant–environment interactions rather than directly controlling growth.

The balance between photosynthetic carbon accumulation and respiratory loss in plants varies depending on temperature. This leads to a situation where the increased need for carbon is not met when a certain temperature threshold is reached. Over the last two decades, temperature thresholds in carbon metabolism in autotrophic systems have been widely studied. However, it remains unclear how these thresholds manifest themselves in the natural growth of individual plant species. To address this issue, we used data from an extensive monitoring of the growth of peat moss Sphagnum riparium over 9 years in mires in Karelia (Russia). We measured the growth of shoots in sample plots and obtained 1609 estimates of growth rates during the monitoring period. Investigating the relationship between growth rate and temperature, we identified two distinct intervals in response to temperature. These two intervals are separated by the temperature threshold of 13.2 °C. The first interval, which covers 42% of the growing season, exhibits a strong exponential dependence of growth rate on temperature, with a coefficient Q₁₀ = 4.01. This indicates that growth is most sensitive to changes in temperature within this range. In contrast, the second interval (58% of the growing season) shows a weaker dependence, with a Q₁₀ coefficient of 1.21, suggesting that growth is less responsive to changes within this temperature range. The temperature threshold was found to be negatively related to May (r = −0.76; p = 0.018) and September (r = −0.78; p = 0.012) temperatures of the previous growing season, and together they best explain (r = −0.91; p = 0.0007) the temperature threshold. Overall, our findings suggest that the temperature threshold does exist in the growth of S. riparium and can be identified in different years. The negative correlation between temperature threshold and May and September temperatures from the previous year indicates that intervals in the growing season with temperatures near the temperature threshold have an impact on subsequent carbon balance and are particularly significant for the further growth and development of Sphagnum mosses.

The growth of Sphagnum is influenced by the lunar cycle, which suggests a corresponding carbon (C) accumulation rhythm in peatlands. However, this rhythm can only occur if C accumulation from Sphagnum growth is not offset by its total losses through respiration and other processes. To address the uncertainty, through correlation-regression analysis we examine the influence of the lunar cycle on recent measurements of ecosystem (ER) and heterotrophic (Rh) respiration conducted by Järveoja and colleagues on the oligotrophic peatland of Degerö Stormyr. We found that ER and Rh accelerated near the full moon and slowed down near the new moon. The response of the hourly ER to the lunar cycle is significant from 22:00 to 8:00 and is not significant beyond this range. This response was concentrated in the initial and finished phases of the season, but during the middle of the season it disappeared. This behavior could potentially be caused by the high sensitivity of the Sphagnum cover to moonlight, as well as the sensitivity to the lunar cycle of only the nocturnal component ER. During most of the day, the lunar cycle had a significant effect on hourly Rh, with the highest impact observed between 5:00 and 10:00 and at 20:00. The greatest impact occurs during those hours when ER declines, and possibly Sphagnum photosynthetic productivity peaks. The findings suggest a circalunar rhythm of C accumulation in peatlands due to the opposite trends between C accumulation during Sphagnum growth and C losses with respiration during the lunar cycle.

Temperature plays an essential role in a plant’s life. The current investigation reveals that photoreceptors, whose activity is affected by the geomagnetic field, are a critical element of its perception. This knowledge suggests that plants’ responses to temperature could shift in different geomagnetic conditions. To test this hypothesis, we studied the change in the growth response of the peat moss Sphagnum riparium to temperature with a gradual increase in the geomagnetic K_p index. Growth data for this species were collected from Karelian mires by detailed monitoring over eight full growing seasons. The growth of 209,490 shoots was measured and 1439 growth rates were obtained for this period. The analysis showed a strong positive dependence of sphagnum growth on temperature (r = 0.58; n = 1439; P = 1.7 × 10⁻¹¹⁹), which is strongest in the K_p range from 0.87 to 1.61 (r = 0.65; n = 464; P = 4.5 × 10⁻⁵⁸). This K_p interval is clearer after removing the seasonal contributions from the growth rate and temperature and is preserved when diurnal temperature is used. Our results are consistent with the hypothesis and show the unknown contribution of the geomagnetic field to the temperature responses of plants.

The influence of solar activity on plant growth has been studied for over 100 years, however, this phenomenon is still poorly understood on a daily scale. The data from extensive monitoring of the growth of peat moss Sphagnum riparium, which we are conducting in the mires of Karelia (Russia), may shed light on this issue. During the 6 years of observation, 161,190 shoots were measured, and 1075 growth rates were obtained. Considering together the growth rates with the sunspot number and involving data on seasonal temperature, we found previously unknown effects of daily‐scale solar activity on plant growth. It was found that the sunspot number weakly but significantly inhibits the growth of Sphagnum. The extreme sunspot number in the 4 days before the growth rate values have a stronger influence. The involvement of temperature data showed that inhibition in growth is observed only in the temperature range from 6.7°C to 15.3°C and disappears beyond these limits. In addition, the data obtained showed that the influence of sunspot number on the growth of Sphagnum is progressively increasing along the gradient from the minimum to the maximum of the 11‐year solar cycle. The study provides one of the first results on the effect of solar activity on plant growth on a daily scale. The results expand our knowledge of the biological effects of solar activity. Indirectly, they can also be useful to better our understanding of the ozone layer's involvement in this process.

Among the bryophytes, biological growth rhythms have not yet been identified due to a lack of long‐term precision observations. Here, we carry out precision field monitoring of the growth of the peat moss Sphagnum riparium using the recent geotropic curvature method. For 4 years, using the observation intervals of 2–5 days, we measured 116 469 shoots and received 4493 estimates of growth rates. We found three rhythmic growth components. The seasonal rhythm of growth has a period of about 180 days, which coincides with the seasonal temperature cycle. The circalunar growth rhythm has a period of about 29.5 days and coincides with the synodic lunar cycle. There is an acceleration near the new moon, and a slowdown in growth near the full moon. The third rhythm has a period of 7–16 days and is always synchronized with the circalunar growth rhythm. From the models of the sums of sinusoids, we found that the total contribution of all three rhythms to the growth rate is R² = 0.51–0.78, and without taking into account the seasonal rhythm, R² = 0.36–0.42. Thus, our study provides the first data on the biological rhythms and the contribution of these rhythms to the growth process of bryophytes. We attribute the unexpectedly high contribution of rhythms to the synchronous growth of the Sphagnum mat, which is necessary to reduce the loss of moisture.

Continuous high-resolution monitoring of Sphagnum growth can provide insights into the biological rhythms of moss growth. Moss Sphagnum riparium is a convenient model for growth monitoring. Application of the method of geotropic curvatures has enabled a three-year monitoring with two to five-day intervals. We measured the increment in ca. 85000 shoots and produced ca. 3500 growth rate estimates, making this study a champion in precision compared to previous efforts. The zeitgeber for seasonal growth rhythms is the temperature seasonal cycle (R ² =0.21–0.52). When the temperature changes by 10 ° C, moss growth rate is modified by 0.10–0.17cm/day according to the linear model, and 1.47–2.06-fold in the exponential model. The zeitgeber for circalunar rhythms is the lunar synodic cycle (R ² =0.14–0.26). The average amplitude of the fluctuations it induces in the growth rate is 0.0425– 0.0572cm/day, which is equivalent to the effect of a 3.43–4.53 ° C change in temperature. The third rhythm can be distinguished in periodograms. Its period ranges from 10 to 16 days, but we did not detect the zeitgeber. In total, three rhythms explain 51–78% of the growth rate. We believe that the strong rhythmicity in Sphagnum growth is associated with shoot growth synchronization.

According to background data, bog systems can be successfully surveyed using the ground penetrating radar (GPR). The high contrast resolution of peat due to its electrical characteristics accounts for this. This paper demonstrates the results of the GPR usage in the Republic of Karelia (Russia). Data collection was carried out by the OKO-2 radar with the 150M antenna unit (150 MHz frequency). Data from stratigraphic columns was used as reference information. The brightest element on the radar profile is the boundary line of the bog mineral base, comprising of sand. All of the GPR traces allow to reliably identify facies, which can be correlated with peat types. The radar profiles were compared with the peat decomposition level indicators. It was defined that change in levels of peat decomposition leads to emergence of new reflective boundary lines. The research conducted demonstrates the high efficiency of GPR in identifying the composition and structure of peat deposits. It is established that different peat types generate specific GPR facies, which can be used as search attributes. The comparison between the GPR interpretation results and core section drilling materials confirms the reliability of the conclusions reached.

In situ growth of Sphagnum riparium Ångstr. shoots were monitored during the 2015 and 2016 growing seasons in Karelia, Russia. It was established that shoot growth rates fluctuated with a period of around 30 days, that is, showed a circatrigintan rhythm. Such rhythms from mosses have not been previously reported. Correlation of growth rates with the percentage of the illuminated portion of the Moon was statistically significant (p<0.01) in both years. Shoot growth rates were reliably higher around the new Moon compared to the full Moon. This phenomenon may be due either to causality or to a pure coincidence of processes with similar rhythms.