ISSN 2075-1117, Russian Journal of Biological Invasions, 2019, Vol. 10, No. 1, pp. 83–91. © Pleiades Publishing, Ltd., 2019. Russian Text © I.F. Chadin, I.V. Dalke, R.V. Malyshev, 2018, published in Rossiiskii Zhurnal Biologicheskikh Invazii, 2018, No. 4, pp. 105–116. Evaluation of Heracleum sosnowskyi Frost Resistance after Snow Cover Removal in Early Spring I. F. Chadina, *, I. V. Dalkea, and R. V. Malysheva aInstitute of Biology, Komi Scientific Center, Ural Branch, Russian Academy of Sciences, Syktyvkar, 167982 Komi Republic, Russia *e-mail: [email protected] Received July 13, 2018; revised October 10, 2018; accepted December 20, 2018 Abstract—The development of environmentally safe and cost-effective methods for controlling invasive spe- cies Sosnowsky’s hogweed (Heracleum sosnowskyi Manden.) is an urgent issue for the European part of Russia. The article presents findings of an experiment on the effect of snow cover removal from the areas occupied by H. sosnowskyi in the early spring period (the beginning of March 2018) in the vicinity of the city of Syktyvkar (Komi Republic, Russia). The snow depth reached 100 cm on the intact plots; the sum of below- zero air temperatures measured at 6 a.m. constituted –448°C, with a minimum of –29.0°C during the exper- iment. The number of H. sosnowskyi plants of all age groups at the experimental plots (with removed snow cover) was shown to be significantly decreased. The median seedling density (pcs. per square meter) was equal to zero. Most of the surviving plants were located along the sides and in the corners of experimental plots. This can be explained by the higher temperature of soil on the borders of plots with an intact snow cover. The results of the experiment may be used for development of invasive plant eradication technology by removal of the snow cover. This technology can be suitable for kindergartens, schools, hospitals, and water protection zones, where the use of chemical methods of plant control is limited or prohibited. The obtained data set with respect to H. sosnowskyi monitoring is available in the repository of Zenodo. Keywords: Heracleum sosnowskyi, biological invasion, frost resistance, snow cover, invasion management DOI: 10.1134/S2075111719 0100 41 INTRODUCTION Rajmis et al., 2016). These plants trigger dermatitis At present, mechanical, chemical, and thermal and burns in humans (Karimian-Teherani et al., 2007, methods are applied to combat invasions of alien plant Jakubowicz et al., 2012). Programs to control species (Invasive Alien Species…, 2001; Invasive Species unwanted overgrowth of the species (O gosudarstvennoi Management…, 2009; Saunders et al., 2010). The podderzhke…, 2016; O gosudarstvennoi podderzhke…, spread and eradication of undesirable dense stands of 2017; Ob oblastnom budzhete Leningradskoi oblasti…, the invasive Sosnovsky’s hogweed (Heracleum sosnows- 2017) have been adopted by the subjects of the Russian kyi Manden.) species have attracted significant atten- Federation. The cost of mapping and eradication of tion in Russia in the last decade. Along with other H. sosnowskyi has amounted to nearly 314 million hogweed species, H. sosnowskyi was farmed on a large rubles in Russia since 2011 (Dalke et al., 2018). scale as forage crop in the Soviet Union and a number Methods for the controlling and effectiveness of of East European countries in the middle of the 20th eradication measures with respect to H. sosnowskyi century (Satsyperova, 1984; Nielsen et al., 2005; continue to remain a matter of urgency in rural loca- Pyšek et al., 2012; Pergl et al., 2016; Ozerova et al., tions (Dalke et al., 2018). As many as eight groups of 2017). In the European part of Russia, H. sosnowskyi methods to combat giant hogweed thickets have been first became naturalized in the 1980s; in Siberia, the suggested in the literature: soil (disk) plowing, pulling first finds of the species outside the agrocoenoses were out of the soil manually (digging out), mowing, umbel reported in 2005 (Ebel’ et al., 2018). Presently, plants cutting (removal), mulching (with a layer of covering of the species have been discovered in 54 subjects of materials), application of herbicides, exposure to the Russian Federation (Panasenko, 2017; Chadin et al., microwave radiation, grazing (Nielsen et al., 2005; 2017; Ozerova and Krivosheina, 2018; Vinogradova Ecology and Management…, 2007; Malyshev, 2014). et al., 2018). The most effective proved to be repeated disk plowing Giant hogweeds are characterized by a high-level and sowing substituting crops, chemical treatment, socioeconomic and environmental impact (Nielsen and application of covering materials (Dalke and et al., 2005; Dergunova et al., 2012; Pergl et al., 2016; Chadin, 2008, 2010). Mowing, soil plowing, and her- 83 84 CHADIN et al. The objective of our work is to investigate the effect 1 5 2 3 7 of snow cover removal on the state and size of the H. sosnowskyi population. Provided a drop in the soil temperature causes the death of plants, this will allow the development of a safe and reasonable method for 6 8 regulating the species abundance in the areas where 4 the use of the chemical control methods is prohibited. MATERIALS AND METHODS The investigations were conducted from March 5 Road through June 10, 2018, in the middle boreal subzone in the vicinity of Syktyvkar. Experimental plots were set up within the typical H. sosnowskyi habitats along roads (Fig. 1). Places for the experiment were selected 1 m on the basis of the median density of generative shoots specific to dense monospecies stands of this species, i.e., 1 plant/m2 (Dalke et al., 2015). The number of Fig. 1. Location plan of the experimental (1–4 snow generative H. sosnowskyi plants from the previous year removed) and control (5–8 snow covered) plots in Heracleum sosnowskyi plant stands (lat. 61.646944° N, long. 50.757277° E). was determined according to retained dry generative shoots and their traces in the soil. The first group included the plots where the snow bicide treatment are commonly preferred to control was removed manually with shovels down to the hogweed in Russia (Dal’ke et al., 2018). However, it is ground surface (experiment, n = 4); plots of the sec- practically impossible to liquidate hogweed entirely by ond group were left snow covered (control, n = 4). The mowing (Dalke et al., 2015). Mechanical control plots were cleared from fallen snow within one to two methods require considerable resources, high-level days from the moment of the precipitation. organization of labor, and close monitoring (Ecology The size of approximately 2 × 2 m was defined for and Management…, 2007); no biological control the plots at the experiment setup. To determine their methods have been developed to date (Reznik et al., area more accurately after the snow melted, we mea- 2008). Herbicide application is seen as the most effec- sured lengths of all sides and diagonals of quadrangle tive for eradication of H. sosnowskyi plants in large to an accuracy of 1 cm. The area of the plots (S) was areas (Sampson, 1994; Caffrey, 2001; Nielsen et al., estimated from the formula 2005; Ecology and Management…, 2007; Yakimovich 2 et al., 2013). Chemical treatment is considered to be 16S=dd2222222 4−−−( b+d a c) , the first step in implementation of the strategy for 12 eradication of plants with a high fecundity, including where a, b, c, and d are the sides and d1 and d2 are the H. sosnowskyi (Ecology and Management…, 2007). diagonals of a plot. Considering the restricted use of pesticides and agro- Seedlings and plants of H. sosnowskyi rapidly chemicals within the limits of populated localities, regrow after the disappearance of the snow cover and water protection zones, specially protected natural can be easily distinguished from other species on the areas (Gigienicheskie trebovaniya…, 2016), there is an basis of the shape and size of its leaves. The number of urgent need to develop and implement safe and effec- the studied plants of different ontogenetic age stages tive methods for containment of unwanted vegetation. was assessed three times during their growth (May 12, In a seasonal climate environment, the thermal May 25, and June 10). The ontogenetic age stages of regime of the soil is among the significant factors individual plants were determined according to the affecting plant survival rates in wintertime. It is possi- extent to which the lamina was incised (Satsyperova, ble to influence this regime by altering the depth of the 1984). We factored in the quantity of plants in the first snow cover. Notwithstanding its high level of effective- year (sprouts and seedlings) and older than a year. The ness in using environmental resources and resistance number of sprouts and seedlings was estimated in a series of 10–11 sample measurements uniformly along to unfavorable conditions during the growing season 2 (Dalke et al., 2015; Veselkin et al., 2017), H. sosnows- the plot diagonals using frames 0.028 m in area. Data kyi was reported to be killed following dormancy in a with respect to the density of hogweed plants were snowless period (Aleksandrova, 1971) or as a result of converted to plants/m2. severe conditions in late fall (Khantimer, 1974). The projective cover of H. sosnowskyi plants was Accordingly, we put forward a hypothesis that dense assessed from photographs using the image processing stands of plants can be destroyed by altering the ther- software package ImageJ (Konukhov, 2012; Schneider mal regime of the soil during the cold season. et al., 2012). The pictures were taken with a Canon RUSSIAN JOURNAL OF BIOLOGICAL INVASIONS Vol. 10 No. 1 2019 EVALUATION OF Heracleum sosnowskyi FROST RESISTANCE 85 Table 1. Effects of exposure of plants to low temperatures during dormancy on population characteristics of Heracleum sosnowskyi plants (June 10, 2018) Indicator Control Experiment P* Density of plants older than a year (median value), plants/m2 3.3 1.8 0.02 Density of first-year plants (median value), plants/m2 321 0.0 4.79 × 10–12 Height of plants older than a year (median value), cm 50 22 1.68 × 10–5 Projective cover, % 64 15 0.02 * P-value calculated by the results of the Kruskel–Wallis test.