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18INVASIVE PLANT SPECIES ON FIRE-DAMAGED AREAS IN THE KERZHENSKY RESERVE DURING THE FIRST TWELVE YEARS AFTER CATASTROPHIC FIRES
N.G. Kadetov1, S.P. Urbanavichute2, A.E. Gnedenko3
1Lomonosov Moscow State University, Russia 2State Nature Reserve "Kerzhenskiy", Russia 3Institute of Geography of Russian Academy of Sciences, Russia e-mail: biogeonk@mail.ru
Received: 29.08.2022. Corrected: 30.09.2022. Accepted for publication: 10.10.2022.
Data on the composition, distribution and dynamics of invasive plant species in the part of the territory of the Kerzhensky Reserve that was affected by the 2010 fires are presented. Data from both route observations and from permanent sample plots were analyzed. A total of 15 invasive species were noted, divided into three groups. The first group (species occurring singly and exclusively on the territory of former settlements and not spreading from known places) includes Lupinus poly-phyllus Lindl., Caragana arborescens Lam., Armoracia rusticana Gaertn., B. Mey. et Scherb., Saponaria officinalis L. and Aronia mitschurinii A. Skvorts. et Maytulina. The second group (species noted in single locations, but at the beginning of their distribution over the territory) includes Acer negundo L., Bidens frondosa L. and Amelanchier spicata (Lam.) C. Koch. The third group (species with noticeable population dynamics, regularly observed in different locations) includes Juncus tenuis Willd., Padus pensylvanica (L. fil.) Sokolov, Epilobium adenocaulon Hausskn., E. pseudorubescens A. Skvorts., Erigeron annuus (L.) Pers., E. canadensis L., Solidago canadensis L. Key words: invasive species, vascular plants, fire, dynamics, Kerzhensky reserve, Nizhny Novgorod region, Zavolzhie
https://dx.doi.org/10.24412/cl-31646-2686-7117-2022-31-163-172
Introduction
The Kerzhensky State Nature Reserve is located in the left-bank part of the Nizhny Novgorod region and associated with broad-leaved-coniferous forests (Zones..., 1999; Kadetov, 2015). According to the map "Biomes of Russia" (2018), the reserve belongs to the Smolensk-Privolzhsky broad-leaved-coniferous-forest bi-ome near the borders with Vyatko-Kamsky biome.
The reserve is located mostly within the vast sandy water-glacial plain with the predominance of pine forests and a noticeable area of bogs (Popov, 2010; Sadkov & Kozlov, 2014).
Catastrophic forest fires are an important feature of the Reserve's territory, which largely determines the present state and structure of its vegetation cover. They have been recurring since the late 19th century once every 40-50 years and affect not less than 40-50% (up to 90%) of lands within its boundaries (Averina, 2001; Kadetov, 2017). Forest fires along with not always successful planting of forest crops were the main reason that up to 90% of pine forests, which occupied at least 60% of the reserve area by 2010, were young and middle-aged plantations. Their weak resistance to fires (Furyaev et al., 2005) caused a significant spread of fire during the
last large fire in 2010, when it covered about half of the entire territory of the Reserve (Kadetov et al., 2011).
The representatives of the Reserve have been carrying out studies of the vegetation cover recovery on the areas passed by fires in cooperation with specialists from the Lomonosov Moscow State University and other organizations since 2011. Their main results are presented in several publications (Kadetov, 2017, 2019; Kadetov & Gnedenko, 2019, 2021; Kadetov et al., 2018; Shopina et al., 2021; Urbanavichute et al., 2022, etc.).
Fires, as well as many other disturbances of the vegetation cover, reducing its stability, make forest communities more vulnerable to the threat of biological invasions. In this connection, special attention was paid to fixing encounters of invasive species in the course of ongoing studies (Kadetov & Urbanavichute, 2016), in particular those given in the lists of the most dangerous species of various levels: both of Nizhny Novgorod region (Mininzon et al., 2021), Central Russia (Vinogradova et al., 2010) and all Europe (Handbook..., 2009). In addition, this special attention was caused by the high activity of some of these species in the territories adjacent to the Reserve.
Material and methods
Studies on post-fire vegetation dynamics were carried out using both stationery and route methods. The basis for stationary observations were 30 permanent sample plots (PSP), set in 2011-2012 on two profiles - submeridional (20 plots) and sublati-tudinal (10 plots). PSPs were set to cover both the areas traversed by different types of fires (upper, lower and intra-soil) and those associated to different forms of mesorelief (tops of sandy ridges, slopes, different in magnitude depressions) and initial phytocenoses. The PSPs were described according to standard methods (Suka-chev & Sonn, 1961; Methods..., 2002) in the first six years annually, and then once every 1-2 years. The size of the PSP was 25x25 m.
The biggest part of all data on the occurrence of invasive species was collected during route observations. Coordinates, number of individuals (or shoots), and habitat were recorded for each location of such species.
For individual species, the density/occurrence of the species was estimated in numbers of individuals per 100 m of the route / 10.000 m2 when they occur massively.
In 2011-2022, 15 invasive species (species with invasive potential) were recorded in the part of the Reserve danaged by fires of 2010: Juncus tenuis Willd., Saponaria officinalis L., Armoracia rusticana Gaertn., B. Mey. et Scherb., Aronia mitschurinii A. Skvorts. et Maytulina, Amelanchier spicata (Lam.) C. Koch, Padus pensylvanica (L. fil.) Sokolov, Lupinus polyphyllus Lindl., Caragana arborescens Lam., Acer negundo L., Epilobium adenocaulon Hausskn., E. pseudorubescens A. Skvorts., Bidens frondosa L., Erigeron annuus (L.) Pers., E. canadensis L., Solidago canadensis L.
Distribution and general features of dynamics during the first decade after the fire were analyzed for each species, and the degree of naturalization was also estimated (Krylov & Reshetnikova, 2009).
Results and discussion
The noted species were divided into three groups according to the type of distribution and activity in the fire-damaged area.
Lupinus polyphyllus, Saponaria officinalis, Armoracia rusticana, Aronia mitschurinii and Caragana arborescens were included in the first group. These species occur sporadically and exclusively in the territory of former settlements and do not disperse from known plots. Thus, Lupinus polyphyllus was noted only in 2011 after the fires at the former settlement site as juvenile specimens, while it had not been found in this location before the fire. Saponaria officinalis, Armoracia rusticana, Aronia mitschurinii and Caragana arborescens re-grew in the former locations.
According to the scale of naturalization degrees of alien plants, almost all of them belong to gradation N6. These are species that have grown in places of skidding, but do not spread beyond these sites. Such species do not disappear when the habitat condition changes, but continue growing when the communities are restored, in particular, they are preserved in the place of ancient parks. The same applies to the noted species. They continue to grow on the sites of abandoned and subsequently burned settlements.
Armoracia rusticana is an exception in this group of species. It belongs to gradation N4 - as a species capable of few and irregular regeneration.
Caragana arborescens from the territory of the former Sazonikha village had two juvenile plants of seed origin near bushes in places of introduction in 2020. Aronia mitschurinii is seen as a N6 species within the fire-affected area in 2010. However, taken into account the fact that its weak dispersal near the settlement, away from the fires of 2010, it is closer to the next group of species as well as Caragana arborescens.
The second group includes species observed during the whole period of observations in single locations, but undoubtedly in the beginning of their dispersal across the territory. They are Acer negundo, Bidens frondosa and Amelanchier spicata. Acer negundo and Amelanchier spicata are recorded in the area of former settlements, but both species are fruiting. Seed regeneration is noted. Bidens frondosa has been registered in the territory of the reserve only in the last ten years of observations, but, undoubtedly, it is actively dispersing in damp biotopes. In the fire-damaged area, Bidens frondosa was found in 2018 in the form of single seedlings in the bottom of the dried waterlogged depression. In 2019, it was found in relatively large numbers, but its place of growth, a forest stream floodplain, was not fire-affected.
According to the scale of degrees of naturalization of alien plants, they all belong to the N8 gradation - alien plants that disperse and naturalize in disturbed, semi-natural and natural habitats. Bidens frondosa and Acer negundo are on the verge of gradation N9 as "transformer" species.
Species from the third group are of most interest. They have often remarkable dynamics of abundance, and during all years of observations were regularly noted in various locations. They are Juncus tenuis, Padus pensylvanica, Epilobium adenocau-lon, E. pseudorubescens, Erigeron annuus, E. canadensis and Solidago canadensis.
At the same time, their prevalence and degree of naturalization are very different. Both Epilobium adenocaulon and E. pseudorubescens belong to the N3 grada-
tion, i.e., they persist in places of occurrence for several years and are capable of few, irregular regeneration. They quickly disappear from the communities. Both species were observed in some years in different habitats, including in the permanent sample site, but they did not show a tendency to disperse, often disappearing for several seasons. The abundance of these species in the PSP, where they were recorded, was noticeably higher in the first years of observations than in subsequent years.
Juncus tenuis was observed only along roads, mainly in the vicinity of cordons and in places of former settlements (Fig. 1). The number of the species is low. There were no signs of its dispersal out of roads. Erigeron annuus is in the similar situation. The species was mainly found in different locations near the former Sazonikha village, but mainly along roads. Both species are classified as N8. In the western part of the Reserve, not affected by catastrophic fire, the frequency and abundance of Erigeron annuus increases significantly, especially in the vicinity of Rustai village (Fig. 2).
Fig. 1. Places of finds of Junsus tenuis in 2011-2022.
Fig. 2. Places of finds of Erigeron annuus in 2011-2022.
Padus pensylvanica is represented by single plants along roadsides and extensive thickets at the Sazonikha village (Fig. 3). In recent years, the occurrence of this species has increased along roadsides. The successful fruiting and subsequent dispersal by birds have been noted. When cut both near Sazonikha village and in other parts of the fire-damaged area, the species gives relatively abundant brushwood in most cases. The species reaches a height of up to five meters rather quickly, in 4-5 years. Thickets of the species are practically mono-species. The presence of a large population of the species along with the described trends and known examples of its invasive activity are a matter of great concern. Particularly disturbing is the fact that apart from a large population near Sazonikha village, there is another source of diasporas. It is the neighbouring village of Rustai, where the Reserve's base (the ecological center and fire-chemical station) is located. Villagers are still cultivating the species in gardens and settling it on weedy places and wastelands. According to the degree of naturalization, Padus pensylvanica is classified as N9 (a "transformer" species).
Fig. 3. Paduspensylvanica near the Sazonikha lodge.
Solidago canadensis is among the most active species that grow in the fire-affected area. The species began to be regularly observed in the Reserve on the eve of the fires, in the vicinity of the Rustai village since 2008, and increased its presence every year. In the permanent sample plots, its first sightings date back to 2013. Later, in these areas, it either disappears from the communities or significantly reduces its abundance. In general, it was observed annually at many sites, more often as solitary individuals, mostly on roadsides and damp biotopes. Not infrequently, as in the PSP, the species was displaced from the composition of communities during some time (usually in the 3rd-4th year).
However, there are locations where the species grows permanently. Among them are the vicinities of the former villages Chernorechye, Chernozerye and Sazonikha where the species appeared after 2010. These places serve as one of the probable centers of its dispersal over the territory. Thus, individuals forming up to 40 and more generative shoots grow on the territories of the former villages of Chernozerye and Sazonikha. Introduction of this species to protected areas after the fires of 2010 is also noted in neighbouring regions (Esina et al., 2022).
There is a particular concern on the high occurrence of the species in black-alder birch and black-alder thickets, which every year occupy more and more areas at the fires. Solidago canadensis has grown there immediately or in the first years after the fire, when any competition in ground-cover was absent or very weak. While esti-
Вып. 31. 2022
mating species density/occurrence per 100 m of trails / 10.000 m2 on control profiles, we noticed a decrease in this indicator over time at all sites (Fig. 4).
(~) >1000
ф 100-1000
о 10-100
О 0-10
2016 2018 2020 2021
Fig. 4. Density/occurrence of Solidago canadensis in number of individuals per 100 m of route / 10 000 m2 on control profiles.
According to the degree of naturalization, Solidago canadensis can be referred to the N7 stage (alien plants, currently actively dispersing and naturalizing in disturbed habitats), although it is close to "transformer" species. In particular, it appears as such in some deposits in the Bor district to the south of the Reserve.
In the first 2-3 years after the fires, Erigeron canadensis dominated in the grass-bush tier in communities of dry biotopes (Fig. 5). It was found sporadically in
60
50 —""
40 _____—.
30 -------
20 ^
10
0
2011 2012 2013 2014 2015 2016
Motinia caerulea — Calluna vulgaris Rumen acctosella Erigeron canadensis
Fig. 5. Projective cover of some species at the PSP13-11 (top of a low ridge).
all other biotopes. It was found practically in all permanent sample plots, except for bogs. Similar high abundance of this species after fires was noted in other areas after the fires of 2010 (Khapugin et al., 2016; Lepeshkina, 2020). In 4-5th years, there was a significant decrease in its abundance and its loss from many communities. In 2015, 2018, and 2020, the density/occurrence of the species was estimated in numbers of individuals per 100 m of route / 10.000 m2 (Fig. 6). Their analysis shows landscape confinement of the species occurrence density and its decrease from 2015 to 2018 with a slight increase in 2020, mostly related to the appearance of areas with disturbances (mostly zoogenic) soil cover. In 2022, the species was observed only near roads and at the only site with zoogenic disturbance of vegetation cover.
Fig. 6. Density/occurrence of Erigeron canadensis in number of individuals per 100 m of route / 10 000 m2 on control profiles.
Conclusion
Thus, at the moment, most of the invasive species do not pose a significant threat to the vegetation cover of the Reserve, and some of them (e.g., Erigeron an-nuus, Caragana arborescens, etc.) can be easily removed. However, a number of the remaining species, such as Padus pensylvanica, Solidago canadensis, and, probably, Bidens frondosa and Acer negundo, pose a significant threat and require development of special measures to control them both within the fire-damaged areas and other Reserve's areas.
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ИНВАЗИОННЫЕ ВИДЫ РАСТЕНИЙ НА ГОРЕЛЬНИКАХ В КЕРЖЕНСКОМ ЗАПОВЕДНИКЕ В ПЕРВЫЕ ДВЕНАДЦАТЬ ЛЕТ ПОСЛЕ КАТАСТРОФИЧЕСКИХ ПОЖАРОВ
Н.Г. Кадетов1, С.П. Урбанавичуте2, А.Е. Гнеденко3
хМосковский государственный университет имени М.В. Ломоносова, Россия 2Государственный природный заповедник «Керженский», Россия 2Институт географии РАН, Россия e-mail: biogeonk@mail.ru
Приводятся данные о составе, распространении и динамике инвазионных видов растений на пройденной пожарами 2010 г. части территории Керженского заповедника. Проанализированы данные как маршрутных наблюдений, так и с постоянных пробных площадей. Всего отмечено 15 инвазионных видов, разбитых на три группы. К первой (виды, встречающиеся единично и исключительно на территории бывших поселков и не расселяющиеся из известных мест) отнесены Lupinuspolyphyllus Lindl., Caragana arborescens Lam., Armoracia rusticana Gaertn., B. Mey. et Scherb., Saponaria officinalis L. и Aronia mitschurinii A. Skvorts. et May-tulina. Ко второй (виды, отмеченные в единичных локациях, но находящиеся в начале своего расселения по территории) - Acer negundo L., Bidens frondosa L. и Amelanchier spicata (Lam.) C. Koch. К третьей (виды с заметной динамикой численности, регулярно отмечавшиеся в различных локациях) - Juncus tenuis Willd., Paduspensylvanica (L. fil.) Sokolov, Epilobium ad-enocaulon Hausskn., E. pseudorubescens A. Skvorts., Erigeron annuus (L.) Pers., E. canadensis L., Solidago canadensis L.
Ключевые слова: инвазионные виды, сосудистые растения, пожар, динамика, Керженский заповедник, Нижегородская область, Заволжье
