Expansion of tree and shrub plant species into undisturbed steppe phytocenoses

The article is devoted to the study of tree and shrub plant species that spontaneously invasively colonize anthropogenically undisturbed steppe ecosystems. The species composition, number and biometric characteristics of tree and shrub plant species are determined. It was established that there are 22 species, among which 8 show the greatest invasive activity, in 6 studied natural beams. These are: Cotinus coggygria Scop., Crataegus fallacina L., Prunus divaricata Ledeb., Prunus stepposa Kotov, Pyrus communis L., Rhamnus cathartica L., Robinia pseudoacacia L., Ros corymbifera Borkh. According to the Serensen index of species composition of tree and shrub plants, comparing the slopes of beams of different exposures, it was found that steppe tracts have different similarities between the slopes, but the highest figure was observed for Balka Demurynа (80%).

СУЧАСНИЙ СТАН РОСЛИННОГО ПОКРИВУ СТРІЛЬЦІВСЬКОГО СТЕПУ (ЛУ-ГАНСЬКИЙ ПРИРОДНИЙ ЗАПОВІДНИК)

Фітоценотичний моніторинг Стрільцівського степу проводиться протягом 50 років, він розпочатий у 1969 р., коли було виконано перше геоботанічне картування території заповідника. З метою продовження моні-торингових досліджень був закладений геоботанічний профіль, що перетинає заповідник у східно-західному напрямі, довжина профілю – 3,254 км. На профілі виконані геоботанічні описи і виділені контури рослинності. Одиниці картування виділялися за домінантними ви-дами. За початковими даними для території дослідження були характерні угруповання фор-мацій Stipeta lessingianae, Stipeta zalesskyi і Festuceta valesiacae. В сучасному розподілі рос-линності уздовж профілю 35,8% займають луки, 32,5% – чагарники, 31% – степ. На ділянці, де степові екотопи складають майже 100% (за виключенням тальвегів глибоких балок – 0,7%), степові угруповання збереглися на менше ніж третині території, що є наслідком дії резерватогенних процесів. Характерний високий сукцесійний потенціал заростей чагарників, половину яких займають вже сформовані і потенційні зарості високих чагарників. Значне по-ширення мають розріджені зарості Prunus stepposa та Rhamnus cathartica на фоні заростей Caragana frutex і Amygdalus nana. На ділянці старого перелогу (близько 30 років) вторинні степи складають приблизно чверть ділянки, що свідчить про слабкі темпи відновлення корін-них степових ценозів. Вперше на території абсолютно заповідної ділянки був виявлений ло-калітет заростей чужорідного виду – Ulmus pumila.

Spontaneous forest communities of introduced species in Kryvyi Rih area

The article is devoted to the study of woody plants communities, that spontaneously form in the abandoned areas of Kryvyi Rih Area as a result of spontaneous-invasive settling of species in previously established plantations. For the study, we laid 16 trial plots in 5 growth sites of such communities. We determined the species composition and biometric characteristics of primary woody plants and those, that formed these communities due to the invasion. In the first such community, which was formed due to the settling of other species in a 40-year-old plantation of Salix alba L., we found on 3 plots with an area of 625 m2 94 medium-sized trees Acer negundo L. having height (h) 11.8–13.6 m, trunk diameter (D) 16.8–17.3 cm and crown projection area (S) 9.5–10.4 m2, as well as 210 young generative trees, their height varies between 6.5–7.3 m, trunk diameter 5.0–5.4 cm, and the projection of the crown 2.5–6.3 m2. In this community also grow young and medium-generative trees of Robinia pseudoacacia L. – respectively 7 individuals – h = 7.2–11.7 m, D = 8.1–10.7 cm, S = 6.1–6.5 m2 and 7 ones – h = 13.5–14.0 m, D = 18.1–27.0 cm, S = 14.0–38.5 m2. Among self-seeding plants, such species predominate: Acer platanoides L. – 3905 specimens and Acer negundo – 1823 specimens. Three species dominate in the three dense forestation massive near the highway, which occupy an area of 250 m2: Robinia pseudoacacia, Ulmus pumila L., Fraxinus excelsior L. and Cerasus avium (L.) Moench. Robinia pseudoacacia is the most common among medium-generative plants, and Acer negundo, A. platanoides, A. tataricum L. – among young generative plants. Self-seeding of Robinia pseudoacacia, Acer platanoides, Fraxinus excelsior and Acer negundo is dominated in this area. In the abandoned Ulmus pumila plantation near the iron ore mine in three areas with an area of 625 m2, 12 to 33 specimens of medium-generative trees of this species with a height of 12.2–13.1 m with a trunk diameter of 14.7–16.0 cm and a crown projection of 25, 5–27.3 m2. Its self-seeding is quite active in all areas. Self-seeding plants of Acer negundo are also present here – 51 specimens and Acer platanoides – 35 ones. Self-seeding plants of A. platanoides – 9837 specimens, A. pseudoplatanus – 2111 specimens, Ailanthus altissima (Mill.) Swingle – 396 specimens dominate in the neglected park on the territory of 500 m2, where Acer pseudoplatanus, Acer platanoides, Robinia pseudoacacia grow. A study was also carried out on the example of the Zelena gully in order to determine how invasive species spontaneously penetrate into the formed steppe feathergrass-fescue phytocenoses. In the upper part of the Zelena gully, located outside of Kryvyi Rih, more than 40 years ago, forest belts were created from many species of shrubs, which have already been listed. Crataegus fallacina Klokov and Rhamnus cathartica L. diffusely inhabit and clearly predominate in the 6 trial plots that were laid on the slopes of the south-eastern and north-western exposures. In the presence of a large number of seed donors from the previously mentioned species on the slopes of the gully firstly Crataegus fallacina settles. Morphometric parameters of shrubs of these species were slightly larger on the north-western slope than on the south-eastern: the height of Crataegus fallacina – 2.5–2.9 m, and the diameter of the crown – 3.5–4.3 m, while in Rhamnus cathartica – the height of the bush was 0.7–0.8 m, and the diameter of the crown – 0.5–1.1 m. Thus, invasive species of Ulmus pumila, Acer negundo, Robinia pseudoacacia and Ailanthus altissima, which are the main in spontaneous communities in abandoned anthropogenically disturbed areas of the city, do not penetrate into stable phytocenoses. Most of these species of woody plants show low invasive activity and do not form multispecies communities in weakly disturbed feather-fescue phytocenoses.

Secondary invasion? Emerald ash borer (Agrilus planipennis) induced ash (Fraxinus) mortality interacts with ecological integrity to facilitate European buckthorn (Rhamnus cathartica)

Invasive insects have been shown to facilitate secondary invasive species by altering forest structure and function. Specifically, invasive insect herbivores may promote the establishment and growth of invasive plants by creating canopy gaps. Such secondary invasions may be influenced by ecological integrity—the degree to which ecosystem composition, structure, and function deviate from their natural or historical range of variation. Here we investigate 1) whether emerald ash borer (Agrilus planipennis; EAB) induced ash (Fraxinus spp.) mortality facilitates European buckthorn (Rhamnus cathartica)—an invasive shade-tolerant shrub; 2) the role of ecological integrity in this relationship. We use a principal component analysis (PCA) to calculate an index of ecological integrity and a zero-altered negative binomial generalized linear mixed model (GLMM) to describe European buckthorn occurrence and abundance. European buckthorn occurrence is influenced by canopy gaps, independent of EAB-induced gap formation. Ecological integrity and EAB-induced ash mortality interact to control European buckthorn abundance, with high ecological integrity limiting EAB-facilitated buckthorn invasion. This is the first evidence for EAB-facilitated buckthorn invasion and for an interaction between a secondary invasion and ecological integrity. Thus, ecological integrity plays an important role in the EAB-buckthorn system and may be used to manage the impacts of secondary invasions.

Fosamine ammonium impacts on the targeted invasive shrub Rhamnus cathartica and non-target herbs

Fosamine ammonium (Krenite®) is a foliar herbicide that primarily targets woody plant species; however, formal evaluations of its efficacy and potential for non-target impacts are scarce in the literature. The few tests of fosamine ammonium that exist focus primarily on its use in open environments, and the value of fosamine ammonium in controlling invasive understory shrubs is unclear. Here, we test the impact of fosamine ammonium on invasive common buckthorn (Rhamnus cathartica L.) and co-occurring herbaceous plants across six forest sites in Minnesota, USA. Rhamnus cathartica treated with fosamine ammonium had a 95% mortality rate, indicating high efficacy of fosamine ammonium for use against R. cathartica. Non-target impacts varied between forbs and graminoids such that forb cover was reduced by up to 85%, depending on site, whereas graminoid cover was sparse and impacts of fosamine ammonium on graminoids were unclear. These results indicate that while fosamine ammonium can provide effective control of R. cathartica and other understory shrubs, there is potential for significant non-target impacts following its use. We therefore suggest that land managers carefully consider the timing, rate, and application method of fosamine ammonium to achieve desired target and non-target impacts.

Genetic comparison of introduced and native populations of common buckthorn (Rhamnus cathartica), a woody shrub introduced into North America from Europe

Introduced from Europe to North America in the early 19th century as an ornamental shrub and for medicinal purposes, common buckthorn (Rhamnus cathartica L.) has since spread and naturalized throughout regions of the United States and Canada. The purpose of this study was to investigate levels of genetic variation and population differentiation in R.cathartica in its introduced range in North America compared with its native range in Europe to better understand patterns of spread. By analyzing introduced and native populations using microsatellite markers, we found that introduced populations generally exhibited similar or slightly lower levels of genetic variation compared with native populations, consistent with a slight bottleneck effect. Introduced populations contained many different genotypes, indicating genetic admixture, rather than one or few genotypes. In a few cases, populations had been misidentified in the field and were glossy buckthorn (Frangula alnus Mill.; syn. Rhamnus frangula L.). Overall, there was no substantial genetic differentiation detected between native and introduced populations of R. cathartica. Invasive spread in this species is likely due to its past horticultural history as well as adaptive biological traits such as competitive behavior, potential allelopathy, and seed dispersal via birds.