Download Part X of the Project

SUMMARY
The aim of this research was to evaluate abundance, distribution and morphological
parameters of invasive plant species as well as to estimate their impact on the stage of protected
species and habitats. In 2014–2015, populations of eleven invasive species (Robinia pseudoacacia,
Impatiens parviflora, Prunus serotina [=Padus serotina], Echinocystis lobata, Amelanchier
spicata, Solidago gigantea, Solidago altissima, Rumex confertus, Cytisus scoparius,
[=Sarothamnus scoparius], Bidens frondosa and Gypsophila paniculata) have been investigated.
Five populations of each species occuring mainuly in nature protection areas were selected for the
investigation.
Analysis of the data collected during the investigation revealed that invasive herbaceous
plant species mainly affect open habitats, their plant communities and species diversity, whereas
woody species threten the stability of both open and forest habitats.
Amelanchier spicata is a widespread species which occupies various types of forest
habitats, but it increasingly frequently invades abandoned fields, meadows and is recorded even in
transitional mire habitats.
Bidens frondosa mostly inhabits coastal habitats of water bodies. This invasive species is
the most frequent in tall eutrophic herbs habitats, muddy river flats or coastal habitats in the
transitional zone between these two habitat types. Bidens frondosa may affect protected native
plant species characteristic to these habitats (e.g. Bolboschoenus maritimus, Cyperus fuscus,
Teucrium scordium etc.). Bidens frondosa in Lithuania is still intensively spreading invasive plant.
In order to identify its impact on native plant communities and plant species it is necessary to
perform systematic studies. Large intervals between investigations do not allow drawing
substantiated conclusions about the performance of populations as well as about impact of this
species on habitats, plant communities and native species.
Cytisus scoparius is the most frequent in regions of Lithuania with prevailing sandy soils
(eastern, southern, western parts and certain areas of the Žemaičių Elevation). This species invades
pine forests (western taiga, lichen pine forests) as well as sand habitats and xerothermic forest
edges. This highly competetive invasive plant alters species composition significantly.
Echinocystis lobata is a widspread species whis is the most frequent and abundant in the
valleys of rivers, where occupies almost all types of habitats, i.e., from muddy flats to alluvial
forests. This annual species does not create long-persistent seed bank, therefore, its control and
eradication are possible if necessary measures are implemented consecutively in territories which
include the invaded area as well as the routs of its spread.
Gypsophila paniculata is the most widespread in the coastal area of the Baltic Sea. It
occupies coastal sand habitats, usually embryonic shifting dunes, white dunes and gray dunes
causing degradation of the habitats, structure of plant communities and species diversity. It can be
assumed that one of the main factors causing the rapid degradation of coastal sand habitats is caused
invasive species (Gypsophila paniculata, Rosa rugosa, etc.). Further studies on the impact of
Gypsophila paniculata on plant communities are required. It is important to prepare and implement
action plans for this species control and eradication in certain protected areas (e.g. Pajūris Regional
Park, Curonian Spit National Park).
Impatiens parviflora is a widespread species in Lithuania which mainly invades forest
habitats. Populations of this species are extensive and extremely abundant, therefore its control and
eradication on a large scale is almost impossible. Therefore, control and eradication of this species
can be substantiated only in the most important and valuable areas where it threatens protected
plant species and habitats.
Prunus serotina is distributed all over the Lithuania, but largest invaded areas are registered
in eastern, southern and western pats of the country. Nevertheless, control and eradication of this
species is still possible, though it can take up to decade ot longer. The main vector for this species
spread are fruit feeding birds.
Robinia pseudoacacia is distributed all over the Lithuania, but largest invaded areas are
recorded in eastern, southern and western pats of the country. In other regions of Lithuania this
species has invaded only small areas. The largest and the most threatening populations of this
species exists in the Curonina Spit. Nevertheless, eradication of this species is possible if necessary
measures are implemented consecutively and for a long time.
Rumex confertus is widely distributed all over the territory of Litbhuania, but in the northern
districts it is somewhat rarer. This species threatens habitats of meadows, especially natural,
seminatural and cultivated meadows located in river valleys. The investigation revealed, that early
mowing of meadows (until the end of June) is very effective measure for control of Rumex
confertus populations and prevents its further spread.
Solidago altissima and Solidago gigantea settles poorly used or abandoned meadows,
fallow lands and other habitats previously affected by anthropogenic impact. Most of investigated
populations of Solidago altissima and Solidago gigantea were located in the semi-natural or
cultural, but now abandoned grasslands. Plant communities, in which grows Solidago altissima
and Solidago gigantea, have relatively high species diversity and are dominated by plant species
characteristic to grasslands: Achillea millefolium, Agrostis capillaris, Agrimonia eupatoria,
Dactylis glomerata, Festuca rubra, Phleum pratense, Rumex acetosa, Vicia cracca etc. According
to the species composition and environmental conditions the majority of the studied populations
occupy communities attributable to degraded mesophile hay meadows; some habitats have features
of steppe meadows.
The main reason for the intense spread of Solidago gigantea and Solidago altissima is
increase of abandoned agricultural lands. Under such conditions Solidago gigantea and Solidago
altissima are not influenced by any mechanical or physical obstacles and, thus, can easily spread
not only over the area of the initial population, but also to inhabit adjacent areas. In order to stop
further spread of Solidago gigantea and Solidago altissima and reduce their negative impact on the
environment, it is necessary to take measures for control and eradication of their populations. It is
important to develop a comprehensive population control action plans and implement them
consistently, particularly in protected areas with concentrations of valuable habitats and protected
species.
Basing on the summarised information collected during the research and data analysis, we
can make recommendations for urgent actions necessary to stop the spread of the studied invasive
species and reduce their negative impact on the habitats, plant communities, native plant species
and biodiversity.
It is necessary to perform thorough research and an inventory of invasive species
populations nationwide, primarily in protected areas (nature reserves, national parks, regional
parks, nature reserves, special areas of conservation). Basing on this information, generalised
action plans for the control and eradication of invasive plant species should be prepared.
Action plans for control and eradication of invasive plant species in certain areas should be
prepared and implemented. Such action plans urgently should prepared for areas with particular
biodiversity and nature values. In cases when several invasive species occur in a certain protected
area integrative action plans should be prepared and implemented. Their implementation would
save a considerable amount of money, and the results would be much better. The removal of single
invasive species populations often facilitates the spread of other invasive plant species occuring in
an area.
Once measures for control and eradication of invasive species are started in a certain area,
work necessary to continue for some time, until the goal is reached, i.e. populations of invasive
species are significantly reduced or completely eradicated in a given area and its surroundings.
This can prevent the possibility of quick regeneration of invasive species population.
Implementation of measures of the action plan should include not less than three years (period must
completely cover the three vegetation seasons from early spring to autumn), and if necessary the
implementation of measures can be divided into stages and last as long as is necessary to achieve
the objectives of the action plan.
It is important to carry out a systematic monitoring of populations of invasive plant species
and repeat tests each year of at least every 3 years. Random surveys and studies being conducted
with large intervals (more than 5 years) does not answer many of the questions concerning the
causes of the spread of invasive species and their impact on plant communities or ecosystems.
The most important and urgent task is to revise all legal acts dealing with measures for
nature protection, forestry, creation and maintenance of plantations, agriculture practices as well
as recommendations to use for rehabilitation of disturbed areas Amelanchier spicata, Cytisus
scoparius, Prunus serotinus, Robinia pseudoacacia and any other woody or herbaceous invasive
or alien plant species.
Urgent changes and adjustments of national legislation should be made. Existing legislation
should be changed in such a way that the property owners should be responsible for the control and
eradication of invasive plant species growing in their lands, especially in abandoned or improperly
used areas. In our opinion certain legal acts should be adopted by the Government of the Republic
of Lithuania.