Inwazyjne gatunki z rodzaju rdestowiec Reynoutria spp. w Polsce - biologia, ekologia i metody zwalczania

Abstract

A publication prepared based on the document “Guidelines on the eradication of knotweed species in Poland”, commissioned by the General Directorate for Environmental Protection. Prevention of invasion is considered to be the most effective method for reducing the environmental and economic consequences of the spread of alien species. In addition to raising awareness of the causes and consequences of biological invasions, an essential element of a preventive strategy is the development of effective organizational and legal solutions, including acts regulating the import of alien plant species and methods of handling plants that already exist in anthropogenic and other habitats. Poland, by ratifying in 1995 the Convention on biological diversity (CBD), committed itself, among other things, to preventing the introduction of, controlling, or eradicating those alien species which threaten ecosystems, habitats or species (as far as possible and as appropriate) (Article 8h). The group of alien plants includes knotweed species Reynoutria spp. (= Fallopia spp.) (Tokarska-Guzik et al. 2012, 2015a). Because of the threats to the biodiversity of plants and animals in specific areas associated with the spread of knotweeds and the formation of communities in which they dominate, often in large areas, these species have been listed in many countries as among those requiring eradication (Child and Wade 2000; Lowe et al. 2000). Failure to adopt measures limiting their occurrence and/or eradicating these plants can promote further invasions and increase the scale of their establishment. Due to certain morphological and biological features of knotweed species and their ability to adapt to various environmental conditions they have also been regarded as plants which are particularly difficult to control (e.g. Bímová et al. 2001; Child et al. 2001; Cronk and Fuller 2001). Regulation of the European Parliament and of the Council (EU) no. 1143/2014 of 22 October 2014 (EU Regulation) on the prevention and management of the introduction and spread of invasive alien species states that “Member States shall have in place effective management measures for those invasive alien species of European Union concern which the Member States have found to be widely spread on their territory, so that their impact on biodiversity, the related ecosystem services, and, where applicable, on human health or the economy, are minimised” (ch. 4, Article 19). The issue of effective eradication of invasive species belonging to the genus Reynoutria has been addressed in many scientific reports and methodological guides (e.g. Child and Wade 2000; Bímová et al. 2001; Kabat et al. 2006; The knotweed code… 2006; Barták et al. 2010). Information about methods of eradication and prevention is also provided in the GISP database (Global Invasive Species Programme) (Mooney 1999). One frequently emphasized fact is that once well-established, populations of knotweed species are very difficult to eradicate. This should be considered when planning actions on national, regional and local levels. The aim of this publication is to summarize current knowledge about the occurrence of alien invasive knotweed Reynoutria spp. (= Fallopia spp.) species in Poland: Japanese knotweed (Reynoutria japonica), giant knotweed (Reynoutria sachalinensis) and their hybrid – Bohemian knotweed (Reynoutria × bohemica), and to prepare guidelines allowing for effective measures to eliminate or minimize the risks associated with their spread. This document is meant to serve as a guideline for local authorities, academic institutions, nongovernmental organizations and citizens, providing them with information on the identification of knotweed species, available legal measures enabling actions to control these species, and, above all, a description of the most effective methods for elimination and minimizing their further spread. This document includes: 1. Characterisation of invasive knotweed taxa Reynoutria spp. (= Fallopia spp.) found in Poland (ch. 2), including: a) classification and nomenclature (ch. 2.1.-2.3.); b) morphology (ch. 2.4.) and problems of taxa identification (ch. 2.5.); c) biology and ecology (ch. 2.6.); d) history, status and forecasts of invasiveness in Poland (ch. 2.7.); e) habitats, including those listed in the Habitats Directive, most frequently invaded by knotweed species in Poland (ch. 2.8.); f) description of the impact on the natural environment, particularly on protected species and habitats listed in the Habitats Directive, and on the economy and humans (ch. 2.9.); g) example estimates of economic damage caused by these species (ch. 2.9.4.); h) description of known methods of applying specific species e.g. in medicine (ch. 2.9.5.). 2. Analysis of existing regulations on measures aimed at the eradication of invasive knotweed species and the minimisation of their spread, as well as proposed modifications to legal and organisational solutions in this area (ch. 3.). 3. Methods for preventing the spread of knotweeds, management of their populations and monitoring (ch. 4.), including: a) measures aimed at preventing the invasion of knotweed species into the natural environment (ch. 4.1.); b) description of methods used for the eradication of knotweeds, with emphasis on their advantages and disadvantages (ch. 4.2.), methods for the disposal of harvested plant material (ch. 4.3.) and the assessment of the efficiency of these methods (ch. 4.4.); c) methods for the ecological restoration of land after the removal of knotweeds (ch. 4.5.); d) proposals for necessary actions aimed at the management of knotweed populations in Poland, including types of priority areas or habitats which should be covered by these actions, and the analysis of costs and benefits from the proposed actions (ch. 4.6.); e) recommendations on a strategy for the monitoring of populations and monitoring of the effects of undertaken actions, as well as an explanation of the objectives of this monitoring (ch. 4.7.); f) example actions associated with the eradication of knotweed species, completed or currently conducted in Poland and other countries (ch. 4.8.). 4. Sources of financing actions aimed at limiting the spread and the elimination of existing sites of knotweed plants (ch. 5.). 5. Informational, educational and communication measures promoting good practices in the management of knotweed populations (ch. 6.). An integral part of this document is a guide to the identification of individual knotweed taxa, with illustrations presenting important diagnostic features. Current knowledge about Asian knotweed species is extensive (cf. references). It has been accumulated through detailed studies and observations carried out for many years in various research centres, especially in countries where knotweed species are a problem in nature conservation or cause economic damage. Results from these studies should be supplemented with data relating to Poland and individual regions of the country, especially in order to assess the role of generative reproduction in the spread of knotweed species and their impact on native species and habitats. Information collected so far illustrating the distribution of invasive knotweed species in Poland does not fully reflect the current status of distribution for these taxa, but it does indicate a clear increase in the density of sites of Reynoutria japonica and R. sachalinensis in south Poland. Their abundant occurrence is promoted by the diversified orography and the dense network of watercourses which are present there. Least is known, based on collected data, about the current distribution range for R. × bohemica. Presumably, the small number of reported sites for this hybrid can be attributed to problems with its differentiation from the parent species. The concentration of sites of these knotweed taxa generally overlaps with the location of urban areas and linear objects, such as roads, railways and rivers (cf. Figs. 31–33). The total area covered by all the three knotweed taxa in Poland has been estimated at 0.12% of the country, i.e. approx. 40,000 ha. This is a relatively modest figure, but the total area is not the best way to measure the risk of invasion. In the case of knotweed species, the risk of invasion results primarily from the fragmented range of distribution with many scattered hot spots, from which the species in question can spread to new areas. Forecasting of the rate and range of the invasion of knotweeds is very difficult because of this spatial model of distribution for knotweed species in Poland, combined with the strong potential of knotweeds for vegetative reproduction and their ability for fast and long- distance migration and colonising further areas with the help of human activity, as well as the growing role of generative reproduction in dispersal. An updating survey of sites should be carried out to correctly estimate the area currently covered by knotweed species, to estimate their rate of spread and to indicate regions most endangered by their spread. On a local (regional) scale it is worth considering the use of modern techniques (modelling of niches and species ranges), including the analysis of aerial and spectral photographs. Protection of biodiversity and control of invasive species has for years been a priority in the European Union, and is the subject of many international agreements, including pan-European ones. Invasive Reynoutria spp. (= Fallopia spp.) species are listed in many legal acts adopted at different administrative levels, both national and international (e.g. Genovesi and Shine 2011). Knotweeds are also included indirectly (as invasive alien species) or directly (listed by name) in international conventions, directives and regulations adopted by European countries and worldwide international organizations. Legal provisions concerning knotweeds are contained in a number of national regulations relating to invasive alien species (e.g. Regulation of the Minister of the Environment of 9 September 2011). Some of them have been adopted after the ratification of international agreements, such as the Berne Convention, the global/UN Convention on Biological Diversity, the Habitats Directive and other EU Regulations. However, the existing legislative measures seem to be sufficient with respect to the regulation of the deliberate introduction of knotweed species into the environment, but insufficient when we consider clauses on limiting the accidental spread of propagules of invasive species, especially knotweed. One particularly important problem is the dispersal of fragments of rhizomes with soil by contaminated machinery used on a sequence of various construction sites, as well as the stockpiling and disposal of plant waste material. Because of EU legislation coming into force, as well as the inclusion of Japanese knotweed, giant knotweed and Bohemian knotweed in the Regulation of the Minister of Environment of 9 September 2011 on the list of alien plant and animal species which, when introduced to the natural environment, pose a threat to native biodiversity or natural habitats, it can be assumed that the intentional introduction of these species in the natural environment will be minimised. Sporadic introductions may possibly be caused by individuals or institutions unfamiliar with these regulations, or by offering plants under a different name – for example, giant knotweed is advertised in Germany under the name Igniscum for cultivation as an energy crop (cf. ch. 2.9.5.). Therefore, it would also be reasonable to extend the list of priority actions to include measures preventing the further spread of knotweed species, which are plant species already common across Poland, from already existing sites. This aim could be achieved through: – eradication of existing populations (ch. 4.2.), – monitoring of existing populations of knotweed plants combined with the assessment of the actual threat they create (ch. 4.7.), – prompt identification of new sites of plants (within an early warning system) supported by relevant regulations (ch. 3.2.) and a large-scale educational campaign (ch. 6.). In addition, preventive actions should include: – the development, implementation and dissemination of rules for the management of these species (codes of good practice), with an indication of the characteristic plant features promoting invasion. The document we deliver here is intended to fulfil this task, and it can be used to prepare other materials (with updated information) such as brochures, flyers with concise descriptions and photographs (in a paper or digital format, depending on needs), and examples of appropriately and successfully completed preventive actions. For example, knotweed plants spread easily by vegetative reproduction, and it is important to prevent the dispersal of their fragments such as rhizomes and stems (e.g. by contaminated machinery or other equipment that has had contact with plants) and soil contaminated with plant material, because plants can regenerate even from the smallest pieces of stems and rhizomes (Brock et al. 1995; Brabec and Pyšek 2000; Rennocks 2007) (ch. 2.6.2.). For this reason, the use of vehicles with caterpillar tracks is not recommended in areas where knotweeds are present, and vehicles leaving these areas or hauling soil that may contain fragments of plants should be thoroughly cleaned (The knotweed code… 2006). It is also important to implement codes of practice for handling plant waste material (particularly fragments of stems and rhizomes). Planned developments should be preceded by a survey of the natural environment, taking into account the presence of invasive alien species (including knotweeds), allowing for the development of a work plan together with an indication of methods for the management of invasive species found on the site in order to prevent their further dispersal to new areas. With respect to highly-invasive knotweed species in cultivation, the following recommendations should be made: 1– monitoring of areas adjacent to the site where knotweed plants are kept, and destruction of plants that escape from cultivation by mechanical control and/or chemical control in specific cases; 2– limiting the spread of populations by: a– planting in containers; b– keeping the size of populations under control by cutting or pulling out some plants on the edge of the cultivated area; 3– prohibition of the transport of soil from sites infested with knotweed; 4– proper disposal of biomass (especially because of vegetative reproduction) after the end of the growing season or during the eradication of plants from the site: a– drying, b– burning, c– prohibition of disposal on illegal waste dumps (e.g. in forests, by watercourses). These recommendations can be considered as suggested preventive measures limiting the spread of knotweed species from the places of their cultivation (storage). Recommendations are addressed to land owners and administrators. Another issue that should also be considered when planning preventive measures concerns periodic surveys of knotweed sites on private land carried out by relevant services, and orders for eradication in the case of sites where knotweeds are out of control (this also requires relevant legislative solutions). Other problems to be solved concern fundraising and organising equipment for the liquidation of knotweed sites (assistance of municipal authorities in this area seems necessary, e.g. through applying for funds to finance actions, and organising work on the system of monitoring plots located within municipalities, for example once every 5 years), and special sites for the stockpiling and disposal of biomass, and organization of work. Currently the elimination of knotweed sites is accomplished using different methods, depending on the size and location of populations (e.g. in protected areas, in river valleys, in built-up areas). The strategy for the eradication of knotweeds is also determined by the biology of these plants. Knotweeds are perennials with a large system of underground rhizomes that spread mainly by vegetative reproduction (ch. 2.6.2.). Because of this they are eradicated mainly by the mechanical removal of above- and underground parts of plants and/or by chemical treatments. Accumulated experience relating to the development and implementation of appropriate procedures, assessment of the effectiveness of various methods and estimation of their costs has been presented in numerous publications (e.g. Holden et al. 1992; Luken and Thieret 1997 and references quoted therein; Child and Wade 2000; Cronk and Fuller 2001; Bimová et al. 2001; Fibichová et al. 2014). The United Kingdom has long experience in eradicating knotweeds because of the increasing scale of invasion of these species in the British Isles. Special programmes have been developed there for the control, eradication and prevention of knotweed spread (The knotweed code… 2006; CABI 2015a–c). Studies and pilot actions aimed at developing the most effective procedures are also carried out in the UK. Knotweed species are controlled using mechanical, chemical, combined (mechanical and chemical) and biological methods. The choice of method should mainly consider: d) its impact on the natural environment (environmental costs), e) presumed effectiveness, f) financial costs. Methods differ in terms of the duration and frequency of treatments which depend on the size and location of knotweed populations. It should be emphasized that occasional and selective elimination of invasive species, including knotweeds, is ineffective. Comprehensive plans have to be developed, including regular control treatments in larger areas and are at best implemented on a national level. However, because of current logistical and financial constraints, the major focus should be on preventive measures, as well as on the eradication of knotweed populations at early stages of their growth. So far, experience has shown that combined methods are the most popular since they bring the best effects (repetitive cutting of canes during the growing season combined with chemical control). However, because of the harmful effects of the chemicals used to eradicate knotweeds their approval is not recommended on wider scale. Replacement of soil (even a 2–3 m deep layer) containing rhizomes is often used as a complementary method or an alternative to chemical control. However, it has a serious disadvantage, being a negative impact on the natural environment (high environmental costs). Apart from the methods listed, there are also tests being carried out, mainly in Western Europe, on biological methods, mostly those involving the use of pathogens. But as long as there is no full guarantee that the tested methods are safe with respect to native organisms they should be treated with limited confidence. Planning eradication treatments should consider the fact that knotweeds, including Reynoutria japonica, are also able to spread by generative reproduction. Therefore, as far as possible, the formation of seeds that can survive in the soil seed bank or contribute to the dispersal of plants to new areas should be prevented. Given the above, cutting down patches of knotweed plants many times during the growing season and over a long period of time, i.e. several or even more than ten years, should be recommended. It is still important to continue studies which may help develop effective methods of eradication (e.g. the development and use of bioengineering methods). Results obtained to date have shown the importance of maintaining and strengthening the competitive role of native plant species or whole plant communities, both in limiting the spread of knotweeds and ecological restoration of areas where populations of knotweed species had been eliminated (Dommanget et al. 2013; Chmura et al. 2015; authors’ own studies). Nevertheless, the growth strategy of knotweeds under different light conditions, including methods of utilisation of nutrients accumulated in underground parts of plants, has still to be fully explained. The effect of light exclusion on limiting the size of the above-ground biomass of knotweed plants also needs to be confirmed under controlled conditions and in field experiments (Dommanget et al. 2013). Currently in Poland there is virtually no national system for the monitoring of populations of knotweeds, as well as for other invasive plant species. An attempt made in 2016 to make it a part of the Integrated Monitoring of the Natural Environment (Zintegrowany Monitoring Środowiska Przyrodniczego, ZMŚP) seems to be insufficient. Therefore, it is necessary to prepare guidelines for data collection from river valleys, especially in sections where the emergence of these problematic species is most probable. However, monitoring alone, as well as its financing, will make sense only if there are legal grounds and organizational potential to carry out preventive actions. The management of the national population of knotweeds should be coordinated on all levels, from central planning to local actions. Particular emphasis should be placed on public education, as an important element of fighting against invasive plants. Actions aimed at limiting the spread and eradication of knotweeds are extremely difficult, costly and time-consuming. Funds should be secured for a programme aimed at eliminating these species. Currently, land owners and authorities managing knotweed-infested areas do not have sufficient funds for such projects, but applications for funding can be filed by non-governmental organisations, national parks, landscape parks, and municipal and county authorities. Unfortunately, private owners/individuals are currently not granted financial support for such activities. Another significant obstacle in starting initiatives associated with the elimination of knotweed sites, apart from limited budgets, seems to be the lack of logistic solutions. This primarily concerns the lack of local or regional sites for stockpiling biomass (containing stems or rhizomes) appropriately prepared for the disposal of waste in a way preventing the spread of invasive knotweed species to new areas.