Research Article |
Corresponding author: Pavel Švec ( pavel.svec1@vsb.cz ) Academic editor: Gerhard Karrer
© 2024 Pavel Švec, Irena Perglová, Václav Fröhlich, Josef Laštovička, Jakub Seidl, Kateřina Růžičková, Ivana Horáková, Jan Lukavský, Martin Ferko, Přemysl Štych, Jan Pergl.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Švec P, Perglová I, Fröhlich V, Laštovička J, Seidl J, Růžičková K, Horáková I, Lukavský J, Ferko M, Štych P, Pergl J (2024) Perseverance of management is needed – Efficient long-term strategy of Reynoutria management. NeoBiota 94: 261-288. https://doi.org/10.3897/neobiota.94.122337
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One of the most problematic invasive species in Europe are knotweeds from genus Reynoutria (Fallopia) which have significant negative impact on the native communities as well on human activities. Therefore, they are a target of many control programmes. Due to their high regeneration potential, their management is problematic, and only chemical treatment is reported to be sufficiently effective.
The aim of this paper was to describe and analyse the patterns of Reynoutria invasion under long-term chemical treatment with glyphosate-based herbicide in The Morávka river floodplain, Czech Republic. The data covers 17 years of management which started with the European project “Preservation of alluvial forest habitats in the Morávka river basin”. We focus on (i) assessment of Reynoutria distribution during long-term management, (ii) analysis of the change of distribution according to the habitat, and (iii) discussion of the optimal management strategy based on the long-term data.
Distribution data was obtained using GNSS field mapping. Before the start of the study in 2007, Reynoutria stands covered 29% of the study area (96.9 ha). As a result of systematic whole area chemical management, the extent decreased to 19.6% (65.3 ha) in 2009, and even reached 14.5% (48.2 ha) in 2013, three years after its end. Due to implementation of local chemical management in the following years, the area of Reynoutria was maintained at similar level, with minimum value 41.8 ha in 2018 and a slight increase in recent mapping in 2023.
Beside the extent, the structure and coverage of invaded sites was analysed. There was a clear trend of fragmentation of larger polycormons with high coverage into many smaller and less dense ones as a result of chemical spraying. The average size of Reynoutria stand decreased from 0.61 ha in 2007 to half in 2013 (0.32 ha) to 0.15 ha in 2023. Testing of the effects of time, habitat, and biotope did not reveal significant differences of changes of extent and abundance over different environments (forest, open, bare ground), which indicates that there are no differences in reaction to management in the studied habitat and vegetation types.
Our study provides a robust and unique overview of the invasion, reinvasion, and suppression dynamics for an important invasive species. If herbicide management is used, chemical treatment must be quite long-term as even three years of intensive glyphosate foliar spray application was not sufficient for the complete eradication of Reynoutria.
Therefore, we propose the following procedure for effective chemical management of Reynoutria:
1) In largely infested sites, the first step is to reduce the distribution of Reynoutria stands to isolated polycormons. This phase can last 3–5 years.
2) After reaching the state of sparse distribution of Reynoutria, we recommend herbicide application only in periods of every 3–5 years depending on the local context and rate of regrowth.
3) At sites exposed to soil disturbances, where the soil is contaminated by fragments of Reynoutria rhizomes, there is a need to apply herbicide immediately to target newly resprouting individuals.
Fallopia, GNSS, knotweed, long-term management, mapping, neophyte, protected area, Roundup
The spread of non-native plant species has a negative impact on the conservation of native communities and is one of the most serious threats to ecosystem biodiversity (
One of the most problematic invasive neophytes in the Czech Republic are species from the genus Reynoutria (syn. Fallopia sp.) (
Even though the use of herbicides is mostly rejected by the public compared to mechanical methods, application of herbicides leads to more effective control of Reynoutria and can therefore lead to a less negative overall effect on the environment in terms of its pollution (
The wide and frequent use of herbicides can be linked to a negative effect on surrounding ecosystems through a direct effect on pollinators, the effects on non-target organisms, and the effects of herbicide residues in the soil and water. Therefore, there is a continuous effort to minimize the use of herbicide applied by spraying. Unfortunately, for large Reynoutria stands the foliar spraying is the only effective management, and therefore we need to identify ways to limit the amount of used herbicide.
The effectiveness of management of invasive species depends largely on the level of invasion. Several studies have shown that the success of eradication depends on time, extent, abundance and regulation of the propagule pressure (
As Reynoutria is one of the most problematic species in Europe, there have been many projects devoted to developing efficient and sustainable control methods (
Distribution of Reynoutria can be mapped relatively easily by the methods of aerial photographs (
Based on the outlined context of invasion of Reynoutria and the possible management options, our study (i) assesses the distribution of Reynoutria in the Morávka riverside during long-term management, (ii) analyses the change of distribution according to the habitat, and (iii) discusses the optimal management strategy based on the long-term data.
The study area of 334.1 ha is located in northern Moravia between the municipalities of Frýdek-Místek and Vyšní Lhoty (the outermost municipality), covering the floodplain landscape in the vicinity of the Morávka River (river kilometre 1.1–11.5) in the elevation range 298–380 m (Figs
The Morávka River (Fig.
The study area (Fig.
The vegetation cover of the floodplain involves mostly floodplain forests and naturally similar habitats, including gravel bars and floodplain. In the more remote parts of the floodplain there are human settlements and arable land. The species composition of the floodplain forests roughly corresponds to the natural potential vegetation of bird cherry-ash woodland (Pruno-Fraxinetum), which in places on the valley slopes change to Carpathian sedge oak-hornbeam woodland (Carici pilosae-Carpinetum) or wet oak-beech woodland (Carici brizoidis-Quercetum) (
The first record of Reynoutria in the study area of the Morávka riverside comes from the 1940’s (
Invasive knotweed from genus Reynoutria (Fallopia) growing in the Morávka river basin includes Reynoutria japonica (native to Japan), Reynoutria sachalinensis (native to East Asia) and their hybrid Reynoutria × bohemica. They are perennial, up to 3 m tall, shrub-like herbs that often form connected, impenetrable stands. Within their primary range, Reynoutria grows naturally and secondarily in nutrient-rich environments, e.g., near rivers, on young lava flows in alpine environments, and in ruderal vegetation (
Reynoutria species reproduce mainly vegetatively within the introduced range. Nevertheless, there are reports of repeated crossing between the species, which is indicated by higher genetic diversity in the stands (
In the study area, the European project “Preservation of alluvial forest habitats in the Morávka river basin” (LIFE-Moravka 2007) was carried out in 2007–2010. The main objective of the project was to suppress the Reynoutria population in the study area. It combined mechanical and chemical treatment throughout the study area.
The control of Reynoutria was done with a 7–10% solution of the herbicide Roundup Biaktiv in years 2007 to 2010 (glyphosate-based herbicide). The herbicide was applied with a backpack sprayer predominantly in August and September. In locations with high Reynoutria coverage, Reynoutria was cut mechanically before herbicide application whereas regenerating plants were treated with a backpack sprayer. With regard to the elimination of environmental risks in the proximity of the Morávka reservoir, foliar spraying was replaced by injecting of herbicide directly into the stems of Reynoutria in this area; a 20–30% concentration was used. The application of herbicide was done once or twice each season depending on the success of the first treatment (
After the end of the LIFE project, which significantly reduced the surface area of the stands, different parts of the study area were treated locally, in different years, depending on financial resources and conservation needs. Most of the study area consists of nature reserves whose authorities (RCMSR and NCA) have continued with chemical treatment using a 4–7% solution of the Roundup Biaktiv herbicide applied by a backpack sprayer. The first application took place after GNSS mapping in 2013 over the entire area of all nature reserves (226.2 ha). In the Niva Morávky Natural Reserve and the Profil Morávky Natural Reserve (124.2 ha), further chemical spraying was carried out in 2014, 2017 and 2019–2023. In the Skalická Morávka National Natural Reserve, the application was carried out once a year for three years, in 2016–2018 on river kilometre 9.4–10.6 (treated area 46.0 ha), and in 2020–2022 on river kilometre 5.5–9.4 (treated area 60.0 ha). The area from the southern boundary of the Skalická Morávka National Natural Reserve to the Žermanice Reservoir inlet was repeatedly chemically treated by the Povodí Odry (Odra River Basin Authority).
Reynoutria is also found in the upper parts of the watercourse below the Morávka Reservoir and above it up to river kilometre 21.1. This poses a risk for the introduction and distribution of Reynoutria rhizomes and repeated further spread. At the same time, repeated irregular chemical control took place in these parts as well.
Data on the occurrence of Reynoutria was obtained using GNSS field mapping. For the purpose of our mapping, we used the GPS system. GPS mapping was conducted in the study area in 2007 prior to the start of management, in 2009 during management, and in 2013 prior to the start of local management. In 2015, 2018, and 2023, it continued during local management. The GPS mapping was done in early summer (June and July) before the application of herbicide. In 2007 and 2009, a TOPCON FC-100 PDA was used in combination with a Navilock BT-338 external GPS module. In 2013, 2015, 2018, a JUNO 3D device by Trimble with an integrated GPS antenna was used. In 2023, we used a Xiaomi Redmi 7 smartphone with an integrated GPS antenna. All measurement methods used were autonomous. The error in this type of measurement is in the order of units of metres (
Monitored attribute type | Monitored attribute category |
---|---|
Coverage (%) | 0.01–0.1; 0.11–1.0; 1.1–10.0; 10.1–50.0; 50.1–100 |
Moisture type | dry; normal; wet |
Vitality | low; average; high |
Vegetation cover type | forest; open stands; bare ground habitats |
The measurement was carried out in such a way that a mapper walked around the perimeter of each Reynoutria polycormon. During the mapping, a polygon edge was automatically recorded every second from the GPS in the ArcPad app. This created areas of different sizes and shapes. Reynoutria was mapped so that the mapped areas were homogeneous in terms of the defined parameters: Coverage, Vitality, Moisture type and Vegetation cover type (see Suppl. materials
During the mapping, we recorded the coverage percentage of Reynoutria according to selected coverage intervals, assessed Reynoutria vitality and habitat moisture according to selected criteria (Table
The moisture-type attribute was categorized according to relief, land cover, and vascular plant species representation. Areas with lowlands, oxbow lakes, pools, clay soils were mapped as wet habitats. Normal habitats were located on flat relief without frequent influence of flood waters, away from river channels and pools. Normal habitats were characterised by loose, organic soils, lacking wetland and xerophytic plant species, whereas mesophilic herbs were common. Dry habitats were mapped on elevated sites, mainly on gravel bars, accompanied by a dry coarse-grained substrate (see Suppl. material
Due to the high dynamics of changes in the relief and course of the channel in the Morávka floodplain, we vectorised the Morávka river in the years that most closely corresponded to each year of mapping based on archival aerial photographs and orthophotomaps.
Aerial photographs and land cover datasets were used as auxiliary data. The Corine Land Cover (CLC) database was used for the land cover data, the orthophoto Web Map Service (WMS) layer and Base topographic map of the Czech Republic at a 1:10 000 scale WMS by State Administration of Surveying and Cadastre in the Czech Republic was used for the aerial photographs.
The Orthophoto is a map service by State Administration of Surveying and Cadastre in OGC (Open Geospatial Consortium) WMS 1.3.0 (https://geoportal.cuzk.cz/(S(zwhj1uzsovk24saxpcdkjjfy))/Default.aspx?lng=EN&mode=TextMeta&side=wms.verejne&text=WMS.verejne.uvod&head_tab=sekce-03-gp&menu=311). The Orthophoto is derived by orthorectification from the aerial photographs product. The product has spatial resolution within 0.2 m. Data is available in JPEG with JGW (world file) in several coordinate systems: S-JTSK, ETRS89-TM33N a ETRS89-TM34N. The temporal resolution of the dataset is two years.
The base topographic map of the Czech Republic at a 1:10 000 scale (ZTM 10) is a map service provided by State Administration of Surveying and Cadastre in OGC WMS 1.3.0 (https://ags.cuzk.cz/arcgis1/services/ZTM/ZTM10/MapServer/WMSServer?). The ZTM 10 includes planimetry (settlements and individual objects, hydrology, communication networks, administrative and cadastral boundaries, boundaries of protected areas, height and planimetric control points, soil surface, vegetation), altimetry (terrain steps, contour lines) and lettering.
The CLC is an open dataset for land cover of European countries provided by the Copernicus Programme. Data is available for download from 1990, 2000, 2006, 2012, and 2018. Datasets are in the vector and raster format with 100 m Minimum Mapping Width (MMW) and the minimum mapping unit (MMU) is 25 ha. Data is distributed over 44 thematic classes. Datasets are downloadable at Copernicus website https://land.copernicus.eu/en/products/corine-land-cover.
Geodata was processed in ArcGIS and QGIS. It was then analysed in SPSS Statistics and Statgraphics software. From the geometric component of the Reynoutria polygons, we calculated their surface area. After we finished data processing, a script using the ModelBuilder tool in the ArcMap programme was created. The script successively created 19 buffer zones increasing in 20 metres up to a distance of 380 metres from the Morávka River. For each buffer zone, the cumulative surface area of the areas invaded by Reynoutria was calculated (see Table
Before the core tests the normality of the Reynoutria stand size data was tested in the Statgraphics programme using the Kolmogorov-Smirnov test. Normality was tested for each year under study. The normality of Reynoutria stand sizes for each year was not confirmed. In all years examined, the p-value was less than 0.001.
Furthermore, we carried out statistical testing of the significance of the difference between surface area sizes without Reynoutria in the studied years at regularly increasing distances from the Morávka River as part of spatial data analysis. Areas without Reynoutria were calculated from the difference between the total size of the buffer zone and the area with Reynoutria, always for a specific distance from Morávka. The change of size patterns of stands with Reynoutria over time was tested by Friedman test. This test was selected as the used variables were colinear and normality tests were not significant (
Since these were categorical variables, we calculated a Chi-square test of independence between the selected pairs of attributes. To perform the calculation well, we aggregated the attributes Area and Coverage. Aggregation was performed to meet the Chi-square test criterion that the smallest expected frequency had to be equal to or greater than 1. Also, the maximum 20% of the areas could have an expected frequency less than 5 (
To ascertain the effect of biotopes and type of vegetation on the pattern of change of extent of Reynoutria polygons over time, linear models (R. 4.3.1) were used. The extent was taken as dependent variable, levels of abundance were 0.05, 0.50, 5.00, 25.00, and 75.00. To analyse the effect of time we specifically analysed the significance of interactions with years.
The following numbers of Reynoutria-invaded areas were mapped in each year of GPS mapping: 2007, N = 160; 2009, N = 171; 2013, N = 149; 2015, N = 352; 2018, N = 530; 2023, N = 345. Analysis of data collected between 2007 and 2023 (Fig.
Area size of invaded areas of Reynoutria and their proportion in the study area by coverage intervals. The data in bold show the highest values of the area of Reynoutria in a given year.
Total area size and proportion of areas with Reynoutria in coverage intervals (ha) and (%) | ||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
2007 | 2009 | 2013 | 2015 | 2018 | 2023 | |||||||
Coverage (%) | ha | % | ha | % | ha | % | ha | % | ha | % | ha | % |
0.01–0.1 | – | – | 8.1 | 2.4 | 24.4 | 7.3 | 4.7 | 1.4 | 5.3 | 1.6 | 10.1 | 3.0 |
0.11–1.0 | – | – | 17.9 | 5.4 | 15.0 | 4.5 | 18.1 | 5.4 | 8.9 | 2.7 | 18.4 | 5.5 |
1.1–10.0 | 22.7 | 6.8 | 30.7 | 9.2 | 8.9 | 2.7 | 19.6 | 5.9 | 8.9 | 2.7 | 12.7 | 3.8 |
10.1–50.0 | 23.7 | 7.1 | 6.4 | 1.9 | – | – | 6.1 | 1.8 | 13.2 | 4.0 | 7.1 | 2.1 |
50.1–100.0 | 50.5 | 15.1 | 2.2 | 0.7 | – | – | 0.6 | 0.2 | 5.4 | 1.6 | 4.4 | 1.3 |
Invaded area (ha) | 96.9 | – | 65.3 | – | 48.2 | – | 49.1 | – | 41.8 | – |
52.6
|
– |
Invaded area (%) | 29.0 | 19.6 | 14.5 | 14.7 | 12.5 | 15.8 |
Development of the total area size invaded by Reynoutria in the study area between 2007–2023.
As a result of Reynoutria management, the structure and coverage of Reynoutria stands also changed, as shown in Fig.
In addition to the changes in Reynoutria coverage, the average area of each stand has also decreased with time elapsed since herbicide application (Figs
Coverage (%) | 2007 | 2009 | 2013 | 2015 | 2018 | 2023 |
---|---|---|---|---|---|---|
0.01–0.10 | – | 36 (21.1%) | 83 (55.7%) | 93 (26.4%) | 180 (34.0%) | 66 (19.1%) |
0.11–1.0 | – | 54 (31.5%) | 48 (32.2%) | 125 (35.5%) | 109 (20.6%) | 102 (29.6%) |
1.1–10.0 | 48 (30.0%) | 61 (35.7%) | 18 (12.1%) | 106 (30.1%) | 117 (22.1%) | 104 (30.1%) |
10.1–50.0 | 40 (25.0%) | 17 (9.9%) | – | 21 (6.0%) | 96 (18.1%) | 53 (15.4%) |
50.1–100.0 | 72 (45.0%) | 3 (1.8%) | – | 7 (2.0%) | 28 (5.3%) | 20 (5.8%) |
Total | 160 (100%) | 171 (100%) | 149 (100%) | 352 (100%) | 530 (100%) | 345 (100%) |
Development of the size of mapped stands invaded by Reynoutria. Outliers are represented by a circle and extreme outliers by an asterisk. The asterisk in the red square shows one area from 2007 of 8.1 ha which is outside the scale range.
During the mapping, the structure of vegetation type where Reynoutria occurred was also monitored in selected years (Table
However, testing of the effects of time, habitat and biotope did not reveal significant differences of changes of extent and abundance over different environments. There were no significant interactions between year, abundance, moisture type (F = 1.86, DF = 2,1536, n.s.), and vegetation cover type (F = 0.71, DF = 2,846, n.s.), which indicates that there are no differences in reaction to management in the studied habitat and vegetation types. Significant effect of year (F= 24.2, DF = 1,1537, p < 0.001) shows that the extent of Reynoutria sites changes. Additional comparisons are shown in Table
The results of GNSS mapping of Reynoutria stands from 2007–2015 were published using the web-based map application http://gisak.vsb.cz/knotweed/. This application allows comparison of the changes in the distribution/spread of Reynoutria stands with the recorded attributes (stand coverage, moisture, vitality, ID number) in each year using OpenStreetMap (Fig.
In the mapped years 2009, 2013, 2015, 2018 and 2023, the dependence between pairs of attributes was tested using Pearson’s Chi-square test of independence in a contingency table. The tests intended to statistically demonstrate the dependence between the categorical attributes were mapped (Table
P-value | 2009 | 2013 | 2015 | 2018 | 2023 |
---|---|---|---|---|---|
Area – Coverage | 0.289 | 0.229 | 0.960 | 0.003 | 0.002 |
Area – Moisture type | < 0.001 | 0.011 | 0.437 | 0.066 | 0.156 |
Area – Vitality | 0.698 | 0.708 | 0.696 | 0.046 | 0.556 |
Coverage – Moisture type | < 0.001 | 0.279 | 0.015 | < 0.001 | < 0.001 |
Coverage – Vitality | < 0.001 | < 0.001 | < 0.001 | < 0.001 | < 0.001 |
Vitality – Moisture type | 0.002 | 0.098 | 0.070 | < 0.001 | 0.026 |
For the Coverage – Vitality attribute pair, we demonstrated statistically significant dependence or relationship in all years under study. This dependence is logical. Areas with Reynoutria stands with high coverage also had high vitality and vice versa. For the Area – Moisture type pair we showed a dependence in 2009 and 2013. Dry habitats have only a local occurrence in the river floodplain and were therefore not frequently represented or occurred less frequently among large areas (0.08–8.10 ha). Normal habitats were more common among small areas (0.01–0.07 ha) in 2009 and 2013. Aggregate area size therefore depended on Moisture type in these years.
For the Coverage – Moisture type attribute pair, dependence was demonstrated in all years examined except for 2013. In these years, the aggregated Coverage depended on Moisture type. Areas with higher coverage of 1.1–100.0% were more likely to occur in the moist habitat type in these years. Conversely, areas with lower coverage of 0.01–1.00% occurred less frequently in the wet habitat type.
In the Vitality – Moisture type attributes we demonstrated a relationship in 2009, 2018 and 2023. The Vitality attribute was therefore dependent on the Moisture type habitat in which the Reynoutria was situated in those years. The wet habitat type had stands with high vitality. On the other hand, in the dry habitat type there were stands with lower vitality. The Area – Coverage attributes were only able to show a relationship between the two most recent years of measurement, i.e., in 2018 and 2023. This suggests that the more extensive the stands were, the higher the Reynoutria coverage was and vice versa. For the Area – Vitality attribute pair, a relationship was only demonstrated in 2018.
Using spatial analysis, we evaluated the distribution and size of Reynoutria stands as a function of distance from the river. For this purpose, we successively created buffer zones around the river with increments of 20 metres, i.e., 19 zones in total (Table
Cumulative area size of Reynoutria at regular distances from the Morávka River. The values below are in hectares (ha).
Year | 2007 | 2009 | 2013 | 2015 | 2018 | 2023 | |
---|---|---|---|---|---|---|---|
Extent of zones from the river | 0–20 | 16.47 | 11.71 | 7.78 | 6.25 | 6.61 | 10.36 |
0–40 | 30.87 | 22.34 | 16.20 | 13.07 | 13.78 | 18.86 | |
0–60 | 45.15 | 32.21 | 25.06 | 20.83 | 20.57 | 26.23 | |
0–80 | 58.24 | 40.91 | 32.49 | 28.34 | 26.23 | 32.21 | |
0–100 | 69.01 | 47.99 | 38.00 | 34.47 | 30.67 | 37.15 | |
0–120 | 77.27 | 53.83 | 42.00 | 39.22 | 33.83 | 40.59 | |
0–140 | 83.64 | 58.33 | 44.74 | 42.84 | 36.26 | 43.87 | |
0–160 | 87.94 | 61.44 | 46.18 | 45.30 | 37.42 | 46.20 | |
0–180 | 90.80 | 63.41 | 47.05 | 47.03 | 38.24 | 47.92 | |
0–200 | 92.66 | 64.48 | 47.59 | 48.01 | 38.90 | 49.17 | |
0–220 | 93.82 | 65.00 | 47.86 | 48.65 | 39.57 | 50.11 | |
0–240 | 94.42 | 65.22 | 48.08 | 48.84 | 40.24 | 50.90 | |
0–260 | 94.83 | 65.26 | 48.22 | 48.93 | 40.85 | 51.52 | |
0–280 | 95.51 | 65.26 | 48.24 | 49.04 | 41.38 | 52.08 | |
0–300 | 96.11 | 65.26 | 48.24 | 49.08 | 41.58 | 52.40 | |
0–320 | 96.49 | 65.28 | 48.24 | 49.08 | 41.73 | 52.60 | |
0–340 | 96.76 | 65.28 | 48.24 | 49.08 | 41.82 | 52.62 | |
0–360 | 96.85 | 65.28 | 48.24 | 49.08 | 41.82 | 52.62 | |
0–380 | 96.85 | 65.28 | 48.24 | 49.08 | 41.82 | 52.62 | |
Quartile (%) | 25 | 24.21 | 16.32 | 12.06 | 12.27 | 10.46 | 13.16 |
50 | 48.43 | 32.64 | 24.12 | 24.54 | 20.91 | 26.31 | |
75 | 72.64 | 48.96 | 36.18 | 36.80 | 31.37 | 39.47 |
Table
The goal of this paper was to describe and analyse the patterns of invasion of Reynoutria and, more importantly, the effectiveness of its management. The data covers 17 years of continuous management which provides a robust and unique overview of the invasion, reinvasion, and suppression dynamics. Given the large area and long timespan, our results can be appreciated by many stakeholders working on the control or suppression of Reynoutria. We hope that this paper will stimulate publishing more studies based on long-term efficiency of management of this important invasive species. Reynoutria is a problematic and persisting invasive species in most of Europe, North America, and Asia and therefore the species has been widely studied. Because of its negative impact on biodiversity as well as other effects, there are numerous studies focused on its regeneration, spread, and management (
Many studies focus on the methods of management of Reynoutria (see overview in
As knotweeds are widely recognized as problematic species and thus are widely managed, they become a suitable model system for various schemes of planning and prioritizing management. Apart from this, the three closely related Reynoutria species are also often studied due to their differences in their invasion potential and regeneration ability (
Our data shows that within a few years after the management of the area started, the extent of the Reynoutria stands sharply decreased and the large polycormons were split to small and less dense ones. Within the first five years of the management, the extent of Reynoutria decreased to 49.7% of initial values (96.9 ha) in 2013, and the size of the average stands (polycormons) decreased to 0.32 ha. Since Reynoutria is a species with a high negative impact on vegetation when growing in large stands (
Another factor in the increase in the total species area may also be the increased flood flows (cca 70 m3/s) reached during the 2020 floods. These flows cause overlaying of the river channel and its course, and the disappearance and creation of new gravel bars and islands. As a consequence, Reynoutria stands are disturbed and their rhizomes fragmented and further spread. These fragments serve Reynoutria to regenerate, as described above (e.g.,
Not only the size of the stands (polycormons) significantly changed, but also the coverage of Reynoutria rapidly decreased. At the time of the start of the chemical spraying, the study area was mainly Reynoutria stands with high coverage and the two categories of areas with the lowest coverage were not at all represented. This changed dramatically as a result of three years of systematic whole area chemical management. There was a significant reduction in areas in the case of higher coverage sites as shown in Fig.
The area size of most Reynoutria stands (except for in 2007) prior to the start of eradication was less than 1 ha throughout the management period. Nevertheless, we identified areas of several hectares in each of the years studied (Fig.
The mapping results indicated that there was a change in the total area of habitat covered with Reynoutria, which was a result of chemical treatment (Fig.
Such changes of invaded population structure are important for neighbouring species. In a study by
In spatial analysis we found (Table
All field measurements of the spatial extent of Reynoutria were made using autonomous GNSS measurements based on ZTM 10 and Orthophoto digital mapping, which were chosen due to the complexity of the field and forest cover where phase measurements would be difficult to implement. Similar GNSS mapping was also carried out by
The most important point in the whole Reynoutria management is to work in long-term scale. It is important to note that any management action must be followed by reasonable land use. It is useless and is only a waste of resources to make any random and single control actions (cutting, herbicide application) without a concept of future land use that will restrict Reynoutria reinvasion. Based on the results from other studies (e.g.,
Therefore, the key message resulting from our study concerns the structure of long-term management by herbicides. Based on the presented data and gained field experience, we propose the following procedure:
The proper application of herbicide is also crucial. Glyphosate dosage/application rates are discussed by
We are aware that herbicide application can be a conflicting issue for the public and also for some parts of nature protection. However, it is clear that the use of herbicides is needed for some highly resprouting species (
To compare the patterns of management effectivity, more long-term studies on management of the species and from other regions/types of habitats are needed. To fulfil such needs, detailed monitoring of the management actions and their results is recommended with specification of the management methods used, costs of treatment, etc. In this study, we were unable to properly cover the issue of costs and effort of management, as management was done by several bodies. Despite this, we believe that the presented study offers a valuable contribution to the proper management of Reynoutria species.
Our appreciation is extended to the editor and the reviewers whose comments contributed to the improvement of the manuscript.
The authors have declared that no competing interests exist.
No ethical statement was reported.
Jan Pergl and Irena Perglová were supported by the project DivLand – Centre for Landscape and Biodiversity from the Technology Agency of the Czech Republic (SS02030018), and a long-term research development project (RVO 67985939) from the Czech Academy of Sciences.
Conceptualization, Pavel Švec; Funding acquisition, Pavel Švec; Methodology, Pavel Švec and Jan Pergl; Resources, Pavel Švec and Jan Pergl; Mapping, Pavel Švec, Václav Fröhlich and Jakub Seidl; Analysis, Pavel Švec, Václav Fröhlich, Ivana Horáková, Jan Pergl and Jakub Seidl; Software, Pavel Švec, Václav Fröhlich, Jakub Seidl and Ivana Horáková; Supervision, Martin Ferko, Přemysl Štych, Irena Perglová, Kateřina Růžičková; Validation, Kateřina Růžičková and Josef Laštovička; Writing – original draft, Pavel Švec and Jan Pergl; Writing – review & editing, Pavel Švec, Jan Pergl, Josef Laštovička and Irena Perglová
Pavel Švec https://orcid.org/0000-0001-9789-292X
Jakub Seidl https://orcid.org/0000-0003-4326-7816
Martin Ferko https://orcid.org/0000-0002-7875-9506
Jan Pergl https://orcid.org/0000-0001-7486-8644
All of the data that support the findings of this study are available in the main text or Supplementary Information.
Example of mapped Reynoutria coverage by each mapped category
Data type: PNG
Explanation note: 1 – Coverage of less than 0.1%. 2, 3 – Coverage of 0.11–1.0%. 4 – Coverage of 1.1–10.0%. 5 – Coverage of 10.1–50.0%. 6 – Coverage of 50.1–100.0% – In this category of coverage, the area is almost impassable.
Example of the impact of chemical control on Reynoutria
Data type: PNG
Explanation note: 1, 2 – Chemically treated area one year after herbicide application (July 2008). The success rate of chemical control is high, Reynoutria regenerates sporadically after spraying. Overall coverage increases and new species with ruderal tendency appear. The photo foreground shows the invasive species Impatiens parviflora and Impatiens glandulifera. 3, 4, 5 – Example of various forms of malformation and necroses after chemical eradication of Reynoutria. The height of Reynoutria, including the leaf forms, is greatly altered, with the formation of various “deformed” forms.
Example of the mapped Moisture types
Data type: PNG
Explanation note: Habitat moisture was categorised by relief, soil cover, and vascular plant species representation. 1 – Areas with lowlands, oxbow lakes, pools, clay soils were mapped and classified as wet habitats or stands. 2 – Normal habitats were located on flat relief without frequent floodwater influence, away from river channels and pools. Normal habitats were characterized by loose, humic soils, lacking wetland and arid-loving plant species, with mesophilous herbs being common. 3 – Dry habitats were mapped on elevated sites, primarily on gravel bars, accompanied by dry coarse-grained substrate.
The Morávka River and its surroundings in the study area
Data type: PNG
Explanation note: 1 – The Morávka River represents a uniquely preserved Carpathian-type stream in the Czech Republic. Especially in the preserved locality Profil Morávky, there are unique pools with clear water. 2 – There are also rock thresholds and rapids. 3 – After the flood, the riverbed is “cleaned” of the vegetation and the position of the riverbed changes. The photo taken after the flood in 2010. 4 – Due to deep erosion, the riverbed is deepened about 10 m below the river floodplain in the lower part of the stream. This process is still ongoing. 5 – The middle part of the stream in the Vyšní Lhoty area differs from the lower part of the stream.