DO RAILWAYS CONTRIBUTE TO PLANT INVASION IN TURKEY?

SUMMARY Intensive trade, transport and travel activities across different geographic regions are prime source of introduction and spread of alien plant species. The role of roadsides in the long distance transport and spread of alien plants has been well explored whereas, railways are less considered in this context. Therefore, current survey was aimed to determine the role of railways as dispersal corridors for alien plants and weeds along the railways connecting Black Sea and Inner Anatolia regions of Turkey. Surveys were accomplished by randomly stopping at every 8-10 km on the railway tracks. Fifty-eight different plant species belonging to 22 plant families were identified during the study. Majority of the identified plant species (68.9%) were native to Turkey whereas, notable numbers of alien plants which have been established in the country (17.2%) were also recorded during the survey. Moreover, 62% of the identified native plants have been regarded as invasive in number of European countries. Weed Science Society of America have listed 72.4% of the identified plants as weeds and 79.3% are accepted as alien/invasive in different European countries. Maximum number of weeds belonged to Asteraceae family among the 22 identified families. Current surveys present the first report on the presence of common ragweed along railways in Turkey. The results indicate that railways are extensively serving as corridors for introduction and dispersal of weedy and alien plants across the regions in the country. It is therefore recommended that rapid surveys should be urgently conducted along the railways network of the country to record the presence of invasive alien plants.


INTRODUCTION
Weeds and invasive alien plants are one of the chief concerns in natural and agricultural ecosystems due to their undue negative impacts on ecosystem productivity and native biodiversity (Zimdahl, 2007;Ozaslan et al., 2016).Introduction of exotic plants to new regions, their subsequent spread and invasion is the second major threat to native biodiversity whereas, habitat fragmentation and disturbance to the established ecosystems stimulate these processes (Sharma and Raghubanshi, 2010;Kumar and Mathur, 2014).Biotic communities on regional and global scales are awfully affected by habitat fragmentation (Debinski and Holt, 2000;Fahrig, 2003).Habitat fragmentation produces small patches which isolate the habitat fragments which act as selective filters for the movement of species across these fragments (Wilcove et al., 1986;Lawton, 1999).Several studies concluded extensive development of infrastructure, especially transport networks as major contributors to plant invasion (Wilson et al., 2009).Highways and railways connect different regions resulting in disturbance of native habitats which accelerate habitat fragmentation (von der Lippe and Kowarik, 2008).Habitat degradation due to highways and railways negatively affect the integrity and survival of native communities (Hansen and Clevenger, 2005;Way and Eatough, 2006;Bangert and Huntly, 2010).
Disturbance to the ecosystems promote introduction and spread of alien plants as, invaders thrive best in disturbed habitats due to their opportunistic nature (Hansen and Clevenger, 2005).Several accidental introductions of alien plants in areas of dense transport system have been well acknowledged (Kowarik and von der Lippe, 2007;von der Lippe and Kowarik, 2008).Similarly, role of vehicles in the transfer of propagates (seeds etc.) of invasive plants have also been cited in some studies (von der Lippe and Kowarik, 2008).Besides, a recent study indicated that railways can better act as corridors for introduction of alien species than habitat disturbance and fragmentation (Bangert and Huntly, 2010).Railways can benefit the invasive plants in dual ways; either by introduction of propagates, or serving as ideal habitats for invasion.
Increased travel is an important source of introduction of exotic plant species of distant exotic origins (Korres et al., 2015a, b).Turkey shares border with many countries in two continents, and have recently increased trade and travel activities with several neghiboring countries.Therefore, transports by roads, railways and aerial roots in the country have been increased many folds than past.Black Sea is the most infested region of the country with exotic plants where a rapid survey study identified the prevalence of 81 alien species (Brundu et al., 2011).Black Sea highways are suspected as the source of introduction of many alien plants in the country as, it is a part of route which connects Turkey with Europe through Georgia (Onen, 2015).Large number of alien species observed in the region has also been discussed in the "Invasive Plants Catalogue of Turkey" (Onen, 2015).Although, several surveys have been accomplished in the country to identify the weedy and invasive plants prevailing in different ecosystems (Çaldıran et al., 2015;Önen et al., 2015a, b;Özaslan et al., 2015a, b;Ozaslan et al., 2016), railways have completely been ignored in this regard.Weed surveys are of greater importance in devising management practices for weedy and invasive plants prevailing in a particular region.Moreover, survey studies also help to identify the native and exotic weed flora present at regional and landscape scales (Korres et al., 2015a, b).Therefore, the current survey study was planned to identify the role of railways in the dispersal of weeds with special focus on alien plants along the railway tracks connecting Black Sea and inner Anatolia regions of the country.The results will identify the weed species distributed along the railways and also will be helpful in devising management strategies against weeds as well as invasive plants.

MATERIAL AND METHODS
The surveys were conducted along the railway tracks between Sivas and Samsun railway stations during September 2013.A total of 38 localities were randomly surveyed by stopping at every 8-10 km.The surveyed area is represented in Figure 1.(Davis, 1965(Davis, -1989)).The frequency of occurrence, general coverage, special coverage, general density and special density of the plants were individually calculated by following Uygur (1991) and Odum (1971).The equations for calculating these parameters are given as under; Life cycle of the plant, nativity and invasion status in the country as well as in other parts of Europe were searched on different plant databases.Weed Science Society of America (WSSA, 2016), European and Mediterranean Plant Protection Organization (EPPO, 2016), Delivering Alien Invasive Species Inventories in Europe (DAISIE, 2016) and Turkish Plant Data Service (TUBIVES, 2016) were the databases searched during the study.Life forms of the plants were also searched on the Turkish Plant Data Service (TUBIVES, 2016) and Flora of Turkey (Davis, 1965(Davis, -1989)).Plants were separated into different categories such as natives, aliens, alien and established, natives and invasive elsewhere and not identified.

RESULTS
Fifty-eight different plant species belonging to 22 plant families were identified during the study.Samsun-Tokat railway track hosted higher number of plant species (65.5% of the total observed weed species) compared with Tokat-Sivas track (Figure 2).Among different weedy and invasive plants identified during the survey, 17 species (29.3%) were commonly observed on both railway tracks (Figure 2).Alien species had the minimum contribution to the identified flora during the survey while, the native species were highest in number (Figure 5).Railways contained considerable number (17.2%) of alien species established in the country.The growth stages of 8.6% species do not allowed exact identification; therefore, their nativity remained anonymous.The frequencies of occurrence of the recorded plant species are represented in Table 1.Bromus sterilis (2.6%) and Cynodon dactylon (68.4%) were the least and most widespread native plants respectively, during the survey.Similarly, Paspalum distichum (2.6%) was the least recorded alien plant which has been established in the country whereas, Clematis vitalba was observed in majority of the sampling sites.Moreover, Ambrosia artemisiifolia was also observed on the railways first time during this survey (Table 1).
The observed plants were also searched for their weedy and invasive status on different plant database.Only one species (Ambrosia artemisiifolia) was listed on the invasive plants lists of EPPO (Figure 5).Weed Science Society of America regards 72.4% od the identified plants as weeds.Similarly, 79.3% of the total plants are regarded as alien/invasive plants in different European countries (Figure 6).
Native plants had the highest general coverage, special coverage, general density and special density followed by alien-established, anonymous and alien plants during the survey (Table 1).Notable coverage areas and densities were recorded for alien-established plants providing sufficient evidence that railways are playing extensive role for the spread of alien plants in the country.

DISCUSSION
Weed surveys allow ecologists and land managers to identify the spatial patterns of plant distribution, help in determining factors affecting weed distribution and assist in devising management practices.Surveys for alien species, particularly of plants have attracted increased attention for inventorying the alien species at regional and spatial scales (Rankins et al., 2005).The role of roadsides in long distance dispersal of weed species has been largely explored (Korres et al., 2015a, b;Ozaslan et al., 2016).However, railways have been ignored for surveying the alien plants.
The results of current survey indicate that railways have notable contribution to plant invasion in Turkey (Table 1, Figure 5).Majority of the identified species were listed as invaders in European plant information databases.The results also specify that transport of the plants from one region to the other can create severe weed infestation problems as the identified species have enormous reproductive and adaptive potentials under different climatic and environment gradients.Therefore, regular inspection and monitoring of the railways throughout the country is immediately needed.Railway tracks surveyed during the current study connect the densely populated regions of the country.Black Sea region have been accepted as the extensively invaded region of the country and many survey studies report infestations of several alien plant species (Burundu et al., 2011;Önen et al., 2013, 2014, 2015a, b).Moreover, majority of the alien plant species observed in the region have been regarded as invasive in the country (Onen, 2015).
Plant distribution along the roadsides and railway tracks decrease the visibility and cause severe roadside accidents (Cederlund, 2006), fire problems, and infra structure losses (Antuniassi et al., 2004).Infestation along the railways is more worst as it cause traction problems (wheel slipping) and make maintenance of tracks challenging (Antuniassi et al., 2004).Moreover, weeds may obscure rails and switches, making inspections of the railway lines difficult.Keeping in view the adverse effects of weeds on railways, mowing and herbicides have extensively been used to manage the weedy species in the country.Development of weed management approaches requires sufficient weed distribution data at spatial scales (Korres et al., 2015a, b).The current survey also gives valuable information in this regard.
Common ragweed (Ambrosia artmeisiifolia) -one of the important allergenic plant-has also been identified first time on railways during the survey.The plant produces the most feared pollens for hay fever suffers (Ozaslan et al., 2016).Widespread presence and invasion of the plant have been recorded along the roadsides and in agricultural fields throughout the country (Onen et al., 2014;Ozaslan et al., 2016).The results indicate that railways can contribute towards the spread of common ragweed across Black Sea and Inner Anatolia regions.Railways have probably transported the seeds of alien species from one place to the other through extensive movement.Moreover, the disturbance caused by railway maintenance might have played a significant role in the invasion of alien plants.The role of railways in propagule transport and disturbance has been reported in several studies (Tikka et al., 2001;Penone et al., 2012;Blanchet et al., 2015).
Differences in frequency of occurrence in the weed species observed during the study are due to the natural climate and landscape variations.Climatic conditions of the area might be most suitable for the frequently faced weeds compared with those of less frequent weed species (Zimdahl, 2007).The variations among the weed species are thought to be the result of the differential adaptive potential to specific soil and climatic conditions prevailing in a particular area.The identified plants during the surveys were distributed alongside and between the railways (Figure 7).
Distribution pattern of weeds indicates that density and coverage area of the weeds can increase with time.The increased densities and coverage of the weed species is suspected to severely interfere with maintenance and other operations at the railway tracks surveyed during the current study.Moreover, presence of invasive plants and extensive invasion potential of these plants can further aggravate the situation.
Figure 7. Distribution of some important plant species observed on the railways during survey CONCLUSION It is concluded that railways are serving as dispersal corridors for plant invasion in the country.Although current survey was conducted on small portion of the railways network of the country, presence of sufficient number of alien plants suspects that the railways might be playing a major role in the introduction and spread of alien species on regional scales throughout the country.It is therefore recommended that rapid surveys of railways to recognize the current status of plant invasion throughout the country is instantly needed.Moreover, environment and eco-friendly management strategies should be developed to eradicate the existing invasive plants along these railway tracks to avoid heavy losses in the future.

Figure 1 .
Figure 1.The map of surveyed site

Figure 2 .
Figure 2. Distribution of different weedy and alien plant species observed during survey on surveyed railway tracks

Figure 3 .
Figure 3. Distribution (%) of the identified plant species in different plant families

Figure 4 .
Figure 4. Percentage of the plants recorded during the survey according to their life cycle

Figure 5 .
Figure 5. Different categories of weedy and invasive plant species in total floristic diversity of the surveyed region according to their origin and invasiveness

Figure 6 .
Figure 6.Classification of the identified plant species according to their global importance based on different monitoring and information database for plants