Investigating the Diversity and Flora of Weeds and the Distribution of Caspian Vetch (Vicia hyrcanica) in Comparison to other Weeds in Kermanshah Wheat and Chickpea Fields

Vicia hyrcanica grows in crop fields and field margins, pastures, meadows, orchards, vineyards, uncultivated areas, and other open areas in western parts of Iran. This is an annual, cool-season weed, which can reduce crop yield substantially. The population of this weedy species during last yeard has been increased and it is now considered as an invasive weed in the cuktivated areas of west of Iran. Hence, the aim of this study was to determine the diversity, density and dominance of Vicia hyrcanica compared with other weed species infesting wheat and chickpea fields in Kuzaran city in Kermanshah province, Iran. Furthermore, another aim of this experiment was to prepare the map of contaminated areas with V. hyrcanica as well as the endanger fields for being invaded by this weedy species.

 For conducting this study, a list of important areas for growing wheat, chickpea, rainfed and irrigated in Kuzran city was prepared, then the distribution of this weed was evaluated during growing season of 2020. 300 farms of both irrigated and rainfed wheat and chickpea farms of Kuzaran city, Kermanshah province, Iran were selected for sampling. The selected fields were monitored in such a way as to cover all important areas of wheat and chickpea production areas in Kuzran city. The selection of farms at a distance of approximately 3-5 km before the emergence of wheat spike gradually began in late April from different parts of the city and continued until late May. Sampling time in different parts of the province was from the beginning of stem emergence to the end of wheat clustering. In order to identify seedlings, they were labeled in the field and seedling identification keys were used to identify them. Parameters related to relative abundance, species richness, density and relative uniformity as well as diversity and dominance indices were measured to determine the importance of the mentioned weed species at the farm level. Through using GIS technique, the distribution map of yellow flower vetch in these areas was drawn.

 In addition to yellow vetch, another 21 species of geraminae weeds were observed. The highest average species density with 35.2 plants per square meter and the highest relative abundance of 36.3% is related to Vicia hyrcanica and two species Tragopogon major and Melilotus officinalis both with 0.27 and 0.26, respectively, had the lowest mean species density and relative abundance. In adition, the most common broadleaf species included Catchweed bedstraw (Galium tricornutum Dandy), yellow vetch (V. hyrcanica), wild mustard (Sinapis arvensis L.) and Makhobeli (Cephalaria syriaca (L.) Roemer & Schultes). Uniformity index in irrigated and rainfed wheat fields of Kuzran city of Kermanshah province shows that the differences between species were very close in terms of uniformity and ranged from 0.53 (Sinapis arvensis) to 95% (related to Silybum marianum).

 The highest prevalence index was related to species (V. hyrcanica) and all other weed species had a dominance index of less than 100. Based on the results obtained, among the species identified in wheat and chickpea fields of Kuzran city, five species with the highest prevalence of Simpson species were introduced as the species with the highest relative importance. Differences in species diversity and dominance indices were related to the amount and type of management operations on farms. Caspian vetch and Catchweed bedstraw were identified as the main invasive species. The predominance of these weeds, especially the Caspian vetch, as a weed, creates problems for farmers in the production of important crops, such as peas, because these crops are similar to vetch, and they separate it from the seeds of the crop. It is difficult and somewhat impossible by Bojari devices. Therefore, presence of this weed in these fields is critical and their spread should be prevented. In addition to seed contamination, endrils of vetchs allow V. hyrcanica to attach to crop plants, which results in hindering crop harvest and reducing its yield. Finally, totally, these attributes help to increase the infestation area by this weedy species and my explain its invasion status in the region.