Preparation of distribution maps and biodiversity assessment of weeds in canola agroecosystems using geographic information system (GIS) (Case study of Sorkhankalateh region, Gorgan County)

Awareness of the existence of specific weeds in an area can be better decided and planned about their control methods. Otherwise, applying different control methods will not have the desired effect. In this study, in order to identify and prepare maps of weed distribution in canola fields of Sorkhankalateh region of Gorgan county, 50 fields were selected and sampled based on W pattern in two stages. Then, using current formulas, frequency, relative frequency, species uniformity and biodiversity indices were calculated. We were recorded the geographical coordinates and altitude of the sampling location by a GPS, Garmin touch model for each field. The obtained information was processed using Arc GIS software (var. 10.3) and the distribution maps of all weeds in canola fields were prepared. The results showed that 41 weed species (20 species in the pre-spraying stage and 21 species in the post-spraying stage) from 14 plant families were present in surveyed fields of Sorkhankalateh region, which Poaceae, Asteraceae, Fabaceae, Brassicaceae and Polygonaceae were the most important plant family. In the pre-spraying stage, the share of annual, perennial and biennial species was 75, 15 and 10%, and in the post-spraying stage, their share was as 66.66, 23.80 and 9.52, respectively. In terms of growth form, in the pre- and post-spraying stages, 8 and 76.19% species were belonged to dicotyledonous and 20 and 23.80% were as monocotyledonous, respectively. According to the results of biodiversity indices, weeds in the post-spraying stage had more diversity than the pre-spraying stage. Also, the results related to weed distribution maps showed that most of the dominant weeds were distributed in the Eastern and southern parts of the studied region.