Weed Flora Change in Irrigated Wheat Fields of Kermanshah after a Decade

A survey was carried out in irrigated wheat fields to assess the flora changes in the weed communities structures and flora change in Kermanshah province in 2002 and 2012. 85 fields from 11 counties were evaluated. Some population indices such as plant species frequency، density and species dominance were calculated for 2012 and were compared to the values for 2002. Results showed that in 2012، 112 weed species were distributed throughout wheat fields consisting of 18 grass weed species and 94 broadleaves. Convolvulus arvensis، Avena ludoviciana، Sinapis arvensis and Hordeum spontaneum were dominant weed species in 2002. In 2012، the respective species not only were found dominant but also showed 128. 3، 29. 14، 51. 46 and 36. 31 percent increase in dominance index، respectively. In contrast، the weed species Galium tricornutum، Glycyrrhizia glabra، and Phalaris brachystachys، respectively showed 10. 45، 52. 27، and 27. 16 percent decrease in dominance index compared to values calculated for 2002. Forty four new weed species were identified in 2012 that were not observed in 2002. In addition، our observations from the areas out of random quadrates sampling resulted in identifying forty eight new weed species. Shannon diversity index showed no difference from 2002 to 2012 for Kermanshah and Kangavar. Simpson dominance index indicated an increase in weed species evenness in Kermanshah county in 2012.