Evaluation of species, functional and structural diversity of weeds in wheat fields of Northern, Southern and Razavi Khorasan provinces

To study weed species diversity and community structure in wheat fields of Khorasan province, a four-year field trial was conducted from 2003-2006 in Khorasan province, Iran. during jointing stage to heading stage of wheat. Density, frequency and homogeneity of weed species in 5-10 randomly dropped 0.5×0.5 quadrates in 259 fields of 21 cities were determined. Data were analyzed by principal component analysis and clustered by hierarchical complete linkage method. The results showed that weeds of wheat fields were belong to 26 families and 120 species. The majority of weed species were of Asteraceae (20 species) and Poaceae (25 species) amongst dicotyledonous and monocotyledonous, respectively. Nishabour and Nehbandan had the most and the least diversity by 52 and 4 species respectively. Mashhad and Quochan showed the highest similarity index (70%) for weed diversity. Esfarayen had the highest shanon-weiner (2.93) and simpson (1) indices between the cities. however, Nehbandan had the lowest shanon-weiner (0.57) and simpson (0.71) indices. Biplot of the first two principal components (covered 61.4%, and 24.8% of variances, respectively) showed that weed homogeneity and frequency had more correlation with each other than weed density. By considering 75% similarity, cities were grouped in two clusters for weed density, homogeneity and frequency in wheat fields. Nehbandan was located in one cluster and the rest of the cities were placed in another. Nehbandan had low weed density compare to the other cities because of the warm and dry climatic conditions.