Quantifying the effects of altitude and soil texture on weed species distribution in wheat fields of Tabriz, Iran.
Correlations between weed species presence with altitude and soil texture data were investigated in 42 wheat (Triticum aestivum L.) fields of Tabriz county (northwest of Iran) in spring 2014. Canonical correspondence analysis (CCA) was used to find relationships between presence and absence of weeds in wheat fields with altitude data received by GPS and soil texture (sand, silt, ans clay) data taken from soil analysis of each field. In this research, 97 weed species were observed. CCA showed that altitude and soil texture can effect on weeds distribution in wheat fields. The first two CCA axes explained 76.7% of the variation in weed species distribution. The first axis had positive correlation with altitude (0.97%) and secondary axis had positive correlation with sand content of the soils (0.84%). Silt and clay vectors were located in opposite of sand vector. Altitude of the fields had highest effect in weeds distribution. Maximum richness was observed in low altitudes. By increasing of field's altitude, species diversity was decreased. Convolvulus arvensis, Acroptilon repens, and Chenopodium album that were observed in the center of CCA biplot, as a dominant and noxious weeds with wide ecological needs were founded in wheat fields with different soil texture and altitude (1320 until 1960 m asl).