drought is universal phenomenon that can occur everywhere and can cause harmful impacts on human beings and natural ecosystems. thus, it is very important to study drought character ristics part of for water resources management. in this study, the standardized precipitation index (spi) is used for drought frequency analysis in isfahan province. after collecting the precipitation data in the pr...

in natural ecosystems, biological relationships have serious effects on system stability. allelopathic is negative or positive effect of a plant on other plant growth. today this word is used for rangelands, same as agricultural areas. because of good herbage production, medicago is most common plant in agricultural rotations and rangelands. therefore investigation of its allelopathic qualities...