Investigating the role of environmental factors on vegetative properties of Rheum ribes L.

Understanding the behavior of plants in relation to ecological factors provides basic information in order to improve and properly use rangeland. Also, determining distribution area of species and studying the characteristics of their habitat helps to choose the right place for their establishment. Rheum species is one of the rangeland species which, in addition to having important medicinal properties, is valuable for soil protection in dry and semi-arid rangeland. Considering the decrease in the density of this species in natural habitats during recent decades, knowing the characteristics of the habitat can be an effective help in the improvement and development of Rheum. Therefore, in this research, the effect of environmental factors on the vegetative characteristics of rhubarb species in three different habitats is investigated.

In this research, the habitat characteristics in three habitats of Chubak, Targh and Karkaz in the Kouhsorkh region located in Kashmar city and the relationship of ecological factors with characteristics of Rheum ribes L. including excluded base weight, stem weight without pods, length of stems of a plant, and number of stems in each base have been investigated. The ecological factors included soil factors such as EC, pH, N, P, K, organic matter, clay, silt, sand and physiographic factors include slope, aspect and altitude. in each the studied habitat, 10 samples of Rheum ribes were collected. In the first stage, the weight of each harvested stem was measured and then the weight of stems without pods was determined. Also, the number of stems in each sample was counted and the length of each stem was measured separately. Finally, the matrix of environmental conditions and vegetative characteristics of Rheum ribes was analyzed using redundancy analysis (RDA).Method

The findings of the research showed that the characteristics of the soil in Chubak, Targh and Karkaz sites are different and in the same site it is different in different soil depths. Among the physiographic factors, the altitude has the greatest role on the characteristics of the Rheum ribes. The altitude has a positive and strong relationship at a significant level of 5 percent with the length and number of Rheum ribes stems. So that with the increase in altitude, the length of their stem also increases. Among the soil characteristics, the percentage of sand, silt, P, K and lime percentage are the most important factors affecting the characteristics of Rheum ribes. The percentage of sand has a srtrong correlation with the weight of the Rheum stem, and with the increase of the percentage of sand, the weight of the stem increases. EC parameters and silt percentage have a negative relationship with Rheum ribes characteristics. So that with the increase of these parameters in the soil, the number and length of stems as well as their weight decreases.

The results of this study showed that Rheum ribes in Chubak site has the highest amount of growth characteristics, therefore Chubak region has provided more suitable conditions for growth of this species than the other regions. In this site, the samples of Rheum ribes have the highest number of stems and the highest average weight of the stems at 1316 gr. Therefore, this site can be introduced as the best growing area for Rheum ribes. Also, in terms of environmental parameters affecting the growth characteristics of Rheum ribes, among the topographic factors, altitude, among soil properties, the percentage of sand, silt, phosphorus, potassium and lime are the most important factors affecting the characteristics of Rheum ribes.