JWSS - Journal of Water and Soil Science

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The effect of nitrogen and phosphorous fertilization on range species production was studied using factor combination method as factorial with 3 blocks and 12 treatments. Nitrogen in 4 levels of 0،25،50 and 75 kg N/ha and phosphorus in 3 rates of 0،30 and 60 kg N/ha were used. Results indicated no significant difference between nitrogen rates in different growth forms of grass, bush and Eurotia ceratoides. Nitrogen in 75 kg/ha rates caused an increase of 40 and 106% in grass and Eurotia production, respectively. The maximum rate of production was seen in N50 with 100 percent increase compared to N0. Moreover, no significant difference in phosphor rates of leguminous and grass was observed. P 60 kg caused 500 and 56 % increase in leguminous and grass production, respectively.

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In order to determine the effect of climatic factors on distribution of Artemisia aucheri and Artemisia sieberi in Isfahan province, thirty nine most important climatic elements in ecological condition of these species were selected. Using a factor analysis method, the most important factors in distribution of these species were determined. These factors which cover 92.3% of the total variance of spatial variation of the species include rainfall, temperature and shining with 41.91, 40.18 and 10.23 percent, respectively. Four most important vegetative types of Artemisia aucheri and Artemisia sieberi in Isfahan province are as follows: 1-Artemisia aucheri and Astragalus,2- Artemisia sieberi,3-Artemisia sieberi as a dominant species, and 4-Artemisia sieberi as a subdominant species. Then the effects of climatic factors on distribution of these species and the average elevation of distribution of these species were determined. The effect of factor analysis on these types shows that rainfall and temperature are the most influential factors in spatial distribution of Artemisia aucheri and Artemisia sieberi in Isfahan province, respectively. In general, Artemisia sieberi has a higher extended tolerance range than Artemisia aucheri, and could be mentioned as a nearly universal species.

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The temporal and spatial vegetation dynamics is highly dependent on many different environmental and biophysical factors. Among these, climate is one of the most important factors that influence the growth and condition of vegetation. Of the abiotic factors affecting the geographic distribution of vegetation type, climate is probably the most important. Ecological research has traditionally aimed to generalize vegetation types that are assumed to be homogenous. Most of climatic classifications related to bioclimate are focused on limited climatic factors such as temperatue, precipitation and combination of them. As climate is a compound phenomena using limited factors cannot show the climate of a region, and as a result most climatic factors must be considered in bioclimatic classification. Therefore, a climatic study using various climatic factors could reveal the effective factors in distribution of vegetation. In order to determine bioclimatic zones in Chahar-Mahal & Bakhtiari province using multivariate statistical method, 71 climatic variables, which were more important in plant ecological conditions, were selected and evaluated by the factor analysis. The factor analysis revealed that the first three factors which explain %91.8 of total variance among the selected variables were temperature, precipitation, and radiation. According to results and using hierarchical cluster analysis in Ward’s method, bioclimatic classification in Chahar-Mahal province was carried out and 5 bioclimatic zones were found. In addition, Chahar-Mahal province was classified by 4 traditional climatic classification methods (Koppen, Gaussen, Emberger and De Martonne) and those classes were compared to climatic classes obtained by multivariate statistical method. The latter comparison was suggestive of the fact that multivariate statistical method provides a more appropriate classification in comparison to the traditional methods, specially because more dominant vegetation species could be defined for each of the newly described climatic classes. Furthermore, dominant species were determined for each climatic region.

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The geographical location of Isfahan province has led the province to be at risk of drought. One of the ways to mitigate drought is evaluation and monitoring of drought based on indices that can determine its intensity and permanence in each region. In this research, for drought and trend analysis standard precipitation index and Mann-Kendall test were used, respectively. Also, monthly precipitation time series of Isfahan province was applied to forecast drought from 1970 to 2009. For this purpose, Box and Jenkins modeling approach (1976) was used which has three main steps, namely model identification, parameter estimation, goodness of fit test or time independency and normal test of residual. The results showed that most of the stations in Isfahan province were faced with severe drought in the year 2000 and this situation was repeated one more time in 2008. Also, the results brought forth multiplicative models in all the stations. ARIMA (1,0,0) (0,1,1) showed the highest correlations between control and forecast data in Isfahan, Meime and Ardestan stations, and the model ARIMA (0,0,1) (0,1,1) displayed the highest correlation between control and forecasted data in Naein, Freydoonshahr, Khansar and Natanz. These models were selected as the best models through which the amount of precipitation was predicted till 2015. The trend of forecast data across Isfahan province showed that in most months the trend is not significant.