A comparison of vegetative climate of Artemisia sieberi Besser and Artemisia aucheri Boiss in Iran

The relationship between plant species and climatic factors has always been a fundamental issue in plant ecology, and the use of multivariate statistical methods can be effective in revealing the relationship between climatic factors and plant species distribution. Therefore, in this study, climatic factors affecting the distribution of Artemisia sieberi and Artemisia aucheri, widely distributed in Iran, were investigated. For this purpose, 117 climatic factors were used, and to reduce the number of factors and determine the most important effective ones, a factor analysis was used by principal component analysis. The results showed that six factors including heating temperature, spring and summer precipitation, wind, autumn–winter precipitation, and dusty and cloudiness days explained 37.32%, 22.54%, 7.18%, 6.6%, 4.22%, and 4.15% of data variation, respectively. Together these seven factors account for 82% of data variation. The autumn–winter precipitation and heating temperature had the greatest impact on the presence of Artemisia sieberi and Artemisia aucheri, respectively, so that the autumn–winter precipitation was negative in areas where Ar.sieberi is observed. The heating temperature factor is negative in areas where Ar.aucheri is present, while it is positive in areas lacking Ar.aucheri. The study of the effect of environmental factors on Artemisia species distribution is very important in the planning and management of natural resources, and Artemisia is one of the most important plants in the country’s rangelands; therefore, the results of this research can be used for practical planning, management, and reclamation of these rangelands.


Introduction
Iranian rangelands with an area of 90 million hectares cover the widest area of the country (about 54%), more than 70% of which are located in arid and semi-arid regions. The general land use of these lands in the country is rangeland, and overgrazing in these regions has often led to changes in the quantity and quality of vegetation and soil, increasing barren lands, and desertification expansion (Azarnivand et al. 2009). Proper management and exploitation of rangelands require identifying the characteristics of the key species and determining the factors affecting their distribution (Azarnivand et al. 2003).
A large part of Iran, especially mountainous areas, is covered by shrubs, and areas with this type of vegetation are among the important rangeland (Mozaffarian 1989). Artemisia L. is the largest genus of the Anthemideae tribe and one of the largest genera in the Asteraceae family. Globally, the number of species of this genus is estimated between 200 and 450 species (Jalili 2015). In Iran, this genus has 34 known species, which is one of the most significant plant species in the flora of Iran in terms of distribution. Different species of this genus in Iran have been distributed from the lowest points of the Caspian Sea to the altitudes of 4000 m above sea level. Artemisia is a plant of the Asteraceae family that has aromatic leaves and flowers and medicinal properties. It is a plant whose stems are woody, surrounded by small leaves covered with white hairs. Its height varies from one span to one or one and a half meters in different species. Some species are spread out on the ground, and some are tall.
Its flowers are usually fragrant, and its taste is bitter. This plant grows both in mountainous areas and in the desert (Mozaffarian 1989) (Fig. 1).
In many areas, some species, including Artemisia sieberi and Artemisia aucheri, are considered the most important forage plants of rangelands. In addition to the forage value, industrial and pharmaceutical applications of different species have caused them to receive special attention (Rashtian and Karimian 2014).
According to Azarnivand et al. (2003) and Jafari et al. (2003), Artemisia sieberi is considered the most important species of this genus in Iran because it is the dominant vegetation cover of the Irano-Turanian region and steppe regions in Iran. This species is highly resistant to harsh environmental conditions due to its prominent features and therefore plays an important role in the stability and survival of vegetation. Also, Artemisia aucheri Boiss is very valuable in arid and semi-arid regions in terms of environmental protection, especially prevention of soil erosion and providing forage for livestock and wildlife (Mozaffarian 1989). Akbarpouryasaghi (1995) studied the ecological characteristics of A. aucheri in the Gorgan and Dasht region and concluded that the minimum altitude of the habitat of this species was 900 m in the Khosh Yilagh region and its maximum altitude was 2700 m in the Chaharbagh region. The highest density of this species was in the altitude range of 2000 m. Azarnivand et al. (2003) investigated the effect of soil properties and altitude changes on the distribution of A. sieberi and A. aucheri in Vardavar, Garmsar, and Semnan rangelands, and after studying vegetation, soil, and topography data from different habitats, they found that organic matter, soil nitrogen, and gypsum, and altitude were the most important factors influencing the distribution of these two species in the study areas.
Climate is a general condition of the prevailing weather conditions of a particular place based on long-term statistics (Bailey 1991). There are different methods for climate zoning, most of which are based on temperature and rainfall, but sometimes zoning is based on important non-climatic factors such as vegetation. Vegetation plays an important role in climatic zoning. In fact, it can be used as a set of different climatic and topographic patterns; therefore, it is possible to use the adaptation of vegetation and climate maps to identify bioclimatic zones (Chamberlain and Matthews 1970). In recent years, valuable studies have been conducted on the vegetative climate and zoning, which can be referred to the studies of Khatibi et al. (2019), Khatibi et al. (2016), Saboohi and Barani (2016), Khodagholi et al. (2015), Saboohi and Khodagholi (2013), Pakzad et al. (2013), Fatemi et al. (2012, Lashani et al. (2011), andKhodagholi et al. (2007). Khatibi et al. (2019) investigate the bioclimatic classification of Southeast Iran. Cluster analysis Ward's method divided the study area into 7 bioclimatic zones. The comparison of the obtained results with the results of four common methods of climate classification (Koppen's, Gaussen's, Emberger's, and de Martonne's methods) suggested the high ability of multivariate statistical methods to discriminate between bioclimatic zones. In a study conducted by Saboohi and Barani (2016), the cooling-humidity temperature, rain-thunder, cloudiness, and wind were reported as the factors affecting the distribution of Astragalus gossypinus in Isfahan province, respectively, accounting for 39.05%, 32.77%, 11.44%, and 8.63% (totally 91.88%) of variation in initial variables of Isfahan's vegetative climate. Khodagholi et al. (2015) studied the climatic characteristics of Quercus brantii in Chaharmahal and Bakhtiari province. The results showed that precipitation, heating temperature, and wind, with 28.79%, 20.13%, and 4.71%, respectively, were the three factors affecting the distribution of this species. For climatic zoning of Sistan and Baluchestan province, Salighe et al. (2008) used 20 climatic variables, and with the methods of factor analysis and climatic clustering of the province concluded that the climate of the province is made up of five factors including rainfall, temperature, radiation, wind, and thunder. Globally, Pineda-Martinez  (2007) zoned the bioclimatic regions of central and northeastern Mexico using factor analysis. Using longterm climate data, Zhou et al. (2009) divided the East Murombej Irrigation Area (MIA) into two classifications via factor analysis and clustering method. Yunus (2011) used factor analysis and clustering method for Malaysian bioclimatic classification, and the results showed a very good effect of these methods on this classification.
Since Artemisia rangelands are affected by destructive human activities and livestock grazing, they are among the ecosystems that need to be conserved. Therefore, the first step to prevent degradation is to identify vegetation and the mentioned plant communities and also the affecting factors.
Using this information, proper management methods for maintaining and improving these important rangelands of the country can be reviewed, and then the right decisions can be made. So the authors aimed to investigate the climatic characteristics of A. sieberi and A. aucheri.

The study area
Iran with an area of 1,648,000 square kilometers is located between latitudes 25° 3′ and 39° 47′ N and longitudes 44° 5′ and 63° 18′ E in Southwest Asia (Raziei et al., 2005). Therefore, in terms of latitude, its southern and northern parts are located in the tropics and subtropical regions, respectively. Iran has different climates due to the 15-degree difference in latitude between southernmost and northernmost points and also owing to the topography and elevations.
Regardless of these two factors, air masses colliding with each other from different lands on the plateau of Iran are considered as important determinants of Iran's climate. Iran's proximity to the Oman Sea and the Persian Gulf on the one hand and the influence of the Mediterranean Sea on the other, as well as the arid deserts of Saudi Arabia and Africa and the Great Siberian Plain in the northeast, have a profound effect on the type of air masses entering Iran (Alizadeh et al. 2012).
As a result, Iran has special characteristics geographically and possesses a very variable climate. Iran is a relatively high land so that its average altitude is more than 1000 m above sea level (Faraji 2005).
The average annual precipitation of the whole country is about 252 mm, and the maximum amount in the Caspian Sea and the sloping areas of the Alborz and Zagros mountains is 1800 and 400 mm, respectively. Moving towards the interior areas in the center and east, depending on the location, the amount of precipitation even reaches less than 100 mm per year, depending on the location (Alizadeh et al. 2012).

Materials and methods
The totality of the climate of each place is achieved through the use of all climatic elements. Therefore, the data of 117 climatic variables in 164 synoptic meteorological stations of the country (Fig. 2) were selected in monthly and annual intervals (Table 1).
It seems that these climatic elements have been effective in the climatic systematization and formation of the region, and directly and indirectly affect the growth of Ar. sieberi and Ar. aucheri in a way that can reflect the acclimation of this species in its habitat. Then, a matrix of 164 × 117 (stations on rows and variables on columns) was formed. The kriging geostatistical method was used to convert station point data to spatial data. The kriging estimator is one of the most important unbiased linear estimators because, firstly, it is without systematic error (Davis 1986) and, secondly, its estimation variance is minimal; therefore, the Kriging method was used in this study. This feature can increase the matching of the maps extracted from factor analysis and vegetation areas of these species in studying the plant species of natural areas. The point data matrix was converted to a spatial data matrix with dimensions of 1267 × 1167 using Surfer Ver14 software during the kriging interpolation process. This matrix covered the whole of Iran and was used as the input of principal component analysis. The principal component analysis, with the Varimax rotation, was used to reduce the number of factors and study the acclimation of Ar. sieberi and Ar. aucheri. The factor load matrix and the factor score matrix were obtained using principal component analysis. The factor load matrix obtained from the principal component analysis on climatic variables determined the effects of each component on them, and the factor score matrix was used to map the factors in Surfer software. Then, the vegetation type map of Ar. sieberi and Ar. aucheri was prepared on a scale of 1:250,000 by field observations and recording the species points using GPS and GIS software. To record the points by GPS, the pixel size of 36 × 36 square kilometers was used, so that the range of each pixel was determined and the coordinates of 40 points containing these species were taken by GPS. The accuracy of the vegetation map was confirmed by the Research Institute of Forests and Rangelands (Research Institute of Forests and Rangelands 2017). Then, the map of factors was adapted to the vegetation map, and the mean factors extracted from factor analysis in the distribution areas of different types of these species were determined.

Results
Applying a factor analysis using the principal component method and with varimax rotation showed that more than 82% of the data variance can be explained by seven factors.
The contribution of these factors from the first to the sixth was 37.32%, 22.54%, 7.18%, 6.6%, 4.22%, and 4.15%, respectively. The contribution of the Eigen variance of the seventh factor was less than 1. In fact, its value was less than the value of the original variables, so it was removed from later analyzes.
Therefore, it can be said that the overall climate of the study area is affected by six factors. Table 2 shows the degree of importance of each of these factors.
Since the purpose of factor analysis is to reduce the number of variables and convert it into several new factors, so after calculating the factor load, it was determined that a set of climatic elements including mean minimum temperature (Jan, Feb, Mar, Oct, Nov, Dec, annual), days with a minimum temperature of 4 °C and lower (Jan, Feb, Dec,  annual), number of frost day (Jan, Feb, Dec, and annual), absolute minimum temperature (annual), mean maximum temperature (Mar, April, May, Jun, Jul, Aug, Sep, Oct, and annual), absolute minimum temperature (annual), and mean temperature (Jan, Feb, Mar, Apr, May, Jun, Jul, Sep, Oct, Nov, Dec, and annual) constituted the first factor. Moreover, since temperature factors with a positive correlation were in this group, the first factor can be called the heating temperature factor.
The second factor was the spring and summer precipitation because the factor loads of a set of climatic variables including relative humidity (Mar, Apr, May, Jun, Sep, Oct, and annual), maximum relative humidity (Mar, Apr, May, Jun, Sep, Oct, and annual), minimum relative humidity (Mar, Apr, Jun, Sep, Oct, and annual), amount of precipitation (May, Jun, Jul, Aug, Sep, Oct), spring precipitation, and summer precipitation had the most weight on these factors.   The third factor includes the average wind speed (January, February, March, April, May, June, July, August, September, October, November, December, annual) with a positive correlation, which was named the wind factor.
The fourth factor was introduced as the autumn-winter precipitation factor, because the factor loads of the total climatic elements of precipitation (January, February, March, April, May, November, December, and annual), winter precipitation, and autumn precipitation had the highest weight.
The fifth factor was named dusty days because the dustyday element (April, May, June, July, August, September, and annual) is in this group with a positive correlation.
The sixth factor includes the number of cloudy days (January, February, March, April, December, and annual) and sunny hours (March, April, May, June, July, August, September, October, and annual). This factor was named cloudiness since the cloudy days and the sunny hours are in this group with a positive and negative correlation, respectively (Table 3). Figure 3 shows the spatial variations of the heating temperature factor. As is clear, the lowest and highest value of this factor is − 1.6 and 2, which is observed in the northwestern region and southern regions of Bandar Abbas, respectively. As shown in this figure, moving from the western to southern regions, the amount of heating temperature increases and reaches the maximum value of this factor in the southern region, especially around Bandar Abbas. The presence of heights (Fig. 4) in the western regions of Iran reduces the temperature in these regions; however, the southern regions of Iran have the lowest altitude, and we can see the highest temperature.
The lowest score of spring and summer precipitation was − 1, related to the central parts to the southeast, and the highest value is equal to 3.2, which is in the northern part of the country. Therefore, the northern regions had more spring and summer precipitation and relative humidity, while the least amount of spring and summer humidity and precipitation was observed in the central and southeastern parts of the province (Fig. 5). Figure 6 shows the spatial variation of the third factor, wind, in the study area. The lowest score of this factor was − 1.4 in all of Iran, except the eastern and southeastern regions, and the highest value was equal to 2.2, observed in all of Iran in a scattered manner. Figure 7 shows the spatial var iation of the autumn-winter precipitation. The lowest value of this factor was − 1.5, observed in the northwest corner, and the highest value was equal to 9 in the eastern part near Shahrekord.
The fifth factor is called dusty days, the highest value of which was observed near Zabol with a score of 9, and the lowest value was near Kerman and Yazd (Fig. 8). The lowest score of cloudiness factor was − 1.8, related to the southern part of the country, and the highest value is 2.2, observed in the northern part of the country (Fig. 9).

Climatic characteristics of Artemisia sieberi and Artemisia aucheri
To determine the distribution of Artemisia sieberi and Artemisia aucheri, the habitats of these two species were determined using the vegetation map prepared by the Research Institute of Forests and Rangelands and field visits (Fig. 10). Then, the vegetation map was digitized, and to investigate the effect of climatic elements on the distribution of these two species, the factor score matrix was used. The vegetation map (Fig. 10) was adjusted with the map of variables and factor scores; the scores of each cell with these species were determined.
According to the extracted scores, the average scores of the six factors were determined and the results are listed in Table 4.

Habitats of Artemisia sieberi
The habitat area of this species in Iran is 345,988.95 square kilometers (20.99%), and this species is observed in all regions except the western half of the country.  Table 4 shows the factor scores of the seven main factors in the distribution range of these species. The scores of heating temperature, spring and summer precipitation, wind, autumn-winter precipitation, and dusty and cloudy days in these areas were calculated to be − 0.21, − 0.19, 0.33, − 0.41, − 0.4, and 0.01, respectively.
Some climatic characteristics of Artemisia sieberi habitats are the average annual precipitation of 158.66 mm, the average annual temperature of 17.71 °C, the average number of frost time of 56.50 days, the average wind speed of 5.46 knots (Table 5), and the average altitude about 1504 m.

Habitats of Artemisia aucheri
The habitat area of Artemisia aucheri is about 145,679.55 km 2 , which occupies about 8.83% of the country's area. Table 4 shows the average factor scores for the areas where Artemisia aucheri is a companion species. The scores of heating temperature, spring and summer precipitation, wind, autumn-winter precipitation, and dusty and cloudy days in these areas were calculated to be − 0.68, 0.38, 0.003, − 0.12, − 0.18, and 0.02, respectively. Some climatic characteristics of these areas are the average annual precipitation of 255 mm, the average annual temperature of 15.27 °C, the average number of  (Table 5), and the average altitiude of 1966 m.

Discussion
The type of climate is one of the most influential factors in the life of a region; thus, the distribution of plants and animals is closely related to the climatic conditions of each region. Therefore, knowing the type of climate of a region and its related dominant elements can help planners to gain a correct understanding of the climatic conditions of the region to carry out macro projects (Shirani et al. 2009).
In this study, the habitats of two important species, distributed widely in the rangelands of Iran, were selected. Therefore, 117 climatic variables, which were more important in the growth of Artemisia aucheri and Artemisia sieberi, were assessed and categorized into six factors.
These six factors accounted for about 82% of the data variance, and in order of importance were heating temperature (37.32%), spring and summer precipitation (22.54%), wind (7.18%), autumn-winter precipitation (6.61%), dusty days (4.22%), and cloudiness days (4.15%), respectively. In many studies conducted by Lashani et al. (2011), Khodagholi et al. (2007, Yunus (2011), Pineda-Martinez et al. (2007, and Hossel et al. (2003), temperature, precipitation, and wind were the most important climatic factors. Hessel and et al. (2003) showed that precipitation, temperature, wind speed, evaporation potential, and sunshine hours accounted for about 97% of the variance of the initial variables and separated the different regions of Ireland and Britain. Differences in other influential variables, except precipitation and temperature, can be due to several reasons, such as the number and type of input variables and the time intervals that can affect the amount of variance of the data.
Comparison of factor scores in Artemisia sieberi and Artemisia aucheri habitats showed that although the heating temperature factor was negative in both habitats, Artemisia sieberi habitats acquired a higher score for temperature as compared with Artemisia aucheri. Actually, Artemisia sieberi is distributed in warmer habitats. Attention to the average height (altitude) and annual temperature of these two habitats confirms this view, so that the average height of Artemisia sieberi habitat is 1503 m, while it is equivalent to 1966 m for Artemisia aucheri. Also, the average temperature in the habitats of Artemisia sieberi is equal to 17.71 °C, and it decreases to about 15.5 °C in the habitats of Artemisia aucheri.
For the second factor (summer spring precipitation), the difference between the two habitats is quite noticeable; while the habitat score of Artemisia sieberi is negative, it is positive for Artemisia aucheri, which indicates that Artemisia aucheri needs more moisture than Artemisia sieberi.
The score of the third factor in Artemisia sieberi habitats is higher than that of Artemisia aucheri habitats. It seems that Artemisia sieberi habitats are located in lowland areas with higher temperatures, which may be due to the fact that Artemisia sieberi habitats are formed in the lowlands and along the central desert and other scattered deserts in central Iran. Besides, the significant difference between the daily and night temperature, as well as the absence of trees and low natural vegetation cover, has provided the conditions for the wind to blow.
Considering that this research was conducted in Iran and especially in the northern regions of the country, which have a precipitation of more than 1500 mm, it makes sense for these two species to receive a low score from the fourth factor (autumn-winter precipitation); however, again, a lower score was obtained for Artemisia sieberi than Artemisia aucheri. The annual precipitation in the habitats of Artemisia sieberi and Artemisia aucheri is equal to 159 and 255, respectively. Therefore, Artemisia aucheri has a higher moisture requirement.
The habitats of the two species received a negative score for the fifth factor, which indicates that the habitats of these two species were distributed in areas with clear weather.
Although the six factors explain small changes, both species get scores around zero.
In general, the comparison of the most important climatic factors affecting the habitat of Artemisia sieberi showed that heating temperature, spring and summer precipitation, autumn-winter precipitation, and dusty days were negative in the areas that include this species. However, wind and cloudiness were positively effective in the habitat of this species.
For Artemisia aucheri, heating temperature, autumn-winter precipitation, and dusty and cloudy days were negative S Fig. 7 Distribution map winter-autumn precipitation factor scores in Iran in the areas that include this species. Therefore, the amount of spring and summer precipitation, which is the precipitation of the growing season, can affect the production of Ar. sieberi.
According to Hanson et al. (1982), moisture from the previous precipitation and the beginning of the growing season remained in the soil as stored moisture, and perennials and shrubs use the moisture stored in the growing season due to their deep roots.
In general, the autumn-winter precipitation factor had the highest effect on the presence of Ar.sieberi, so that this factor was negative in the areas where the species was present and showed a significant difference with areas lacking this species; thus, this species can grow in areas with low precipitation.
The heating temperature factor had the highest effect on the presence of Ar. aucheri, so that the amount of this factor was negative, indicating that this species prefers cold regions. Since Ar. sieberi grows in the plains and Ar. aucheri in the highlands, the heating temperature has a negative effect on Ar. aucheri. Therefore, the relatively high areas are the habitats of this plant. Hosseini et al. (2013) also reported altitude and climatic conditions as factors affecting the presence of A. aucheri. Zare Chahuki (2001), in the study of the distribution of vegetation types of Poshtkouh rangelands of Yazd province, concluded that A. aucheri was distributed from an altitude of 2400 m and above on relatively sloping  Azarnivand et al. (2003) studied the growth characteristics of Ar. sieberi and Ar. aucheri in the rangelands of Vardavard, Garmsar, and Semnan, and the altitude above sea level was found effective in the establishment of these two species. The comparison between Ar. sieberi and Ar. aucheri showed that the amount of spring and summer precipitation and the cloudiness factor had an opposite effect in both species. Ar. sieberi is a thermophilic species distributed in the lowlands, indicating the positive effect of the cloudiness factor, while Ar. Aucheri is distributed at high altitudes and prefers sunny hours. Also, Ar. sieberi species is more resistant to low precipitation during the growing season than Ar. aucheri, indicating the positive effect of spring and summer precipitation. Artemisia species and the study of the effect of environmental factors on their distribution are of great importance in the planning and management of natural resource areas. Moreover, Artemisia is one of the most important plants in the country's rangelands. Hence, the results of this study can be applied to planning for the conservation, management, and reclamation of rangelands.
However, the relationship between plants and environmental factors is very complex and delicate, the study of which requires long-term and complete studies. Given the importance of these rangelands, proper and planned management is essential in these areas.   Data availability The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.

Code availability
The authors do not have any code availability, but the article code is TAAC-D-21-00074R1.

Declarations
Ethical approval • The manuscript has not been submitted to more than one journal for simultaneous consideration.
• The submitted work is original and has not been published elsewhere in any form or language.
• A single study is not split up into several parts to increase the quantity of submissions and submitted to various journals or to one journal over time.

Consent for publication
All authors agree with the publication of the article.

Consent to participate
All authors contributed to the study's conception and design. Material preparation, data collection, and analysis were performed by Morteza Khodagholi, Razieh Saboohi, and Ehsan Zandi Esfahani. The first draft of the manuscript was written by Morteza Khodagholi and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.