Abstract: Firozeh watershed with an area of 270 km² is located in 20 km South of Bojnord (North Khorasan Province). The altitude of the area ranges is 1280-3010 m. The mean annual rainfall is 385.7 mm and the mean annual temperature is 8.9°C. In order to floristic study in this watershed, plant samples were collected during six growing seasons (2003-2008) and identified using different flora references. The life forms were determined and the biological spectrum of the area was plotted. The position of the area related to phytogeographical classification was investigated based on geographical data and references. In this research 56 family, 243 genera and 405 species were identified. The largest families of region are: compositae with 52 species and poaceae with 47 species. Hemicryptophyte with 149 species are the most frequent life forms in the area. The distribution of the 262 species is restricted to Irano-Turanian region. Of these, 47 species are endemic of Iran. Furthermore, according to the IUCN, three categories of plant species so called vulnerable, lower risk and data deficient are determined. There are total 60 threatened plant species in this area.

INTRODUCTION

The diversity of plant life is an essential underpinning of most of the terrestrial ecosystems. Humans and most other animals are almost totally dependent on plants, directly or indirectly. Another important role of plant life is the provision of ecosystem services the protection of watersheds, stabilization of slopes, improvement of soils, medicinal plants, moderation of climate and the provision of a habitat for much of the wild fauna. While, it is generally accepted today that the conservation of all biodiversity should be the goal, understanding the natural distribution of plants (Floristic studies) is central to conserving biodiversity and managing ecosystems for long-term viability and sustainability. Iran is a country with high divers climate and topography, which leads to diversity in natural and biological resources. Therefore, for management in order to conservation of this diversity, prevention from destruction of habitats, determining the native and resistant species and endangered species and supporting them, recognition of medicinal plants for proper use of them, floristic studies is necessary.

Nowadays, many studies in this field have been doing by researchers, such as: Floristic study of Genu Hormozgan (Najafi et al., 2005), plant species of Vanak-Semirom-Isfahan (Parishani, 2003), Floristic study of Sangdeh-sari (Akbarinia et al., 2004), Floristic study of Darrah Damgahan-Mehriz (Zarezadeh et al., 2007), Floristic study of Ghasemloo (Shohada) Valley, Forest reservoir (Malekmohammadi et al., 2007). While, this sort of studies is very useful for planning with refer to protection, reclamation and management of valuable species, present study was done in Firozeh region in 2003-2008.

MATERIALS AND METHODS

Firozeh region with 270 km² area is located on the Northern slopes of Aladagh elevations in North East of Iran (North Khorasan Province). This region is situated between 57°02'-57°25' East longitudes and 37°13'-37°23' North latitude. This region is located between the cities of Bojnord and Esfarain. The altitude of the area ranges from 1280-3010 m. The rainiest month is March. The mean annual rainfall is 385.7 mm and the median annual temperature is 8.9°C. The average maximum temperature is 26.5°C in August and minimum temperature is -2.6°C in December (Fig. 1). The climate of this region with using of Emberger method is cold semi-arid to climatic heights. The embrothermic diagram show that drought period is for five months of year and wet season stars in November and continues until May (Fig. 2).

In order to presentation the flora of Firozeh, at first related information such as: Meteorological statistics, Topographic maps were gathered. Then, the specimens were collected in different seasons. The collected samples were then identified and named on classification and terminology applied to various Flora, such as: Flora Iranica Rechinger (1963-1998), Flora of Iran Assadi (1988-2003), Flora of Iran Parsa (1943-1950), Colored Flora of Iran Ghahreman (1975-2002), Astragalus communities of Iran Maasoumi (1986-2000). In this manner geographical plant distribution also determined according these Flora. Determining the life form was done by Raunchier (1934)’s method, Endemic species of Iran was determined according to Red data book of Iran Jalili and Jamzad (1999) and chorology of species is based on Zohary (1973) and Takhtajan (1986).

Fig. 1:	The line chart of temperatures

Fig. 2:	The lines on 2 Axes chart of embrothermic curve

RESULTS AND DISCUSSION

The results of study show that about 405 species belong to 243 Genera and 56 Families have been recognized. Among the existing Families, 47 Families are Dicotyledonous, 7 Families are monocotyledon and 2 Families (Ephedraceae, Cupressaceae) are Gymnosperms. Compositae with 30 Genera and 52 species is the most abundant family in the area, followed by families of Poaceae, Labiatae, Papilionaceae, Brassicaceae and Apiaceae with 47, 35, 31, 28 and 21 species, respectively (Fig. 3 and 4).

Table 1 is a list of all species collected in the area with information about scientific name, chorology, life form and medicinal use.

The life form spectrum of plant species is as follow: Hemicryptophyte 36.79%, Therophyte 25.68%, Chamaephyte 14.07%, Geophytes 13.58% and Phanerophyte 9.88% (Fig. 5).

The Chorotype distributions of species are as follow: Irano-Turanian 64.69%, Irano-Turanian and Mediterranean 11.35%, Cosmopolitan 8.15%, Irano-Turanian, Mediterranean and Euro-Siberian 5.93%, Irano-Turanian and Euro-Siberian 5.18%, Irano-Turanian and Sahara-Sindian 2.47%, Irano-Turanian, Mediterranean and Sahara-Sindian 1.48% and Irano-Turanian, Euro-Siberian and Sahara-Sindian 0.75% (Fig. 6).

Among 405 plant species distributed in the studied area, 47 species are endemic to Iran. Furthermore, according to the IUCN, three categories of plant species so called vulnerable, lower risk and data deficient are determined. There are in total, 60 threatened plant species in this area (Table 2).

Among all plants Hemicryptophyte with 36.79% is dominant and Therophyte with 25.68% is in the next order. In fact life forms of the plants indicate the possibility of adaptation of plants to environmental factors especially climatic condition. According to Archibold (1995) the frequency of Hemicryptophyte plants is due to cold and to altitude climate. On the whole frequency of Hemicryptophyte among the plants of the region show that the effect form of climate area is cold semi-arid to climatic of heights. Therophyte adapted to the dryness of the region and shortage rainfall, because these plants spend vegetative period in the form of seed (Asri, 2003).

Hemicryptophyte adapted to condition of area. They adapted and developed themselves to area by using different ways such as: reserving water, using ground water, reducing their water by loosing their leaves and reduction of vegetative growth.

Dominance of Hemicryptophyte and Therophyte clearly indicate the adaptation of these plants to aridity of area.

The low percentage of Chamaephyte, Geophytes and Phanerophyte shows that they are not adapted to existence climate and edaphically situations. Each plant species has it’s special ecological area with a known tolerance to life conditions of area. Therefore, the geographical distribution of plant species depending on life conditions of area and adaptation of plants to area (Asri, 2003).

Astragalus diversity with its 12 species in this area which is mountainous shows that Astragalus has adapted to the mountainous conditions.

The Chorotype distribution of plants reflects the climate conditions. Considering to this fact that 64.69% plant species in a region are IT elements, so this region belong to IT. IT (the Irano-Turanian region) is characterized by low rainfall and a long dry season.

The existence endemic species indicate diversity in Iran climate. Among 405 plant species distributed in the studied area, 47 species are endemic to Iran. They compose about 11.6% of the total number of species.

Fig. 3:	The column chart of frequency of species in family in Firozeh watershed

Fig. 4:	The column chart of frequency of genus in family in Firozeh watershed

Table 1:	Floristic list of firozeh watershed

Fig. 5:	The column chart of life form of species in Firozeh watershed

The existence of Compositae family with large diversity is the result of destruction in this region. It is experience understood that the increasing of the number of some plant families including Asteraceae accompanied with destruction in area, following studies support the mentioned fact (Vakili et al., 2001; Archibold, 1995).

Fig. 6:	The column chart of percentage of chorotype of species in Firozeh watershed

According to rich biodiversity of study area, which resulted from floristic study, it is quite possible to concentrate the improving practices and reclamation to area again.

About 141 medicinal species were determined in this area that was shown in Table 1. Some of most important species are as follow: Capsella bursa-pastoris, Descurainia sophia, Ephedra intermedia, Glycyrrgiza glabra, Ziziphora clinopodioides, Ferula gummosa, Thymus kotschyanus, Dracocephalum kotschyi, Stachys lavandulifolia, Eremurus olgae.

Table 2:	Plants species list of rare and endangered of firozeh watershed
Vu = Vulnerable, LR = Lower Risk and DD = Data Deficient

CONCLUSION

The study area is very rich with refer to plant diversity. This conclusion is supported by the existence 56 families, 243 genera and 405 species.