Floristic characteristics of the Hyrcanian submountain forests (case study: Ata-Kuh forest)

 F. Bazdid Vahdati¹, S. Saeidi Mehrvarz¹*, A. R. Naqinezhad², R. Shahi Shavvon¹

 1-Dept. of Biology, Faculty of Science, University of Guilan, Rasht, Iran

2-Dept. of Biology, Faculty of Basic Sciences, University of Mazandaran, Babolsar, Iran

 * Corresponding author’s E-mail: saeidimz@guilan.ac.ir

ABSTRACT

Ata-Kuh forest, a preserved area within Hyrcanian relict forests, with an area of 700 ha is located in north of Iran. Based on floristic studies from 2011 through 2012, 194 vascular plant species were identified belonging to 143 genera and 66 families. Among our samples, 24 taxa were endemic to Hyrcanian area. The largest families in the area were Rosaceae (10.3 %), Poaceae (9.7 %), Asteraceae (6.7 %), Fabaceae (5.6 %) and Lamiaceae (5.1 %). The genera represented by the greatest number of species were Rubus (8 species), Carex (7 species), Viola and Euphorbia (each with four species). Classification based on life form indicated that geophytes comprise the largest proportion of the plants in the studied area. From the chorological point of view, the largest proportion of the flora belonged to the Euro-Siberian elements (60 taxa, 31.1%). In this study, a comparison was performed between our results and other studies on the northern Iranian forests with respect to life forms and phytochoria. Psilotum nodum is reported here again from a new locality in North Iran, indicating the old Tertiary history of this forest.

INTRODUCTION

The knowledge of the floristic composition of an area is perquisite for any ecological and phytogeographical studies and conservation management activities. The Hyrcanian area, unlike the arid and semiarid landscape throughout most of central and southern Iran, is one of the remnants of natural deciduous forests (Naqinezhad et al., 2008), which form a vegetation belt in the southern shores of the Caspian Sea. It is located in the northern slopes of Alborz Mountains in North Iran and covers Guilan, Mazandaran and Golestan provinces. The Hyrcanian forests are the most important relicts of the so called Arcto-Tertiary forests and many tree genera like Pterocarya, Albizia, Parrotia or Gleditsia survived the last ice age only in this area (Scharnweber et al., 2007).The northern slopes of Alborz Mountains are climatically very different from the southern slopes by having a high annual precipitation and high air humidity. These features make this area suitable for temperate forest and provide divers habitats for plant.

There have been a number of floristic and vegetation researches on Hyrcanian forests in the past (e.g. Djazirei, 1965; Mobayen & Tregubov 1970;Zohary,1973;  Dorostkar & Noirfalise 1976; Mossadegh, 1981; Assadi, 1988; Hamzeh’ee, 1994; Akhani, 1998; Ghahreman et al., 2006;Hamzeh’eeet al., 2008; Naqinezhad et al., 2008; Akhaniet al., 2010; Naqinezhad et al., 2010; Siadati et al., 2010; Abedi & Pourbabaei, 2011; Asadi et al., 2011; Ghahremaninejad etal., 2011). There is no previous floristic information about the flora of Ata-Kuh forest. The main objectives of this paper were: 1) providing a first floristic checklist of the vascular plants of the study area 2) Determining the life forms and chorology of each taxon. This not only provides a current view of plant species diversity in the studied area, but also creates the foundation for biodiversity conservation and future management on Ata-Kuh forest.

MATERIALS AND METHODS

Study Area

Ata-Kuh forest is located on the northern slope of Alborz Mountains, 10 km to the southeastern of Lahijan (Guilan Province), between 37º 09′ 28.4ʺ-37º 09′ 23.4ʺ N and

50º 05′ 06.9ʺ-50º 06′ 04.1ʺE, with an altitude ranging from 240 to 684 m a.s.l. (Fig.1).The northern section of Alborz is a geologically young area which was subsiding and under the Paratethys Ocean until the middle Miocene about 10-15 Ma (Berberian &King 1981). Moreover, in these areas, Mid-Jurassic to Upper Cretaceous limestone formations had already become much more important and form some very high rock cliffs along the East-West directed thrust fault zones (Stöcklin, 1974).

Fig 1. Location of Ata-Kuh forest in Guilan province (North Iran).

Based on Global Bioclimatic Classification System (Rivas-Martinez et al., 1997, 1999) the area is characterized as temperate oceanic bioclimate (submediterranean variant) or Tocsm (Djamaliet al., 2011). In the studied area, most of the precipitation occurs from early autumn to early spring. The autumn months (October to December) are the most humid months of the year. There are two general peaks of precipitation, first one in October and the second in February Siberian anticyclone, formed over North Eurasia and occasionally extending into Central Asia, blocks the eastward penetration of Westerly disturbances during the autumn and winter months but results in high rainfall during the summer and especially autumn in the Caspian coastal area (Khalili, 1973; Alijani & Harman 1985). The mean monthly temperature is the lowest in January and February and the highest in July and August. The maximum and minimum mean temperatures are 22ºC, and 10.2ºC, respectively. The average total annual precipitation and average annual temperature are 1459.4 mm and 16.47 ^°C, respectively (Fig. 2). Climatically, the Caspian lowland may be regarded, on the whole, as a region of rainy summers and mild winters which are reminiscent of a typical oceanic climate, not unlike that of the Atlantic coast of Europe (Zohary, 1973).

Data Collection

Data collection was performed during four seasons from March 2011 through March 2012. The voucher specimens were deposited in the Herbarium of University of Guilan (GUH). The identification of specimens was performed by Rechinger, 1963-2010; Assadi et al., 1988-2011; Davis,1965-1988; Tutin et al., 1964-1980; Komarov, 1934-1954 and Townsend et al., 1966-1985.The classification of flowering plants was based on the APGIII (2009) and the name of taxon authors was coordinated using IPNI (2012). Some references (Frey et al., 2006; Smith et al., 2006; Khoshravesh et al., 2009) were used for determination of Monilophytes species. Some seedlings of forest plants were determined based on Aghabeigi (1997). In addition, plant formations were recognized using a physiognomical approach and field observations.This method was used in other studied ecosystems (e.g. Naqinezhad et al., 2006; Khodadadi et al., 2009).

Fig. 2.Climatological diagram from Lahijan station (1982-2010).

Life-form categories were identified according to Raunkiaer’s system of classification (Raunkiaer, 1934). Detailed information about phanerophytes was based on Pears (1985), (megaphanerophytes = more than 30 m high, mesophanerophyte = 8–30 m high, microphanerophyte = 2-8 m, nanophanerophyte= less than 2 m height, liana = no height restriction).

The species distribution was based on the reviews, monographs and floras, particularly the Flora Iranica (Rechinger, 1963-2010), Flora of Turkey (Davis, 1965-1988) and Flora of Europaea (Tutin et al., 1964-1980). The terminology and delimitation of the main phytogeographical area was according to the standard reference works, particularly those of Zohary (1973) and Takhtajan (1986). Based on author’s assessments, IT (plants distributed in the Irano-Turanian region), M (plants distributed in the Mediterranean region), ES (plants distributed in the Euro-siberian region), PL (Pluriregional elements, referring to plants that are ranging over three phytogeographical regions), PON (plants distributed in the Pontic region), COS (cosmopolitan elements, refering to plants that have a broad worldwide distribution) and SCOS (subcosmopolitan elements, refering to plants ranging in distribution over most continents, but not all of them).

RESULTS ANDDISCUSSION

As a result of our fieldwork, the vascular flora of Ata-Kuh forest contains a total of 194 taxa from 66 families and 143 genera (Appendix 1). Eleven families of Monilophytes (Pteridophytes) and 55 families of Angiosperms constitute the studied flora. Eudicots with 45 families, 98 genera and 135 species are the richest group, while monocots have 10 families, 31 genera and 39 species in the studied flora (Table 1). Rosaceae, Poaceae, Asteraceae, Fabaceae, Lamiaceae, all exceed 10 taxa and show the highest species richness, respectively (Table 2). The families Cyperaceae (8), Brassicaceae, Dryopteridaceae and Polygonaceae (each 6 taxa), Euphorbiaceae (5 taxa) are the next species-rich families. Four families are represented in four taxa, six families with three taxa, 10 families with two taxa and 36 families have only a single taxon. Five families, including Poaceae (17), Asteraceae (12), Rosaceae (9), Fabaceae and Lamiaceae (8), contain more than eight genera and are

the most genera-rich. Four families have four genera, one family has three genera, 14 families have two genera and the rest (42 families) are unigeneric. The genera with the highest species richness are Rubus with eight taxa, Carex with seven taxa, Viola and Euphorbia each with four taxa, Dryopteris, Polystichum, Geranium, Hypericum, Polygonum, Rumex and Poa all with three taxa. There are 18 genera with two taxa and 114 genera with only one taxon.

Table 1. Number of families, genera and species in main plant groups of Ata-Kuh forest.

Table 2. Number of species and genera of the richest plant families of Ata-Kuh forest.

Life Form Spectrum

The floristic analysis of the vegetation from life form point of view is widely used as a criterion for describing it (Raunkiaer, 1934). According to Box (1981), the study of plant life forms is important, because it provides the basic structural components of vegetation stands and explains vegetation structure. In the assessment of life form spectrum, geophytes with 73 taxa, rhizomatous geophytes (60 taxa, 31%), stoloniferous geophytes (6 taxa, 3.1%), bulbiferous geophytes (4 taxa, 2.1%), tuberous geophytes (2 taxa, 1%) and geophytes with corm (1 taxa, 0.5%) are the dominant life form, which constitute 37.7% of studied flora, followed by the therophytes (44 taxa, 22.7%), hemicryptophytes (41 taxa, 21.1%), phanerophytes (34 taxa, 17.5%), chamaephyte and parasitic (each with one taxa, 0.5%, see Fig. 3). Detailed classification of phanerophytes shows that they consist of nanophanerophytes (with 12 taxa, 6.2%), microphanerophytes (with 11 taxa, 5.7%), megaphanerophytes (with 7 taxa, 3.6%), lianas and mesophanerophytes (each 2 taxa and 1%). The high proportion of geophytes in the studied area primarily reflects the long period of wetness during the growing season and relatively high annual precipitation (Danin & Orshan 1990). However, geophytes can occur in many habitats (Esler et al., 1999; Proches et al., 2006). Therophytes and hemicryptophytes are the most prominent life form after geophytes. Since life form classification is based essentially on plant reaction to extremes of climate, the individual spectrum or the variation when two or more spectra are compared should tell us much about macroclimatic patterns at the field sites (Pears, 1985). Also, a comparison between the life forms in Ata-Kuh forest and those in the other forests in northern Iran are shown in Fig. 4 (Naqinezhad et al., 2010; Siadati et al., 2010Asadi et al., 2011;; Ghahremaninejad et al., 2011;). The highest concentration of geophytes is found in Ata-Kuh and Kheyrud. Moreover, these results are consistent with those found in the other forest areas of the Hyrcanian area (e.g. Akbarinia et al., 2004;Ghahreman et al., 2006; Razavi, 2008). It seems that these concentrations exhibit the best correspondence with a normal structure and flora of lowland Hyrcanian forests (Zohary, 1973; Rastin, 1983). Hemicryptophytes show peak of presence in Ramsar. The occurrence of a high proportion of Hemicryptophytes in Ramsar is typical of a temperate climate (Naqinezhad et al., 2010). Although, therophytes occur abundantly in desert area (Archibald, 1995), a high proportion of this life form is present in Semeskandeh and Dasht-e Naz (Ghahremaninejad et al., 2011). This is due to the more affected faces of this site caused by human activities and extensive grazing. Likewise, these results are in agreement with Grime’sstudies (2001).

Fig. 3.Life form spectrum of plants studied in Ata-Kuh forest.

Fig. 4.Variation of each life form over the sites Ramsar forest (Naqinezhad et al. 2010); Khybus forest (Asadi et al. 2011); Kheyrud forest (Siadati et al. 2010); Semeskandeh and Dasht-e Naz forests (Ghahremaninejad et al. 2011). Abbreviations: Cha= Chamaephyte, Geo= Geophyte, Hel= Helophyte, Hem= Hemicryptophyte, Hyd= Hydrophyte, Pha= Phanerophyte, Par= Parasite, Thr= therophyte

Chorotype Spectrum

In terms of geographical distribution, the flora of the studied area is composed mostly of ES elements (60 taxa, 31.1%), followed by PL elements (57 taxa, 29.5%), ES- M- IT (21 taxa, 10.9%), ES-IT(17 taxa, 8.8%), ES-M (14 taxa, 7.3 %), SCOS (12 taxa, 6.2 %), COS (5

taxa, 2.6 %), M-IT (3 taxa, 1.6 %), IT (2 taxa, 1%), IT-M-PON and M (each 1 taxon, 0.5%, see Fig. 5). The occurrence of a high

proportion of Euro-Siberian elements indicates a phytogeographical floristic link between Ata-Kuh forest and Euro-Siberian forest.

Fig. 5. Proportion of different phytochoria elements of plants in  Ata-Kuh forest. Abbreviations:ES= Euro-Siberian, PL= Pluriregional, M= Mediterranean, IT= Irano-Turanian, COS= Cosmopolitan, SCOS= Subcosmopolitan

Iranian endemics. The detailed assessment of phytogeographical element demonstrates that some of these genera contain a relatively high proportion (26 species or 13.4% of all species) of Iranian endemics, of which 24 taxa (12.4%) are endemic or nearly endemic to the Hyrcanian area. The Hyrcanian forests are known as a refuge for many Arcto-Tertiary relict elements (Zohary, 1973; Leestmans, 2005). These species are grouped into Hyrcanian and Euxino-Hyrcanian elements (Akhani et al., 2010). Some species are endemic or nearly endemic to the Hyrcanian area, such as Ilex spinigera, Hedera pastuchovii, Epimedium pinnatum, Campanula rapunculus subsp. lambertiana, Gleditsia caspica, Quercus castaneifolia subsp. castaneifolia, Parrotia persica, Scutellaria tournefortii, Teucrium hyrcanicum, Primula heterochroma, Rubus esfandiarii, Rubus grantii, Rubus lahidjanensis, Rubus persicus, Rhynchocorys maxima, Ornithogalum sintenisi, Scilla hohenackeri, Ruscus hyrcanus. The presence of these endemic taxa reveals the special ecologic and biogeographic importance of the area.

Phytogeographical comparison of Ata-Kuh forest and the other forests in North Iran are demonstrated in Fig. 6. Two peaks in phytochoria curves are identified, one in Euro - Siberian and the other one in the Pluriregional elements.

Some phytogeographical elements such as ES-M-IT, ES-IT, ES-M, SCOS, COS, M-IT, IT, M-IT-PON, M do not demonstrate high variations among the sites, while ES and PL elements show more variation between the sites. The highest proportion of Euro-Siberian elements present in Khybus, while the lowest one is seen in Semeskandeh and Dasht-e Naz forests. Also, the Semeskandeh and Dasht-e Naz demonstrate the highest amount of Pluriregional elements. Our results indicate that due to the high Euro-Siberian elements, the Khybus forest has the highest correspondence with a common Euro-Siberian forest.

Fig. 6.Variation of each phytochoria over the sites. Abbreviations:Ata= Ata-Kuh, Ram= Ramsar, Khy= Khybus, Khe= Kheyrud, Sem & Dash= Semeskandeh and Dasht-e Naz, ES= Euro-Sibirian, PL= Pluriregional, M= Mediterranean, IT= Irano-Turanian, COS= Cosmopolitan, SCOS= Subcosmopolitan