The effect of grazing and anthropogenic disturbances on floristic and physiognomic characteristics in oriental beech communities, Masal Forest, Iran

[Research]

The effect of grazing and anthropogenic disturbances on floristic and physiognomic characteristics in oriental beech communities, Masal Forest, Iran

Ebrahimi S.S.¹, Pourbabaei H.¹*, Pothier D.²

1. Department of Forestry, Faculty of Natural Resources, University of Guilan, Sowmeh Sara, Guilan, Iran

2. Centre d’étude de la forêt (CEF), and Département des sciences du bois et de la forêt, Pavillon Abitibi-Price, 2405 rue de la Terrasse, Université Laval, Québec, QC G1V 0A6, Canada

Corresponding author’s E-mail:hpourbabaei@gmail.com                      (Received: May 23. 2018 Accepted: Nov. 20. 2018)

This study aimed to investigate floristic and physiognomic characteristics of all plant species in relation to grazing and anthropogenic disturbances. So that, 100 ha beech communities were studied  including 50 ha as protected and 50 ha as unprotected area of oriental beech communities in Masal forest, Guilan Province, Iran. The results indicated that the number of all species were higher in the protected area. The main family of the protected area was the Rosaceae, while in the unprotected area the Asteracea had the highest frequency. To identify and classify forest types in both areas, we used the proportion of each tree species larger than 7.5 cm in diameter to determine species dominance according to the classification method of Gorji Bahri. The applied tree classification method indicated that there were three main types and two secondary types in the protected area, whereas six main types were identified in the unprotected area. Physiognomic studies indicated that trees from both areas were in the same height classes, whereas, the total canopy cover percentage was higher in the protected area. Height classes and canopy cover percentage of deciduous broadleaf in shrub layer, were significantly higher in unprotected area than in protected one. In the latter area, the coverpercentage of herbaceous species was different. So that, forbs species had the highest coverpercentage. According to these results, destructive factors have altered the main composition in these communities. So that, avoid of livestock grazing and local people in these areas or livestock exclusion can be recommended as a management.

INTRODUCTION

In each plant community, floristic and physiognomic composition is the result of long-term variations on the earth's surface (Giliam 2007). Vegetative forms is a  major criteria for the description and classification of plants, whereas physiognomy, structure, plant community dynamics and vegetation type of a given environment have been considered as basic criteria (Küchler & Zonneveld 1977). Forest communities represents the final or climax state of plants in the area with specific characteristics and conditions, while vegetation type indicated current status of plants (Marvi Mohajer 2007). Forests cover 12 million ha of the Iranian territory (7% of the total land area), of which about 1.8 million ha are located in the northern part of the country, i.e., the Hyrcanian or Caspian forest ecoregion. This forest type, composed of broadleaf deciduous trees, is located on the northern slopes of the Alborz Mountains overlooking the Caspian Sea (Sagheb-Talebi et al. 2004). Hyrcanian forests are one of the most important floristic regions of Iran with more than 80 tree species and 50 shrub species. The presence of deciduous trees, the wide range of forest mixture and structure, the diversity in plant communities, and the relatively steep slope are important characteristics which have provided suitable vegetative conditions for the establishment of these plant communities (Eshaghi Rad et al. 2009). Fagus orientalis Lipsky is the dominant species of these forests that include 25.3% of all plant species to form the richest forest communities of the country, a major carbon pool (Hall et al. 2001) as well as an important source of income, soil protection and recreational activities (Adel et al. 2012). Forest ecosystems are dynamics systems of different ages that are effected by biotic and abiotic factors (Portela & Santos 2009). Biotic factors such as human and livestock can significantly contribute to modify plant communities (Mirdavoodi et al. 2013). The presence of livestock, dairy farmers and local people in northern forests of Iran are associated with the degradation and even the destruction of ecological values. Livestock grazing is known to be one of the most destructive pressures on forest ecosystems in developing countries which can change structural characteristics of communities, the composition and abundance of plant species, the competitive balance between species and species dominance (Ausden et al. 2005). The effects of livestock grazing as a destructive factor on Hyrcanian forest diversity and structure have been studied by authors (Asadollahi 2000, Mohamadi Golrang et al. 2007, Aghakhaniet al. 2010) but the main objectives of our study was study the effects of these factors on floristic and physiognomic characteristics that did not examine in this forest yet. Over the past 35 years, almost one-third of the Iranian forests have been eliminated (FAO, 2005). If this rate is maintained, the remaining forest will be destroyed during the next 30 to 40 years (Marvi Mohajer 2007). Considering the frequent disturbances in the studied forests, forest typology can be a practical tool to study the current ecological conditions as well as planning and providing management measures to protect and restore these forests. Physiognomic systems are associated with floristic systems because environmental conditions not only influence floristic characteristics, but also life forms (Mohamadi Golrang et al. 2007). Therefore, this study aimed to investigate floristic and physiognomic characteristics of vascular plants in relation to grazing and human disturbances. The specific objectives of this study were: (1) evaluate the effects of grazing and human activities on plant life forms, composition and dominance of trees, shrubs and herbaceous species, and (2) identify forest types based on tree composition in protected and unprotected areas.

MATERIALS AND METHODS

Study area

The study was conducted in June, 2012 in a 100-ha forested area located in the Masal of Guilan province in northern Iran (37˚ 14 ̕ 00˝ to 37˚ 19˚ 20˝ N and 48˚ 55̕ 19˝ to 49˚ 02̕ E). Elevation within the study area ranges from 300 to 2000 m a.s.l., and was largely restricted to the eastern aspects. Common forest soils are acidic with a pH varying between 5.5 and 6.5. Parent materials include shill, sand stone and calcareous. Mean annual precipitation and temperature are 990 mm and 16˚C, respectively (information from station of Hydrology and Meteorology Shanderman). While there is no permanent residential land in this area, dairy farmers and local people use the territory for animal husbandry during 2-4 months in spring and summer in each year. Over the years, the primary structure of these forests was modified by disturbances such as heavy grazing livestock, tree girdling, and excessive cutting of trees and shrubs to supply fuel wood. The forest is uneven-aged and is composed of mixed deciduous broadleaved trees and sometimes of unmixed beech (F. orientalis Lipsky). A protection program was initiated 7 years ago by fencing about 50 ha of these forests to reduce the effect of grazing pressure and the entry of livestock and humans.

Data collection

A protected area and an unprotected area of 50 hectares were selected on the sides of a road close to each other. These areas were similar in terms of altitude, slope and aspect. In each of the two sites, 25 1000-m² circular sampling plots were systematically positioned on a 100 m × 200 m grid (Zobeiri 2002). In each area, we used a random systematic 100 m × 200 m gird sampling plan to establish 25 1000-m² circular plots. Type of tree and shrub species were identified, then in each plot, the diameter at breast height (DBH) of trees larger than 7.5 cm in diameter was measured (Adel et al. 2013). Also, Whittaker’s nested plot sampling and minimal area method were used to determine plots size for sampling of herbaceous species and percentage cover of each species was estimated according to Domin scale of cover/ abundance(Mueller & Ellenberg 1989). Finally, a sample of each herbaceous species was collected. The species collected in each area were dried and pressed before they identified using Iranica flora (Rechinger 1963-1998), Turkey flora (Davis 1965-1985), Iran flora and the colorful flora of Iran (Asadi et al. 2011).

Fig. 1. Location of study area of Hyrcanian forest, north of Iran.

Data Analysis

To identify and classify forest types in both areas, we used the proportion of each tree species larger than 7.5 cm in diameter to determine species dominance (Table 1) according to the classification method of Gorji Bahri (2000). Kuchler’s physiognomic method was used to study the physiognomy of each of these types. Finally, life form classes and structural classes (height and canopy cover) were determined for woody and herbaceous plants according to the method of Kuchler & Zoneveld (1977)

(Table 2).  For statistical analyses, at first, Kolmogorov–Smirnov tests were used to verify the normality of their distributions. Normality tests were followed by means comparisons between B and UB using two-sample t-tests or their non-parametric equivalents (Mann-Whitney U-tests) if the data were not found to be normally distributed. All statistical analyses were performed in SPSS (version 16.0, SPSS Inc., Chicago, IL). Significance levels were set to P = 0.05.

Table 1. Classification method of forest’s types in protected and unprotected areas according to mixture percent of trees (Gorji Bahri 2000).

Table 2. A description of the Kuchler’s method to describe the structure of vegetation (Kuchler & Zoland 1977).

RESULTS

Floristic characteristics

We identified 60 species from 35 families (3 tree, 6 shrubs and 51 herbaceous species, respectively) and 58 species from 33 families (3 tree, 6 shrubs and 48 herbaceous species) in protected and unprotected areas, respectively. The Rosaceae was the most frequently encountered family in the protected area.

In contrast, the grazed plots were dominated by the family Asteracea. Three species including Fagus orientalis Lipsky, Carpinus

betulus L. and Alnus subcordata C.A.Mey were present in both areas and broadleaf deciduous (D) was the only life form that was identified in areas (Table 3). Statistical analyses indicated that the density of trees was significantly higher in the protected area than in the unprotected area. Whereas, the mean number of shrubs per hectares and herbaceous cover percentage were greater in the unprotected area (Table 4).

Table 3. Life forms and families of woody and herbaceous species in the protected (P) and unprotected (UN) areas.

*Indicates the present and – indicates absence of species in each area.

Table 4. Density and cover percentage of vegetation layers in protected and unprotected areas.

Notes: **Indicate significant differences at the 99% level between protected and unprotected areas.

Physiognomy characteristics

Woody layer

The physiognomy studies in tree layer indicated that trees of both areas had same height classes (10 to 20 and 20 to 35 m classes), while the total percent canopy cover was significantly higher in the protected area than in the unprotected area. In the protected area, the canopy cover occupied by each tree species varied from 25 to 100% and was dominated by F orientalis. In the unprotected area, the canopy cover of each tree species was lower than 25% and was dominated by C betulus (Table 5).

In shrub layer, life forms of species were also similar between both areas. Deciduous broadleaf, including Mespilus germanica L., Prunus divaricate L., Crataegus microphylla K. Koch, Crataegus ambigua  Becker, and evergreen broadleaf, including Ruscus hyrcanus Woronow and Ilex aquifolium L. were present in both areas (Table 6). In the unprotected area, shrub species were observed in height classes 0.5-2 m and 2-5 m and in canopy cover classes 6-25% and 25-50% but in the protected area, the height classes (0-0.5 m and 0.5-2 m) and canopy cover classes (1-5% and 6-25.5) of the shrub layer were lower than those of the unprotected area (Table 5). The applied tree classification method indicated that there were three main types and two secondary types in the protected area.

The most common type was the pure Fagus orientalis with covers 40% of the area, mostly on southwestern and northeastern slopes and secondary type was Fagus orinetalis- Alnus subcordara that covers 32% of this area. The Fagus orientalis Lipsky, Ruscus hyrcanus Woronow and Ilex aquifolium species were dominated species in these types. Whereas, the lowest cover percentage belonged to Fagus orinetalis- Carpinus betulus- Alnus subcordara and Fagus orinetalis- Alnus subcordara-

Carpinusbetulus types that covers only 8% of the protected area. In the unprotected area, six main types and two secondary types were identified: Fagus orinetalis- Carpinus betulus, Carpinus betulus- Alnus subcordara and Carpinus betulus- Fagus orinetalis with 20% surface area each had highest cover in this area. Fagus orinetalis, Carpinus betulus, Mespilus germanica and Prunus divaricata Ledebwere dominated species in these types. whereas the lowest percent coverage were observed for Fagus orinetalis- Carpinus betulus- Alnus subcordara and Carpinus betulus- Fagus orinetalis- Alnus subcordara types (Table 5).

Finally, statistical analyses indicated that evergreen broadleaf species such as Ilex aquifolium and Ruscus hyrcanushad similar height and canopy cover in both areas. While, deciduous broadleaf species were different, significantly (Table 6).

Herbaceous layer

In herbaceous layer, life forms of grasses and forbs species in the protected area were similar to those in the unprotected area (Table 3). According to physiognomy formula in the protected area, herbaceous species were in the same height class (0.1-0.5 m class), but their percent covers were different. So that the percent cover of forbs and perennial species with an average 47%was between 25 and 100% class, whereas grass species was never higher than the 6-25% class (19.8%) (Tables 5 and 6). Herbaceous species were present in unprotected area with two storey, the first storey by height classes of 0.5-2 meter and canopy cover classes of 75-100%, 50-75% and 25-50% and second storey by height classes of 0.1-0.5 meter and canopy cover classes of 1- 5% and 6- 25% (Table 5).

Table 5. Dominant species (according to the mixture cover), cover percentage and physiognomy formula in each natural vegetation types identified in the study area.

Table 6. Variability (Mean± SE) of structural categories of life form classes in protected and unprotected areas.

Note: ^* indicate a significant difference at the 95 % level; ^** indicate a significant differences at the 99 % level between protected and unprotected areas.