Floral diversity and phytosociological studies on vegetation of agror valley, district Mansehra

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Introduction

Biodiversity may be defined as the variety of life forms i.e., all species of plants, trees, other flora, insects, animals, and other microorganisms. Khyber Pakhtunkhwa Province has an enoromous diversity of flora and a huge variety of ecological zones scattered throughout the province from the plains in the south to high mountains in the north (Champion et al., 1965), the forests fall under the major type “Montane temperate forests” (Shah and Khan, 2006). Tehsil Oghi (Mansehra), Pakistan, has a rich plant biodiversity due to the presence of diverse microhabitats and topographic features (Ahmed et al., 2018).

Biological spectrum is the percentage ratio of life form of plant present in an area (Sarmiento and Monasterio, 1983). Biological spectrum is used both for the life form distribution pattern of vegetation and environmental conditions under the prevailing life forms progressed. Same climatic conditions in different regions can be specified by occurrence of similar biological spectra (Raunkiaer, 1934). Leaf size classes have been found to be very useful for plant associations. Size and shape of leaves associate strongly with environmental variables like temperature and moisture (Bailey and Sinott 1995). The physiological processes of plants can be accessed through leaf size (Oosting, 1956).

Floristic studies across the globe have been documented by several field investigators. Cain and Castro (1959) and Shimwell (1971) reported that hemi cryptophytes are characteristic of temperate zones; therophytes of desert climate and geophytes of the Mediterranean climate. Ram and Arya (1991) examined and stated phanerophytes dominant life form before degradation and therophytic and hemicryptophytic after degradation in the alpine meadows of Central Himalaya, India.

Phenology is the relationship of plant growth stages and calendar date. The calendar is based on the solar year. The information of phenology shows relationship of plant growth to seasonal changes and changes in length of day light or photoperiod to program their growth stages and biological activities appropriated with the seasonal conditions (Manske, 2006). Phenology is the timing of recurring of biological events, among phases of plant species, which provide a background for collecting and synthesizing detailed quantitative information on rhythm of plant community (Sing and Sing, 1992). According to Ahmed (2017), the flowering and fruiting could be related with the climatic conditions for offspring survival. Cornejo-Tenoria and Ibarra-Manriquez (2007) recorded flowering and fruiting behavior on monthly basis. Keeping these points in view, the current study was designed to evaluate and document the floristic composition, biological spectra and phenological behaviour of the local flora of an unexplored valley (Agror Valley), Mansehra, Pakistan.

Materials and Methods

Study area

The Agror Valley is located in Mansehra District of Hazara Division, Khyber Pakhtunkhwa. It is situated between 34˚29' and 34˚35'N and 72˚58' and 75˚09'E (Hunter, 1885). It lies at the base of Black Mountain and is segregated from Pakhli by the Tanglai Mountain (Mustafa, 2003). On its east lies Battal, on north lies Batagram and from Agror southward are Tanwal Mountains. The old name of Oghi was Agror Valley, and since the town Oghi is in close proximity to the centre city and being an old town (1000 year), the entire area is currently being known as Oghi. The total study area comprises of 22,991 acres. The valley consists of five union councils; Oghi, Belian, Kathai, Shamdarha and Dilbori (Ahmed et al., 2017). Total population of Tehsil Oghi is 265,728 (Pakistan Bureau of Statistics, 2017) (Fig. 1).

Fig 1: Map of Agror valley.

Field surveys

Field surveys were carried out to investigate and examine the biodiversity of the study area in different seasons. Every study trip was well planned and performed effectively. Phenology of the species was recorded in different intervals of field year (Singh and Singh, 2010). Surveys were conducted during flowering and fruiting stages. Significant plant affiliations were studied, with relationship to altitude and environmental conditions. Timings for the field work were preferred according to the growth and collection season of plants. Each specimen was assigned collection number with the aid of tags. Field data were noted in field notebook. Collection number was given to each specimen with the help of tags. Each collected plant specimen was serially tagged and placed in the field presser (Ijaz et al., 2015).

Herbarium work

The collected specimens were poisoned using mercuric chloride (2gm) and absolute alcohol (1000 ml). The poisoned species were pasted on the herbarium sheets having standard size (11.5 × 17.5 inches) (Ijaz et al., 2016). Field notebook data were shifted to herbarium slip (4 × 6 inches) glued underside on right part of herbarium sheet (Ijaz, 2014). For the identification of plants taxonomic literature, previously published credentials and for authenticity Flora of Pakistan was consulted (Ali and Nasir, 1970-2002). The plants names were also validated and brought up to date with the online internet site (www.theplantlist.org) of the Royal Botanic Gardens, Kew. The voucher specimens were placed in Herbarium, Department of Botany, Hazara University Mansehra, Pakistan (HUP).

Biological spectrum

The two parameters of biological spectrum i.e., life form classes and leaf spectra of all plant species were recognized and categorized after Raunkiaer (1934).

Life form

Life form indicates the adjustment of plant life to various climatic events. Based on position of the perennating buds, the Raunkiaer (1934) proposed life form classes.

Phanerophytes (P)

Phanerophytes includes all tall woody trees and shrubs. Perennating buds emerges 25 cm, or more above the grounds. Phanerophytes were subdivided into following four sub-classes.

1) Mega phanerophytes (Mp): Trees with more than 30 m height.

2) Meso phanerophytes (Ms): Trees with height between 8-30 m.

3) Micro phanerophytes (Me): Trees and shrubs comprising height in range of 2-8 m.

4) Nano phanerophytes (NP): Shrubs with 25 cm - 2 m height.

Chameophytes (CH)

Perennating buds lying above the soil surface up to 25 cm. This class mostly includes small sized shrubs.

Hemicryptophytes (H)

Hemicryptophytes includes plant species having their perennating buds on the surface of soil. This group includes all grasses.

Geophytes (G)

Perennating buds are present under the ground surface. They include bulbs, tuber, corm, and rhizomes.

Therophytes (Th)

This class included annual plants species which completes their life cycle during favourable conditions throughout the year. Their perennating buds are present in the form of seeds e.g., the members of Asteraceae family.

Leaf Spectra

Leaf size classes were determined by following Oosting (1956).

Leptophyll (L)

The leaf area is 25 square mm.

Nanophyll (N)

The leaf area is 225 square mm.

Microphyll (Mi)

The leaf area is 2025 square mm.

Mesophyll (Me)

The leaf area is 18225 square mm.

Megaphyll (Ma)

The leaf area is 164025 square mm.

Phenology

The phenological attributes of plant species i.e., flowering and fruiting were recorded during the field visits of the study area every month during 2018-2019.

Results

Floristic composition

The flora of Agror Valley comprised of 142 species belonging to 124 genra and 66 families. Asteraceae was the dominant family with 17 species, followed by Rosaceae 12 species, Lamiaceae 09 species and Polygonaceae 06 species. Based on plant growth habit, herbaceous growth form dominated the study area with 96 species (67.60%), followed by trees with 29 species (20.42%) and shrubs 17 (11.97%) species (Table 1).

Table 1. Life form and Leaf spectra of different taxa reported from Agror Valley.

Clasification of plants based on life form and leaf spectra

Life form

The results revealed that the dominant life form in the study area was Therophytes with 61 plant species (42.95%), followed by Megaphanerophytes and Hemicryptophytes 20 species (14.08%) each, Nanophanerophytes 17 plant species (11.97%), Geophytes 12 species (8.45%), Mesophanerophytes05 plant species (3.52%), Chamaephytes 04 plant species (2.81%), Microphanerophytes 02 plant (1.40%), Lianas 01 plant species (0.70%) (Tables 1 and 2).

Table. 2. Life form of different taxa recorded from Agror valley.

Leaf spectrum

The leaf size spectra were dominated by Microphyll flora with 73 species (51.40%), followed by Mesophyll 32 (22.53%), Nanophyll 26 (18.30%), Leptophylls 10 (7.04%) species and Megaphyll contributing 01 species (0.70%) only (Tables 1 and 3).

Table 3. Leaf size spectra of different taxa recorded from Agror valley.

Phenological behaviour

Phenology of the plant species was documented through several visits in research area.

Flowering

The results revealed that two flowering seasons were recorded in the study area, one from May to August and second from September to November (Tables 1 and 4). Mostly plants flowered in the first spell (May to August) during which a total of 137 (96.47%) plant species flowered including herbs 92 (67.15%), trees 28 (20.43%) and shrubs17 (12.40%). During the second flowering season, plant species flowered were 4 (80%) herbs, and 1 (20%) tree. Maximum flowering (42 plant species) occurred in the month of March i.e., the peak month of spring. Further, major flowering months were April, May, June, August, and July where 27, 22, 18, 15 and 13 species showed flowering respectively. On the contrary no flowering was observed during January, February, October, November and December and the most credible cause attributed is low temperature, cold injury, and less metabolic activities.

Table 4. Flowering sessions of plant species in Agror Valley.

Fruiting

The phenomenon of fruiting specificly belongs to angiosperms but in broad sense it refers to the formation of cones and sorii etc. In the study area July was the peak fruiting month in which 29 (20.42%) plant species developed fruiting, followed by June 27 (19.01%) plant species, May 24 (16.90%) plant species, August 22 (15.49%) plant species, September 17 (11.97%) plant species while minimum fruiting was produced in the months of April 11 (7.74%) plant species, October 6 (4.22%) plant species, November 5 (3.52%) plant species, followed by December with 1 plant species (0.70%) (Tables 1 and 4). During January, February, and March none of plant species developed fruiting occurred.

Discussion

Phyto diversity of Agror valley

Flora is priceless and valuable endowment of nature to mankind upon which human race has always been dependent. A flora encompasses all the plant individuals in any geographic area, which are attributes of a geological period or in habit a particular ecosystem. The flora comprises several species, while vegetation indicates the distribution, number of plant species and size of each (Durani et al., 2005). More than 0.25 million plant species are recognized, and an enormous number is still to be investigated and documented (Thorne, 1992). Floristic checklists provide most basic, productive, and key botanical information of a particular region. To formulate conservation and management strategies it is imperative to have detailed floristic interpretation of that particular area (Manikandan and Lakshminarasimhan, 2012). The total floral diversity in the study area consisted of 142 plant species belonging to 124 genra and 66 families. The area’s physiognomy was dominated by 96 species (67.60%), followed by trees with 29 species (20.42%) and shrubs 17 (11.97%) species. Our findings are in agreement with many researchers of allied, neighboring and national regions (Khattak et al., 2015; S.M. Saeed et al., 2018; Shah et al., 2015; Ahmad et al., 2016 and Rahman et al., 2016b,c).

Family contribution

Asteraceae was the leading family with 17 species followed by Rosaceae 12 species, Lamiaceae 9 species and Polygonaceae 6 species. Flora of the study area displayed strong alliance with neighboring areas on account of families. i.e, in the western Himalayan region Asteraceae, Rosaceae and Poaceae were paramount and leading families (Rau, 1975). Whilst many other researchers such as Mehmood et al., (2015) documented Asteraceae as the dominant family from District Tor Ghar on whose foothills the present research area is located. Saeed et al., (2018) also reported Asteraceae as the leading family with 15 species from Datta, District Mansehra.

Life form spectra

Life form provides indication of the climate and depicts plant -environment interaction (Raunkiaer, 1934). The life form classes were dominated by Therophytes with 61 plant species (42.95%), followed by Megaphanerophytes and Hemicryptophytes with 20 species (14.08%) each. The dominancy of Therophytes indicates the harshness as the huge section of study area is dry subtropical in nature. Such results clearly indicate that flora is severely under pressure due to human activites, over grazing and deforestation. Our results are in accordance with Khan et al. (2013) who stated that therophytes dominated the study area with 40 species followed by Megaphanerophyte with 09 species of all the plants. Similar studies were accomplished by Rahman et al., (2018) from Manoor Valley and documented Therophytic life form as the dominant one.

Leaf size spectra

In present study Microphyll flora was dominanat with 73 species, followed by Mesophylls 32, Nanophylls 26, Leptophylls 10 species and Megaphylls 01 species. The dominancy of microphylls and mesophylls signifies that majority of the area is mesic and has plenteous and temporal distribution of precipitation. Our results are in line with Batalha and Martins (2004) who acknowledged Microphylls and Mesophylls as leading leaf size spectra in the vegetation of Azad Kashmir. Haq et al. (2015) also documented Microphylls and Mesophylls as dominant leaf spectra classes from Nandiar Khuwar Catchment, Battagram.

Conclusion

Exploration of Agror Valley accounted 142 plant species recorded. The study depicted that the area hosts diverse ecological habitat and plant diversity. Vegetation mostly signifies subtropical forest flora, humid ecotone and moist temperate forest vegetation in research area. It was observed that floral diversity varies with seasons and soil composition. The dominancy of Therophytes in study area clearly indicates that a significant proportion is dry subtropical in nature. The ecological attributes such as density, frequency and abundance were highly influenced by anthropogenic pressure. Density and frequency values were at peak in rainy season while were least in cold winter season. It was observed that majority of people are uneducated regarding biodiversity and natural resources. Deforestation of fuel wood and timber wood species, exploitation of medicinal plants and overgrazing is posing serious threats to the biodiversity. The participation of general populace in tree plantation and conserving nature is the need of the hour.

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