Asian Journal of Plant Sciences

Year: 2020 | Volume: 19 | Issue: 2 | Page No.: 91-106
DOI: 10.3923/ajps.2020.91.106

Floristics, Leaf Size Spectra and Life-form Distribution of Riparian Vegetation along a Hill Stream, Bhaderwah, Jammu and Kashmir, India

Anu Sharma and Neeraj Sharma

Abstract: Background and Objective: The complexity of riparian vegetation can be analyzed through the functional groups based on a variety of characteristics, including morphology, physiology, competition and geography. The present study aimed to understand the composition, distribution pattern, phenology and physiognomic traits of riverine vegetation in Bhaderwah, Jammu and Kashmir, India. Materials and Methods: Organized field surveys were conducted in a mountainous riparian corridor of Neeru stream in Bhaderwah during 2016-2017. The study area forms a linear hydro-morphological unit spanning 30 km in length and ~15-100 m wide located along an elevational range of 850-2200 m. A random sampling technique was used for vegetation sampling. Results: The study corridor is well represented by subtropical, sub-temperate, temperate and alpine elements of vegetation. In all, 248 plant species contained in 193 genera and 78 families were recorded from 45 sampling stations surveyed for all the seasons. Asteraceae dominated the area with 27 species in 20 genera. The life-form spectra revealed thero-hemicryptophytic type of phytoclimate with the prevalence of microphylls (46.37%). Conclusion: The study area comprises of rich diversity of herbs followed by shrubs and trees with a pronounced mid domain effect observed for species and familial richness. The observations on leaf size and biological spectra reflect the characteristics of moderately disturbed temperate ecosystem. The flowering and fruiting commence early at the lower elevations and vegetation remains dormant during winters. Other drivers of richness and diversity of riparian vegetation needs to be integrated in future studies.

Keywords: Neeru stream, riparian corridor, life-form spectra, mid-domain effect, phytoclimate, microphylls and Floristics

INTRODUCTION

The plant communities are classified mainly based on the floristics, habitat and physiognomy or geographical characteristics. Vegetation is the collective growth of plants combined in a specific area characterized by component species or structural and functional combination of features that make their physiognomy^1,2. The vegetation forms a critical component of the ecosystem and serves to describe many facets of ecological patterns across the landscape. The flora of an area measure and record the types of plant species, their number, population size, distribution and composition within these communities³. The flora of any region is vital to understand the prevailing environment and the environmental interactions in the ecosystems⁴. Its documentation serves as a future reference to assess the changes in habitats and plant responses to the changing environment^5-7. The vegetation varies across time and space in physiognomy which describes a set of functional and morphological attributes of the dominant plant communities in a particular area⁸. The climatic outlook of the vegetation is expressed in the form of life forms as the morphological adjustment to the environmental constraints.

Plants can be grouped in life-form classes based on their similarities in structure and function and plant adaptation to certain ecological conditions⁹. A life form of the plant is the sum of all life processes that evolved directly in response to the environment^10,11. These are the critical physiognomic attributes that express the harmony between plant and its surroundings. Biological spectrum is the percentage distribution of different life-forms for a given flora¹⁰ used as an index for comparing geographically separated plant communities in a given set of climatic and environmental factors^12,13. While the Raunkiaer’s biological spectrum defines the phytoclimate, the leaf size spectrum provides an idea of the floristic adaptation¹⁴. Raunkiaer¹⁰ system of plant life form classification is based on the position, degree of protection of the perennating buds¹⁵. These are categorized as phanerophytes, therophytes, cryptophytes, hemicryptophytes and chamaephytes¹⁶.

The biological spectra of the Indian region are related to specific climatic, edaphic and altitudinal factors¹⁷. India, as a geographical entity, expresses a phanerophytic type of phytoclimate¹⁷. The Hemicryptophytes are characteristics of temperate regions and the therophytes indicate desert climate^18,19. While the life form spectra are the indicators of micro and macro climate²⁰, the leaf size information helps to understand the kind of physiological processes of plants and plant communities²¹. The relationship between leaf size and ecological factors plays a significant role in studying vegetation at a regional scale. The phenology, another physiological aspect that is governed by climate, involves the plant life cycle stages, such as flowering, leafing and maturation of plants. The phenology of a species includes understanding the seasonal and inter-annual difference in climate on the life-cycle actions and behaviour of the species²². Though a lot has been explored for the terrestrial landforms, the information on riparian life forms, especially for the Mountain Rivers is scanty for Indian Himalayan Region. Natural riparian zones are the most diverse, dynamic and complex biophysical interfaces between aquatic and terrestrial ecosystems. The nature of plant communities in the riverine ecosystems are largely influenced by altitude, total rainfall, duration of the rainy season, wind and temperature along with soil characteristics²³.

While many floristic explorations have been done in the whole Chenab valley^24-26, including the study area^27-36, the hill riparian forests received the least attention. Earlier, some of the studies highlighting life forms and phytoclimate have been reported from the study area using Raunkiaer’s system^27-30. Still, any such information on phytoclimate of the riparian forests is missing from the region. The current study aimed to find the composition of vegetation, the dominant life forms and phytoclimate of the study area.

MATERIALS AND METHODS

Study area: The study area comprised of 35 km long and ~1.5 km wide corridor lying between 32°55'32" to 33°08'26" N and 75°32'41" to 75°45'78"E along an elevational range of 850 m (its confluence with River Chenab at Pul Doda) to 2200 m near Thanalla close to its origin including the river bed, flood plain and the edge up-slopes on the either sides (Fig. 1).

Methodology: Divided into fifteen sites, the surveys were conducted in the riparian and upland matrix of 200 m on either side of the stream during March, 2016 to November, 2018. The plants were classified into different life form classes on the basis of perennating buds¹⁰. These included the Phanerophytes with perennating buds lying above 0.25 m from the soil surface, chamaephytes (perennating buds above 25 cm from soil surface), hemicryptophytes (perennating buds lying at the soil surface), geophytes (perennating buds buried in the soil) and therophytes (complete their life cycle from seed in one season).

Life form for each species was noted and biological spectrum prepared to note the phytoclimate of the study area. The leaf size classes were classified as leptophil, nanophyll, microphyll, mesophyll, macrophyll and megaphyll following Raunkiaer¹⁰, Hussain³⁷ and Haq et al.³⁸. The identification of plants, leaf size measurement and statistical analysis of the data was performed in the forest ecology laboratory of Institute of Mountain Environment, Bhaderwah Campus.

Statistical analysis: The statistical analysis was performed in MS Excel 2007 and open source software PAST 4.0 for the creation of column/bar charts and rarefaction curves.

RESULTS

Neeru watershed is well represented by subtropical, sub-temperate, temperate and alpine elements of biodiversity along the elevational gradient. The landuse/landcover map prepared from digital classification of IRS ID LISS IV image of 2016 depicts seven different categories (Fig. 1) based on the spectral signatures of ground realities. It supports Ban Oak-Chir pine-Himalayan Alder (Quercus leucotrichophora, Pinus roxburghii, Alnus nitida), Moru Oak-Blue pine-Himalayan Alder (Quercus baloot, Pinus wallichiana, Alnus nitida, associations at lower elevations followed by Blue pine-Himalayan Alder-Deodar (Pinus wallichiana, Alnus nitida, Cedrus deodara), Moru Oak-Deodar-Blue pine (Quercus baloot, Cedrus deodara, Pinus wallichiana) at mid, and, Deodar-Spruce-Fir (Cedrus deodara, Picea smithiana, Abies pindrow) at higher elevations till tree line at 3200 m which is subsequently taken over by Rhododendron-Juniper scrub and Krumholtz above 3400 m.

Floristic composition: A total of 248 plant species contained in 193 genera and 78 families have been recorded from the riparian and adjoining upland forests along Neeru stream. Of these, 39 are trees (15.72%), 49 shrubs (19.75%) and 170 herbs (68.54%). The list of plant specimens collected along with their habit, habitat, life form, flowering, fruiting, leaf size, altitude wise distribution and familial description has been given in Appendix 1. Of the total species observed, 5 species namely Pinus roxburghii, Pinus wallichiana, Cedrus deodara, Abies pindrow and Picea smithiana are gymnosperms while 243 (97.98%) are angiosperms. All the gymnosperms are represented in a single family i.e., Pinaceae. Pteridaceae comprised of 3 species in two genera. Among the Angiosperms, Asteraceae dominates the area with 27 species (10.88%) in 20 genera followed by Rosaceae (22 species/ 16 genera, 8.87%), Lamiaceae (15 species/14 genera, 6.04%), Fabaceae (11species/10 genera, 4.43%), Poaceae (9 species/ 9 genera, 3.62%) and Moraceae (8 species/3 genera, 3.22%) respectively (Fig. 2). As many as 36 families show monotypic representation in the area as they are represented by a single genus and single species, while 42 families are polytypic.

Distributed in three elevational bands (low, mid and high), 126 species were observed in band-1 (850-1300 m), 200 in band-2 (1300-1800 m) and 192 in band-3 (1800-2200 m), clearly exhibiting the mid domain affect. 130 species were encountered along the riparian, 236 along the left and 199 species along the right banks, respectively. The species richness along various elevations ranges in general as well as species contained in ten dominant families in different elevational bands is presented in Fig. 2.

The rarefaction curves drawn for the trees, shrubs and herbs for the riparian and upland (left and right banks) have been presented as Fig. 3a-c. As the cumulative count, the riparian forests comprised 15 trees, 20 shrubs and 105 herbs while the upland forests supported 32 trees, 47 shrubs and 120 herbs. The trees exhibited less species richness and more homogeneity along the riparian corridor than the upland forests. The left bank supported more trees in comparison to the right bank (Fig. 3a). Similarly lesser number shrubs were encountered in the riparian forests followed by upland right and left bank upland forests (Fig. 3b). The herbaceous layer showed the lower species richness along the riparian and right bank upland forests, while the left bank upland forests showed high richness and heterogeneity (Fig. 3c).

Biological spectrum: The assessment on the biological spectrum of the study corridor is based on the seasonal observations of life forms in a span of two years. Life forms recorded for all the species revealed the highest percentage of therophytes (TH 67 species, 27.01%) followed by hemicryptophytes (H 53, 21.37%), nanophanerophytes (N 49, 19.37%), macrophanerophytes (M 39, 15.72%), chamaephytes (CH 25, 10.08%), geophytes (G 10, 4.03%), hydrophytes (HH) and epiphytes (E 2, 1.20%) and Liana (L 1, 0.40%).

The bio-spectrum suggests thero-hemicryptophytic type of phytoclimate. When compared with the normal spectrum of Raunkiaer, the Therophytes revealed the maximum deviation (+14.01%), while naophanerophytes show +4.37 and chamaephytes the minimum (+1.08%). On the contrary, a negative deviation of -12.28% has been observed for macrophanerophytes followed by hemicryptophytes (-4.63%) and epiphytes (-1.8). Other life forms show minor deviation from normal spectrum (Fig. 4).

Leaf spectra: An analysis of the leaf size spectra revealed that the vegetation of the study corridor is Microphyllus type with 115 species (46.37%) followed by Nanophylls (52 species, 20.96%) and Mesophylls (47 species, 18.95%). Leptophylls and Megaphylls were observed in less numbers with 19 (7.66%) and 15 plant species (6.04%) respectively, observed in the study area. The dominance of microphylls and nonophylls is attributed to the moderate slopes, dry substratum and mild climate of the study corridor.

Phenology: The phenophases (flowering and fruiting) of plants were recorded for all seasons during the study period. The plants have been grouped in three main categories which coincide with their flowering. The flowering season commences during March at lower elevations and it prolongs till September for few species. Current observations revealed that 77 i.e., 31% of plants in the study area started bearing flowers during March to May while a majority (138, 56%) bloomed during June and July. Flowering phase starts declining after July where a limited species (33.13%) were recorded bearing flowers during August and September (Fig. 5). These are mostly restricted to the tail zone of the study corridor. Most of the plants that bloomed during July and August belong to mid and higher elevations (1300-2200 m).

The fruiting corresponded with the flowering stages as a usual phenomenon. Maximum fruiting was observed post rainy season with 133 (53%) plants species recorded bearing fruits during September to November. One hundred and twelve species (45%) exhibited fruiting phenophase during moderately warm months of June, July and August. The period from March to May showed less fruiting with only three species observed bearing fruits (Fig. 5).

The senescence generally commences after September where many deciduous species start shedding their leaves. The riparian vegetation comprising of dominant trees like Alnus nitida, Melia azedarach, Ailanthus altissima, Ficus palmata and Robinia pseudoacacia exhibit the complete senescence by mid of November and remain dormant till late February at lower elevations. Likewise, the evergreen species like Pinus roxburghii, P. wallichiana, Cedrus deodara and Picea smithiana at mid and higher elevations also remain dormant during the autumn and winters.

DISCUSSION

The vegetation is a fundamental component of ecosystems that reflects the effect of total environment. During the surveys, a total of 248 plant species contained in 193 genera and 78 families were recorded from the riparian and adjoining upland forests along Neeru stream. Thirty nine among these were trees (15.72%), 49 shrubs (19.75%) and 170 herbs (68.54%) with a pronounced mid domain effect observed for the study corridor. Among the angiosperms, Asteraceae dominates the area with 27 species (10.88%) in 20 genera. The significant studies highlighting the composition, distribution and community structure of the vegetation in Neeru watershed include those by Dutt²⁷, Najeeb²⁸, Singh³⁰, Sharma³¹, Sharma et al.³², Sharma and Baloria³³ and Singh et al.³⁴. All the above explorations restricted to the mountain ecosystems until the recent surveys in the riparian forests along Neeru, a typical hill stream in Bhaderwah by Sharma²⁹, Sharma et al.³⁵ and Sharma and Sharma³⁶. The floristic explorations from the adjoining states of Himachal Pradesh and Uttarakhand (Pharswan et al.³⁹, Rana and Kapoor⁴⁰, Kumar et al.⁴¹, Kanwal and Joshi⁴²) and across the border in few pockets of Pakistan and Pakistan Occupied Kashmir (Khan et al.⁴³, Rahman et al.⁴⁴, Asif et al.⁴⁵, Zeb et al.⁴⁶, Haq et al.⁴⁷) reveals the predominance of herbs followed by shrubs and trees with Asteraceae always at the top among other families. In terms of species richness, the study revealed a hump shaped distribution explaining the mid-domain effect supported by Zhang and Mi⁴⁸, Kharkwal⁴⁹, Zhang and Ru⁵⁰, Shaheen et al.⁵¹, Mandal and Joshi⁵² and Dar and Sundarapandian⁵³. Lower and mid elevational bands are more species rich when compared to higher altitudes as observed by Kumar and Ram⁵⁴.

Different life form classes of plant species change with elevation which is evident with current results showing the predominance of therophytes (67 species, 27.01%) followed by hemicryptophytes (53, 21.37%) thus suggesting thero-hemicryptophytic type of phytoclimate. While the therophytes indicate the disturbed habitats, the hemicryptophytes are the indicators of temperate climate. These results are in consonance with the findings of Dutt²⁷, Najeeb²⁸, Sharma²⁹ and Sharma et al.³⁵ who worked in Neeru catchment. The dominance of hemicryptophytes and chamaephytes is typical of a temperate climate and is attributed to many factors which operate at macro, meso and micro climatic levels (Khan et al.⁴³, Zeb et al.⁴⁶). The dominance of therophytes is usually associated with unfavorable dry environmental conditions (Haq et al.⁴⁷). Similar results have been obtained for the ecosystems exhibiting same climatic regimes in north western Himalayas (Pharswan et al.³⁹, Khan et al.⁴³, Asif et al.⁴⁵, Zeb et al.⁴⁶, Haq et al.⁴⁷, Qureshi and Bhatti⁵⁵, Qureshi and Ahmed⁵⁶, Qureshi et al.⁵⁷, Khan et al.⁵⁸, Nazir et al.⁵⁹, Qureshi et al.⁶⁰). Of the very limited studies available for the riparian habitats, Haq et al.⁴⁷ and Srivastava and Singh⁶¹ recorded the dominance of therophytes followed by hemicryptophytes. The predominance of maga phanerophytes along the riparian corridors reflects the climax vegetation (Qureshi and Bhatti⁵⁵).

The leaf size plays a significant role in studying the vegetation as it increase with humidity, rainfall and soil fertility. The leaf size spectrum in the study area shows the dominance of microphylls (115 species) followed by nanophylls (52) and mesophylls (47). Microphyllus vegetation is the characteristics of steppes and indicator of the steep conditions while nanophylls indicate dry and warm climatic conditions (Ali et al.³ and Khan et al.⁴³). The small leaf size is seen as an adaptive strategy for retaining soil moisture (Khan et al.⁴³). Observations for the current study are in consonance with those of Khan et al.⁴³, Haq et al.⁴⁷, Asim et al.⁶² who reported the dominance of similar leaf size spectra in their study areas. Phenological attributes of the plants in the Himalayas are controlled by the physiographic (mainly the elevation) and climatic factors (temperature). Our observations revealed that one third of the plants started bearing flowers during March to May, about half from June and July and only a few species post rainy season. Interestingly, the flowering phase at lower elevation coincides with fruiting stages at higher elevations where most of the plants remain in late fruiting or dormant phase from late October to March. Similar observations were recorded by Ali et al.³, Khan et al.⁴³, Asif et al.⁴⁵, Zeb et al.⁴⁶, Haq et al.⁴⁷, Srivastava and Singh⁶¹, Singh and Singh⁶³, Rai⁶⁴ and Dar and Malik⁶⁵. The fruiting phase was observed during June to August and September to November. Haq et al.⁴⁷, Asim et al.⁶² and Malik and Malik⁶⁶ and also reported two flowering seasons in other parts of the Himalayan region.

CONCLUSION

The present documentation of taxonomic and functional diversity in a riparian hill corridor reveals rich phytodiversity with 248 species of plants, mostly herbs, dominated by the family Asteraceae. The predominance of thero-hemicryptophytic and microphyllus type of vegetation speaks of the kind of climate and nature of the habitat in the corridor. The peak flowering and fruiting were observed during July-August and September-November while most of the deciduous vegetation remains dormant during winters. The vegetation indicators call for effective ecological management of the corridor.

SIGNIFICANCE STATEMENT

The study highlights the factors that govern the phytoclimate of a typical riparian corridor. It also provides a piece of first-hand information on species response to the changing climate and human disturbances. The understanding of phenology on how species respond to the changing climatic regime and patterns need to be scientifically investigated on broader spatial and temporal scales. Other drivers of richness and diversity of riparian vegetation need to be integrated with future studies. The study helps to uncover the critical ecotones that many researchers were not able to explore in the region.

ACKNOWLEDGMENT

The authors are grateful to the Rector, Bhaderwah Campus and University of Jammu for providing the necessary support for the smooth conduct of the research work. Acknowledgments are also due to Mr. Dinesh Singh and Mr. Ajaz Ansari, the researchers at Institute of Mountain Environment for their kind help.

REFERENCES