Phenological Characteristics of Rhododendron Species in Temperate Mixed Broad-Leaved Forests of Arunachal Himalaya, India
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Regular Article pISSN: 2288-9744, eISSN: 2288-9752 J F E S Journal of Forest and Environmental Science Journal of Forest and Vol. 34, No. 6, pp. 435-450, December, 2018 Environmental Science https://doi.org/10.7747/JFES.2018.34.6.435 Phenological Characteristics of Rhododendron Species in Temperate Mixed Broad-leaved Forests of Arunachal Himalaya, India Ashish Paul1,*, Mohamed Latif Khan2 and Ashesh Kumar Das3 1Department of Forestry, North Eastern Regional Institute of Science and Technology (Deemed to be University), Nirjuli 791109, Arunachal Pradesh, India 2Department of Botany, Dr. Hari Singh Gour Central University, Sagar 470003, Madhya Pradesh, India 3Department of Ecology and Environmental Science, Assam University, Silchar 788011, Assam, India Abstract Phenological events of four Rhododendron tree species (viz. R. arboreum, R. arboreum ssp. delavayi var. delavayi, R. barbatum and R. kesangiae) was monitored in temperate mixed broad-leaved forests of Arunachal Pradesh, India. Phenological events like flower bud formation, flowering, fruit setting, fruit maturing, seed dispersal, leaf bud formation, leaf flushing, and leaf shedding were recorded. Indices i.e., phenophase sequence index (PSI), active phenophasic period of the species (APS) and index of reproductive/vegetative activity (RVA) were also calculated. Present study revealed that bark consistency, growth form and leaf pattern of the studied species have showed variations among the species. Rhododendron species exhibited the phenological events overlapping with other phenophases. The peak flower bud formation was observed during the winter; R. arboreum ssp. delavayi var. delavayi start flowering from December, while the flowering in rest three species exhibited during February to April. Fruit setting occurred during summer to autumn while fruit maturation revealed peak during November. Leaf bud formation illustrated two peaks in April and May, leaf flushing exhibited peak in June, while leaf shedding peaked during October to November. Active phenophasic period of the species were found 12 months, which revealed that species engage in various phenophase activities throughout the year. Phenophase sequence index ranged between 0.8 to 0.9 (PSI ≥0.6), signifies that species have a sequential arrangement of phenophases. Index of reproductive/vegetative activity of the species exemplified ＞1, indicate that the reproductive phenophases were dominance over vegetative phenophases. The study have provided substantial insight on the life cycle events of Rhododendron species and ecological approaches for further scientific study with recent climate change and effective management and conservation. Key Words: phenology, phenophase, reproductive, rhododendrons, vegetative Introduction (Fenner 1998). The life cycle events timing throughout the year is the key for plants to adapt the seasonal ecological The life cycle events are the most vital phenomena re- changes (Orshan 1989; Schwartz 2003). Systematic ob- lated to time and seasons. In temperate and Polar regions, servation of life cycle events of plant species is most im- changes of annual temperature play a great role in the cyclic portant for better understanding of vegetation dynamics events of development and reproduction of the flora within the intricate ecological context (Liang and Schwartz Received: April 25, 2018. Revised: November 11, 2018. Accepted: November 21, 2018. Corresponding author: Ashish Paul Department of Forestry, North Eastern Regional Institute of Science and Technology (Deemed to be University), Nirjuli 791109, Arunachal Pradesh, India Tel: 91-9862035885, Fax: 91-360-2257872, E-mail: [email protected] J For Environ Sci 34(6), 435-450 435 Phenological Characteristics of Rhododendron Species 2009). Changes in phenological events influence the re- Parmesan and Yohe 2003; Root et al. 2003). In the higher production, population existence, limitations of organisms elevational environments, the impact of climate change con- and ecosystem services (Kameyama and Kudo 2009; sidered the most pronounced (IPCC 2007) and these are Chuine 2010; Miller-Rushing et al. 2010). Phenology is severe risk to the biological diversity. Limited photo- one among the most initial and perceptible characters by synthetic activity and a very short growing season are the means of which organisms response to change of climate characteristics of high altitude regions, which interlinked (Parmesan and Yohe 2003; Parmesan 2006; Bertin 2008; with the snow or ice (Inouye and Wielgolaski 2003). Wolkovich et al. 2014). Studies on phenology are also sig- Naturally, the annual life cycle events of plant species in the nificant to understand the interactions among the species high altitude regions including alpine and montane zones and the function of community in the altitudinal gradient having temperate weathers is determined by the climatic (Fenner 1998). Generally, in high seasonal climate, like condition like, snowmelt, soil defrosting and the fulfillment temperate and dry tropics the life cycle evens of the com- of scary necessities (Inouye and Wielgolaski 2003; Körner munity largely follow the related pattern year after year with 2003; Luedeling et al. 2011). Thus, the phenology of the the alterations due to climatic changes between the years plant species of the high altitudinal regions affected by the (Fenner 1998). Most significant aspects of phenological changing global climate (Inouye and Wielgolaski 2003). studies are to explore the factors that elucidate the pheno- Phenophase represent the periodic phenomenon and logical behaviour of the species. Several studies have re- their distribution throughout the year, which constitutes the vealed the biological changes due to the present change of plants’ phenological pattern. Plants dispense phenological climate (Parmesan and Yohe 2003; Root et al. 2003; Bertin events like shoot growth, flowering, fruit setting, seed dis- 2008), particularly spring phenology in temperate regions persal, leaf shedding, etc. across the seasons of the year. (Menzel et al. 2006; Ibáñez et al. 2010). Factors like pre- These are an imperative element of the plant’s technique to cipitation, temperature, soil and photoperiod trigger the perform with the seasonal changes (Beatley 1974; Mooney phenology of plant species (Blake and Harris 1960; Lucier 1983; Diaz and Cabido 1997) and these facts are con- and Hinckley 1982; Jackson and Bliss 1984; Johansen et al. tributing to the familiarity of ecosystem function (Körner 1985; van Schaik et al. 1993; Newstrom et al. 1994a; Min 1993; Paruelo et al. 2001; Liang et al. 2011). Phenological 2000; Morellato et al. 2000; Sparks et al. 2000; Fitter and study pay for the facts on growing form and progress of Fitter 2002; Borchert et al. 2004; Menzel et al. 2005; plant species along with the environmental consequences Miller-Rushing and Primack 2008; Kalbarczyk 2009; like behaviour of flowering and fruiting (Marques et al. Seghieri et al. 2009; Körner and Basler 2010; Tooke and 2004; Zhang et al. 2006). These studies are too essential to Battey 2010; Primack and Miller-Rushing 2011; Robbirt comprehend the ecosystem processes like growth, biomass et al. 2011; Ranjitkar et al. 2013). While, edaphic factors and water stress to plants (Kikuzawa and Lechowicz 2011). (like, soil nitrogen and organic matter), canopy cover and Presently, more concentration are given to the studies on other ecological factors (Joiner and Gruis 1959; Blake and phenology owing to significant mechanism in environ- Harris 1960; Ma et al. 1997; Wielgolaski 2001; Dahlgren mental response to the global changes of climate (Morisette et al. 2007; Kudo et al. 2008; Nord and Lynch 2009) are al- et al. 2009; Korner and Basler 2010). Studies on life cycle so influencing the plant phenology. Likewise, type of fruits, events at the species level are very much important for elu- pollination and dispersal of seeds are also essential to under- cidating the reaction of plants to different micro-climatic stand the plant species flowering and fruiting patterns circumstances. Therefore, it is very significant to perceive (Bawa et al. 1985; Ibarra-Manriquez et al. 1991; Ibarra- the plant species phenological changes in regards to Manriquez and Oyama 1992; van Schaik et al. 1993; changes of climate. Moreover, owing to hilly, undulating Newstrom et al. 1994b; Wright and Calderon 1995; Poulin topography and remoteness, no extensive study has been et al. 1999; Spina et al. 2001; Bolmgren et al. 2003). carried out in the eastern Himalayan region. Santy of liter- Biodiversity dispersion and effective measures are influ- atures on phenology and insufficient research amenities is enced by the changes of climate (Walther et al. 2002; additional constrictions at species level long term records, 436 Journal of Forest and Environmental Science http://jofs.or.kr Paul et al. especially in the eastern Himalayan region. gion of Indian Himalayas. Only limited information are Rhododendron L. is the largest genus in the family available in few flora or taxonomic monographs in which Ericaceae having over 1000 species distributed throughout the life cycle events appear in the form of herbarium speci- Asia, Europe, North America and. Australia (Chamberlain mens but not as periodical field observations. The foremost et al. 1996; Fang et al. 2005; Gibbs et al. 2011). Habit of purpose of this study was to document phenological events rhododendrons ranged from tiny mat-like (2.5 cm) to large of selected rhododendrons (viz., R. arboreum,