Taxonomic and Functional Plant Diversity Patterns Along an Elevational Gradient Through Treeline Ecotone in Kashmir
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Tropical Ecology 59(2): 211–224, 2018 ISSN 0564-3295 © International Society for Tropical Ecology www.tropecol.com Taxonomic and functional plant diversity patterns along an elevational gradient through treeline ecotone in Kashmir SUBZAR AHMAD NANDA, ZAFAR A. RESHI*, MANZOOR-UL-HAQ, BILAL AHMAD LONE & SHAKOOR AHMAD MIR Department of Botany, University of Kashmir, Srinagar 190006, J&K, India Abstract: Species distribution and community assembly patterns along elevation gradients have been studied world over but not much information in this regard is available about the Indian Himalayan region, including the Kashmir Himalaya. It is in this context that we studied elevational (2200–3800 m) patterns in plant species richness, functional and taxonomic diversity of various plant groups with particular reference to treeline ecotone (3200–3700 m). Present study revealed that the patterns of species richness were not consistent across taxonomic or functional groups of plants. Four patterns of species richness in relation to elevation were observed: low- elevation plateau with a mid-peak in bryophytes and lichens, mid-peak pattern in pteridophytes and inverted hump-shaped pattern in monocots. During the present investigation, rapid changes in species composition and physiognomy were recorded in the treeline ecotone over small elevational increases. Number of tree species in this zone declined rapidly from four species at an elevation of 3200 m to one at 3700 m. While from 2200 m to 3200 m the vegetation was predominated by fir (Abies pindrow) forming a closed canopy forest, but beyond 3200 m its density decreased rapidly with concomitant increase in the density of birch (Betula utilis). Ultimately birch was the dominant treeline species and grew in association with Rhododendron campanulatum up to 3700 m, beyond which treeless alpine meadow existed. The present study is first of its kind carried out in Kashmir Himalaya and would hence serve an important baseline for similar such studies that would pave way for better understanding and conservation of plant communities in such mountainous regions. Key words: Birch, elevation pattern, fir, species richness, treeline, timberline. Guest editor: S.P. Singh Introduction govern such elevational patterns in species diversity not only constitutes a central theme of Vegetation in mountainous areas varies in macroecology, but also has practical implications in physiognomy, species richness and diversity along discerning the response of species to climate elevational gradients (Kluge et al. 2017; Manish et change, particularly in mountainous areas (Saikia al. 2017; Peters et al. 2016). A number of studies in et al. 2017; Yadav et al. 2017). The recent meta- different parts of the world have revealed that analyses of the studies have enhanced our species diversity shows monotonic, unimodal or understanding of the effect of climatic and spatial multimodal patterns in relation to elevation factors on elevational species richness species and (Rahbek 2005). Mid-gradient peaks of species community assembly (Kessler et al. 2011; richness (Mid Domain Effect) have also been McCain 2007; McCain 2010; Romdal & Grytnes reported (Colwell & Lees 2000; Colwell et al. 2004; 2007). Grytnes & Vetaas 2002; Grytnes 2003). Most of the studies that have examined Understanding the underlying mechanisms that the patterns of species diversity along elevational *Corresponding Author; e-mail: [email protected] 212 ELEVATIONAL PLANT DIVERSITY PATTERNS IN KASHMIR Fig. 1. Location map of the study area and study site. gradients have used species richness as a surrogate diversity is the excessive focus only on one or the for diversity, thereby assuming taxonomic, other plant group assuming that diversity patterns functional and phylogenetic equivalence among are uniform across different groups of organisms. different species (Swenson et al. 2012). Patterns of However, such an approach limits our under- taxonomic biodiversity along elevational gradients standing of the response of different organisms or are also used as proxies for variation in taxa to complex gradient of elevation wherein other environmental characteristics (Körner 2007) such factors such as temperature, precipitation and as, climate (Schwörer et al. 2014; Tuhkanen 1993), other local ecological factors co-vary (Grytnes et al. temperature and length of growing season 2006; He et al. 2018). (Holtmeier 2009; Hustich 1979; Schickhoff 2005), It is also becoming increasingly apparent that local climate, topography, site history, and ecology taxonomic approach does not adequately capture of plant species, current biotic and anthropogenic variation in functional and phylogenetic dimensions influences (Holtmeier 2009). Another limitation of of diversity which often respond to environmental studies dealing with elevational pattern in species gradients differently than does the taxonomic NANDA et al. 213 dimension (Chun et al. 2017). Disentangling the general climate of Kashmir Valley. Average annual underlying processes that govern taxonomic, temperature is 12.8 °C. Precipitation here averages functional and phylogenetic patterns is of pivotal 1035 mm. It is largely non-monsoonal and most of importance (Chun et al. 2017) because of their the rain falls in March. conservation implications particularly in the context of Himalayas which are warming 2–5 times Vegetation sampling more than the global average. It also needs to be For vegetation sampling, the altitudinal emphasized that changes in species diversity are gradient of 2200 to 3800 m in the study area was not uniform along the entire elevational gradient; divided into seventeen (17) altitudinal bands of 100 instead changes are more rapid in the treeline m each. Three plots of 50 × 50 m area were ecotone which extends from the forest limit or the established in each of these altitudinal bands. In upper limit of the continuous closed forest canopy to each plot ten (10 × 10) quadrats for trees, 20 (5 × 5 the treeless alpine zone above (Dutta et al. 2014; m) for shrubs and 40 (1 × 1 m) for herbs were laid Körner 2012; Tranquillini 1979; Wielgolaski et al. randomly for vegetation sampling. Thus, in each 2017; Wieser & Tausz 2007). elevational band, 30 quadrats were laid for Thus, the present study was carried out in the documenting the diversity of trees, 60 quadrats for Kashmir Himalaya to document taxonomic and shrubs and 120 quadrats for herbs. Across the functional diversity of all major plant groups, entire elevational gradient, in all 510 quadrats were including angiosperms, gymnosperms, ferns, sampled for recording tree species richness, 1020 bryophytes and lichens along an elevational quadrats for recording species richness of shrubs gradient. The present study is significant since it and 2040 quadrats for recording species richness of simultaneously studied pattern of taxonomic and herbs. functional diversity in different groups of plants unlike most previous studies that have studied only Taxonomic diversity taxonomic diversity mostly of one or the other plant group. Furthermore, the present study is first of its It was quantified on the basis of collection, kind in the Kashmir Himalaya and hence would identification and inventorization of species add to the body of knowledge about the elevational belonging to angiosperms, gymnosperms, patterns of species richness in different parts of bryophytes, ferns, lichens from each of the Himalaya which is necessary to have an elevational bands employing quadrat method. overarching understanding of species diversity patterns along elevational gradients particularly in Functional diversity the context of climate change and other anthro- Following functional traits of spermatophytes pogenic stressors. were studied during the present study: Materials and methods Growth form: Trees (>2 cm dbh, height 5–15 m), shrubs (height <2 m) and herbs (height <0.5 m). Study area Life span: Annual/Perennial Stem tissue: Herbs/shrubs/trees Present study was carried out in the Daksum For bryophytes and lichens following growth and Sinthan Top area of the Kashmir Himalaya forms were recognized: (Fig. 1). Daksum lies within the geographical coordinates of 33°36'43"N 75°26'6"E and is located Bryophytes: Liverworts (leafy) and mosses at an altitude of 2,200 m above the sea level at a Lichens: Thallus growth form (foliose, fruticose, distance of 40 km from the main district crustose, leprose, etc.) headquarter of Anantnag and about 85 km from Species accumulation curves for trees, shrubs Srinagar. Sinthan Top (3800 m) lies within the and herbs and rarefaction curves for trees and geographical coordinates of 33°34'N and 75°30'E shrubs were computed using EstimateS (Colwell and a road (NH1B highway) traverses through this 2013). Species accumulation curves, sometimes top that connects Kashmir valley with Kishtwar called collectors curves, plot the cumulative number which lies in Jammu province of the State. of species recorded as a function of sampling effort, Daksum-Sinthan Top area is about 130 km south such as number of samples laid (Colwell & of Srinagar, 73 km from Anantnag and 48 km from Coddington 1994). They were used to indicate the Kokernag. Climate of the study area is akin to adequacy of sampling effort in different elevational 214 ELEVATIONAL PLANT DIVERSITY PATTERNS IN KASHMIR 140 collection and identification of 425 plant species 120 belonging to 268 genera and 117 families (Table 1). Amongst these, the flowering plants were 100 s e i predominant, with dicots sharing 175 species in 131 c e p 80 genera and 44 families, and monocots only 19 s f o species in 16 genera of 10 families. Gymnosperms r e 60 b were represented by 4 species belonging to 4 genera m u N 40 and 2 families. Besides, 33 species of pteridophytes in 16 genera and 9 families, 39 species of bryophytes 20 in 33 genera and 22 families and 155 species of 0 lichens in 68 genera and 30 families were also 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 recorded from the area.