Plant diversity patterns and conservation status of eastern Himalayan forests in Arunachal Pradesh, Northeast India

Saikia et al. Forest Ecosystems (2017) 4:28 DOI 10.1186/s40663-017-0117-8 RESEARCH Open Access Plant diversity patterns and conservation status of eastern Himalayan forests in Arunachal Pradesh, Northeast India P. Saikia1, J. Deka2, S. Bharali3, Amit Kumar1, O. P. Tripathi4, L. B. Singha4, S. Dayanandan5 and M. L. Khan6* Abstract Background: The State of Arunachal Pradesh is part of the Himalaya biodiversity hotspots distributed over an area with the largest elevation gradients in the world, ranging from lowland tropical forests to alpine vegetation. Methods: The vegetation was surveyed along an elevation gradient ranging from 87 to 4161 m in 354 belt transects (500 m × 10 m in size) and analyzed using various ecological indices. Results: A total of 482 (458 identified, 24 unidentified) plants were recorded in the present study, of which 153 are nonwoody herbs and grasses (145 identified) belonging to 55 families, and 329 are woody trees and shrubs (313 identified) belonging to 74 families. The 458 identified species belong to 117 families and 251 genera, of which 94.10% are phenerogams (Angiosperms: 421 species [spp.] and Gymnosperms: 10 spp.) and 5.90% cryptogams (Pteridophytes: 27 spp.). The family Fabaceae contributed the greatest species diversity with a total of 27 plant species (Papilionaceae: 10 spp., Mimosaceae: 9 spp. and Caesalpinaceae: 8 spp.) followed by Poaceae (21 spp.), Ericaceae (20 spp.), Asteraceae (18 spp.), Lauraceae (17 spp.), Euphorbiaceae (16 spp.), Urticaceae (15 spp.) and 49 monotypic families. The most dominant trees were Castanopsis indica (24 individuals per ha), followed by Quercus semicarpifolia (12 individuals per ha) and Pinus roxburghii (12 individuals per ha) and some bamboos (Dendrocalamus strictus: 69 individuals per ha; Bambusa pallida: 16 individuals per ha). The studied forest stands were rich in various bamboos; a total of 14 different bamboos were recorded in the present study including Dendrocalamus strictus, Bambusa tulda, B. pallida etc. Common IUCN red-listed species were Aquilaria malaccensis, Begonia tessaricarpa, Gledetsia assamica, Gymnocladus assamicus, Livistona jenkinsiana, Rhododendron meddenii, Rhododendron thomsonii collected from the Dirrang, Tawang, Yamcha, Itanagar, Along and Mebo areas of Arunachal Pradesh. Conclusion: The results confirm that the Eastern Himalayan forests are very rich in terms of species diversity which decreases with increasing elevation. Species richness and distribution patterns of plants are largely regulated by altitude and other environmental factors. Intensive monitoring and management is needed to protect this fragile ecosystem from the ever-increasing anthropogenic pressure and changing climatic conditions. Keywords: Species richness, Endemic species, Forest ecosystems, Eastern Himalayan region Background The vegetation is a fundamental component of ecosystems that reflects the effects of the total environment (Billings 1952). Plants grow collectively in a specific ecosystem and have a mutual relationship among themselves as well as within the local environment (Mishra et al. 1997), which results in the formation of different vegetation types in * Correspondence: 6 Department of Botany, Dr. Harisingh Gour Central University, Sagar, Madhya Pradesh 470003, India Full list of author information is available at the end of the article different regions. Forests are important as they provide various ecosystem services such as species conservation, prevention of soil erosion and preservation of habitat for plants and animals (Li et al. 2003; Armenteras et al. 2009). Tree species diversity is the determinant of total forest biodiversity as trees provide resources as well as habitats for almost all other forest species (Haung et al. 2003). In forest ecosystems, tree species diversity varies greatly from place to place mainly due to variation in biogeography, habitat and disturbance (Whitmore 1998). Environmental variability in terms of climatic factors, social resources, © The Author(s). 2017 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. Saikia et al. Forest Ecosystems (2017) 4:28 grazing by herbivores and human interference are the critical factors which regulate the spatial and temporal patterns of the vegetation of an ecosystem (Chapin et al. 1993). However, the composition of vegetation is fluctuating and continuous modification takes place depending upon the temperature, moisture, sunlight and available nutrients (Heady 1958). Tropical forests constitute the most diverse plant communities on earth. However, these forests are disappearing at the alarming rate of 13.5 million hectares per year globally (Kobayashi 2004). It is estimated that around 7500 species of organisms are becoming extinct every year (Chatterjee 1995) and many of them disappear even before they are known to the scientific world (Myers et al. 2000; Pimm and Raven 2000). Ecological and environmental problems such as soil degradation, soil erosion and overexploitation of natural resources are just some of the negative effects resulting from the destruction of natural ecosystems (Hundera et al. 2007). Furthermore, floristic diversity along with the respective habitat is also rapidly declining. The loss of any such forest resource will have great implications for the environment, the biological diversity as well as the socio-economic setup of local communities. The state of Arunachal Pradesh located in the eastern Himalayan region is part of the Himalaya biodiversity hotspots. It is the largest mountainous state of India and recognized as a globally important eco-region (out of 200). It comprises over 5000 species of plants, which are distributed along one of the largest elevation gradients in the world, ranging from lowland tropical forests to alpine vegetation in the Himalayan Mountains. According to FSI report (2015), forest cover in Arunachal Pradesh is 67,248 km2; it is ranked as second in terms of forested areas after Madhya Pradesh (77,462 km2). On the other hand, it ranks 4th in terms of percentage of forest cover (80.30%). In the Himalayan ranges of Arunachal Pradesh, the vegetation ranges from tropical mixed and broadleaf evergreen forest to alpine meadow and scrub, across large elevation gradients. Knowledge of ecological processes and biotic interference helps in understanding the stability of well-established plant communities as ecological, biotic and anthropogenic disturbances are prevalent all over the Himalaya (Singh and Singh 1991). Determining the composition, structure and function of forest ecosystems is of great ecological value not only (...truncated)