Addition to the liverwort flora (Marchantiophyta) of Arunachal Pradesh, India

: The present study identified 20 liverwort species from Tirap district, Arunachal Pradesh, India, marking the first ever documentation of bryophytes from the region. The specimens were collected from various locations within the study area and subsequently brought to the laboratory. Micromorphological and anatomical characteristics of the specimens were analysed and identified by consulting relevant literatures. Three species, viz. Plagiochila himalayana Schiffn., P. khasiana Mitt., and Solenostoma lanigerum (Mitt.) Váňa & D.G.Long, are newly reported for the first time from the state of Arunachal Pradesh. The species were found to be an integral part of ecosystem growing in association with various plant species, providing soil stability, and shelter for other organisms. The study is important for understanding bryophyte diversity and ecosystem health of the region. In addition, it will also help in planning conservation strategy and sustainable management of bryophytes, their habitat or host species and the overall biodiversity in the region.

Tirap district is a part of the Eastern Himalayas, one of the biodiversity hotspots of the world.It is located in the southernmost part of the state and lies between the latitude 27.018 °N, 95.519 °E (District website of Tirap 2022, accessed on 22 September 2022).The elevation of the district ranges 200-4,000 m in the northwest to the Patkai hills.Tirap is bounded by Changlang district in the east, Assam state in the north, Longding district and Nagaland in the west, and Myanmar in the south (Wangpan et al. 2019).The district has an annual rainfall of 2,754 mm per year and temperature ranges 14-25 0 C (World Data Atlas 2023).The vegetation of Tirap is primarily comprised of tropical and subtropical evergreen forests, with interspersed grasslands and temperate forests in the upper elevations.The temperature in Tirap is moderate to warm with frequent rainfall.The district offers a virgin area for the diverse and luxuriant growth of many plants including bryophytes.The inhabitants of Tirap, revere and offer prayers to nature for their reliance on plants for food, shelter, livelihood, and wellbeing.Wangpan et al. (2019) and Tangjang et al. (2011) documented flowering plants for various purposes such as food, medicine, and house construction.The district remained unattended for the lower plant groups like bryophytes and pteridophytes which provide the intricate relation with the higher plants.Therefore, the present study was undertaken to survey and document the bryoflora of the region (Figure 1).

MATERIALS AND METHODS
Liverwort samples were collected from the Tirap district, Arunachal Pradesh, India, during May 2021 and 2022.Field data, including habit, habitat, temperature, humidity, and soil types, were recorded for each species.The specimens were initially stored in ziplock plastic bags, air-dried, and later transferred to paper bags in the laboratory.To aid in identification, the specimens were rehydrated in water until they regained their original shape.Micromorphological and anatomical characteristics were studied using a stereo zoom microscope (Zeiss Stemi 508) and a compound microscope (Zeiss Lab A.1). Identification was based on relevant literature.Voucher specimens were deposited in the Herbarium of Arunachal University (HAU) and the Delhi University Herbarium (DUH), following the classification system by Crandall-Stotler et al. (2009).

RESULTS
Throughout the study, 20 liverwort species from 15 genera and 11 families were documented in the Tirap district of Arunachal Pradesh, representing the initial record of bryophytes in this area (Table 1).
Habitat: Epixylic, growing on rotten wood.The species was found in the reproductive stage with gynoecium and androecium branches.
Habitat: Terrestrial, growing on soil in moist and shady areas.The species was in the reproductive stage.

Plagiochila khasiana
Habitat: Epilithic, growing on rock.The species was found in the vegetative stage.
Habitat: Epilithic, growing on rock.The species was in the vegetative stage.

Plagiochila uniformis
Habitat: Epilithic, growing on rock.The species was found in the vegetative stage.

DISCUSSION
The study area represents a diverse species of liverworts, owing to its mild temperature, high humidity, and frequent rainfall.Dumortiera hirsuta and Targionia hypophylla were the most frequently recorded species in the area, while Lejeunea tuberculosa and Notoscyphus darjeelingensis var.darjeelingensis were found only in small patches.The species were found inhabiting different habitats, for example, in damp shady locations, thriving on various substrates such as soil, rocks plant debris, etc.The prevalence of species in various habitats highlights the adaptability and resilience of liverworts in diverse environmental conditions.The observation of epiphytic species and those found on multiple substrates further emphasizes the ecological versatility of liverworts in colonizing different microhabitats.The frequently recorded species indicate their ecological importance and potential role in the local ecosystem.In addition, the species found in small patches signal the necessity to take conservation actions in order to safeguard them from the risk of extinction.
Many of the presently collected bryophyte samples were found growing exclusively on certain J TT tree species.These host trees must be considered in conservation efforts as they serve as essential habitats for various species.Bryophytes enhance water-holding capacity, nutrient status, and soil particle aggregation.Consequently, other plant species associated with bryophytes may also benefit from them.Additionally, Tirap's hilly terrain makes it highly susceptible to landslides.The widespread practice of Jhum cultivation in the area leads to deforestation, destroying natural habitats, and increasing soil erosion.Bryophytes, with their ability to naturally cover and restore disturbed habitats, can potentially play a crucial role in mitigating these environmental challenges in the region.
Therefore, this study contributes to the scientific understanding of liverwort diversity as well as the ecological importance of these understudied bryophytes in maintaining the balance and resilience of the region's ecosystem.Continued research and conservation efforts are crucial to further unravel the intricate relationships between liverworts and their environment, ensuring the preservation of this unique botanical heritage in the eastern Himalaya.

Table 1 . Liverwort species of Tirap District, Arunachal Pradesh, India.
Terrestrial and epilithic, growing abundantly on soil and rock.The species was in the vegetative stage.