Tree species richness and phytomass carbon stock along the urban-rural gradient in trees outside forests of Kathmandu valley, Nepal

ABSTRACT

Trees outside forests (TOF) are woody plants found on land which is less than 0.5 ha. These are important for biodiversity conservation and carbon storage. This study was conducted in Kathmandu Valley, central Nepal to determine tree species diversity and phytomass carbon stock patterns along the urban to rural spatial gradient of TOF. A detailed inventory was conducted across a total of 209 randomly selected points generated by MS Excel using circular plots of 20 m radius each. A total of 6,210 trees from 150 species belonging to 111 genera and 57 families were recorded under three strata (urban, suburban and rural). Out of 150 species, 53.33% were native and 46.67% were exotic. The average tree density was found to be higher in the suburban stratum (248.44 ha⁻¹) compared to the urban (232.58 ha⁻¹) and the rural (224.88 ha⁻¹) strata. Species richness was found to be higher in the rural stratum (14.09 ha⁻¹) compared to the urban (9.85 ha⁻¹) and the suburban (9.70 ha⁻¹) strata. But average species richness was found to be highest in the urban stratum (55.95 ha⁻¹) followed by the suburban (46.31 ha⁻¹) and the rural (45.74 ha⁻¹) strata, respectively. Similarly, the average phytomass carbon stock recorded was highest in the urban stratum (39.41 t ha⁻¹) compared to the rural (29.19 t ha⁻¹) and the suburban (26.06 t ha⁻¹) strata. The average phytomass carbon stock varied significantly between the native and the exotic species only in the urban stratum but not in the suburban and the rural strata. This study provides baseline data useful for green urban planning and development as well as carbon sink management.

KEYWORDS:

• Diversity
• exotic species
• native species
• phytomass carbon
• species richness

Acknowledgments

We acknowledge Mahendra Shrestha, Mayukh Shrestha, Laxmi Joshi Shrestha, Prativa Paudel and local people for their support during field visits and data collection. Mayukh Shrestha is acknowledged for assisting in plot location map preparation. We also acknowledge Sanjaya Shrestha, resident of UK and an employee at Barclays, London for proof reading and grammar corrections of the manuscript.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Author contributions

All authors contributed to concept development, research design, defining the intellectual content and literature research. B. Shrestha and B. K. Sharma collected the data. B. Shrestha, R. K. P. Yadav and C. B. Baniya analysed data and prepared the manuscript. R. K. P. Yadav and B. K. Sharma reviewed the manuscript.

Additional information

Notes on contributors

Babita Shrestha

Babita Shrestha is working as a lecturer in the Department of Biology at Reliance International Academy, Kathmandu and is a Ph.D. research scholar at the Central Department of Botany, Tribhuvan University, Kirtipur, Kathmandu, Nepal. Her research focuses on plant diversity and ecosystem services in urban ecosystems. She contributed to the research design through data collection, data analysis, interpretation and preparation of the manuscript.

Bhuvan Keshar Sharma

Bhuvan Keshar Sharma is a biodiversity coordinator at Conservation Development Foundation, Kathmandu, Nepal. His research interests are in biodiversity, non-timber forest products and water. He contributed to the research through data collection and reviewing the manuscript.

Chitra Bahadur Baniya

Chitra Bahadur Baniya is an associate professor at the Central Department of Botany, Tribhuvan University, Kirtipur, Kathmandu, Nepal. His research interests are in biodiversity, community ecology and gradient analysis. He participated in data analysis and reviewing the manuscript.

Ram Kailash Prasad Yadav

Ram Kailash Prasad Yadav is a professor at the Central Department of Botany, Tribhuvan University, Kirtipur, Kathmandu, Nepal. His research interests are in agroecology, vegetation ecology and plant-soil-microbial interactions. He contributed to the research design, data collection, analysis and interpretation. He also contributed towards manuscript preparation and review.