Research in the forests of Nepal

Uday Thapa

Research Q & A

What’s your hometown?

I am originally from Bhairahawa (near Lubmini), a small town in the lowlands of central Nepal.

What are you currently working on?

With support from the Bell Museum Award, I generated tree-ring width measurements during the summer of 2018 from the tree-core samples I collected from pine forests in eastern Nepal’s Koshi River watershed. Initially, I proposed to use these tree-ring records to produce long surrogate estimates of streamflow for the Koshi River. After preliminary analysis, I learned that these trees were not tuned to Koshi River flow and cannot be used to investigate river flow history in eastern Nepal. Because the Koshi pine forests were relatively accessible to local people and subject to human disturbances, I used the tree-ring data to investigate the influence of climate and human activities on pine growth.

As part of my final dissertation chapter, I am currently investigating the behavior of the sub-tropical jet stream, a band of high-speed winds in the upper atmosphere, over the Himalayas during the past four centuries using tree-ring width chronologies from Pakistan, India, Nepal, and Bhutan. This study also uses some of the tree-ring records I produced during the summer of 2018 with support from the Bell Museum.

How are you working toward that goal?

I already published my work on detecting the competing effects of climate and human disturbances on the growth of pine forests in eastern Nepal last year in Forest Ecology and Management. I also presented this research at the American Geophysical Union (AGU) meeting in December 2018.
I am currently preparing manuscript based on my work on jet stream dynamics in the Himalayas. I presented the outcomes of this research last December at AGU. I plan to submit the manuscript describing the behavior of the Himalayan jet to Geophysical Research Letters in April 2020. With this paper, I will complete my doctoral degree requirements, and am working to defend my dissertation in May 2020.

Why are you focusing your work in that area?

Pine forests in the Koshi River watershed provide crucial resources including timber, firewood and resins, contributing to the livelihood of about 10 million people in eastern Nepal. My research suggests that in order to accurately model future distribution of these critical forests it is important to consider winter moisture balance, which primarily controls the growth of these forests. Until my research, it was not clear what climatic factors primarily controlled the Koshi pine forests. These forests are also subject to human use, but the effects of human activities on their growth was unknown. My research also showed that the current human use practices have overall negative effects on the health of these forests, and therefore should apply sustainable management practices.

The Himalayan jet acts to guide the winter and spring storms, which are the primary source of precipitation in the Himalayan regions, providing water to more than one billion South Asian populations for their agriculture and energy production during the dry seasons. Changes in the behavior of the jet affects the distribution, frequency and intensity of these storms and thereby water availability. My research has shown that the Himalayan jet has made frequent poleward excursions in the recent decades, making the region hotter and drier. My study suggests that in order to accurately predict the dry season weather in the Himalayas, it is important to consider the poleward displacements of the jet rather than only its mean position.

Where are you working on research/field work?

My research on forest ecology was based on tree-ring samples I collected from eastern Nepal. My current research covers the larger Himalayan region and utilizes publicly available tree-ring data from Pakistan, India, Nepal, and Bhutan.

What will your next steps/research be?

Building up on my dissertation research on dendroclimatology and jet stream dynamics, I want to expand future work to study long-term changes in water availability associated with atmospheric storms using tree rings and climate model simulations in central Asia and North America.

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