Dr Shankar Panthi, PhD - Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences - Postdoctoral Research Fellow

Dr Shankar Panthi

PhD

Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences

Postdoctoral Research Fellow

Menglun, Yunnan | China

Main Specialties: Biology

Additional Specialties: Global Change Ecology

ORCID logohttps://orcid.org/0000-0002-3522-5555

Dr Shankar Panthi, PhD - Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences - Postdoctoral Research Fellow

Dr Shankar Panthi

PhD

Introduction

Research: Global change ecology, Climate change, growth & physiological responses of forests to environmental changes;
Research Area: Global change ecology in Himalayas & Chinese Mountain systems, Open for regional/global collaboration across different biomes;
Methods/techniques: Tree rings & stable isotope analysis across elevation & environment gradients;
Projects: Climate variability, & Long-term growth & physiological responses of high-elevation forests across Himalaya-Hengduan-Tibet complex

Primary Affiliation: Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences - Menglun, Yunnan , China

Specialties:

Additional Specialties:

Research Interests:

Education

Dec 2017
Xishuangbanna Tropical Botanical Garden Chinese Academy of Sciences
PhD
Global Change Ecology
Feb 2012
Central Department of Botany, Tribhuvan University
MSc
Botany

Publications

4Publications

Reads

84Profile Views

Abies spectabilis shows stable growth relations to temperature, but changing response to moisture conditions along an elevation gradient in the central Himalaya

Dendrochronologia

Abstract

A better understanding of growth-climate responses of high-elevation tree species across their distribution range is essential to devise an appropriate forest management and conservation strategies against adverse impacts of climate change. The present study evaluates how radial growth of Himalayan fir (Abies spectabilis D. Don) and its relation to climate varies with elevation in the Manaslu Mountain range in the central Himalaya. We developed tree-ring width chronologies of Himalayan fir from three elevational belts at the species’ upper distribution limit (3750-3900 m), in the middle range (3500-3600 m), and at the lower distribution limit (3200-3300 m), and analyzed their associations with climatic factors. Tree growth of Himalayan fir varied synchronously across elevational belts, with recent growth increases observed at all elevations. Across the elevation gradient, radial growth correlated positively (negatively) with temperature (precipitation and standardized precipitation-evapotranspiration index, SPEI-03) during the summer (July to September) season. However, the importance of summer (July to September) temperatures on radial growth decreased with elevation, whereas correlations with winter (previous November to current January) temperatures increased. Correlations with spring precipitation and SPEI-03 changed from positive to negative from low to high elevations. Moving correlation analysis revealed a persistent response of tree growth to May and August temperatures. However, growth response to spring moisture availability has strongly increased in recent decades, indicating that intensified spring drought may reduce growth rates of Himalayan fir at lower elevations. Under sufficient moisture conditions, increasing summer temperature might be beneficial for fir trees growing at all elevations, while trees growing at the upper treeline will take additional benefit from winter warming.

Keywords

Climate change, 
Dendroecology, 
Growth 
response, 
Elevation gradient, 
central Himalaya, 
Tree rings

View Article
February 2020

Long-term physiological and growth responses of Himalayan fir to environmental change are mediated by mean climate.

Glob Chang Biol 2019 Nov 7. Epub 2019 Nov 7.

Forest Ecology & Forest Management Group, Wageningen University, Wageningen, The Netherlands.

High-elevation forests are experiencing high rates of warming, in combination with CO2 rise and (sometimes) drying trends. In these montane systems, the effects of environmental changes on tree growth are also modified by elevation itself, thus complicating our ability to predict effects of future climate change. Tree-ring analysis along an elevation gradient allows quantifying effects of gradual and annual environmental changes. Here, we study long-term physiological (ratio of internal to ambient CO2 , i.e., Ci /Ca and intrinsic water-use efficiency, iWUE) and growth responses (tree-ring width) of Himalayan fir (Abies spectabilis) trees in response to warming, drying, and CO2 rise. Our study was conducted along elevational gradients in a dry and a wet region in the central Himalaya. We combined dendrochronology and stable carbon isotopes (?13C) to quantify long-term trends in Ci /Ca ratio and iWUE (?13C-derived), growth (mixed-effects models), and evaluate climate sensitivity (correlations). We found that iWUE increased over time at all elevations, with stronger increase in the dry region. Climate-growth relations showed growth-limiting effects of spring moisture (dry region) and summer temperature (wet region), and negative effects of temperature (dry region). We found negative growth trends at lower elevations (dry and wet regions), suggesting that continental-scale warming and regional drying reduced tree growth. This interpretation is supported by ? C-derived long-term physiological responses, which are consistent with responses to reduced moisture and increased vapor pressure deficit. At high elevations (wet region), we found positive growth trends, suggesting that warming has favored tree growth in regions where temperature most strongly limits growth. At lower elevations (dry and wet regions), the positive effects of CO2 rise did not mitigate the negative effects of warming and drying on tree growth. Our results raise concerns on the productivity of Himalayan fir forests at low and middle (<3,300 m) elevations as climate change progresses.

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Source
http://dx.doi.org/10.1111/gcb.14910DOI Listing
November 2019
8.044 Impact Factor

Tree rings reveal recent intensified spring drought in the central Himalaya, Nepal

Global and Planetary Change

Abstract

To better understand long-term drought variations in the central Himalaya, we developed new tree-ring width chronologies of Himalayan spruce (Picea smithiana (Wall.) Boiss.) from three sites in the north-western Nepal. The local site chronologies showed high cross correlations and similar growth-climate responses to regional spring drought variability. We thus combined all site chronologies into a regional composite (RC) standard chronology that spans 516 years (1498–2013 CE). The RC chronology showed significant positive (negative) correlations with spring (March–May) precipitation (temperature) variability. Meanwhile, RC chronology showed the highest correlation with spring self-calibrating Palmer drought severity index (scPDSI, r = 0.652, p < 0.001), indicating that radial growth of P. smithiana is strongly limited by spring moisture availability. Using RC chronology, we reconstructed the spring drought variability for the period 1725–2013, which explained 42.5% variance of the actual scPDSI during the calibration period 1957–2012. Our reconstructed spring drought variability in the central Himalaya showed consistent wet-dry episodes with other regional drought and precipitation reconstructions from the Himalaya and nearby regions. Spectral peaks and spatial correlation analysis indicate that spring drought variability in the central Himalaya may be linked to large scale climatic drivers, mainly Atlantic Multidecadal Oscillation activities due to sea surface temperatures variation in the Atlantic Ocean. Our reconstruction revealed a continuous shift toward drier conditions in the central Himalaya since early 1980s that coincide with continental-scale warming and reduced spring precipitation in the central Himalaya.


Keywords

Central Himalaya, 
Dendroclimatology, 
Nepal, 
Picea smithiana, 
Spring drought, 
Tree-rings

View Article
October 2017

Top co-authors

Pieter A Zuidema
Pieter A Zuidema

Utrecht University

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