Bharat B Shrestha | Tribhuvan University (original) (raw)

Papers by Bharat B Shrestha

Authorea (Authorea), Jun 5, 2023

Comparisons of plant traits between native and invasive congeners are useful approaches for ident... more Comparisons of plant traits between native and invasive congeners are useful approaches for identifying characteristics that promote invasiveness. We compared germination patterns and seedling growth of locally sympatric populations of native Mimosa himalayana and two varieties of invasive M. diplotricha (var. diplotricha and var. inermis) growing in southeastern Nepal. Seeds were germinated under 12h photoperiod or complete dark, low (25/15°C day/night) and (30/20°C) high temperatures,

Arctic, Antarctic, and Alpine Research, Jan 2, 2021

Though variability in morphological features along the environmental gradients has been extensive... more Though variability in morphological features along the environmental gradients has been extensively studied, less information is available on possible adaptations and trends of anatomical features. We examined the variation in morphological and stem anatomical features of a widely distributed (2,200-5,300 m a.s.l.) Rhododendron lepidotum across elevation gradients in Langtang and Sagarmatha National Parks of Nepal Himalayas. Plant samples in each site were collected from three elevation bands (ca. 3,000, 4,000, and 5,000 m a.s.l.). In both study sites, all morphological features measured had their highest value at the lowest elevation and vice versa. Vessel density of basal stem increased but diameter and area of xylem vessels, and length of vessel element and fiber tracheids decreased as elevation increased. Similarly, height and the number of cells in uniseriate rays and height, width, area, and density of multiseriate rays also decreased toward the highest elevation. However, anatomical features of the ultimate branch did not show any distinct pattern with elevation. Morphological features showed more plasticity than anatomical features along the elevation gradients. Decreased plant height, individual leaf area, specific leaf area, and the existing trade-off relationship between vessel diameter and density could have supported a wide distribution of R. lepidotum in Nepal Himalayas.

Weed Research, Feb 11, 2019

SummaryBiological invasion is increasing worldwide and the management of invasive species is beco... more SummaryBiological invasion is increasing worldwide and the management of invasive species is becoming an important priority for vegetation managers. Success of invasive species management depends on a thorough understanding of the biology of the organism in question and the effectiveness of current management efforts, in order to identify the best practices for management improvement. In this review, we synthesised current biological knowledge of a noxious invasive weed Ageratina adenophora to identify knowledge gaps and assessed management efforts to identify best practices. Finally, we proposed some priority areas for future research to fill knowledge gaps and improve management. Our analysis showed that A. adenophora has already invaded 40 countries, mainly in Asia, Oceania, Africa and Europe. Phenotypic plasticity, allelopathic interference and invasion‐mediated changes in the soil microbial community are the proposed mechanisms that facilitate rapid spread of this weed. However, allelopathy as a mechanism of invasion success of this weed has not been supported by ecologically meaningful experiments. Though mechanical, chemical and biological control measures have been used, their success remains limited and the weed continues to spread in new regions. Among seven biological control agents examined to date, gall fly (Procecidochares utilis) and leaf spot fungus (Passalora ageratinae) have been effective in limited areas to suppress growth of this weed. Some perennial native grasses (e.g. Setaria sphacellata and Lolium perenne) have shown potential to competitively suppress A. adenophora. In conclusion, understanding the invasion mechanisms, exploring further to identify effective biological control agents, combined with approaches of ecological restoration, could help in the management of this weed.

Banko Janakari, 2020

Extent of plant invasions has been expected to be low in protected areas such as national parks d... more Extent of plant invasions has been expected to be low in protected areas such as national parks due to low anthropogenic activities and high wilderness. However, recent researches across the world have revealed that plant invasions can be severe in the national parks with negative impacts on the protected species and ecosystems. Unfortunately, the status of plant invasions in the national parks of Nepal is mostly unknown. In this study, we sampled at seven locations inside the Parsa National Park (PNP) to document diversity and abundance of invasive alien plant species (IAPS) and their impacts on tree regeneration. Altogether, 130 quadrats of 10 m × 10 m were sampled. We recorded 14 IAPS in the PNP. Three of the IAPS (Chromolana odorata, Lantana camara and Mikania micrantha) were among the 100 of the world’s worst invasive alien species. C. odorata was found to be the most frequent IAPS with the highest cover. The frequency and cover of the IAPS were higher at the sites close to the...

Banko Janakari, 2018

A wide range of habitat conditions including elevation determine adaptative variation in a specie... more A wide range of habitat conditions including elevation determine adaptative variation in a species. The study was carried out to investigate the anatomical variation of two common species of Rhododendron (R. anthopogon and R. lepidotum) growing between 3200 and 4700 m asl in Gokyo valley of Sagarmatha National Park, Khumbu, eastern Nepal. Seven anatomical characters viz. pore area (PA), pore density (PD), vessel element length (VEL), fiber tracheid length (FL), ray density (RD), uniseriate ray height (URH) and uniseriate ray cell number (URCN) of twenty-three samples for two species (12 samples of R. anthopogon and 11 of R. lepidotum) were studied by making permanent slides of transverse, tangential longitudinal and radial longitudinal stem sections. In R. anthopogon, out of three non- anatomical characters (plant height, soil nitrogen and leaf nitrogen) the nitrogen content in leaf increased with increasing elevation. However, the plant height and nitrogen content in soil did not v...

PloS one, 2018

Invasive alien plant species (IAPS) can pose severe threats to biodiversity and stability of nati... more Invasive alien plant species (IAPS) can pose severe threats to biodiversity and stability of native ecosystems, therefore, predicting the distribution of the IAPS plays a crucial role in effective planning and management of ecosystems. In the present study, we use Maximum Entropy (MaxEnt) modelling approach to predict the potential of distribution of eleven IAPS under future climatic conditions under RCP 2.6 and RCP 8.5 in part of Kailash sacred landscape region in Western Himalaya. Based on the model predictions, distribution of most of these invasive plants is expected to expand under future climatic scenarios, which might pose a serious threat to the native ecosystems through competition for resources in the study area. Native scrublands and subtropical needle-leaved forests will be the most affected ecosystems by the expansion of these IAPS. The present study is first of its kind in the Kailash Sacred Landscape in the field of invasive plants and the predictions of potential dis...

ISBN 978 92 9115 591 0 (electronic) Production team Beth Duncan (Consultant editor) Christopher B... more ISBN 978 92 9115 591 0 (electronic) Production team Beth Duncan (Consultant editor) Christopher Butler (Editor) Dharma R Maharjan (Layout and design) Photos: Photos by Bharat Babu Shrestha, Jitendra Bajracharya, Neha Bisht, and Srijana Joshi Reproduction This publication may be produced in whole or in part and in any form for educational or non-profit purposes without special permission from the copyright holder, provided acknowledgement of the source is made. ICIMOD would appreciate receiving a copy of any publication that uses this publication as a source. No use of this publication may be made for resale or for any other commercial purposes whatsoever without express written consent from ICIMOD. The views and interpretations in this publication are those of the author(s). They are not attributable to ICIMOD and do not imply the expression of any opinion concerning the legal status of any country, territory, city or area of its authorities, or concerning the delimitation of its frontiers or boundaries, or the endorsement of any product.

Journal of Tropical Ecology, Jan 7, 2022

Invasive alien species are a major threat to global biodiversity due to the tremendous ecological... more Invasive alien species are a major threat to global biodiversity due to the tremendous ecological and economic damage they cause in forestry, agriculture, wetlands, and pastoral resources. Understanding the spatial pattern of invasive alien species and disentangling the biophysical drivers of invasion at the forest stand level is essential for managing forest ecosystems and the wider landscape. However, forest-level and species-specific information on Invasive Alien Plant Species (IAPS) abundance and their spatial extent are largely lacking. In this context, we analysed the cover of one of the world’s worst invasive plants, Chromolaena odorata, in Sal (Shorea robusta) forest in central Nepal. Vegetation was sampled in four community forests using 0.01 ha square quadrats, covering the forest edge to the interior. C. odorata cover, floral richness, tree density, forest canopy cover, shrub cover, tree basal area, and disturbances were measured in each plot. We also explored forest and IAPS management practices in community forests. C. odorata cover was negatively correlated with forest canopy cover, distance to the road, angle of slope, and shrub cover. Tree canopy cover had the largest effect on C. odorata cover. No pattern of C. odorata cover was seen along native species richness gradients. In conclusion, forest canopy cover is the overriding biotic covariate suppressing C. odorata cover in Sal forests.

Biological invasion is a global problem with adverse impacts on all types of ecosystems and human... more Biological invasion is a global problem with adverse impacts on all types of ecosystems and human welfare. The invasive alien species (IAS) is considered as the second greatest threat to native biodiversity after habitat loss in global context. The rapidly accelerating international trade and tourism have dramatically enhanced
the spread of IAS and caused adverse impacts on agriculture, forestry, fisheries, and other human enterprises including health. Recognizing as one of the greatest threats to natural environment and human health some useful initiatives is being taken all over the world for their effective management and is now becoming a major focus of international conservation concern and the subject of cooperative efforts. The knowledge base on IAS is rather meager and limited in Nepal. There are about 218 species of naturalized alien plants and about two dozen highly invasive species in our ecosystems. The number of invasive alien animal species is not known but 27 alien animal species have been reported. Empirical data on the ecological impact of
IAS is meager while the economic cost related to IAS has not been estimated. However, the country has recognized the threats posed by IAS, and incorporated the issues of IAS in different national strategy (e.g. Nepal Biodiversity Strategy 2002), reports (Fifth National Report to the Convention on Biological Diversity
2014) and legal instruments (e.g. National Wetland Policy 2003, revised 2012). Besides, the country has also formulated several sectoral laws and established quarantine offices to control and eradicate the germs, pests and weeds of agricultural crops. But, these efforts are not directly related to prevent the introduction
and spread of IAS. Hence, revision of the sectoral laws is needed to address the IAS problems. Further, the specific strategy and laws are expecting to regulate and control the introduction IAS. Being a signatory to many global environmental treaties and conventions pertaining to IAS, it is mandatory for Nepal to fulfill obligations under these treaties and conventions. Paradoxically, the management of IAS is still not a national priority; the existing legal instruments are not effectively implemented; the commitments made have not been fulfilled.

Invasive Alien Species cause tremendous ecological and economic damage in agriculture, forestry, ... more Invasive Alien Species cause tremendous ecological and economic damage in agriculture, forestry, aquatic ecosystems, and pastoral resources. They are one of the major threats to biodiversity conservation. Understanding the spatial pattern of invasive species and disentangling the biophysical drivers of invasion at forest stand level is essential for managing invasive species in forest ecosystems and the wider landscape. However, forest-level and species-specific information on invasive species abundance and area of extent is largely lacking. In this context, we analysed the cover of one of the world’s worst invasive plant species Chromolaena odorata in Sal (Shorea robusta Gaertn.) forest in central Nepal. Vegetation was sampled in four community-managed forests using 0.01 ha square quadrats, covering forest edge to the interior. Chromolaena cover, floral richness, tree density, forest canopy cover, shrub cover, and tree basal area were measured in each plot. We also estimated the le...

Climate, 2017

Nepal has an extreme altitudinal range from 60-8850 m with heterogeneous topography and distinct ... more Nepal has an extreme altitudinal range from 60-8850 m with heterogeneous topography and distinct climatic zones. The country is considered a biodiversity hotspot, with nearly a quarter of the land area located in protected areas. Nepal and the surrounding Himalayan region are particularly vulnerable to climate change because of their abrupt ecological and climatic transitions. Tens of millions of people rely on the region's ecosystem services, and observed and modeled warming trends predict increased climate extremes in the Himalayas. To study the ecological impacts of climate change in Nepal and inform adaptation planning, we review the literature on past, present, and predicted future climatic changes and their impacts on ecological diversity in Nepal. We found few studies focusing on organisms, while research on species and communities was more common. Most studies document or predict species range shifts and changes in community composition. Results of these few investigations highlight major lacunae in research regarding the effects of changing climate on species comprising the Himalayan biota. Further empirical work is needed at all levels of biological organization to build on information regarding direct ecological impacts of climatic changes in the region. Countries face an ever-increasing threat of climate change, and Nepal has strong physiographic, elevational, and climatic gradients that could provide a useful model for studying the effects of climate change on a mountainous, and highly biodiverse, area.

Journal of Mountain Science, 2020

Changes in population structure and plant functional traits across environmental gradient in the ... more Changes in population structure and plant functional traits across environmental gradient in the near natural treeline is a critical determinant of environmental changes in treelines. In this study we analyzed population characteristics and leaf traits of Rhododendron campanulatum across treeline ecotone in a trans-Himalayan region of Mustang district in central Nepal. Along 4 vertical transects, a total of 72 quadrats (5 m × 5 m)-34 above Betula utilis treeline and 38 below treeline-were sampled to analyze the population structure, regeneration, specific leaf area (SLA) and leaf-stem relationship of R. campanulatum. Our results showed that the regeneration of R. campanulatum was fairly good in both habitats, as evident from density-diameter curve. The species showed type III survivorship curve in both habitats with the highest mortality during early stage of life. However, the seedling density and mortality was higher below treeline than above treeline. Canopy cover and basal cover were found to be the major factors affecting regeneration, as indicated by higher number of juveniles in relatively open areas above treeline. The total leaf area increased (p <0.001) with stem cross-section area in both habitats. However, the SLA was higher below treeline (55 cm 2 /g) than above (47 cm 2 /g) (p < 0.001); it also increased with the canopy cover of trees (R² = 0.59, p <0.001) below the treeline. In conclusion, high density of juvenile, low mortality of seedlings, and low SLA above treeline indicated that the species has successfully adapted in climatically stressful alpine habitat with potential to expand upward.

Pakistan Journal of Botany

Urban areas often provide suitable microhabitats for the establishment of invasive alien plants (... more Urban areas often provide suitable microhabitats for the establishment of invasive alien plants (IAPs), which subsequently disseminate their propagules for further spread in surrounding landscape. Periodic survey of IAPs in urban areas not only brings opportunities for early detection and eradication of the invaders but also generate science-based information for the management of established IAPs. In this study, we inventoried IAPs and documented their spatial distribution in Pokhara valley, a popular tourist destination in Nepal. Using a checklist of 26 IAPs that have been reported from Nepal, we examined roadside vegetation in 201 plots (size: 5 m  5 m) located at the interval of ca. 500 m in the valley. In each plot, the IAPs present were recorded along with geographic coordinates and land use type. Field data were used to calculate species richness, frequency, and prepare distribution maps of the IAPs. In Pokhara valley we recorded 20 IAPs, i.e. 77% of the total number of IAPs reported from Nepal. Four of the recorded IAPs: Chromolaena odorata, Eichhornia crassipes, Lantana camara and Mikania micrantha were among the 100 of the world's worst invasive species. Bidens pilosa had the highest frequency (63%), followed by Ageratum houstonianum (61%) and Lantana camara (44%). Small population of Alternanthera philoxeroides, and Mesosphaerum suaveolens were spotted at a single locations and Mikania micrantha at two locations, suggesting that they were at the early stage of invasion in the valley. Richness of IAPs was the highest in shrub land, followed by agriculture fallow land, and forest. Our data revealed that the Pokhara valley has already been invaded by a large number of IAPs, with possibility of arrival of new IAPs in near future. Periodic inventory and mapping of the IAPs would be helpful in identifying new IAPs and making management decisions timely.