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Dr. Avishesh Neupane
University of Tennessee, Knoxville

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Research Keywords & Expertise

0 Global Change
0 soil health
0 soil ecology
0 Soil Biogeochemistry
0 Soil carbon and nutrient cycling

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Short Biography

soil biogeochemistry, soil ecology, global climate change, soil carbon

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Journal article
Published: 30 May 2021 in Sustainability
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Mustang valley in the central Himalaya of Nepal is a unique landscape formed by massive soil mass during a glacial period, which is attributed to a mix of vegetations and long agricultural history. Soil nutrients and their sourcing is highly important to understand the vegetation assemblage and land productivity in this arid zone. Twenty soil samples (from 0 to 20 cm depth) were collected from three landscape positions in Mustang district: valley, ridge, and midslope. We explored nutrient sourcing using natural abundance carbon (δ13C) and nitrogen isotope (δ15N) employing isotope ratio mass spectrophotometry. The results showed that the total soil carbon (TC) and total nitrogen (TN) ranged from 0.3 to 10.5% and 0.3 to 0.7%, respectively. Similarly, the CN ratio ranged from 0.75 to 15.6, whereas soil pH ranged from 6.5 to 7.5. Valley soil showed higher values of TN, CN, and soil pH than the ridge and midslope soils. The valleys had more positive δ15N signatures than ridge and midslope, which indicates higher inorganic and organic N fertilizer inputs in the valley bottom than in the midslope and ridge. This suggests that a higher nutrient content in the valley bottom likely results from agro-inputs management and the transport of nutrients from the ridge and midslope. Soil pH and CN ratio were a non-limiting factor of nutrient availability in the study regions. These findings are crucial in understanding the nutrient dynamics and management in relation to vegetation and agricultural farming in this unique topography of the Trans-Himalayan zone of Mustang in central Nepal.

ACS Style

Roshan Ojha; Sujata Manandhar; Avishesh Neupane; Dinesh Panday; Achyut Tiwari. Carbon and Nitrogen Sourcing in High Elevation Landscapes of Mustang in Central Nepal. Sustainability 2021, 13, 6171 .

AMA Style

Roshan Ojha, Sujata Manandhar, Avishesh Neupane, Dinesh Panday, Achyut Tiwari. Carbon and Nitrogen Sourcing in High Elevation Landscapes of Mustang in Central Nepal. Sustainability. 2021; 13 (11):6171.

Chicago/Turabian Style

Roshan Ojha; Sujata Manandhar; Avishesh Neupane; Dinesh Panday; Achyut Tiwari. 2021. "Carbon and Nitrogen Sourcing in High Elevation Landscapes of Mustang in Central Nepal." Sustainability 13, no. 11: 6171.

Research article
Published: 24 March 2021 in PLOS ONE
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Combined application of biochar and nitrogen (N) fertilizer has the potential to reduce N losses from soil. However, the effectiveness of biochar amendment on N management can vary with biochar types with different physical and chemical properties. This study aimed to assess the effect of two types of hardwood biochar with different ash contents and cation exchange capacity (CEC) on soil N mineralization and nitrous oxide (N2O) production when applied alone and in combination with N fertilizer. Soil samples collected from a temperate pasture system were amended with two types of biochar (B1 and B2), urea, and urea plus biochar, and incubated for 60 days along with soil control (without biochar or urea addition). Soil nitrate N, ammonium N, ammonia-oxidizing bacteria amoA gene transcripts, and N2O production were measured during the experiment. Compared to control, addition of B1 (higher CEC and lower ash content) alone decreased nitrate N concentration by 21% to 45% during the incubation period while the addition of B2 (lower CEC and higher ash content) alone increased the nitrate N concentration during the first 10 days. Biochar B1 also reduced the abundance of amoA transcripts by 71% after 60 days. Compared to B1 + urea, B2 + urea resulted in a significantly greater initial increase in soil ammonium and nitrate N concentrations. However, B2 + urea had a significantly lower 60-day cumulative N2O emission compared to B1 + urea. Overall, when applied with urea, the biochar with higher CEC reduced ammonification and nitrification rates, while biochar with higher ash content reduced N N2O production. Our study demonstrated that biochar has the potential to enhance N retention in soil and reduce N2O emission when it is applied with urea, but the specific effects of the added biochar depend on its physical and chemical properties.

ACS Style

Xiuwen Li; Sutie Xu; Avishesh Neupane; Nourredine Abdoulmoumine; Jennifer M. DeBruyn; Forbes R. Walker; Sindhu Jagadamma. Co-application of biochar and nitrogen fertilizer reduced nitrogen losses from soil. PLOS ONE 2021, 16, e0248100 .

AMA Style

Xiuwen Li, Sutie Xu, Avishesh Neupane, Nourredine Abdoulmoumine, Jennifer M. DeBruyn, Forbes R. Walker, Sindhu Jagadamma. Co-application of biochar and nitrogen fertilizer reduced nitrogen losses from soil. PLOS ONE. 2021; 16 (3):e0248100.

Chicago/Turabian Style

Xiuwen Li; Sutie Xu; Avishesh Neupane; Nourredine Abdoulmoumine; Jennifer M. DeBruyn; Forbes R. Walker; Sindhu Jagadamma. 2021. "Co-application of biochar and nitrogen fertilizer reduced nitrogen losses from soil." PLOS ONE 16, no. 3: e0248100.

Journal article
Published: 23 November 2020 in Soil Biology and Biochemistry
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Tropical forest soils contain some of the largest carbon (C) stocks on Earth, yet the effects of warming on the fate of fresh C entering tropical soils are still poorly understood. This research sought to understand how the fate of fresh C entering soils is influenced by warming, soil weathering status, and C chemistry. We hypothesized that compounds that are quickly incorporated into microbial biomass (i.e., greater C use efficiency [CUE]) subsequently have longer-term (255 days) retention in soil. We also hypothesized that relatively weathered soils with greater sorptive capacity also retain more fresh C in the short and longer-terms, and that C in these soils is more resistant to weathering loss compared with less weathered soils. We tested these hypotheses by adding two 13C-labeled compounds (glucose and glycine) to three tropical forest soils from a weathering gradient in Hawai'i, and then incubating soils at ambient (16 °C), +5 °C, and +10 °C for 255 days. We found that 255-day 13C retention in mineral soil across sites and temperatures was best predicted by two factors: initial retention of 13C in mineral soil and initial microbial 13CUE (Adjusted R2 = 0.78). Carbon compound type influenced 13C initial retention, with greater glucose-13C retention versus glycine-13C retention in mineral soils and microbial biomass, corresponding to greater glucose-13C retention in soil at 255 days. Warming had a negative longer-term effect on the retention of 13C only in the least-weathered soil, supporting our hypothesis. These results show that initial retention of fresh C in soils via mineral sorption and microbial uptake is a strong predictor of longer-term retention, indicating that immediate C losses are a major hurdle for soil C storage. Also, retention of fresh C appears most sensitive to warming in less-weathered tropical soils, supporting the idea that mineral sorption may provide some protections against warming. Understanding the interaction between soil sorptive properties and warming for C cycling could improve predictions of forest-climate feedbacks for tropical regions.

ACS Style

Avishesh Neupane; Sasha C. Reed; Daniela F. Cusack. Warming and microbial uptake influence the fate of added soil carbon across a Hawai'ian weathering gradient. Soil Biology and Biochemistry 2020, 153, 108080 .

AMA Style

Avishesh Neupane, Sasha C. Reed, Daniela F. Cusack. Warming and microbial uptake influence the fate of added soil carbon across a Hawai'ian weathering gradient. Soil Biology and Biochemistry. 2020; 153 ():108080.

Chicago/Turabian Style

Avishesh Neupane; Sasha C. Reed; Daniela F. Cusack. 2020. "Warming and microbial uptake influence the fate of added soil carbon across a Hawai'ian weathering gradient." Soil Biology and Biochemistry 153, no. : 108080.

Papers on original research
Published: 06 October 2020 in Soil Science Society of America Journal
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The potential nitrogen (N) losses from soils with fertilizer addition can be reduced when biochar is co‐applied, but this effect is influenced by the methods of biochar and fertilizer application. In a 60‐day laboratory incubation experiment, we investigated how two fertilizer application methods (surface placement and soil incorporation) affected N transformation in soils under following treatments: control (soil with no biochar and urea) hereafter C, biochar (150 mg N g−1 soil) hereafter B, urea (150 mg N g−1 soil) hereafter U, and the combination of B+U (75 mg N g−1 soil each B and U). Our results showed that at day 30, the concentrations of soil ammonium‐N and nitrate‐N remained significantly higher for U but were relatively similar to control for biochar included treatments indicating the presence of biochar slowed the mineralization of urea during that period. The concentration of soil nitrate‐N and cumulative nitrous oxide production under B+U treatment at 60 days was around two times higher for incorporation treatment compared to the surface treatment, indicative of a longer‐term N regulatory effect of biochar with the surface application method. Additionally, we observed a higher number of amoA gene transcripts when B+U was incorporated in the soil compared to applied to the surface at the later stage of incubation, indicative of higher potential nitrification activity. These results suggest that the surface application of B+U can be used as a slow release N source that can provide long term N supply to the crops, while the soil incorporation method could be used for crops that need low N at the beginning of the growth but require a substantial amount of it later. Furthermore, surface co‐application of B+U can be a good strategy to reduce the soil N losses by slowing down ammonification, nitrification, nitrous oxide emission, and ammonia oxidizing bacteria activity. This article is protected by copyright. All rights reserved

ACS Style

Xiuwen Li; Avishesh Neupane; Sutie Xu; Nourredine Abdoulmoumine; Jennifer M. DeBruyn; Forbes Walker; Sindhu Jagadamma. Application methods influence biochar–fertilizer interactive effects on soil nitrogen dynamics. Soil Science Society of America Journal 2020, 84, 1871 -1884.

AMA Style

Xiuwen Li, Avishesh Neupane, Sutie Xu, Nourredine Abdoulmoumine, Jennifer M. DeBruyn, Forbes Walker, Sindhu Jagadamma. Application methods influence biochar–fertilizer interactive effects on soil nitrogen dynamics. Soil Science Society of America Journal. 2020; 84 (6):1871-1884.

Chicago/Turabian Style

Xiuwen Li; Avishesh Neupane; Sutie Xu; Nourredine Abdoulmoumine; Jennifer M. DeBruyn; Forbes Walker; Sindhu Jagadamma. 2020. "Application methods influence biochar–fertilizer interactive effects on soil nitrogen dynamics." Soil Science Society of America Journal 84, no. 6: 1871-1884.

Article
Published: 25 September 2019 in Biogeochemistry
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Humid tropical forests contain some of the largest soil carbon (C) stocks on Earth, yet there is uncertainty about how carbon dioxide (CO2) fluxes will respond to climate change in this biome. The magnitude of change in soil respiration over seasonal wetting and drying cycles can provide insight to how CO2 fluxes might respond to precipitation changes. We measured soil respiration in 15 distinct forests across rainfall and soil fertility gradients in lowland Panama to assess spatial variation in seasonal patterns. We predicted that seasonal changes in soil respiration would be related to soil moisture, and that the ratio of wet to dry season CO2 fluxes across landscape gradients would be regulated by soil organic C and nutrient availability. We found that soil respiration during the dry season was relatively stable across the rainfall gradient, averaging 4.3 ± 0.3 µmol CO2 m−2 s−1. In contrast, wet season respiration varied markedly, ranging among sites from a decline of 19% to an increase of 360% in comparison to dry season values. Soil moisture, air temperature, and rainfall were the best predictors of instantaneous soil respiration (R2 = 0.18). Meanwhile, ratios of wet to dry season CO2 fluxes were best predicted by site-scale resin-extractable phosphorus (P; R2 = 0.48). That is, soil respiration in P-rich sites increased more during the wet season relative to respiration in P-poor sites. Also, sites with Wet:Dry season CO2 flux ratios < 1 were all poor in soil P, defined as resin P concentrations < 2 mg P kg−1. Although soil organic C was not related to instantaneous soil respiration rates, forest floor biomass accumulation during the dry season was positively correlated with soil respiration during the wet season (R2 = 0.26), indicating the contribution of microbial decomposition to wet season soil respiration. Overall, nutrient availability regulated soil respiration responses to increased moisture during the wet season, while low soil moisture uniformly suppressed soil respiration across sites during the dry season. Phosphorus availability might therefore regulate feedbacks to climate change among humid tropical forests.

ACS Style

Daniela F. Cusack; Daniel Ashdown; Lee H. Dietterich; Avishesh Neupane; Mark Ciochina; Benjamin Turner. Seasonal changes in soil respiration linked to soil moisture and phosphorus availability along a tropical rainfall gradient. Biogeochemistry 2019, 145, 235 -254.

AMA Style

Daniela F. Cusack, Daniel Ashdown, Lee H. Dietterich, Avishesh Neupane, Mark Ciochina, Benjamin Turner. Seasonal changes in soil respiration linked to soil moisture and phosphorus availability along a tropical rainfall gradient. Biogeochemistry. 2019; 145 (3):235-254.

Chicago/Turabian Style

Daniela F. Cusack; Daniel Ashdown; Lee H. Dietterich; Avishesh Neupane; Mark Ciochina; Benjamin Turner. 2019. "Seasonal changes in soil respiration linked to soil moisture and phosphorus availability along a tropical rainfall gradient." Biogeochemistry 145, no. 3: 235-254.

Journal article
Published: 29 August 2016 in Reviews of Geophysics
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Government and international agencies have highlighted the need to focus global change research efforts on tropical ecosystems. However, no recent comprehensive review exists synthesizing humid tropical forest responses across global change factors, including warming, decreased precipitation, carbon dioxide fertilization, nitrogen deposition, and land use/land cover changes. This paper assesses research across spatial and temporal scales for the tropics, including modeling, field, and controlled laboratory studies. The review aims to: 1) Provide a broad understanding of how a suite of global change factors are altering humid tropical forest ecosystem properties and biogeochemical processes; 2) Assess spatial variability in responses to global change factors among humid tropical regions; 3) Synthesize results from across humid tropical regions to identify emergent trends in ecosystem responses; 4) Identify research and management priorities for the humid tropics in the context of global change. Ecosystem responses covered here include plant growth, carbon storage, nutrient cycling, biodiversity, and disturbance regime shifts. The review demonstrates overall negative effects of global change on all ecosystem properties, with the greatest uncertainty and variability in nutrient cycling responses. Generally, all global change factors reviewed, except for carbon dioxide fertilization, demonstrate great potential to trigger positive feedbacks to global warming via greenhouse gas emissions and biogeophysical changes that cause regional warming. This assessment demonstrates that effects of decreased rainfall and deforestation on tropical forests are relatively well understood, whereas the potential effects of warming, carbon dioxide fertilization, nitrogen deposition, and plant species invasions require more cross-site, mechanistic research to predict tropical forest responses at regional and global scales.

ACS Style

Daniela F. Cusack; Jason Karpman; Daniel Ashdown; Qian Cao; Mark Ciochina; Sarah Halterman; Scott Lydon; Avishesh Neupane. Global change effects on humid tropical forests: Evidence for biogeochemical and biodiversity shifts at an ecosystem scale. Reviews of Geophysics 2016, 54, 523 -610.

AMA Style

Daniela F. Cusack, Jason Karpman, Daniel Ashdown, Qian Cao, Mark Ciochina, Sarah Halterman, Scott Lydon, Avishesh Neupane. Global change effects on humid tropical forests: Evidence for biogeochemical and biodiversity shifts at an ecosystem scale. Reviews of Geophysics. 2016; 54 (3):523-610.

Chicago/Turabian Style

Daniela F. Cusack; Jason Karpman; Daniel Ashdown; Qian Cao; Mark Ciochina; Sarah Halterman; Scott Lydon; Avishesh Neupane. 2016. "Global change effects on humid tropical forests: Evidence for biogeochemical and biodiversity shifts at an ecosystem scale." Reviews of Geophysics 54, no. 3: 523-610.

Journal article
Published: 04 September 2015 in Soil Biology and Biochemistry
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Termites inhabit a large portion of land covered by temperate forests. Climate warming and urbanization will likely extend their range and increase their densities in these ecosystems but, compared to their tropical counterparts, little is known about their effects on soil properties and processes. If temperate termites have the strong ecosystem engineering effects of tropical termites, then knowledge of their ecology and impacts will be vital for predicting how temperate systems respond to environmental change. We investigated how feeding and tunneling by the eastern subterranean termite, Reticulitermes flavipes, affected wood decomposition and soil properties under decaying wood. Twelve laboratory microcosms filled with mineral soil and with wood blocks of four common temperate tree species, received R. flavipes soldiers and workers at field densities, with an additional five termite-free microcosms serving as controls. After 25 weeks, the effects of termites on wood mass loss, and on carbon and nitrogen dynamics, differed across tree species, yet their effects on soil properties were consistent regardless of wood type. Microbially-available carbon in soil was 20% higher with termites and soil moisture content 20% lower. Soil pH was more acid with termites and their effects on soil microbial biomass were positive but non-significant. These soil responses were consistent regardless of the wood species, suggesting that termite effects on soil are dictated largely by their activity within the soil matrix and not by their feeding rate on specific wood substrates. These results are among the first to quantify the effects of temperate forest termite activity on soil properties, demonstrating the potential for these termites to shape biogeochemical cycling and plant communities through their alteration of the soil environment.

ACS Style

Avishesh Neupane; Daniel S. Maynard; Mark Bradford. Consistent effects of eastern subterranean termites (Reticulitermes flavipes) on properties of a temperate forest soil. Soil Biology and Biochemistry 2015, 91, 84 -91.

AMA Style

Avishesh Neupane, Daniel S. Maynard, Mark Bradford. Consistent effects of eastern subterranean termites (Reticulitermes flavipes) on properties of a temperate forest soil. Soil Biology and Biochemistry. 2015; 91 ():84-91.

Chicago/Turabian Style

Avishesh Neupane; Daniel S. Maynard; Mark Bradford. 2015. "Consistent effects of eastern subterranean termites (Reticulitermes flavipes) on properties of a temperate forest soil." Soil Biology and Biochemistry 91, no. : 84-91.