Oxygen and hydrogen isotopic characterization of rainfall and throughfall in four South Korean cool temperate forests

Gautam, Mukesh Kumar,Lee, Kwang-Sik,Bong, Yeon-Sik,Song, Byeong-Yeol,Ryu, Jong-Sik Taylor Francis 2017 Hydrological sciences journal Vol.62 No.12

Deposition pattern and throughfall fluxes in secondary cool temperate forest, South Korea

Kumar Gautam, Mukesh,Lee, Kwang-Sik,Song, Byeong -Yeol Elsevier 2017 Atmospheric environment Vol.161 No.-

<P>Chemistry and deposition fluxes in the rainfall and throughfall of red pine (Pinus densiflora), black locust (Robinia pseudoacacia), and chestnut (Castanea crenata) monocultures, and mixed red pine black locust chestnut stands were examined in a nutrient-limited cool temperate forest of central South Korea. Throughfall was enriched in both basic and acidic constituents relative to rainfall, suggesting that both dry deposition and canopy leaching are important sources of throughfall constituents. Net throughfall fluxes (NTFs) of cations and anions significantly differed among four different stands as well as seasonally. Red pine exhibited highest fluxes (TF and NTF) for Ca2+, black locust for K+, mixed stands for Mg2+, and chestnut for Na+. In contrast, NTF of SO42-, NO3-, and NH(4)(+)was highest in the red pine, intermediate in the chestnut and mixed stands, and lowest in the black locust. In general, canopy uptake of H+ and NH4+ for all stands was higher in summer than in winter. Dry deposition appears to play a major role in atmospheric deposition to this cool temperate forest, especially in summer. Dry deposition for both cations and anions displayed high spatial variability, even though stands were adjacent to one another and experienced identical atmospheric deposition loads. Canopy leaching of K+ (95-78% of NTF), Mg2+ (92-23% of NTF), and Ca2+ (91-12% of NTF) was highest for the black locust, lowest for chestnut, and intermediate for the red pine and mixed stands. The present study documented significant changes in throughfall chemistry and NTF among different forest stands, which presumably be related with the differences in the canopy characteristics and differences in their scavenging capacity for dry deposition and canopy exchange. Difference in the canopy retention of H+ and base cation leaching suggests that canopy exchange was mainly driven by weak acid excretion and lesser by H+ exchange reaction. Our results indicate that despite a high base cation deposition, a combination of higher input of acidifying constituents, low soil pH, and total acidic deposition approaching South Korean critical loads make regional forest vulnerable to acidification. (C) 2017 Elsevier Ltd. All rights reserved.</P>

Trends of major, minor and rare earth elements in decomposing litter in a cool temperate ecosystem, South Korea

Gautam, Mukesh Kumar,Lee, Kwang-Sik,Berg, Bjö,rn,Song, Byeong-Yeol,Yeon, Jeh-Yeong Pergamon Press 2019 Chemosphere Vol. No.

<P><B>Abstract</B></P> <P>The decomposition dynamics of 34 different elements in four different litter types (foliar and woody litter) from <I>Pinus densiflora</I> (Korean red pine) and <I>Castanea crenata</I> (Korean chestnut) was investigated in a cool temperate ecosystem using the litterbag method. Two contrasting trends were observed in the dynamics of elements with accumulated mass loss of litter and carbon. Leaf litter of Korean chestnut, which was richer in elements, showed a general decrease in concentrations of elements with accumulated mass loss of litter and carbon on a dry mass basis during decomposition in the field. Other litter types, with initially lower concentrations of elements, exhibited an increase in concentration on a dry mass basis during field incubation. Highest relative increase in the concentration was noticed for the minor elements, and for the woody litters. Concentrations of major and minor elements increased by factors ranging from 1.07 for antimony (Sb) to 853.7 for vanadium (V). Rare earth elements (REE) concentrations increased by factors ranging from 1.04 for scandium (Sc) to 83.5 for thorium (Th). Our results suggest that litter type plays an important role for nutrient dynamics. Results from principal component analysis for major, minor, and rare earth elements showed grouping of elements and high correlation among them (<I>P</I> < 0.05), which suggests a common source. At both sites, element concentrations were high in the soil, especially for REE. This suggests that increase in element concentrations during field incubation probably was due to transfer of elements from soil to the overlying decomposing litter.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The dynamics of major, minor, and rare earth element was studied in decomposing forest litter. </LI> <LI> Angiosperm and gymnosperm leaf litter showed contrasting patterns of changes in concentrations of the studied elements. </LI> <LI> Rare earth elements showed identical pattern of accumulation in woody litters after one year of decomposition. </LI> </UL> </P>

Patterns of diversity and regeneration in unmanaged moist deciduous forests in response to disturbance in Shiwalik Himalayas, India

Mukesh Kumar Gautam,Rajesh Kumar Manhas,Ashutosh Kumar Tripathi 국립중앙과학관 2016 Journal of Asia-Pacific Biodiversity Vol.9 No.2

We studied vegetation attributes in Indian tropical moist deciduous unmanaged forests to determine the influence of forest disturbances on them. We enumerated 89 species: 72 under moderate disturbance and 54 under least disturbance. The data from 3399 stems [>5 cm diameter at breast height (dbh)] decreased linearly along the disturbance gradient. The basal area was largest in least disturbed forests (61 m2/ha) and smallest in intensely disturbed forest (41 m2/ha). Under least and moderate disturbance, tree density-diameter distribution had negative exponential curves, whereas highly disturbed forests had unimodal-shaped curves where a few trees 5–10 cm and >50 cm in diameter were recorded. Most tree and shrub layer species under heavy and intense disturbance had impaired regeneration. Moderate disturbance intensity thus apparently benefits species diversity, stand density, and regeneration. Decline in seedlings and saplings, especially tree species, threaten forest regeneration and the maintenance of species diversity of unmanaged tropical forests.

Isotopic composition of throughfall nitrates in suburban forests with different vegetations

연지형,Mukesh Kumar Gautam,김인수,이선혜,이동호,안현주,이광식 한국지질과학협의회 2015 Geosciences Journal Vol.19 No.1

Isotopic studies on throughfall (precipitation shedfrom foliages) nitrates are rare despite their importance as amajor nitrogen source in forest ecosystems. This study was conductedto examine a seasonal and species-related variability in isotopiccomposition of throughfall nitrates and its implications onforest nitrate sources. Event based throughfall samples were collectedfor a year from three locations (Chestnut, Pinus, and Mixedforests) along with rainfall (uninterrupted precipitation to the ground)samples from an open canopy location, and analyzed for nitrogenand oxygen isotopic composition of dissolved nitrates. δ15NNO3 andδ18ONO3 values of rainfall nitrates were greater during the nongrowingseason (Nov.~Mar.) than the growing season (Apr.~Oct.)as expected from the atmospheric nitrate cycles and associated isotopiceffects. Although the isotopic composition of throughfallnitrates followed a similar seasonal pattern with that of rainfalls,their δ15NNO3 and δ18ONO3 values were consistently higher (Sep.~Dec.)or lower (Jan.~Apr.) than rainfalls and showed an abrupt decreasein July, possibly related to the incorporation of nitrates from soiland foliar origin. Isotopic composition of throughfall nitrates alsovaried systematically with vegetation types, indicating isotopic effectsassociated with nitrate uptake and release at the forest canopy. The seasonal and species-related variability in the isotopic compositionof throughfall nitrates indicated combined effects of atmosphericNOx cycles, dry and wet depositions, and species-specificisotopic effects associated with nitrate use.

Origin Assessment of Domestic and Imported Beef Sold in the Korean Markets Using Stable Carbon and Oxygen Isotopes

봉연식,Mukesh Kumar Gautam,이광식 한국식품과학회 2012 Food Science and Biotechnology Vol.21 No.1

In this study, stable carbon and oxygen isotope data were used to determine the country of origin of imported beef circulating in the Korean market. Using carbon isotopes closely related to the animal diets, Korean beef could easily be distinguished from United States (US)and New Zealand beef. However, oxygen isotopes were more effective in distinguishing the Korean from Australian beef. The oxygen isotopes have specific characteristics reflecting the latitude where cattle feed. Statistical analyses indicate that analyzing both carbon and oxygen isotopes is very useful to assess the country of origin of beef sold in the Korean market. Additionally, we compared the carbon isotopic compositions of defatted and non-defatted beef to evaluate the effect of fat content on carbon isotope values. Our results suggest that by using muscles or tissues that have small amounts of fat, carbon isotope analysis of beef samples may be performed without the inconvenient conventional pretreatment procedure, allowing for easier and faster isotopic analysis.

Effects of bedrock on the chemical and Sr isotopic compositions of plants

Song, Byeong-Yeol,Gautam, Mukesh Kumar,Ryu, Jong-Sik,Lee, Dongho,Lee, Kwang-Sik Springer-Verlag 2015 Environmental Earth Sciences Vol.74 No.1

Investigation of phase segregation in sol–gel derived ZnMgO thin films

Singh, Amanpal,Vij, Ankush,Kumar, Dinesh,Khanna, P K,Kumar, Mukesh,Gautam, Sanjeev,Chae, K H Institute of Physics 2013 Semiconductor science and technology Vol.28 No.2

<P>Highly c-axis-oriented Zn<SUB>1-x</SUB>Mg<SUB>x</SUB>O multilayered thin films have been deposited on p-type Si substrates with different concentration of Mg (x = 0.00−0.40) using a sol–gel spin-coating technique. The x-ray diffraction (XRD) shows that single-phase wurtzite thin films start showing phase segregation for a Mg content of x = 0.25 for the sol–gel-derived ZnMgO thin films. The element specific near edge x-ray fine structure (NEXAFS) collected at O K-edge also clearly evidence the phase segregation at x = 0.25. These results also show that films are deposited with wurtzite structure as dominant phase even after phase segregation. The NEXAFS spectra collected at Zn L<SUB>3</SUB>-edge rule out the presence of any Zn-related defect due to Mg doping. The atomic force microscopy (AFM) depicts the spherical shape of nanosized grains, and grain size varies slightly with Mg content. The single-phase ZnMgO thin films show a band gap tuning from 3.38 to 3.84 eV, which is also consistent with blue shifting of near-band edge PL emission. The electrical resistivity of thin films increases with Mg content before phase segregation. However, the optical band gap, photoluminescence and electrical resistivity show anomalous behavior at phase segregation limit which has been discussed and correlated with each other.</P>