Browsing by Author "Thakur, Bijay"

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    Heavy Metal Contamination of Forest Soils by Vehicular Emissions: Ecological Risks and Effects on Tree Productivity
    (springer, 2022-01-29) Malunguja, Gisandu K.; Thakur, Bijay; Devi, Ashalata
    An ecological study was conducted to evaluate the levels and effects of heavy metals on forest surface soils along highways. We hypothesized that vehicles in highways emit considerable levels of metals, affecting plant diversity and productivity. Pearson correla- tion, cluster, and regression analysis were used to prove these relationships. Furthermore, ecological risk assessments were quantified using the geo-accumulation index, pollution index, pollution load index, and ecological risk index. Results indicated soil samples from Site II (roadway) had higher levels of metals than Site I (control), suggesting that highway traversing via forests emit considerable amounts of metals into the surface soil. The most intriguing aspect is that species such as Bidens Pilosa and Arundo donax were frequently recorded at Site II. The predominance of such species indicates contaminated sites favour- ing metal tolerance species. Ecological risk indices revealed that Cd, Mn, and Pb contrib- uted to ecological risk; their pollution ranged from unpolluted to heavily polluted ecosys- tem. Correlation analysis found a pronounced negative link between metals and diversity; the correlation matrix was −83%, −94%, −65%, −75%, −47%, −57% and − 38% for grass diversity, and − 59%, −74%, −89%, −66%, −81%, −81% and − 83% for forb diversity with Cd, Cr, Ni, Pb, Zn, Cu and Mn, respectively. Furthermore, negative correlations for tree production of −80%, −79%, −76%, −71%, −67%, −53% and − 41% were recorded with Cd, Cr, Ni, Pb, Zn, Cu and Mn, respectively. Nevertheless, metals accounted for 74% vari- ance in tree productivity. The strong negative link observed in this study demonstrates the effects of metals on diversity and productivity, which requires monitoring for preventing serious environmental consequences. Highlights • Excessive road traffic contributes to the release of heavy metal in forests. • Heavy metals in surface soils threaten plant diversity and productivity. • Cd, Mn and Pb are the most substantial contributors to ecological risks.
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    Heavy Metal Contamination of Forest Soils by Vehicular Emissions: Ecological Risks and Effects on Tree Productivity.
    (Springer, 2022-01-29) Malunguja, Gisandu K.; Thakur, Bijay; Devi, Ashalata
    An ecological study was conducted to evaluate the levels and effects of heavy metals on forest surface soils along highways. We hypothesized that vehicles in highways emit considerable levels of metals, affecting plant diversity and productivity. Pearson correlation, cluster, and regression analysis were used to prove these relationships. Furthermore, ecological risk assessments were quantified using the geo-accumulation index, pollution index, pollution load index, and ecological risk index. Results indicated soil samples from Site II (roadway) had higher levels of metals than Site I (control), suggesting that highway traversing via forests emit considerable amounts of metals into the surface soil. The most intriguing aspect is that species such as Bidens Pilosa and Arundo donax were frequently recorded at Site II. The predominance of such species indicates contaminated sites favouring metal tolerance species. Ecological risk indices revealed that Cd, Mn, and Pb contributed to ecological risk; their pollution ranged from unpolluted to heavily polluted ecosystem. Correlation analysis found a pronounced negative link between metals and diversity; the correlation matrix was −83%, −94%, −65%, −75%, −47%, −57% and−38% for grass diversity, and−59%, −74%, −89%, −66%, −81%, −81% and−83% for forb diversity with Cd, Cr, Ni, Pb, Zn, Cu and Mn, respectively. Furthermore, negative correlations for tree production of −80%, −79%, −76%, −71%, −67%, −53% and−41% were recorded with Cd, Cr, Ni, Pb, Zn, Cu and Mn, respectively. Nevertheless, metals accounted for 74% variance in tree productivity. The strong negative link observed in this study demonstrates the effects of metals on diversity and productivity, which requires monitoring for preventing serious environmental consequences.
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    Relationship between Forest Biodiversity Attributes and Potential Carbon Stocks in Dry Tropical Reserve Forests of Assam, Northeast India
    (University of Latvia, 2021) Malunguja, Gisandu K; Thakur, Bijay; Devi, Ashalata
    Potential forest carbon stocks are significantly correlated to forest biodiversity attributes such as diversity, density, and richness. However, there is little such information on dry tropical reserve forests of Assam, a state in northeast India. We studied this relationship in two reserve forests. Pearson correlation, cluster analysis, and regression analysis were used to explore these relationships. The estimation of plant carbon stocks was made using both destructive methods for herbaceous and non-destructive allometric methods for trees. The most dominant plant species in the Bhomoraguri reserve forest were Cynodon dactylon, Datura stramonium, Clitoria ternatea, and Tectona grandis for grasses, forbs, climbers, and trees, respectively. Cymbopogon nardus, Colocasia esculenta, Mikania micrantha, and Shorea robusta, were dominant species in the Balipara reserve forest for grasses, forbs, climbers, and trees, respectively. The presence of Lantana camara, Smilax ovalifolia and Piper betle in the studied forests suggests disturbed ecosystems. Other observed species such as Aristida spp., Cenchrus spp., Ipomoea cheirophylla, and Sida spp. are indicators of disturbed ecosystems as well. The biomass stock differed significantly among plant growth forms. Carbon stocks were 302.93 and 283.97 t ha–1 in the Bhomoraguri reserve forest and Balipara reserve forest, which were equivalent with 555.87 and 521.30 t ha–1 of CO2 sequestration, respectively. Tree species contributed the greatest amount (54.80%), followed by forbs (21.36%), climbers (19.35%), and least for grasses (4.49%). Correlation analysis indicated a strong positive relationship between the density of trees and climber species with carbon stock potentials, suggesting that increase of their density favoured carbon sequestration in forest ecosystems. Diversity of grasses was negatively correlated with potential carbon stock in the examined forests. The unique contribution of each group to carbon stock was 91.8, 58.01, 51.3, and 11.11% for climbers, trees, grasses, and forbs, respectively. Thus, it is important to examine biodiversity attributes in estimation of forest carbon stocks.