Carbon isotopic ratios of modern C3–C4 plants from the Gangetic Plain, India and its implications to paleovegetational reconstruction

Mid-late Holocene vegetation response to climatic drivers and biotic disturbances in the Banni grasslands of western India

“…1B and 2B). Corg values have been widely used to estimate relative abundances of C3 (mainly trees and shrubs) versus C4 plant cover (grasses) in the past owing to differences in isotopic fractionation that arise from different carbon fixation pathways (Cerling et al, 1989;Leng and Marshall, 2004;Sanyal et al,2004, Basu et al, 2015. For carbon isotope ratios and weight percent TOC analysis, powdered core sediment samples were pre-treated with 0.5 N HCl to remove inorganic (carbonate) carbon, following which samples were centrifuged in deionized water.…”

“…The 13 C isotopic composition of organic matter is predominantly used for source (C3 versus C4) apportionment in limnological systems to understand paleoclimate changes (e.g., Leng and Marshal, 2004). 13 Corg values of C3 plants typically lie between 31.5 ‰ to 23 ‰ (average 28.57 ‰), whereas C4 plants show 13 C values of 16 ‰ to 10 ‰ (average 13 ‰) (Cerling et al, 1989;Cerling et al,1997;Kohn, 2010, Basu et al, 2015. However, in lacustrine environments, 13 Corg value may be influenced by (i) diagenetic changes in organic matter 19 (Macko and Estep, 1984) and (ii) eutrophication resulting in enriched 13 C value of aquatic organic matter (Meyers, 1997;Leng and Marshall, 2004).…”

Stable Isotopes from Museum Specimens May Provide Evidence of Long-Term Change in the Trophic Ecology of a Migratory Aerial Insectivore

“…Nitrogen isotope ratios in consumers (δ 15 N) are influenced by diet and nutritional status, but on average are ∼ 3‰ higher than those of their prey due to the lighter isotope of nitrogen ( 14 N) being preferentially excreted in urea (Peterson and Fry, 1987;Sears et al, 2008). In contrast, C isotope ratios (δ 13 C) are relatively conserved across trophic levels, but vary depending on the photosynthetic pathways and the degree of water stress experienced at the base of the food web (Peterson and Fry, 1987;Still and Powell, 2010;Basu et al, 2015).…”

“…In terrestrial communities, plant foliage forms the base of many food chains. Foliage isotope values vary across spatial and temporal scales depending on climate, disturbance, and nutrient availability (Amundson et al, 2003;Craine et al, 2009;Pardo and Nadelhoffer, 2010;Popa-Lisseanu et al, 2015;Moreno et al, 2016;Taki et al, 2017) and with physiological differences between plant species, including variation in photosynthetic pathways (Basu et al, 2015;Courty et al, 2015;Taki et al, 2017) and mycorrhizal associations (Evans, 2001;Craine et al, 2009;Hynson et al, 2016). At longer time scales changes in atmospheric baselines, climate, and habitat succession can all cause progressive change in foliage isotopic signatures (Evans and Belnap, 1999;FoxDobbs et al, 2007;Wang et al, 2007;Taki et al, 2017).…”

“…Because atmospheric CO 2 is the sole source of carbon integrated into tissues of producers, we can correct for this change over time (Verburg, 2007). Temperature and rainfall can influence fractionation of carbon between the atmosphere and plant tissues, but the direction of change differs depending on the photosynthetic pathway involved (Basu et al, 2015) and this variation is ∼1/10th that of the differences in fractionation between C 3 plants than for C 4 plants (Peterson and Fry, 1987). Successional changes in mean foliage δ 13 C values are therefore most likely to represent changes in community composition (Taki et al, 2017).…”