Canadian Journal of Earth Sciences, 1974, Vol. 11, No. 1 : pp. 79-88 Seasonal Variations in the Isotope Ratios of Carbon in Maple Leaves and Other PlantsJ. A. Lowdon, W. Dyckhttps://doi.org/10.1139/e74-007

ABSTRACT: A seasonal cycle in δ13C, varying between −22‰ in early spring and −28‰ in late fall, has been observed in maple leaves growing under natural conditions. A similar δ13C cycle, varying between −25‰ and −30‰ is indicated for grass growing in the same location as the maple leaves. The seasonal cycle appears to be analogous to the diurnal δ13C cycle.14C/12C ratios of various plants from different parts of Canada show that the 14C produced by thermonuclear bombs has approximately a half-life of eleven years in the atmosphere over Canada. When due allowance is made for the isotope fractionation effect produced by plants, no significant variations in the 14C content in plants from different localities across Canada can be detected. The reported 14C peak observed in atmospheric CO2 in late summer also shows up in maple leaves but with reduced intensity. 14C levels show clearly that the first leaves in spring are composed primarily of carbon assimilated in the previous fall.

Variations in carbon isotope ratios of plants across a temperature gradient along the 400 mm isoline of mean annual precipitation in north China and their relevance to paleovegetation reconstruction( Quaternary Science Reviews,Volume 63, 1 March 2013, Pages 83-90 )

Abstract:Carbon isotope values (δ13C) of plants reflect the balance between photosynthesis and stomatal conductance and vary with environmental conditions. Temperature is an important influential factor for plant δ13C; however, variations of plant δ13C across temperature gradients have yet to be quantified. This impedes interpretation of variability of δ13C in ancient terrestrial organic matter and reconstructions of paleoclimate and paleoecology. In this study, the effect of temperature on δ13C of C3 and C4 plants was assessed by comprehensive investigation of a large number of species (118 C3 plants and 17 C4 plants) from 29 sites across a temperature gradient along the 400 mm mean annual precipitation isoline in north China. After deducting the effects of precipitation on plant δ13C, a strong positive relationship is found between δ13C values of C3 plants averaged for each site and mean annual temperature, with a coefficient of 0.104‰/°C; however, no significant correlation is found for C4 plants. Based on our results, we conduct a sample reconstruction of paleovegetation of the central Chinese Loess Plateau and demonstrate that, to a certain extent, our paleovegetation reconstruction is affected by temperature corrections.

Variations in the relative abundance of the carbon isotopes in plants( Geochimica et Cosmochimica Acta,Volume 2, Issue 4, 1952, Pages 243-254 )

Abstract: The C12-C13 ratio of 105 plants representing all the major systematic groups has been determined. Except perhaps for gymnosperms there are in principle no systematic differences between the groups. Characteristic differences occur, however, between plants grown in different biotopes, and these differences are related to the varying intensity of the local carbon-dioxide cycle.

It may be due to 1. variations of environmental parameter , for example, isotope composition in the atmosphere 2. variation in the carbon fixation pathway correlated with environmental parameters ( like temperature, illumination, water availability ) and 3. biologic parameters ( for example, age).

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