Stable Isotopes in Plant Ecology

Abstract

▪ Abstract The use of stable isotope techniques in plant ecological research has grown steadily during the past two decades. This trend will continue as investigators realize that stable isotopes can serve as valuable nonradioactive tracers and nondestructive integrators of how plants today and in the past have interacted with and responded to their abiotic and biotic environments. At the center of nearly all plant ecological research which has made use of stable isotope methods are the notions of interactions and the resources that mediate or influence them. Our review, therefore, highlights recent advances in plant ecology that have embraced these notions, particularly at different spatial and temporal scales. Specifically, we review how isotope measurements associated with the critical plant resources carbon, water, and nitrogen have helped deepen our understanding of plant-resource acquisition, plant interactions with other organisms, and the role of plants in ecosystem studies. Where possible we also introduce how stable isotope information has provided insights into plant ecological research being done in a paleontological context. Progress in our understanding of plants in natural environments has shown that the future of plant ecological research will continue to see some of its greatest advances when stable isotope methods are applied.

Uncertainties of fluxes and <sup>13</sup>C ∕ <sup>12</sup>C ratios of atmospheric reactive-gas emissions

“…Briefly, the isotopic compositions of those differ conspicuously owing to the differences in the photosynthesis mechanisms, yielding typical compositions of −27 ‰ for C 3 plants and −12 ‰ for C 4 plants (see, e.g. Dawson et al, 2002). The expected composition of the mixture is hence constrained by these values.…”

“…Sharkey et al (1991) measured the carbon isotopic composition of the emitted isoprene and found it to be dependent on the composition of the reservoir of recently fixed carbon (CO 2 incorporated in the plant material during the initial step of the photosynthetic cycle). The isotope effects related to the plant activity and plant-CO 2 exchanges are extensively studied (see, for instance, Dawson et al, 2002). They usually operate with the isotope discrimination , a representative parameter describing the fractionation of the plant tissue relative to the atmospheric reservoir (Farquhar et al, 1989):…”

Shading and litter mediate the effects of soil fertility on the performance of an understorey herb

“…Ten or more individuals were collected per plot for mycorrhizal colonization and traits associated with low soil nutrients and climate (Diaz et al, 1998;Dawson et al, 2002;Wright et al, 2004;Ordonez et al, 2009). The traits measured, specific leaf area (SLA), leaf C:N and carbon isotope ratio (d 13 C), were chosen because they indicate a resource conservation strategy with high leaf C:N and low SLA, and high water use efficiency as measured by d 13 C (Dawson et al, 2002;Lavorel and Garnier, 2002;PerezHarguindeguy et al, 2013). Leaves were collected and maintained in cool, moist conditions, either in a cooler or refrigerator, and scanned within 24 h of collection.…”

Abiotic, Biotic, and Evolutionary Control of the Distribution of C and N Isotopes in Food Webs

“…Changes in the plant nutrient pools along elevation were accompanied by variation in the same direction of d 15 N values; thus, both d 13 C and d 15 N may serve to infer patterns of N cycling across environmental gradients. This coupling has been described in ecosystems in which climate chiefly controls plant nutrient uptake and storage (Dawson et al 2002;Craine et al 2009) but not in systems where grazing is the main environmental perturbation. Nitrogen input from herbivore waste contains large amounts of 15 N-enriched ammonium and depleted nitrate (Frank et al 2000); thus, plant communities tend to homogenize with respect to nitrogen content but split with respect to d 15 N values (Högberg 1997;Dawson et al 2002).…”

“…This coupling has been described in ecosystems in which climate chiefly controls plant nutrient uptake and storage (Dawson et al 2002;Craine et al 2009) but not in systems where grazing is the main environmental perturbation. Nitrogen input from herbivore waste contains large amounts of 15 N-enriched ammonium and depleted nitrate (Frank et al 2000); thus, plant communities tend to homogenize with respect to nitrogen content but split with respect to d 15 N values (Högberg 1997;Dawson et al 2002). The above-described results suggest that soil chemistry is often the prime target of biotic and abiotic forces, thus representing a key component of nutrient cycles that should be addressed to fully comprehend ecosystem processes.…”