Continuous ¹³C and ¹⁵N Labeling of Tree Litter using a Climate-Controlled Chamber

Abstract

Substrates with a unique stable isotope signature provide researchers with the ability to trace nutrients through food webs. Plant material labeled with carbon (¹³C) can be produced by exposure to carbon dioxide (CO₂) with an isotopic composition that differs from ambient conditions during photosynthesis. Labeling can occur continuously or be repeated over several “pulses.” Each method has a high cost either in the form of expensive control systems or significant time investments. In 2012, we built a large growth chamber and used an inexpensive, open-source Arduino^TM microcontroller to monitor and control interior conditions so that we could produce leaf litter dually enriched in ¹³C and nitrogen (¹⁵N) for future incubation experiments. We performed a labeling experiment on 73 saplings representing seven species in 2012 and repeated the labeling on 30 saplings of one species in 2013. We successfully produced over 1 kg of litter enriched in both isotopes; ¹⁵N-enrichment (δ¹⁵N: 759.2 ± 133.7‰) was much greater than ¹³C (δ¹³C: 11.2 ± 3.4‰). Roots (161.0 ± 8.6‰) were much more enriched in ¹³C than litter (11.2 ± 3.4‰), indicating significant translocation of newly fixed carbohydrates. Some species allocated more resources toward their leaves as trees with the most enriched litter had the least enriched roots. ¹³C litter enrichment in 2012 was at the lower end of the range reported by similar studies; however, litter from trees labeled over two seasons achieved a higher level of enrichment (401.4 ± 65.5‰).

Keywords:

• Carbon
• ¹³C, ¹⁵N
• nitrogen
• stable isotope
• testing methodology
• tree leaf litter

ORCID

Katalin Szlavecz

http://orcid.org/0000-0003-2504-0298

Additional information

Funding

Financial support was partially provided by Microsoft Research and the National Science Foundation (EEC-0540832, ACI 1244820, and EAR-0748574).