Carbon Allocation and Residence Times in
Owens Valley Soils and Plant Communities

Mariah Carbone, Department of Earth Systems Science, UC Irvine
PhD advisor: Susan Trumbore, Department of Earth Systems Science, UC Irvine

In the Owens Valley, there has been an observed shift in community composition from perennial grasslands to perennial shrublands. We are studying how these changes in the vegetation cover affect carbon (C) cycling on both short and long timescales. In particular, we are focusing on the differences in belowground C allocation and cycling between the shallow-rooted perennial grasses and more deeply-rooted perennial shrubs.

Site 1. Grassland

Site 2. Shrubland

To do this, we are using a combination of isotopic tracers to measure C storage in soils, C allocation and root dynamics in these two plant functional types with differing depth to water table. The isotopic signatures of 13C and 14C in vegetation and respired CO2 inform us about differences in the overall residence time of C in each vegetation type on multi-annual to decadal and longer timescales. To investigate C allocation on shorter timescales (years or less) we developed a novel dual C isotope (13C and 14C) pulse-chase tracer method to quantify the timing and contribution of current photosynthetic products to respiration, growth, and storage in different plant components.*

Automated chambers continually measure the CO2 flux from the soil surface (soil respiration)

The large portable dome allows us to introduce our isotopic tracer which is photosynthetically assimilated by the enclosed plants; and also measure ecosystem CO2 exchange (net ecosystem exchange, light and dark)

*work funded by the Kearney Foundation