Debby C. Barsi

Comparative nutrient economy, stable isotopes, and related adaptive traits in Picea rubens, Picea mariana, and their hybrids

Nutrient- and water economy-related traits in plants have significant implications for growth and fitness. We explored, examined, and compared nutrient concentrations, use efficiencies, assimilation, and informative isotopic elements in a seedling provenance experiment, and in seedling and mature tree controlled-cross hybrid experiments of red spruce (RS) (Picea rubens Sarg.) and black spruce (BS) (P. mariana (Mill.) BSP). Provenance experiment results showed RS had consistently lower carbon (C) and nitrogen (N) concentrations, and N assimilation ratio (NAR), but higher N-use efficiency (NUE), C:N ratio, water-use efficiency (WUE), and needle calcium (Ca) and magnesium (Mg) concentrations than BS. The hybrid seedling experiment showed similar results and additive inheritance for needle N, C:N ratio, NAR, Ca, and Mg, evident by a near-linear progression from one species to the other. Within both species, seedling height showed a negative relationship with needle N and a positive relationship with NUE. However, across hybrid indices, seedling height showed a positive relationship with needle N and a negative relationship with NUE. Also across hybrid indices, seedling height showed a negative relationship to Ca and C:N, and a positive relationship with NAR and 13C discrimination (without hybrid 25). Mature tree hybrid experiment results were similar to those of the seedling experiment, but with a dampening of differences caused by low nutrient availability and possibly age effects. The similarity was not true for 13C discrimination as mature tree height showed a strong negative relationship to 13C discrimination, indicating that BS had greater WUE. The reversal is most probably caused by the large difference in water availability.