Carbon allocated belowground to roots accounts for a large portion of net primary productivity, but the fate of that carbon is poorly understood. Absorptive fine roots are the primary way in which roots acquire resources and these roots release carbon dioxide through respiration. Previous studies have evaluated relationships among root morphological traits, including specific root length, root tissue density, and mycorrhizal colonization, across broad functional and taxonomic groups to evaluate the existence of a “root economics spectrum”. Other studies have found relationships between these morphological traits and root respiration within a single tree species. The objective of this study was to measure a suite of root traits in six co-occurring temperate tree species that represent a diverse set of nutrient acquisition and growth strategies to determine whether and how root characteristics influenced root respiration both within and among species. At the Harvard Forest in Petersham, MA, we measured fine root respiration, root morphology, percent colonization for ectomycorrhizal species, and carbon and nitrogen concentrations on a total of 292 roots from six tree species in June and July 2018.
Results/Conclusions
We found that there was as much variation in fine root morphology within each tree species as there was among the six species. Root traits were dynamic over time during the two months of our study. Strong correlations among traits suggested trade-offs on a spectrum from resource acquisition (long, thin, high nitrogen roots) to resource conservation (thick, dense, low nitrogen roots), but roots from all six species were distributed across this spectrum. Along with temperature and seasonal patterns, the resource acquisition strategy was associated with higher root respiration, and this relationship was consistent among the six species. This study supported a strong link between the root economics spectrum and respiration independent of species identity, which provides insight into potential variables for scaling root respiration from individual trees to the forest stand to better quantify belowground carbon flux.