LINKING COMPETITION AND NONSTRUCTURAL CARBON DYNAMICS IN AMERICAN CHESTNUT (CASTANEA DENTATA)
thesisposted on 2021-04-25, 01:30 authored by Madeline S MontagueMadeline S Montague
Nonstructural carbohydrates (NSC) are involved in essential plant functions and are closely associated with growth and mortality mechanisms. Quantifying NSC reserves can indicate a plant’s resistance and resilience to stress or injury through damaging agents and environmental change. In this work, we studied seasonal NSC dynamics and responses to inter- and intra-specific competition in American chestnut (Castanea dentata (Marsh.) Borkh.), a species of high restoration interest. This research project is comprised of two experiments; first, we delineate seasonal NSC dynamics in mature chestnut to identify critical periods in NSC reserve dynamics that could help evaluate the condition of trees (Chapter 2). We used a custom-built allometric model to scale NSC concentration measurements into pool sizes. By assessing the magnitude and location of NSC pools, we found that chestnut stores most of its NSCs belowground and demonstrated an ability to mobilize root NSCs to fuel growth and metabolism. These results support the idea that chestnut could thrive under disturbance-based management. In the second experiment, we use the knowledge of chestnut biology gained in Ch. 2 to examine a fundamental question in the NSC literature: How does competition affect the internal balance of carbohydrate allocation to growth vs. storage? We studied the effect of intra- and inter-specific competition on American chestnut biomass accumulation and NSC reserves using mixtures of species with strong functional differences in a mature plantation experiment. Coarse root total NSC pools responded to density and species composition through their combined effects on NSC concentrations and tree biomass. There was a strong density × composition interaction: while NSC pools were largest in plots with the lowest planting density where chestnut was planted with black cherry or in a three-species mixture with black cherry and northern red oak, chestnut NSC pools were reduced when planted in monoculture or in a two-species mixture with northern red oak. Therefore, neighbor identity was more important than species richness for NSC pools in our system. Taken together, this body of work contributes to our understanding of the regulation of NSCs in temperate deciduous trees, and to our understanding of chestnut’s unique biology in particular.