Ariel Brown | ALES Graduate Seminar

A graduate exam seminar is a presentation of the student’s final research project for their degree.
This is an ALES MSc Final Exam Seminar by Ariel Brown. This seminar is open to the general public to attend.
Thesis Topic: The composition of cutin and suberin in tissues of mixed-wood boreal forest species and their use as markers

MSc with Dr. Justine Karst.

Seminar Abstract:

Quantifying above and belowground inputs to soil organic matter is an important component in assessing forest soil health and in developing practices to increase the soil organic matter present in forest soils. Cutin and suberin are biopolymers found in leaves and roots, respectively, that protect plants from desiccation. Due to their specific locations within plant tissues, cutin and suberin have been used to identify the origin of organic matter in soils. Specifically, the identity of the monomers comprising these biopolymers is used to infer the contributions of leaves and roots to organic matter. However, previous studies have identified monomers in tissues of leaves or roots that do not concur with published lists of markers, highlighting the importance of using markers that are appropriate for plant species in a given area. To test for interspecific variation of the monomers that make up cutin and suberin, I collected leaf, root and bark samples from the eight most-dominant species in a boreal mixed-wood forest in Alberta, Canada, and hydrolyzed them to release the cutin and suberin constituents. Additionally, I sampled soils from the interface of the organic and mineral soil, treated with the same hydrolysis process to investigate if the monomers present in the plant tissue samples were detectable in soils. The monomers were identified via GCMS and compared to published lists of cutin and suberin markers. Across roots and leaves of eight species, a total of 142 monomers were identified. Soil samples returned only 48 monomers, five of which were not present in any of the plant tissues., Due to their presence in other plant tissues aside from leaves and roots, and in microorganisms, several classes of compounds identified in this study cannot determine the origin of soil organic matter. When compared to published lists of cutin and suberin markers, I found that while a select number of markers held true for the samples analysed in this study, others were not appropriate for use in study areas with vegetation similar to the one in this study due to their presence in multiple tissue types. The inconsistencies between the monomers identified in this study and those in published reports highlight the importance of using cutin and suberin markers specific to the dominant species of plants present in the area.