Patterns of carbon allocation, storage and remobilization in a common resprouting savanna species - Acacia karoo

• Main Author: Wigley, Benjamin
• Other Authors: Bond, William J
• Format: Others
• Language: English
• Published: University of Cape Town 2017
• Subjects: Botany; Plant Ecology
• Online Access: http://hdl.handle.net/11427/26019

The aim of this study was to gain a comprehensive understanding of the patterns of carbon partitioning, storage and remobilization in Acacia karroo during the juvenile life history stage. Tuber total nonstructural carbohydrate (TNC) concentrations and δ¹³C values were determined in plants from two different stages in the juvenile life history of A. karroo. These were one year after a fire when the plant consisted of numerous leafy shoots or coppices (coppicing stage) and three years after a fire when the plant consisted of one pole like stem (gulliver stage). Gullivers were found to have mean TNC pools of 150g and mean TNC concentrations of 33%. Coppices had mean TNC pools of97g and TNC concentrations of 24%. Both total TNC pools and TNC concentrations in gullivers were significantly higher (p < 0.05) than in coppices. Carbon isotopes were used to determine whether growth was based on carbon reserves as heterotrophic growth shows a distinct enrichment in δ¹³C. The water relations of plants can also influence the δ¹³C values of plant growth. However, there were no significant differences in root size and depth between the stages, indicating that all plants had access to similar water sources. Mean δ¹³C values from the stems of plants in the gulliver stage were significantly enriched(> 1‰) in ¹³C compared to both coppicing plants (p < 0.01) and adults (p < 0.05). The negative δ¹³C values in coppice stems suggest that their growth is not based on stored carbon. The enriched δ¹³C values found in the gulliver stems support the hypothesis that carbon reserves are utilized to achieve fast growth rates in an attempt to escape the fire trap. However, the small magnitude of the differences in δ¹³C between the two stages suggests post-burn regrowth is derived from both current photosynthate and stored carbon.