Browsing by Author "Wigley, Benjamin"
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- ItemOpen AccessAn isotopic assessment of the water sourced by Ischyrolepis Sieberi (Restionaceae) growing at high altitudes in the Cedarberg : does fog play an important role?(2004) Wigley, Benjamin; February, Edmund CThe main aim of this study was to determine if Ischyrolepis sieberi, a common restiod species found at high altitudes in the Cederberg captures fog to supplement its water needs. This was done by comparing the isotopic ratios of δD and δ¹⁸O in captured fog, rainwater, and stream water and comparing these to the δD and δ¹⁸O values found in the xylem water of Ischyrolepis sieberi plants growing at the study site. The δD values of the collected fog samples were enriched relative to rainwater, stream water, and xylem water from I. sieberi, however these differences were not significant. The δ¹⁸O values of the I. sieberi xylem water were significantly (p < 0.01) more enriched than rain, stream, and fog water. The xylem water of I. sieberi was depleted in δD and enriched in δ¹⁸O relative to all other water sources. The plants therefore did not appear to be utilizing fog during the three months of this study. The δ¹⁸O values of I. sieberi were consistently 4-6‰ enriched compared to rainwater, suggesting that they are utilizing rainwater, which has undergone fractionation due to evaporation in the soil before being taken up by the plants. This study was run during the wet winter months. The δD and δ¹⁸O values from previous data suggest that the I. sieberi plants do utilize fog during the dry summer months.
- ItemOpen AccessPatterns of carbon allocation, storage and remobilization in a common resprouting savanna species - Acacia karoo(2004) Wigley, Benjamin; Bond, William J; Cramer, Michael DThe 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.