The role of water and nutrient availability in determining above and below ground allocations in a C4 grass Stipagrotis ciliata desf. de Winter

• Main Author: Moore, Timothy E
• Other Authors: Carrick, Peter J
• Format: Others
• Language: English
• Published: University of Cape Town 2017
• Subjects: Botany
• Online Access: http://hdl.handle.net/11427/26459

In order to understand the impacts climate change will have on plants it is important to understand the role of functional diversity in determining plant success across a range of environments. Two populations of Stipagrostis ciliata were compared at two sites - drier coastal and wetter inland - that varied in their water and nutrient availability. Analysis indicates an inverse relationship between rainfall and N availability, with the drier coastal site having significantly lower soil and plant δ¹⁵N (Zadi= -1.964, p<0.05). Plant percent N decreased by 63% between the coastal and inland site. Mean root: shoot ratios also differed significantly between sites (Zadi= -1.964, p<0.05). Although total rooting depth did not appear to differ between sites, in total more root material was found per plant at the inland site, with 40% of all root material occurring directly below the plant. At the coastal site, a greater proportion of root material was allocated laterally in the upper 10cm of soil. As expected, water use efficiency, based on δ¹³C, was higher at the drier coastal site. It is proposed that plants will alter above and below- ground allocation depending on the nature of the limiting resource. In dry environments, more root material in upper soil layers, and a faster growth rate associated with higher shoot allocation, may enhance water uptake. Where nutrients are limiting, increased root biomass might increase nutrient, especially N interception. Competition may also be higher at low nutrient sites.