Resprouting of the Mediterranean-type shrub Erica australis with modified lignotuber carbohydrate content

Abstract

1. The vigour of plant resprouting after fire may be driven by the amount of stored non-structural carbohydrates (NC). However, the extent to which NC reserves limit this response in woody plants has not been established. 2. This study analyses the effects of modifying NC concentrations in the lignotuberous Mediterranean-type shrub Erica australis, on resprouting after experimental burning. A factorial experiment with two treatments (shade and burn) was carried out, with three levels per treatment. Plants were shaded (exposure to 100%, 50% or 20% of incident radiation for 1 year), following which they were clipped (control, no fire), or clipped and burned at one of two levels of severity. After this, they were allowed to resprout and grow for 2 years. 3. Shading modified NC concentrations in the lignotuber, but not in the roots. Two years after burning, plants subjected to the greatest shading, which reduced their NC concentrations to 44% (sum of NC) or 19% (starch) of that of control plants, had suffered higher mortality after resprouting, had a significantly lower number of resprouts, of shorter length, and had produced lower biomass per plant than less shaded or unshaded plants. However, plants subjected to intermediate shade, which suffered a reduction in NC concentrations to 70% of that of control plants, did not differ in resprouting response from control plants. 4. Burning caused more direct mortality, and a severe reduction in both number or biomass of resprouts, than just clipping. There were no significant shade x burning interaction effects. 5. While reductions in NC may limit resprouting, such limitation may only occur when NC is reduced to much lower concentrations than caused by commonly experienced conditions. The role of NC reserves in limiting resprouting of lignotuberous, woody plants such as E. australis might therefore not be as important as is commonly assumed.