Fire affects soil organic matter and the emergence of Pinus radiata seedlings

Abstract

These results present great interest for the knowledge of fire effects and the regeneration capacity of the ecosystems, which is essential to minimise the long-term fire impacts. This study integrates thermal analysis of soil with tests of fire effects on Pinus radiata seeds germination and field seedling emergence in P. radiata plantations. The consequences of fire intensity P. radiata plantation regeneration can be predicted from the results. This study aims to identify the effects of fire on soil organic matter and emergence of P. radiata seedlings in a stand in NW Spain and to test the response of seeds from two provenances of P. radiata to smoke and heat. Burnt, unburnt and laboratory-heated samples of dry soil were analysed in a differential scanning calorimeter. Based on the comparison between heat released during the combustion of the organic matter of these samples, we estimated the fire severity. Early emergence of P. radiata seedlings was recorded in the field after fire. Finally, the effects of fire on seeds germination were tested in the laboratory. The limited loss of soil organic matter indicated that the fire had been of low severity and that the temperatures reached during the fire remained below the ignition temperatures of soil organic matter. The germination rate was high in controls and the lowest fire severities but decreased with fire intensity. The two provenances differed in their response to fire intensity. Seedling emergence was moderate and varied over time. The intensity of the investigated fire remained moderate, with a limited loss of soil organic matter. It limited seedling germination and emergence. Nevertheless, despite the scarce seedling emergence observed in the field, re-establishment of the population was possible.