Post-fire invasion in Torres del Paine Biosphere Reserve: the role of seed tolerance to heat

Abstract

Biological invasions are one of the major causes of biodiversity loss. Anthropogenic alteration in fire regimes has promoted plant invasion in several regions and ecosystems worldwide, especially in those where fires are historically rare. This is the case of the UNESCO Biosphere Reserve Torres del Paine National Park (TPNP), located in southern South America. In this study, we hypothesised that the seeds of native species of the TPNP do not resist fire-related high soil temperatures as do exotic plants, which could facilitate the spread of exotic plant invasion in post-fire environments. To test this hypothesis, we exposed seeds of plant species collected from the TPNP to different heat doses (60°C, 5\u2009min; 90°C, 5\u2009min; 90°C, 10\u2009min; 120°C, 5\u2009min) and compared their final germination and viability with those of unheated seeds. The study was conducted on five native species and three aliens inhabiting the TPNP. Almost all the seeds of native species died after exposure to temperatures higher than 60°C, whereas seeds of the alien species resisted higher heat doses. The on-site resistance of the aliens (through fire-tolerant soil seed banks) and the fire sensitivity of native seeds contribute to our understanding on post-fire invasion in the TPNP.