Post-burning regeneration of the Chaco seasonally dry forest: germination response of dominant species to experimental heat shock

JAUREGUIBERRY, PEDRO; DÍAZ, SANDRA

OECOLOGIA

SPRINGER

Lugar: Berlin; Año: 2015 vol. 177 p. 689 - 699

0029-8549

Plant species of the Chaco seasonally dry forest of central Argentina presumably have been under a low evolutionary pressure to develop specialized fire-response traits, such as heat-stimulated germination. Nevertheless, other historical factors such as seasonal drought and/or endozoochorus dispersal could have led some species to develop heat-tolerant seeds. Therefore, heat-tolerant germination should be more common than heat-stimulated or heat-sensitive germination. To test this we exposed seeds of 26 dominant species from the Chaco region to a broad range of experimental heat treatments and incubated them for 30 days at 25°C and 12 hs photoperiod. We then scored the percent germination and classified them as heat-stimulated, heat-tolerant or heat-sensitive based on their germination following heat treatments relative to control. Seventeen species showed heat-tolerant germination, including all native graminoids. Seven species showed heat-stimulated germination, under the less intense heat treatments. Only two species showed heat-sensitive germination. Endozoochory had no influence on germination responses. We suggest that unlike Mediterranean-climate ecosystems fire was not a major evolutionary force in the development of Chaco forests, and our results provide greater understanding of the potential response of Chaco plant communities in the face of increasingly frequent fires.