Datos de la publicación "Fire effects on the reproductive success of two dominant woody species along an elevation gradient in central Argentina"

Abstract

Fire and elevation might determine the proportion of woody species in the landscape through their influence on reproductive success, but the effects of both factors are often confounded. Our objective was to investigate the combined effects of fire and elevation on woody species reproductive success in a seasonally dry mountain ecosystem. We tested the hypothesis that the negative effects of fire on tree reproductive success are greatly enhanced with increasing elevation due to low temperatures. Our study was carried on in the mountains of central Argentina, from 800 to 1700 m a.s.l. We selected individuals of two dominant woody species within burned and comparable unburned areas (198 Vachellia caven and 85 Lithraea molleoides individuals). We estimated pre-fire tree size and monitored parameters related to reproductive success during four post-fire fruiting seasons. Our main results for Vachellia caven show negative fire effects on most measured reproductive parameters, and on the number of germinable seeds per tree, which was estimated as an integrated parameter. The negative fire effects decreased over time, until the fourth post-fire fruiting season, when we detected almost no fire effects. Moreover, the negative fire effects were greatly enhanced with elevation. For large trees located at low elevation, fire damage reduced the number of germinable seeds per tree by a factor of nearly six during the third post-fire fruiting season (from 2020 to 358 germinated seeds), while at high elevation fire reduced germinable seeds by a factor of 15 (from 106 to 7 germinated seeds) for similarly large trees. Small trees had a lower reproductive success and showed smaller but noticeable negative fire effects, which also increased with elevation. For Lithraea molleoides we found similar patterns as with V. caven but few trees produced seeds during the study, so we did not compute formal statistics. We conclude that the negative fire effects are greatly enhanced with increasing elevation. Our focus on reproductive success suggests that reducing fires should eventually increase forest cover at high elevation even when survival is not affected by fire nor by elevation in the study species.