How do fire and harvesting affect the population dynamics of a dominant endemic Velloziaceae species in campo rupestre?

Abstract

Understanding the role of the environmental drivers that determine plant population dynamics is essential to promote the conservation of target species and their habitats. Vellozia aff. sincorana is an endemic key species from the rupestrian grasslands (campos rupestres) of the Chapada Diamantina region in the Brazilian savanna (Cerrado). The branches are important in the local culture and are harvested to light wood stoves. Synchronized flowering is triggered by fire, and no flowers have been recorded in the absence of a recent fire. We built matrix population models to project the demography of six V. aff. sincorana populations, three that had recently burned and three that had not burned for four years. Based on local harvesting practices and our population models, we assessed the long-term effects of two common harvesting techniques and different fire intervals on this species’ demography. Fire is necessary for the long-term persistence of V. aff. sincorana populations; adult survival is the most important vital rate for population persistence and it is mostly unaffected by fire. Recent fires primarily caused increases in reproductive rates, and populations are projected to decrease in size (λ<1) under fire intervals longer than 25 years. Harvest effects depend on its frequency and intensity; our models indicated that harvesting may be sustainable as long as it is low-intensity and fire also occurs periodically. As in many other fire-prone ecosystems, this species benefits from fire occurrence. These results indicate that the ‘zero-fire’ policy currently in place in the Brazilian savanna is inadequate for the conservation of this, and probably many other, Cerrado species.