Local environmental factors drive understory plant richness and composition in an isolated, relict Scots pine forest in central Iberian Peninsula

Resumen

Background and aims
Understory plants are important determinants of plant diversity in most forest ecosystems, which also play a key role in maintaining forest structure and function. Understory vegetation responds to local environmental gradients, so understanding the main drivers of plant diversity and composition in the understory is important for the conservation of forest diversity and ecosystem functions under current global change scenarios.

Methods
We quantified plant species richness and composition for four groups (woody species, grasses, forbs, and a group of shade tolerant species), and examine their relationship to local environmental factors in the understory of the Hoyocasero forest, an isolated Mediterranean Scots pine (Pinus sylvestris) forest that harbors several singular understory plant taxa.

Results
Our results indicate that soil water content, light conditions in the understory, and overstory composition were important factors determining species richness and floristic composition within the forest. Soil characteristics explained some spatial variation in species richness for all understory plants and the group of shade species, and modulated the response of individual species.

Conclusion
The conservation and management of this singular forest should promote its natural regeneration and the restoration of degraded areas, and forestry activities should be compatible with the maintenance of the moisture and shade conditions that allowed the preservation of a rich and diverse flora in this pine dominated forest surrounded by more human impacted oak forests and deforested areas.