Is Baccharis paniculata (Asteraceae) an effective nurse plant in the matorral of central Chile? Soil vs microclimate effects

Abstract

Background and aims

Shrubs of the genus Baccharis are considered key nurse plants for the Chilean matorral, but some species have allelopathic compounds in their leaves. These compounds can leach into the soil, casting doubt on their nurse role. We assessed the nurse effect of B. paniculata, a species with allelopathic compounds in their leaves, in a central Chilean matorral site by determining the richness and cover of species growing beneath the shrub canopy and open areas, by quantifying the microclimate beneath the canopy and by experimentally assessing the microclimate versus the soil effect of this species on planted seedlings of tree dominant tree species.

Methods

Beneath shrubs and in open areas we recorded the number and cover of species as well air and soil temperature, relative humidity of the air, photosynthetic photon flux density (PPFD) and soil water content. We planted seedlings of Lithrea caustica, Quillaja saponaria, and Cryptocarya alba in both habitats using soils from open areas and from beneath Baccharis to distinguish their effects on seedling’s photochemical efficiency and survival.

Results

No woody species grew beneath B. paniculata. Air temperature was similar in both habitats, but soil temperature and PPFD were lower, and soil moisture was higher beneath shrubs. Seedling’s photochemical efficiency and survival were generally higher beneath canopies but were negatively affected by soil from beneath Baccharis shrubs.

Conclusion

Our findings question the nurse role of B. paniculata in the Chilean matorral, emphasizing the need to consider other shrub species for restoration initiatives for central Chile.