Microsite abiotic conditions and juvenile response under three early successional shrub/tree species in a SEMI-ARID region

In environments with water and nutrient constraints, some early successional shrub/tree species may promote facilitation by ameliorating the microclimate and increasing resource availability. We ask whether early successional semi-arid shrub/tree species have facilitation effects for other woody species and if they do, which mechanisms are involved and how they affect the water status of juvenile plants. Three early successional woody species; Combretum leprosum, Cenostigma bracteosum and Mimosa tenuiflora, were chosen for investigation. The richness of regenerating woody species and their leaf water potential were used as response variables, while air and soil temperature, leaf area index, humidity and soil attributes were used as explanatory environmental variables. Species growing under the canopy of C. leprosum had better water status and growth at higher soil moisture and lower thermal and solar radiation stress, receiving a facilitative effect. The lower leaf area index, higher radiation and more negative soil water content under the canopy of C. bracteosum in comparison to C. leprosum may have a small negative effect on species richness. M. tenuiflora did not reduce environmental stress, and the species associated with it had low water potential, thus no increase in species richness was detected under its canopy. C. leprosum and C. bracteosum improve the environmental conditions under their canopies and provide favourable microsites for the establishment of other species. The positive effects may be generated by functional traits that modify microclimatic characteristics under the nurse species' canopy and lead to a higher water status of the juveniles growing under it.

Automated summary

In environments with water and nutrient constraints, early successional shrub/tree species can promote the growth of other woody species by ameliorating the microclimate and increasing resource availability. Combretum leprosum and Cenostigma bracteosum improve the environmental conditions under their canopies and provide favorable microsites for the establishment of other species, while Mimosa tenuiflora does not have this facilitation effect.