Evidence of facilitation between early‐successional tree species and the regenerating plant community in a tropical seasonally dry environment

Abstract

AbstractEarly‐successional tree species may facilitate the establishment of the regenerating plant community in semi‐arid environments by creating more favourable microenvironments and reducing environmental stress. However, it is not clear how these tree species can influence morphofunctional and physiological responses of the regenerating plant community. In field conditions, we used three early‐successional tree species in the adult stage (Combretum leprosum, Cenostigma bracteosum and Mimosa tenuiflora) as potential facilitators, and two regenerating ones as target species (Cordia oncocalyx and Croton blanchetianus). We then evaluated the effect of the former on the leaf anatomy, physiology and growth of the latter. We found that C. leprosum and C. bracteosum acted as facilitators, resulting in a 55% and 22% reduction in solar radiation in the rainy season, and an 11% and 10% reduction in the dry season, respectively. In addition, we observed a higher soil moisture under the canopy of nurse species, especially under C. leprosum, which showed an increase of over 38% in gravimetric water content in the rainy and dry seasons. These results favoured gas exchange (CO2 uptake, stomatal conductance and transpiration) and growth in Cordia oncocalyx and C. blanchetianus. Furthermore, we did not observe any stress reduction under the canopy of M. tenuiflora and in the open area, where target species showed reduced gas exchange and growth. The positive morphological and ecophysiological responses of the target species under C. leprosum and C. bracteosum reinforce the importance of studying microenvironments created by early‐successional tree species. This way, we can understand the mechanisms promoting facilitation and the influence of this positive interaction on the restructuring process of the plant community in a semi‐arid environment.