The importance of facilitation on community assembly disappears under severe drought stress

Despite the recognition of positive interactions as an important driver of species coexistence and community structure, the underlying mechanism of how facilitation affects assembly processes along stress gradients is poorly explored. Understanding the responses of functional diversity to benefactor species at the extreme end of the stress gradient could provide valuable insight about facilitation-involved assembly mechanisms and contribute to the predictions of species coexistence under climate change.
In the drought-stressed community in the Badain-Jaran Desert, the responses of the local community to the nurse shrub species Calligonum mongolicum Turcz. were evaluated using hierarchical Bayesian models. For the 3-year experiment, summer rainfall in each year formed a natural gradient of drought stress. To evaluate the shrub’s effects on the assembly process along that gradient, individual samples were collected in pairwise under-shrub and open habitats, and four traits related to stre...