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 stress tolerance and resource acquisition were measured simultaneously.
This study focused on water-limited community that lies at the driest end of drought gradient and confirmed that facilitation can drive the assembly process through both environmental filtering and niche differentiation. More importantly, these assembly mechanisms are proven to become less efficient under extreme drought stress, which may suggest the occasionally disappearing role of benefactor plants on community assembly and an increasing risk of biodiversity loss in the context of climate change.
Emsp; The data quality is good.
To measure species relative abundance, a single 2 m × 2 m quadrat was established beneath the canopy of stand-alone Calligonum mongolicum, while another quadrat of the same size was placed in an open area. In these quadrats, species was identified, and the species-specific abundance was recorded.
To measure functional traits at different years and habitats, we randomly selected 2-5 adult individuals for every observed understory species according to their abundance in each selected quadrat at both habitats. Five species were omitted from the analyses because they were too rare to accurately estimate trait values. To obtain robust estimation, more than 30 individuals for each species were sampled in different years and habitats. When the suitable samples of a species did not reach this amount, we randomly collected additional individuals from the same habitats in the fenced plots.
Lateral spread (cm) was measured as the maximum crown width of individuals in the understory community. Height (cm) was measured as the distance between the extended upper boundary of the crown and the ground level. SLA (cm∙g-1) was determined as the ratio of fresh leaf area to leaf dry mass. LDMC (mg∙g-1) was determined as the ratio of leaf dry mass to fully rehydrated fresh mass.
To measure soil moisture/water content (SWC), we collected four soil cores (5 cm diameter, 10–20 cm in depth) along the diagonal of each quadrat, and determined them gravimetrically after oven-drying for 48 h at 110°C.
To measure soil organic matter (SOM), we randomly chose 10 pairwise quadrats each year, collected four soil cores within each quadrat, and applied the dichromate oxidation method.
The data quality is good.
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CSTR:11738.11.NCDC.ZENODO.DB3949.2023
10.5061/dryad.2547d7wsc