Drought-mediated stem and below-ground bud dynamics in restored grasslands

Abstract

Question

Does the below-ground bud bank mediate response to drought in restored grasslands?

Location

Platte River Valley region of south-central Nebraska, USA.

Methods

We imposed severe drought for one growing season using rainfall manipulation structures and measured the response of above- and below-ground plant communities (ramet and below-ground bud densities) with respect to non-drought controls during the drought year and a recovery year.

Results

Drought reduced below-ground bud bank density and above-ground stem density. However, bud bank density recovered, and bud production was higher on previously droughted subplots relative to controls in the year following drought. The response of below-ground bud and above-ground stem density to drought differed according to functional identity (C₃ grass, C₄ grass, and forb), with forbs least resistant to, but having the greatest recovery from, drought.

Conclusions

While overall density in restored grasslands was resilient, drought effects on below-ground bud banks may have longer-term impacts on plant community structure. Reduced density above- or below-ground during the growing season following drought may allow for the persistence of species relatively more reliant on recruitment from seed banks in favourable micro-sites.

Remnant grassland losses and increasing grassland restoration activities highlight the importance of restored grasslands. Here, aboveground stem and belowground bud densities in young (4 yr-old) restorations were reduced by drought, and drought response differed among functional groups. This research provides insights into how projected increases in drought frequency might affect establishment trajectories in restoration projects.