How changes in belowground processes affect the recovery of aboveground vegetation after Hurricane Wilma

Background/Question/Methods: Understanding and predicting responses to and subsequent recovery of plant communities after large, infrequent perturbations; such as intense hurricanes, remains one of the most challenging tasks for ecologists. Previous studies have documented the affects of hurricanes on aboveground vegetation; yet little is known about how hurricanes affect belowground processes. Furthermore, changes in belowground processes could help explain the recovery of aboveground vegetation after a severe perturbation. We examined the immediate impact and recovery of both aboveground vegetation as well as belowground process after Hurricane Wilma in a seasonally dry tropical forest on the Yucatan Peninsula, Mexico. This study was replicated within three forests undergoing different stages of secondary succession, which allowed us to also investigate the importance of site history for ecosystem resilience and recovery.

Results/Conclusions: All successional forests experienced a significant reduction in leaf area index (LAI) after Hurricane Wilma (P < 0.001). However, the subsequent recovery differed significantly amongst the different successional forests. Two years after Hurricane Wilma, LAI in early- and mid-successional forests recovered to pre-hurricane conditions. In fact, LAI in early successional forests surpassed pre-hurricane conditions after two years. In contrast, LAI in late successional forests remained significantly reduced after Hurricane Wilma (P < 0.001). Recovery of belowground processes also differed amongst the different successional forests. Fine root bulk density was reduced by ~50% immediately after the hurricane in the late successional forests and remained reduced after two years (1.92 cm/cm³ and 1.08 cm/cm³; respectively, P = 0.08). On the other hand, fine root bulk density in early- and mid-successional forests did not change throughout the study. Immediately after Hurricane Wilma arbuscular mycorrhizal (AM) colonization was significantly reduced in all forests (P = 0.05). However, early successional forests recovered to pre-hurricane conditions within one year, whereas AM colonization remained slightly reduced in older successional forests. In summary, our data suggests that site history strongly influences the recovery of aboveground vegetation after large, infrequent perturbations. Aboveground vegetation in late successional forests was unable to recover to pre-hurricane conditions two years after Hurricane Wilma, whereas early-to mid-successional forests were able to fully recover. Fine root bulk density and AM colonization were also reduced in late successional forests, suggesting changes in belowground processes may influence the recovery of aboveground vegetation. By understanding how changes in belowground processes influence the recovery of aboveground vegetation researchers are able to better predict the recovery of plant communities to large, infrequent perturbations.