A dynamic reference model: a framework for assessing biodiversity restoration goals in a fire-dependent ecosystem.

Area of Science:

• Restoration Ecology
• Fire Ecology
• Plant Community Dynamics

Background:

• Assessing ecosystem restoration progress using historical reference models is complicated by natural temporal variations.
• The longleaf pine ecosystem's restoration is particularly challenging due to its fire-dependent nature and scarcity of intact reference sites.

Purpose of the Study:

• To evaluate the effectiveness of different hardwood removal treatments on longleaf pine ground-cover vegetation over 15 years.
• To apply the dynamic reference conceptual framework for assessing biodiversity restoration in a fire-excluded ecosystem.
• To investigate the temporal variability of reference sites and their implications for restoration goals.

Main Methods:

• Utilized a 15-year vegetation dataset from an experimental restoration site in longleaf pine sandhills.
• Compared ground-cover vegetation response to herbicide application, mechanical removal, and fire-only treatments.
• Employed nonmetric multidimensional scaling (NMDS) ordinations and proportional similarity analyses to assess vegetation changes.

Main Results:

• Vegetation composition changed across all treatments over the 15-year study period.
• No significant differences in ground-cover species composition or hardwood density were detected among treatments after 15 years.
• Reference sites exhibited considerable temporal variability, demonstrating that restoration targets are dynamic.

Conclusions:

• Frequent prescribed fire alone did not lead to distinct vegetation outcomes compared to treatments involving hardwood reduction after 15 years.
• The dynamic reference conceptual framework provides a valuable tool for understanding and integrating spatial and temporal variations in restoration ecology.
• This study offers a practical statistical approach for defining reference sites and measuring restoration success in fluctuating environmental conditions, applicable to diverse ecosystems.