Multivariate indicators reveal status of ecosystem composition, structure, and function following forest restoration. Soil

Integrated assessments of above- and belowground indicators can support estimates of the status of restored ecosystems. We measured 58 indicators, a priori classified into nine components of ecosystem composition, structure, and function, within reference and restored montane forests in south-eastern Australia. Using a hierarchical model, we estimated trends among individual indicators; the nine ecosystem components; and an integrated estimate of ecosystem status. Integrated ecosystem status was lower on average within restoration forests but increased with restoration site age. Indicators of above- and belowground ecosystem structure, organic matter supply, and carbon stability were greater within reference forests. Our results provide evidence for coupling of above- and belowground structure and function during recovery, but suggest diverging patterns of nutrient cycling and soil carbon stability among restoration and reference forests. The findings support predictions that soil carbon may be more vulnerable to loss owing to climate variability and disturbance within restoration forests. A combination of four indicators (bacterial biomass, the ratio of resistant to total soil organic carbon, litter cover, and shrub richness), was found to provide a good estimate of overall ecosystem status at less than 1/2 the cost of considering all nine components of the above- and belowground ecosystem. More cost-effective combinations of indicators were identified, but with reduced predictive accuracy. Although ecosystem status could be monitored with a small set of above- and belowground indicators, a greater diversity of indicators can provide a more robust and comprehensive assessment of recovery.