Towards harmonised monitoring of grassland restoration: a review of ecological indicators used in the temperate region

Abstract

Monitoring restoration success should be consistent with the scope of restoration, therefore indicators are usually target and ecosystem specific. At the same time, there is a growing need to introduce ecosystem-specific standardisation to allow comparison of different restoration methods between regions and to help select best practices. This study aims to review the ecological indicators applied to assess the success of grassland restoration in temperate regions, to determine their frequency of use and to identify indicators suitable for future standardisation. Based on 322 publications on monitoring and evaluation of temperate grassland restoration in the Northern Hemisphere, a large variety of metrics (85 ecological indicators in total) exists with no obvious standardisation. We categorise indicators according to the three main ecosystem attribute classes (vegetation structure, diversity & composition, ecosystem function) proposed earlier in restoration literature. Diversity & composition (mainly species richness) is the most commonly measured characteristic when monitoring grassland restoration, followed by vegetation structure (mainly plant cover). The class of ecosystem function has the largest variety of indicators, but none is widely used. Many studies are already using indicators from at least two ecosystem attribute classes to follow grassland restoration, which is a good start towards the goal of monitoring all three classes. Based on our results, monitoring of grassland restoration could be harmonised by including a minimal set of core indicators that are already widely used: plant cover, a diversity indicator focusing on naturalness, and soil organic C, which indicates the carbon storage function of the ecosystem.