Comparing survey methods for monitoring vegetation change through time in a restored peatland

Monitoring is an essential step to assess vegetation trajectories post-restoration and ultimately evaluate success. In this paper, we compare two monitoring methods, the line-point intercept (LPI) and the permanent plot (PP) methods, for evaluating plant recovery of a restored cut-over peatland (8.5 ha), following a “moss layer transfer technique”. We used the LPI method to estimate covers (from frequency measures) for each plant species using a systematic grid of approximately 5,700 points (every 3 m × 5 m). In parallel, 43 PP (3 m × 8 m) were established and used to evaluate plant covers. The post-restoration recovery of vegetation was assessed against a reference ecosystem encompassing the variation in species cover from natural undisturbed peatlands in the same region. For all plant groups considered, the LPI consistently showed higher cover estimates than the PP method. Discrepancy between the two methods was particularly evident for the Ericaceae group. A complementary sampling method, the line-intercept (LI), showed strong correlations with the visual estimations of Ericaceae covers (akin to PP), suggesting an overestimation from the LPI method. Most life form groups of the restored peatlands are developing a structure similar to the regional reference ecosystem 8 years post-restoration with the herb group being still most dissimilar. Indeed, when analyzing the temporal evolution of the different key peatland plant components, several are within the range of regional abundance values or moving positively towards range of cover abundance of the reference system such as Sphagnum cover, a key peat-accumulating plant group.