Initiation of microtopography in re‐vegetated cutover peatlands: evolution of plant species composition

Abstract

Questions How has plant species composition changed following initiation of microstructures in re‐vegetated cutover peatlands? How many years are required for plant species composition of re‐vegetated cutover peatlands to resemble natural boreal bogs? Location Newly formed Sphagnum carpets on restored, cutover peatlands (in Canada) or re‐vegetated spontaneously after site abandonment (in Estonia) and on undisturbed natural bogs nearby. Methods Plant frequencies (point intercept method) and abundances (vegetation quadrats) were assessed along linear transects. At each assessment point, moss surface height was measured relative to a local reference point (lowest point on a given transect) to associate frequencies or abundances to a position in the gradient of microtopography. PCAs (separately for Canada and Estonia) were conducted to follow evolution of plant species frequency in the gradient of microtopography in re‐vegetated sites and similarity with those of natural peatlands. In Canada, regressions were also performed to estimate relationships between moss surface height and vascular plant cover (ericaceous shrubs and Cyperaceae) as well as time required for vascular plant cover to become similar to that of natural bogs. Results Species composition was still dissimilar to microstructures of natural bogs 10 yr post‐restoration and 70 yr post‐abandonment; however, some trends were observed in re‐vegetated peatlands. The greatest differences were for ericaceous species (two‐ to three‐fold less abundant in re‐vegetated peatlands), dominant Cyperaceae, and relative proportions of Sphagnum. In addition, hummock formation was closely related to dense (>50%) ericaceous cover. Conclusions All species tolerant to abiotic conditions prevailing in re‐vegetated sites contributed to initiation of microtopography, although some species were found in atypical positions within the gradient of microtopography. Random events and establishment priority seemed initially to be more important in temporal evolution of microstructures than plant interactions. However, ecological restoration could effectively reduced time needed for species occurrences to approach those in natural peatlands, relative to time required for recovery of spontaneously re‐vegetated peat extraction sites.

Impact of water table level on annual carbon and greenhouse gas balances of a restored peat extraction area

“…Highly variable N 2 O emissions ranging from < 0.06 to 26 kg N ha −1 yr −1 have been previously reported for drained organic soils, with the highest emissions occurring from mesic and nutrient-rich sites (Martikainen et al, 1993;Regina et al, 1996;Maljanen et al, 2010). In contrast, N 2 O emissions are generally low in natural peatlands because environmental conditions (i.e., uptake of mineral N by the vegetation and anaerobic conditions due to high WTL favoring the complete reduction of N 2 O to dinitrogen) diminish the potential for N 2 O production (Martikainen et al, 1993;Regina et al, 1996;Silvan et al, 2005;Roobroeck et al, 2010). Thus, while the focus of most previous studies in restored peatlands has been limited to the CO 2 and CH 4 exchanges, accounting for N 2 O emissions might be imperative when assessing the climate benefits of peatland restoration as an after-use option for abandoned peat extraction areas.…”

“…The residual Sphagnum peat layer depth is about 2.5 m. A section approximately 0.24 ha in size within the abandoned site was restored in April 2012. The restoration was done following a slightly modified protocol of the moss layer transfer technique (Quinty and Rochefort, 2003) aimed at restoring the growth of Sphagnum mosses and initiating the development of a natural bog community. The first restoration steps included stripping the uppermost oxidized peat layer (20 cm) and flattening the freshly exposed surface.…”

“…This highlights the implications of hydrological differences and the associated vegetation development on plant-related CO 2 fluxes. Furthermore, it has been suggested that the presence of vascular plants can facilitate greater survival and better growth of the re-introduced mosses as they can provide shelter from the intense solar radiation and wind and thus create a more favorable micro-climate (Ferland and Rochefort, 1997;Tuittila et al, 2000b;McNeil and Waddington, 2003;Pouliot et al, 2012). Since Sphagnum mosses are generally more sensitive to drought compared to vascular plants, restoration strategies allowing the development of a diverse vegetation cover (i.e., bryophytes accompanied by vascular plants) could therefore be considered to have greater potential for limiting the CO 2 loss and regaining the C sink function (Tuittila et al, 1999).…”

“…However, due to the harsh environmental conditions of bare peat surfaces and the lack of a propagule bank, spontaneous regeneration of self-sustaining ecosystems rarely occurs and thus human intervention is necessary to initiate this process. For instance, active reintroduction of natural peatland vegetation communities (i.e., primarily fragments of Sphagnum mosses and companion species) combined with rewetting has been shown to be an effective method to initiate the recovery of Sphagnumdominated ecosystems with resumed long-term peat accumulation (Quinty and Rochefort, 2003).…”

Understorey vegetation gradient in a Eucalyptus grandis plantation between a savanna and a semideciduous forest

“…In disturbed areas, plasticity and order of establishment usually have more pronounced effects on species' abundances than biotic interactions (Pouliot et al 2012). Competition among native species is expected to be low at the current study site due to the low density of native trees.…”