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




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?


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.


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.


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.


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.