Pilot site La Guette: state of play
Scientific context, objectives and expected results
Restoring disturbed peatlands could be an effective means of mitigating the effects of anthropogenic disturbances on the climate. Restoring peatlands contribute to the sustainable storage of C in the soil and thus mitigate climate change. Until now, peatland restoration success was estimated mainly with flora and fauna criteria. The criterion ‘storage of C’ should become more and more important. Little is known on this subject and the transfer of knowledge towards site managers is very poor. Managers are probably less aware of restoration action leading to the recovering of the C storing capacity than actions promoting biodiversity. This is why, through the setting up of 5 pilots in the North-West European region, the Care-Peat project aims to highlight good management practices for the restoration of C storage capacity of peatlands.
The La Guette peatland (Neuvy sur Barangeon, 200 km south of Paris) is one of the five European sites on which a pilot would be installed. This site is drained by a ditch located along a road at the outlet of the peatland. This disturbance leads to a drop in the water table level and an increase in the water table fluctuations favourable to the appearance of banal pioneer species (Molinia caerulea, Betula spp) at the expense of typical peatland species (Eriophorum angustifolium, Rynchospora alba) including Sphagnum, a major producer of peat. Restoration works were carried out as part of a regional project. The results showed, on reduced surfaces, the positive effect of adding Sphagnum on C fluxes and vegetation. The objective for this pilot is to increase the scale of the restoration tested in the previous project by stripping peat on the first 5 cm and adding Sphagnum in patches in 2 zones of approximately 20 m x 30 m. The stripping of the peat will induce the growth of several plant species of interest. The expected results are an increase in floristic diversity typical of peat and plant species of interest, beyond the quantities present before the management action, as well as an increase in the capacity to store C through a significant increase of the Sphagnum percentage cover.
Strategy, tasks and calendar
In La Guette peatland, restoration works will be done at the end of 2020. It will consist in the stripping of the peat (uprooting of the plants and about 5 cm of peat), and installation of patches of Sphagnum in 2 areas of 600 m2. The 2 areas chosen will differ by the water level to test the in-situ effect of the water table level on Sphagnum growth. Once completed, C fluxes measurements (carbon dioxide and methane) will be conducted to estimate a greenhouse gas (GHG) budget. This budget will be compared to the one measured in a control area to assess whether the restoration action is effective in storing C. Peat cores will also be collected regularly to measure soil C stocks and highlight variations. The variations in stock will be compared to GHG budget.
The experimental stations will be implemented in 2 zones of the peatland to have 2 different hydrological contexts. In each zone, 2 areas of 600 m2 will be delimited: 1 area that will be restored (stripping + Sphagnum) and 1 control area zone (Control in Fig.1). In total, 1,200 m2 will be restored and 1,200 m2 will be used as control (Fig. 3).
Peat stripping, ancillary works and caution to be taken
The Sphagnum present in the restored areas will be removed during the peat stripping and re-planted in the areas to be restored. Molinia caerulea litter will be torn off and set aside in bags to be used as stabilizing mulch when Sphagnum is implanted. The stripping will consist in cutting the aerial vegetation of the plants, the basal part of the Molinia caerulea tussocks and removing the peat on about 5 cm to limit the return of Molinia caerulea and remove a large fraction of the viable seed stock of this plant. A preliminary inventory of the bryophytes in the restored area will be carried out, inducing, if necessary, adjustments of the restored sectors and it will carried on in the next years.
Once the stripping of the peat done, Sphagnum mosses will be collected from the entire site, with the help of UO and CNRS partners. Sphagnum previously set aside will be integrated into this stock and will not be lost. A minimum of 6 patches of a minimum of 1 m2 patches will be done, depending on the amount of collected Sphagnum. The mass effect of a Sphagnum carpet keeps the carpet moist and increases the chances of Sphagnum survival. To stabilize and protect Sphagnum at the beginning of their implantation, the litter of Molinia caerulea set aside will be placed on Sphagnum. To avoid too much peat erosion during rainfall and soil temperature increase, Molinia caerulea litters taken from the whole site will be spread in the restored area. Finally, to give Sphagnum a growth support, 5 sticks (e.g. bamboo) will be installed in each patch. To avoid the destruction of the site by repeated trampling in the same places, 20 light and removable wooden walk-boards will have to be built.
State of Play
The restoration works at the French pilot site, La Guette, took place from the 24th of November to the 5th of December 2020. As planned, the vegetation and the first 10 cm of peat were stripped in two areas of about 600 m2.
One area was slightly wetter than the other to test the effect of water table depth on the growth of Sphagnum. Common vegetation composed of Molinia caerulea and Ericaceous shrubs were removed to let a typical peatland plant biodiversity to set up. The restoration works were undertaken by Jura Natura Service, a company specialised in peatland restoration works located in the Jura mountains region
Sphagnum was collected within the stripped areas and taken in nearby areas to compose 7 high density patches of about 1 m in diameter. In addition, low density Sphagnum patches will be tested by planting clusters of Sphagnum, about 10 cm apart (beginning of 2021). The aim is to test whether a low amount of Sphagnum is able produce a dense lawn. This can be an alternative to the formation of dense patches. Indeed, in disturb peatlands, Sphagnum species may be not abundant enough to compose dense patches. We hypothesise that 1) high density patches could resist better desiccation if drought occurs than low-density patches, and 2) low density patches may grow faster than high density patches, if there is no drought. The growth of Sphagnum patches will be monitored with drone images.
The restoration works were presented to the stakeholders (manager of the site, county council, Forest National Office) during the site comity on the 4th of December. Also a newspaper article on the La Guette peatland restoration was published in “Le Berry Républicain”.