Peatland monitoring - forest

Background and Objective

The Peatland Monitoring Programme for Climate Protection – Forest (MoMoK-Wald) aims to improve the reporting of greenhouse gas emissions of forested peatlands in a comparable and representative way. This nationwide basis can then also be used to derive measures for peatland soil protection.

Natural "wet" peatlands are of particular importance for climate protection, as they store large amounts of organic carbon. Drained peatlands, on the other side, emit this carbon into the atmosphere in the form of carbon dioxide (CO₂). Despite a small area share of approx. 5% (=1,8 million hectares) drained peatlands (non-forested and forested) and other organic soils (e.g. Histic Gleysol) contribute to approx. 6,7% of German greenhouse gas emissions (as of 2021). These emissions are accounted for in the land use, land use change and forestry (LULUCF) sector. Currently, CO₂ accounts for a large part (> 90 %) of these emissions. Thus, the preservation of carbon already stored in peatlands and other organic soils or a renewed sequestration plays an important role in climate protection. Around 15% of Germany’s peatlands are forested. This corresponds to about 2.4% of the German forest area. Despite this small area share, they represent a significant carbon stock and are a strong source of CO₂ in the case of drainage. Currently, it is assumed that nearly all forested peatlands are drained. The Peatland Monitoring Programme intends to improve greenhouse gas reporting to the IPCC by recording changes in carbon stocks in peatlands and other organic soils and their controlling factors across Germany. In addition, potential measures are to be derived on this basis. To this end, a nationwide network will be established on peatland sites and other organic soils, with the openland peatlands covered by the Thünen Institute for Climate-Smart Agriculture and the forested peatlands covered by the Thünen Institute for Forest Ecosystems.

The overall objective is therefore to determine site-specific emission factors and to regionalise greenhouse gas fluxes in order to improve Germany-wide greenhouse gas reporting. For this purpose, i) the carbon stocks in soil and trees are recorded, and ii) carbon stock changes are recorded in continuous measurement intervals.

Especially, in the case of heavily degraded organic soils, the question arises as to how large the carbon sequestration from the remaining peat layer is in comparison to the carbon sequestration in the tree stand. Furthermore, based on the results it will be possible to derive site-specific recommendations for forest management.

Approach

50 monitoring sites, each with an area of 2500 m², are categorised according to the type of peatland (raised and transitional bog; fen), the hydrological condition (drained; non-drained) and the tree population. Only areas with a homogeneous (>80 %) share of spruce, pine, birch or alder tree species are selected.

In order to determine the current carbon stock in the soil, detailed soil surveys are carried out on a representative basis. In addition to the peatland thickness, important soil physical parameters (e.g. dry bulk density) and soil chemical parameters (e.g. C and N contents) are determined. The change in terrain elevation serves as the basis for calculating the change in soil carbon stocks. In the case of peatland subsidence, i.e. loss of terrain height, peat mineralisation occurs in addition to consolidation and shrinkage. During mineralisation, the carbon stored in the peat is released as CO₂. Based on the losses of peat thickness, which are measured after defined time intervals (once a year), the CO₂ release rate can be modelled. The change in terrain height is recorded with ten measurement poles per site, which are anchored in the mineral subsoil of the peatland. At non-drained sites, where peat surface oscillation and/or also carbon fixation through peat accumulation may occur, additional grids or volume elements are introduced into the topsoil to measure potential peat accumulation. The important control parameter peatland water level is recorded at each site with a water level data logger (hourly measurement interval).

To determine the carbon fixed in the stand and in the above-ground deadwood, as well as the vitality and vigour of the trees, additional stand surveys are carried out. For this purpose, the deadwood volume plus growth and vitality parameters of the individual trees (e.g. tree height diameter, total height) are recorded in a sampling circle of 12,62 m. In addition, four sampling circles (r = 5 m) are recorded to survey the regeneration. The procedure is based on the standardised protocols of the National Forest Soil Inventory (NFSI), so that the collected data of both programmes can be compared with each other.

In addition, a representative vegetation survey is carried out on 400 m² at each site. This serves the basic ecological characterisation of the site and is the basis for the long-term monitoring of the ecological condition and vegetation development. Thus, a contribution is made to the capturing and preservation of biodiversity. By recording functional traits of the existing vascular plants and peat mosses, it is tested, whether conclusions can be drawn about the conservation status and thus the carbon sequestration performance of the individual peatland sites from relatively easy-to-record biotic parameters.

In order to improve the understanding of the greenhouse gas dynamics, two areas will also be equipped with intensive measurement technology, on which a direct analysis of greenhouse gas emissions will be carried out using automated chamber technology ("Measurement of GHG emissions from forest peatlands"). The results of these gas measurements will be used to validate the results of the peatland soil monitoring by comparing the C- emission factors, determined based on the measurement parameters "water level" and "terrain elevation change", with those from directly measured emissions.

The results of each monitoring site are used for a combined modelling of carbon dynamics (soil and stock of trees) including control variables (e.g. peatland water levels, terrain elevation change, temperature, etc.). The consideration of regionalisation parameters (e.g. annual precipitation, annual average temperature, geomorphology) allows a regionally differentiated estimation of carbon dynamics in forested peatlands for IPCC reporting. Emission factors for different types of forested peatlands and their tree stocks are derived from the measured data and the modelling results. Up to now, these have only existed as estimated values. The peatland monitoring thus provides the long-term and area-wide emission data of organic soils under forest needed for the IPCC reporting.