Background

Based on the experience from the BioSoil project, the FSCC noticed that there were clear differences in sampling of peat soils between different countries. So it seems the manual on Sampling and Analysis of Soil (2010) is not yet fully harmonized related to the sampling of peat lands, or at least, the current description is simple not good enough.

The aim of setting up this discussion, is to improve the description of the sampling approach of peat lands based on the experience of the experts in the field. Based on the outcome of this discussion, FSCC will formulate an amendment to the Soil Manual, to be presented for the manual update in 2014.

The discussion isorganised in the following way. First we cite the current description in the manual. Then we described the problems. In case you can identify additional problems related to the this subject, feel free to define additional problems (include a number for ease of reference). Subsequently the floor is open for suggested solutions. 

Current description in the manual

(page 16, Cools and De Vos, 2010)

The sampling design is based on the WRB definition of Histosols (= peat soils) which is based on the 40 cm boundary. As long as the peatlayer is less than 40 cm the existing sampling design for mineral forest soils shall be applied (separate sampling of the organic layers and mineral soil according to the fixed depth layers). From the moment the peat is ≥ 40 cm, the peatlayer shall be sampled according to the peatland sampling design.

This means that the peatlayer is sampled at fixed depths, mandatory 0 – 10 and 10 – 20 cm and optionally at 20 – 40 and 40 – 80 cm. In the reporting forms a separate name for the peatlayers shall be used, namely H01, H12, H24 and H48 in the records for the organic layers. The list of parameters (mandatory and optional) follow the rules for the OF, OH or OFH layer.

If the conditions allow (lower water table), the mineral soil below the peat soil (> 40 cm) can be further sampled till a depth of 80 cm (where the 0 cm reference is at the top of the peat layer). The standard sampling depths should be followed as much as possible.

So the manual asks to place the 0 cm line at the upper boundary of the peat layer (when the peat layer is thicker than 40 cm). In case the peat is < 40 cm, the peat layer is considered part of the forest floor and the 0 cm line is put between the forest floor and the mineral soil.

The sketches are included in the guidelines of the manual (Annex 2):

H1, H2,….H6: horizon number

1. The first figure is a mineral soil without forest floor. The 0 line is at the surface.
2. In the second figure, there is a forests floor of 30 cm, including a thick OH layer (which might be a thin peat layer). The 0-line is at boundary between the OH and A horizon.
3. In the third figure, there is a peat layer of 42 cm thickness (but not forest floor). There the 0 –line is at the surface since the peat layer is thicker than 40 cm.
4. In the fourth figure, there is a forest floor on top of the peat layer. So the 0-line is between the boundary of the forest floor and the top of the peat layer.

The depth limit of all layers above the 0-line receive negative values, the depth below receive positive values.

Problem 1

In the BioSoil survey, case 4 was found difficult to sample where the 0 cm line is located at the boundary between the organic layer above the peat layer and the peat layer itself. So in practise, they put the 0 cm line in such a case at the surface (contact with air). 

Problem 2

Next to the cases illustrated above, it often happens that living mosses grow on top of the dead organic material. On top of these living mosses, sometime a thin forest floor is being formed. 

Citation: “In our forests we have a very sparse litter layer (OL = needles, leaves, small twigs, litter of ground vegetation) on the top of moss layer, then OF or Hf, then maybe OH or Hh and finally mineral soil. We have very seldom a distinct litter layer on the top of organic layer, as in deciduous forests or in very dense spruce forests with no ground vegetation.

The problem is here, how to treat the moss layer between sparse OL layer and the actual organic layer? If we estimate carbon amounts in forests, mosses are much more important than OL, especially in peat soils with thick Sphagnum layer above the actual peat. I hope that either OL could be left out of the reporting or either the moss layer is added to the OL. Otherwise the information about temperate and boreal forests is not equal.”

The floor is open!

Nathalie