Hey, Hi, Hey, Ho, to the profile we go

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1 Soil Science Society of Belgium Excursion to Gd. Duchy Luxembourg May 2nd, 2012 Personal Report Roger Langohr, for ASDIS (Assoc. Diffusion Sciences, non-profit assoc.) Hey, Hi, Hey, Ho, to the profile we go Général This report gives some personal comments on the visited sites The document is completed with profiles that were discussed, in the office at Diekirch, with Simone Marx, Jerôme Juilleret, Jean Chapelle, Antoine Bouhon. 16/05/2012 ASDIS SSSB Exc. Gd. D. Lux

2 Abréviations Horizon symbols.bi: biologically active horizon, due to strong bioturbation by roots and/or fauna; relatively loose horizon (high porosity)..d: dense to such degree that roots have difficult to penetrate. Bw or (B): structure and/or colour B horizon. Bh: organic matter accumulation through chelate migration (Podzols). The degree of certitude In this document the degree of certitude is often indicated by a number expressed on 10 (certain) This evaluation is function of the person who is evaluating at the moment of redaction of the document. 10/10 = certain; 5/10 = 5 chances on 10 that it is correct.. In word these numbers correspond more or less to: 10 = certain, 8,5-9,5 = nearly certain, most probable. 7,0-8,5 = probable, 4,0-6,5 = possible, 2,5-3,5 = there is a chance, may be, could be. 0,1-2.0 = there is a small chance, not completely excluded. 0 = certainly not, excluded.. Références JAMAGNE M., Grands paysages pédologiques de France. Quae, RD10, Cedex, France, 535 pp. LANGOHR, R., Types of tree windthrow, their impact on the environment and their importance for the understanding of archaeological excavation data. Helinium, XXXIII/1, pp LANGOHR R., Soil bioturbation by trees the visible and the invisible, ASDIS, 43 pp. LANGOHR R.. SCOPPA C.0., VAN WAMBEKE A The use of a comparative particle size index for the numerical classification of soil parent materials: application to Mollisols of the Argentinian Pampa. Geoderma 15, p /05/2012 ASDIS SSSB Exc. Gd. D. Lux

3 What can so much interest people standing in the rain in a muddy environment? She s a lady! and not just any!!!. (listen also Tom Jones 1974) 16/05/2012 ASDIS SSSB Exc. Gd. D. Lux

4 Profile 10.27, without lady (less elegant), but with variability The Ruptic subgroup of the USDA Taxonomy Same site, but dug some time ago Windthrow? (7,5/10) (Langohr 1993); This explains the large Bt band now in a higher position (arrows) Read first this side! Part of profile WITHOUT Bt Part of profile WITH Bt 0-30 cm Ap Reference profile or normal soil /85 cm: E or Bw; about 2 mm thick 0-30 cm: Ap clay+humus migration band at 45 cm (not 30-65/70 cm: E (clay eluviation), with a few fragments of more observable on photo: active agric migration reddish Bt (arrows) due to former bioturbation (see windthrow) and (USDA Taxonomy))(cfr profile 10.19). in upper part traces of biogalleries (moles) with crotovinas. This No clear Bt on top of C+R, except a few horizon can also be considered as a colour B horizon or Bw (or (B) irregular pockets within C+R. in former labelling systems), corresponding to the B.bi during the The absence of the Bt can be related to, for thousands of years that the soil was under forest (see profile 9.08) example, a windthrow (see picture former (Langohr, 2010) profile pit above right) (6,5/10). 65/70-90/100(120) cm: More reddish Bt, with tongues going down between some C+R units. Clay coatings common. 16/05/2012 ASDIS SSSB 90/100(120) Exc. Gd. + cm: D. C+R, Lux locally calcareous. 4

5 9.04 Other profiles on calcareous sandstone, not observed during excursion but providing an idea about some of the variability of these soils (photos extracted from reports of G. Lippmann Centre and slightly adjusted for colours) 9.05 Can be compared with the reference profile described in previous page Probably eroded soil (9/10), the E or Bw is absent Can be compared to reference profile, but under forest. 0-3/5 cm: A 3/5-48/55 cm: E.bi or B.bi with abundant roots; bioturbation is a dominant active process. 48/55-65/70: Bt 65/ cm: C+R (poor picture) Example of variability of rock (R) and C horizons 16/05/2012 ASDIS SSSB Exc. Gd. D. Lux

6 Can be compared with visited profile, left side, with little or no Bt Thick E or Bw horizon. Interpreted as colluvium against a former hedge (upper, convex part of slope!). Rest of profile comparable to reference profile A thin veneer of Mn on top of the R horizon. Difficult to esplain today. Could date from period of periglacial climate (4/10) Nice example of active clay+humus migrations. At least recently still active. Probably good colloid dispersion conditions (ph H ?). Typical: upper limit bands sharp, lower limit more irregular. This is now possible since soil under crop production as the biological activity of roots and burrowing animals is minimal (cfr profile 10.20). This process is also well preserved here thanks to the concomitant gradual densification of the E/Bw horizon 16/05/2012 ASDIS SSSB Exc. Gd. D. Lux

7 Variability of rock substratum. Maybe result of karst Under forest, with weakly developed Podzol. Under dissolution (6,5/10). Bh.bi, the B.bi horizon with weakly developed Bt bands (balance between processes of bioturbation and Bt band development (cfr 10.19) Colluvial soil on top of eroded soil. Probably a footslope position where the soil is first eroded before being buried by colluvium that gradually fills the depression. Bt band in the non-calcareous sandy facies (Cd+Bt) of the rock substratum. Fill of a quarry, with layers of A, Bt and Bw earth. Locally calcareous sand and sandstone. Probably the quarry was made for sandstone exploitation. Afterwards filled and levelled with the earth that was of no interest. And then put into crop production parcel. 16/05/2012 ASDIS SSSB Exc. Gd. D. Lux

8 Well developed Bt, due to rock facies producing more reddish colour upon lime dissolution? Or remnant of an old soil? (Eem?) see also Terra Fusca earth (Jamagne, 2011, p ) Difficult to discuss because of profile wall preparation. Possibly comparable to 11.34, but deeper solum Comparable to reference profile but thinner E or Bw, maybe due to some erosion. Comparable to reference profile 16/05/2012 ASDIS SSSB Exc. Gd. D. Lux

9 Final discussion on the soils developed on the Luxemburg sandstone Reference side of profile Part of profile WITHOUT Bt Part of profile WITh Bt The story telling Most probably the soil genesis of these soils started towards the end of the Pleniglacial (around years BP) when the climatic conditions became mild enough for a permanent vegetation cover and a complete soil stability. The soil contained at that moment free lime from the surface. Under the leaching climatic conditions of the Late Glacial (more or less years BP) and the Holocene, lime has been gradually leached from the upper horizons. Once the ph did reach values between 5.0 and 6.5, clay colloids became mobile through dispersion and migrated downwards until reaching the still calcareous part of the solum. As long as soils were under forest, roots and tree trunks represented the major process of bioturbation. The soilscape was stable (no erosion). The soil horizon sequence was of the A.bi/B.bi (or E.bi)/Bt/C+R type along the plateau and smooth slope positions. Men s interference reactivated direct and indirect erosion processes. Much of the variability among these soils today is related to: variability in the rock parent material with more sandy and less sandy facies and layers with more hard rock (stronger cemented) favouring preferential water flow and karst type of dissolution; land use and associated erosion/sedimentation processes; tree uprooting (windthrow) over the last years (maybe already stability since beginning of Late Glacial, some years ago) is a supplementary factor of disturbance. Considering that most profiles have an upper solum of A and E or Bw horizons of several decimetres thickness over a more clay rich horizon, mostly in contact with the still calcareous sandstone layers, is an important argument to consider the more clayey, brown/reddish horizon as a Bt horizon rather than just a more clay rich facies of the rock that is decarbonated in this position. This Bt horizon (clay coatings have been observed in the field) is probably the result of the illuviation of most of the clay that came free in the upper part of the solum during the gradual decarbonation since the start of soil stability. It would be interesting to run the similarity index of the particle size fractions, after subtraction of the clay fraction (Langohr et al. 1976) The classification in WRB All these soils are very sandy, except for the Bt horizon. Most E/Bw horizons are too sand to fit for cambic. Many of the profiles have a Bt that does match for argic. In that case they go among the Luvisols. Where the Bt does not match for an argic, soils will move into the Arenosols. Profile observed during the excursion is an Arenosoll on the left side and a Luvisol on the right side. In USDA taxonomy this could be described at subgroup level as a ruptic profile, with 2 names. This is not foreseen in WRB.. For soil mapping, according to the scale of survey, in function of the proportions of the different soil types, one can use the concepts of complexes and inclusions. 16/05/2012 ASDIS SSSB Exc. Gd. D. Lux

10 Auger intermezzo, same meteorological conditions.. Sequence of soils on the same sandstone parent material Left: non-eroded soil, with E/Bw horizon with traces of biogalleries and crotovinas. Middle: strongly eroded, no races of bioturbation. Right: colluvium, probably on eroded soil on footslope position (7,5/10)(cfr profile 10-29). The colour of the colluvium is rather homogeneous indicating probably a relatively recent colluvial deposit. 16/05/2012 ASDIS SSSB Exc. Gd. D. Lux

11 Second profile, 11-36, same meteorological conditions.. Once more: what can so much interest people standing in the rain in a muddy environment? Once more: She s a lady! and the same.. (same song) About smooth slopes on clayey soils.. 16/05/2012 ASDIS SSSB Exc. Gd. D. Lux

12 - Most profile and land use data are indicative for a Vertisol, except the clay content of the upper 20 cm (29,8 instead of 30 or more). - The observation of structure is hampered by the high water saturation of the profile at the moment of visit. However the self-mulching of the first 25 cm is clearly visible and deeper, some slickensides can be seen, some of which are intersecting (white lines on profile down right). In the dry season cracks of at least 1 cm large down to 50 or more are mentioned to occur. - As was mentioned, we cannot classify the soil as Vertisol with these data. It could be that the texture analysis has to be controlled. Several participants felt more clay by the finger test in the field. However one has to be careful: wet soils feel more clayey than normal ( soil maps in the wet season turn out to be more clayey (ED)); 16/05/2012 ASDIS SSSB Exc. Gd. D. Lux

13 Site 3: the world of periglacial processes and soil development Solid as a rock. The sections show the high variability of periglacial erosion/sedimentation processes and the soil development that originally is still strongly influenced by permafrost and freeze/thaw processes. Succession of Pleniglcial and Late Glacial environment. Sections show also the absolute need for 3D observations (as mentioned by the guide) Although particularly interested, I have no time here to go further into the discussion of these sections. 16/05/2012 ASDIS SSSB Exc. Gd. D. Lux

14 Last stop: the beaver world, or major soil bioturbation And what are they now looking at.? No, no lady this time (she left) but instead Beaver land. About digging, cutting, transporting, constructing in a world without syndicates. 16/05/2012 ASDIS SSSB Exc. Gd. D. Lux

15 The jackpot: for more than 20 years I am searching for photos about these ditches dug by beavers. This is an important paragraph in the book about soil bioturbation and gives problems on archaeological sites in old alluvial plain deposits. Once buried under new alluvial sediments, such structures can be attributed to drainage works made by human populations living in the past in such areas. 16/05/2012 ASDIS SSSB Exc. Gd. D. Lux

16 The Emperor Or: would you like a giant standing on your little home? 16/05/2012 It s never finished, but for the moment it s the end ASDIS SSSB Exc. Gd. D. Lux