The Role of Soil Organic Matter and Manures in Sustainable Nutrient Cycling - Sustainable Management of Soil Organic Matter - page 323

Study area

We have chosen our test area near the shores of the Yenisei river in central
Siberia between Turukhansk (65 ° N) and Dudinka (70 ° N). Mean annual

temperature varies between C (Dudinka).

Corresponding mean summer (July, August and September) temperatures
are 10.4 and 5.7

− 7.6 ° C (Turukhansk) and − 10.7 °

C, respectively; summer precipitation was ~150-200 mm
in the whole study area. The permafrost characteristics closely follow the
temperature gradient. The depth of the active layer increases from 0.6-2 m
in the north to > 3 m in the south (J.G. Karpov and E.L. Baranovskij,
1998, personal communication). Concurrently, the thickness of the
permafrost decreases from 100-200 to < 50 m. Parent materials in the
study area are Quaternary sediments, primarily derived from the Zyryansk
stage (122-59 kyears BP) and the Karginskaya interstage (59-24 kyears
BP) of the last glaciation (Sachs, 1948). The soil samples were all taken in
watershed areas of the Karginskaya terrace that is of glaciofluvial to
glaciolimnic genesis. The Karginskaya terrace follows the Yenisei river from
Turukhansk to the mouth of the river. The terrace is located 50 m (south)
to 30 m (north) above the Jenisseij, and is composed of homogeneously
coarse silty to fine sandy substrate. Only little disturbed forested sites were
chosen, with dense Larix sibirica , Picea obovata and Pinus sibirica stands in
the south, becoming less dense to the north. L. sibirica represented the only
larger tree species at the northern treeline in the forest tundra.

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Methods

Soil pits of ~2 m 1 m depth were dug with a spade. Following field

description, the profiles were sampled by horizon from three sites of the pit
beginning with the deepest horizon. Classification of soils was carried out
according to Soil Survey Staff (1998). The samples were oven dried (40

× 1m ×

C)
within 2 days. In the laboratory, samples were analysed with standard
methods for pH, texture, pedogenic Fe- and Al-oxides, and contents and
stocks of total organic carbon and nitrogen. SOM was analysed for primary,
secondary and tertiary resources. Plant-derived lignins (primary resource)
were assessed by the CuO oxidation method according to Hedges and Ertel
(1982). VSC is the yield of lignin-derived vanillyl, syringyl and cinnamyl
units, and (ac/al) V is the acid to aldehyde ratio of the vanillyl units indicat-
ing the degree of oxidative lignin degradation. The method of Zhang and
Amelung (1996) was used to analyse microbially synthesized amino sugars
(secondary resource). The yield is given as the sum of glucosamine, gluN;
galactosamine, galN; mannosamine, manN; and muramic acid, mur. The
ratio of gluN to mur indicates the relative proportion of fungal and bacterial
cell wall residues. Pyrogenic C (tertiary resource) was quantified as benzene

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