In podzolic environments the distribution of organic matter (SOM) in soil is related to the characteristics of the litter and to the dynamics of water percolating through the profile. SOM distribution may be therefore influenced by disturbances to tree cover and site hydrologic conditions, such as those occurring after clear-cutting. In a 35 years old clear-cut boreal forest stand (Ust-Kulom, Russian Federation) we selected two soil profiles and evaluated SOM stocks and characteristics: P1 is located within the stand and little influenced by physical disturbances to soil cover, P2 was opened where the forest road built for harvesting was still visible The C stock calculated down to 60 cm was 4.4 kg m-2 in P1, and 8.0 kg m-2 in P2. The increase was associated to changes in profile morphology and development of EBh and Bh horizons. These horizons have formed through an enhancement of SOM migration which was only partially related to the classical process of podzolisation. In fact, while the elemental composition of fulvic acids (FA) in organic layers was similar in P1 and P2, in P2 the FA from deep mineral horizons were enriched in N and polysaccharides, and less enriched in aromatic compounds. The thin sections confirmed the process of SOM migration: homogeneous brown coatings of monomorphic organic matter were the dominant features in the Bh horizon of P2. After clear-cutting SOM migration capacity has been enhanced, but the process was only partially related to the chemical properties of organic compounds. As the accumulation has involved also a less decomposed and less mobile fraction, an important pool of SOM has been translocated at the borders of the stand, probably because of the development of preferential water flows with physical soil disturbances. These movements have determined a mosaic of different SOM concentrations in the landscape.
Organic matter after clear-cutting: decrease, increase or translocation?
FALSONE, GLORIA;
2010
Abstract
In podzolic environments the distribution of organic matter (SOM) in soil is related to the characteristics of the litter and to the dynamics of water percolating through the profile. SOM distribution may be therefore influenced by disturbances to tree cover and site hydrologic conditions, such as those occurring after clear-cutting. In a 35 years old clear-cut boreal forest stand (Ust-Kulom, Russian Federation) we selected two soil profiles and evaluated SOM stocks and characteristics: P1 is located within the stand and little influenced by physical disturbances to soil cover, P2 was opened where the forest road built for harvesting was still visible The C stock calculated down to 60 cm was 4.4 kg m-2 in P1, and 8.0 kg m-2 in P2. The increase was associated to changes in profile morphology and development of EBh and Bh horizons. These horizons have formed through an enhancement of SOM migration which was only partially related to the classical process of podzolisation. In fact, while the elemental composition of fulvic acids (FA) in organic layers was similar in P1 and P2, in P2 the FA from deep mineral horizons were enriched in N and polysaccharides, and less enriched in aromatic compounds. The thin sections confirmed the process of SOM migration: homogeneous brown coatings of monomorphic organic matter were the dominant features in the Bh horizon of P2. After clear-cutting SOM migration capacity has been enhanced, but the process was only partially related to the chemical properties of organic compounds. As the accumulation has involved also a less decomposed and less mobile fraction, an important pool of SOM has been translocated at the borders of the stand, probably because of the development of preferential water flows with physical soil disturbances. These movements have determined a mosaic of different SOM concentrations in the landscape.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
