OCCURRENCE, DISTRIBUTION AND FATE OF THE LIPID PLANT BIOPOLYMERS CUTIN AND SUBERIN IN TEMPERATE FOREST SOILS

The occurrence, distribution and decomposition of the lipid plant biopolymers cutin and suberin have been investigated in forest soils and in an in vitro experiment. Samples were taken from the individual horizons of temperate forest soils receiving their litter input either from Fagus sylvatica L. or from Picea abies (L.) Karst. trees in NE Bavaria, FRG (two sites each). The soil samples were subjected to BF3/CH3OH-catalyzed transesterification. The depolymerisates (identified by capillary gas chromatography-mass spectrometry and quantified by capillary gas chromatography) consisted of the methyl esters of alkanoic and alkanedioic, omega- and 2-hydroxyalkanoic and di-, tri- and epoxyhydroxyalkanoic acids as well as of 1-alkanols and alpha,omega-alkanediols. The monomers released were characteristic of the cutins and suberins of the two dominant tree species. Concentrations of cutin and suberin monomers, on a dry soil-basis, were highest in the organic L and 0 horizons while, on an organic carbon-basis, high concentrations were also detected in the underlying mineral horizons. The results are discussed in terms of the contributions of cutin and suberin to the total lipid biopolymer contents of soils and the decomposition and turn-over of cutin in forest soils. Total inventories and depth profiles of soil cutin and suberin per ground area are estimated. Evidence is presented for the preferential storage of cutin in the mineral horizons with total inventories exceeding yearly inputs by factors of 17 (P. abies) and 22 (F. sylvalica).