Influence of forest vegetation anthropogenic transformation on dynamics of humus content and composition in burozems of the island territory in the southern part of Primorskii Krai (Russia)

The dynamics of humus content and humus composition in burozems of Russky Island, formed under the vegetation community of different stages of anthropogenic transformation, is considered. Progressive anthropogenic degradation of Island vegetation and active geochemical influence of the sea on their soil cover, condition humus-formation and humus-accumulation processes in the burozems and create preconditions for developing humus-illuvial pedogenesis. It manifests itself in the dynamics of profile differentiation of humus content, its group and fractional composition, type of humus and determines morphological diversity. The structure of the soil cover of Russky Island includes typical burozems, dark burozems and dark humus-illuvial burozems. Typical burozems are spread under oak and oak-lime forests with undereveloped grass and shrub layers. Dark burozems are formed under light oak forest with more developed grass and shrubs. Dark humus-illuvial burozems are found under light oak forests with very developed grass and shrub layers. Investigated burozems differ considerably in humus contents, humus fractional composition and mobility level of their certain fractions. We found out that typical burozems are characterized by much lower humus content on all their profile, by humus composition of humate-fulvate type and the accumulative type of its profile distribution. Humic acids dominate in humus composition of dark burozems and dark humus-illuvial burozems in humus-accumulative horizon and humate-fulvate type of humus-formation is replaced by the fulvate-humate type. One of the typical features of humus composition of dark humus-illuvial burozems is the fulvate-humate type of humus both in the humus-accumulative horizon and in the humus-illuvial horizon. Profile distribution of humus of this burozems is defined by the combination of the humus-accumulative and humus-illuvial processes of pedogenesis. Morphological differentiation of humus profile of burozems of the island is specific profile distribution of brown humic acids, black humic acids and black humic acids combined with fulvic acids. The content of black humic acids, black humic acids combined with fulvic acids in humus composition of investigated burozems and humus mobility (content of ГК-1) increases considerably from burozems found under oak and oak-lime forests with underdeveloped grass and shrub layers to burozems, found under light oak forests with very developed grass and shrub layers. This conditions different intensity of development of humus-formation and humus-accumulation pedogenesis processes and predetermines formation of their morphological diversity.

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