Humic substances formation as a result of biogenic-abiogenic interactions in epiphytic structures of the south vietnam tropical forest

Abstract

There are a number of ways to implementation the epiphytic biogenic-abiogenic interaction in plant communities. Epiphytic plants form a special type of organic or organo-mineral substrate—suspended soils. This study is devoted to the investigation of the biogenic-abiogenic interactions in epiphytic formations and characteristic of the suspended soils, which are formed in them with special reference to the assessment of stabilization rates and structural composition of humic acids in the suspended soil in tropical forests of South Vietnam. General properties of the soil and the elemental composition of suspended soils were determined, and the humic substance chemical composition was evaluated using solid state 13C-NMR. The soils formed by epiphytes show a positive correlation in the isotopic composition of nitrogen with epiphyte tissues and to a greater extent with forophyte tissues and, probably, take part in their nitrogen nutrition, concentrating zoogenic nitrogen due to ant presence. The most comparable soil type in terms of organic matter composition is Cambisols from humid forests of subboreal and subtropical zones. The results we obtained are consistent with the concept of soil organic matter stabilization: the proportion of aliphatic compounds in the component composition in bulk organic matter is higher than in humic acids, isolated from soils investigated. Thus, it can be concluded that in suspended soils soil organic matter stabilization processes active and expressed in formation and accumulation of humic substances.