Previous studies have shown that increasing rubber plantation in Xishuangbanna has caused a lot of ecological consequences including loss of native forests and biodiversity and, emission of biogenic volatile organic compounds, alteration of hydrology, and increased soil-water evaporation in dry season. However, the influences of rubber planting on carbon cycling of rubber plantation remain largely unclear for its mechanistic cause.
Researchers from Xishuangbanna Tropical Botanical Garden (XTBG) used solid-state carbon-13 nuclear magnetic resonance (NMR) to compare chemical compositions of carbon in plant litter, forest floor and soil in a native seasonal rain forest with those in a rubber plantation in XTBG (21°54′N, 101°46′E). The objectives of the study were to (1) examine changes of organic carbon in NMR spectra during decomposition from fresh leaf litter to forest floor mass to soil organic carbon; (2) identify chemical changes in soil organic carbon during laboratory sequential fumigation–incubation (SFI) procedure without new C inputs and soil fauna; (3) compare carbon changes between (1) and (2), and between a seasonal rain forest and a rubber plantation in tropical China.
Their study found that litters of rubber trees were rich of alky C and less decomposable than that of seasonal rain forests. Conversed from native forests, rubber planting has led to C loss and extensive decomposed soil organic carbon. Degradation of labile organic carbon in fresh litter was primarily limited to O-alkyl and O2-alkyl C. Carbonyl, alkyl and aromatic C fractions were readily decomposable during soil labile organic carbon decomposed.
Their data indicated that rubber planting induced carbon loss and extensive humification in the soil, and altered the degradation process of C fraction during the soil LOC decomposition.
The study entitled “Decomposition differences of labile carbon from litter to soil in a tropical rain forest and rubber plantation of Xishuangbanna, southwest China” has been published in European Journal of Soil Biology, 55 (2013): 55-61.
