Accumulation of humic acid and fulvic acid during root humification of three diameters of two dominant subalpine trees in western Sichuan, China
Aims Plant roots store large amount of terrestrial carbon,but little is known about humus formation processes during the decomposing root litter.Compared with coarse roots,fine roots have greater nutrients,which may be favorable to humus formation.The objective of the study was to examine how root diameters affect their humus formation processes.Methods In this study,in order to examine the accumulation of humic acid and fulvic acid of three root diameter classes (0-2,2-5 and 5-10 mm) of two subalpine tree species (Abiesfaxoniana and Picea asperata) on the eastern Qinghai-Xizang Plateau of China,a two-year field experiment was conducted using a litter-bag method.Air-dried roots of A.faxoniana and P.asperata were placed in litterbags and incubated at 10 cm of soil depth in October llth,2013.Duplicate litter bags were collected in May (late winter) and October (late in the growing season) of 2014 and 2015,respectively.Concentrations of humic acid and fulvic acid were measured,and net accumulations were calculated for different periods.Important findings The concentrations of humic acid and fulvic acid were significantly influenced by root diameter that humic acid and fulvic acid decreased with increase in root diameter.Root diameter had significant effects on the net accumulation of humic acid,but not for the accumulation of fulvic acid.However,there were no significant differences in both humic acid and fulvic acid between A.faxoniana and P.asperata roots.Regardless of tree species,humic acid degraded during the winter but accumulated during the growing season.After two years of decomposition,the net accumulations of humic acid in 0-2,2-5 and 5-10 mm roots were 8.0,10.8 and 7.6 g·kg-1 for P asperata and 15.2,8.0 and 7.8 g·kg-1 for A.faxoniana,respectively.Conversely,the degradation of fulvic acid in 0-2,2-5 and 5-10 mm roots were 178.0,166.0 and 118.0 g·kg-1 forP.asperata and 170.0,160.0 and 128.0 g·kg-1 for A.faxoniana,respectively.Our results suggest that diameter-associated variations in substrate quality could be an important driver for root litter humification in this subalpine forest.Moreover,diameter effect is dependent on decomposition period in this specific area.
NETL
NSTL
万方数据
维普
