Effect of leaves damaged by Dendrolimus punctatus and insect frass on soil priming effect.

Insect herbivory in the forest canopy leads to a large amount of damaged leaves and frass input to soil, with consequence on soil carbon cycle. However, the influence of damaged leaves and frass from insect canopy herbivory on the soil priming effect is unclear. We examined the effects of leaf litter, leaf damage caused by Dendrolimus punctatus, and insect frass on soil priming effect by using the 13C natural abundance technique. The results showed that the addition of leaf litter, damaged leaves, and frass significantly increased native soil organic carbon mineralization, producing a positive priming effect. Moreover, significant differences were observed among treatments. The accumulative priming effect induced by frass was the largest, followed by damaged leaves, and that of leaf litter was the smallest. The priming effect was positively correlated with total P, condensed tannin, total phenolic content, and the ratio of condensed tannin to P (condensed tannin/P), and negatively correlated with C/N, lignin/N, C/P, and lignin/P in the early stage of incubation. There was a significant negative correlation between the priming effect and lignin content in the later stage of incubation. Our results indicated that damaged leaves and frass increased the magnitude of positive priming effect, which was influenced by different factors at different incubation stages. Our results would strengthen the understanding in the effects of insect herbivory on soil carbon cycling in forests, and improve the accuracy of the assessment of its effects on forest carbon sink.

[Effects of addition of organic carbon with different chemical structure on the fate and accumulation of exogenous carbon in red and sandy soils]. / çº¢å£¤å’Œé£Žæ²™åœŸæ·»åŠ ä¸åŒåŒ–å­¦ç»“æž„æœ‰æœºç¢³å¯¹å¤–æºç¢³åŽ»å‘åŠç´¯ç§¯è´¡çŒ®çš„å½±å“.

Plant litter input has important influences on soil CO2 emission and soil organic carbon (SOC) formation in terrestrial ecosystem. However, it is not well known for the fate of carbon when exogenous organic matters with different chemical structures are added to soil with different textures. In this study, we added the uniformly 13C-labelled substrates of glucose, starch, and cellulose to red soil and sandy soil, and compared the net 13C accumulation and recovery and its proportions in soil releasing CO2, SOC, dissolved organic carbon (DOC) and microbial biomass carbon (MBC) pools. The results showed that δ13C values increased after exogenous substrate additions in CO2, SOC, DOC, and MBC, and that the peaks of δ13C in CO2 pool appeared delay with increasing chemical structure complexity. The fate of exogenous C and its contributions of different C pools were significantly influenced by exogenous C types, soil types, and incubation times. In sandy soil, the added exogenous C was more mineralized as CO2, with the net accumulation and recovery of 13C in CO2 pool decreasing in the order of glucose>starch>cellulose. In red soil, more exogenous C was transferred to SOC pool, with the net accumulation and recovery of 13C in SOC pool decreasing in the order of glucose>starch>cellulose. Our results implied that the chemical structure of exogenous substrates and soil texture together controlled the fate and accumulation of exogenous organic carbon.