4). Apart from PLFA nor16:0, the highest proportions of the plant litter-derived 13C were detected in 18:2ω6,9 and 18:1ω7 (Table S2). Readily available C of both plant litter types thus promoted mainly fungi and Gram-negative bacteria, which is in accordance with recent studies. The rapid labelling of the fungal biomass after only 1 month of incubation was recently explained by fungal hyphae that grow into the litter from the mineral soil layer (Moore-Kucera & Dick, 2008). Twelve weeks after litter application, a large difference between L. corniculatus and C. epigejos was observed as a result of the

lack of Gram-positive bacteria in L. corniculatus (nor14:0, iso15:0, ant15:0), but also because of a decreased proportion of Selleck INK128 13C in fungi (18:2ω6,9) in C. epigejos. This result underlines the competition between fungi and Gram-positive bacteria as discussed above; in C. epigejos treatments, a decrease in fungi results in

a decreased litter-degrading activity, which in turn promotes Gram-positive bacteria in the decomposition process. In both treatments, an increased proportion of litter-derived 13C was detected in Gram-negative bacteria, indicated by 16:1ω5, 18:1ω7, 18:1ω9 and cy19:0 (Table S2; Fig. 4). These results generally confirm the recent findings of Kramer & Gleixner (2006), who postulated a preferential uptake of litter C by Gram-negative bacteria, while Gram-positive bacteria utilized soil-derived C. The low C content of the soil might explain the outcompetition of Gram-positive bacteria mainly in the L. corniculatus treatments by fungi as long as available N from the litter material is present. Forty weeks after the application of litter selleck compound material, samples from L. corniculatus and C. epigejos treatments again showed a similar 13C distribution among the PLFA biomarkers. In contrast to the samples at 12 weeks, an increase of 13C in a number of Gram-positive cAMP (iso15:0, iso16:0, iso17:0, 10ME17:0) and Gram-negative biomarkers (17:1ω8, 16:1ω5)

was observed in both treatments. This result is in accordance with experiments performed with soils from climax ecosystems, where, in the later phase of litter decomposition, the 13C distribution among a high diversity of microbial communities indicates a system in a steady state, where incorporated litter C has been recycled throughout the microbial community structure (Rubino et al., 2010). Both Gram-negative as well as Gram-positive bacteria have been found in context with complex and recalcitrant litter material decomposition (Peacock et al., 2000; Elfstrand et al., 2008). Overall, the results of the present study show (1) a stronger influence of litter quality on biological interactions between bacteria and fungi during the decomposition process compared with litter degradation in climax ecosystems, which in turn alters the process of litter decomposition and results in different rates of litter degradation of the two colonizer plants L. corniculatus and C. epigejos.