, 2006). On the other hand, the results may indicate that a shift in the microbial community was already occurring due to an increasing complexity of the available substrate after 4 weeks (Poll et al., 2008). However,

increased proportions of Gram-negative bacteria (16:1ω7; 16:1ω11) might indicate high contents of labile compounds in the early stages of decomposition, which usually attracts fast-growing bacteria (Kuzyakov et al., 2000; Fioretto et al., 2005). After 12 weeks of incubation, a significant population shift in L. corniculatus treatments was observed on both principal Pictilisib purchase components PC1 and PC2. This shift was based on low proportions of short-chained iso- and anteiso-branched PLFA (iso15:0, ant15:0, iso16:0), which were, in some cases, below the detection limit and thus indicated a reduced Gram-positive bacteria population (Zelles, 1999).

In L. corniculatus treatments, a large decrease in the ubiquitous nor16:0 (Zelles, 1999) was observed, which was consistent with the decline in the microbial biomass that was discussed previously. In C. epigejos treatments, however, a decrease in the fungi PLFA 18:2ω6,9 was largely responsible for the treatment separation on PC1, whereas the proportions of Gram-positive PLFA did not change relative to the 4-week sampling time point. Obviously, fungi have outcompeted Gram-positive bacteria Galunisertib ic50 for the available substrate, because both groups have been reported in association with complex substrates (Kuzyakov et al., 2000; Dilly et al., 2004; Rubino et al., 2010). At the end of the experiment, a similar microbial community structure was observed in the detritusphere of L. corniculatus and C. epigejos Cetuximab cost treatments. High proportions of short-chained and iso-/anteiso-PLFA

were detected in both treatments. This result indicated that high proportions of Gram-positive bacteria were present in the microbial decomposer community and were utilizing recalcitrant plant litter compounds at the end of the experiment (Kuzyakov et al., 2000; Rubino et al., 2010). These results are in contrast to many studies where litter degradation in well-developed soil ecosystems has been investigated. In most of these studies, a clear increase of fungal biomass over time has been described (Aneja et al., 2006; Oyun et al., 2006; Williams et al., 2006). Obviously, fungi are highly dependent on N; hence, as in our study, N was limited in soil, there was a need to use plant-derived N. The low amounts of available N in C. epigejos litter material after 12 weeks and in both litter types after 40 weeks might therefore explain the reduced fungal biomass, from which Gram-positive bacteria could benefit. By investigating the 13C signature of the corresponding PLFA, the active microbial community structure directly involved in the litter decomposition was assessed. After 4 weeks of incubation, a similar 13C distribution was observed in L. corniculatus and C.