The decomposition of green leaf litter is less temperature sensitive than that of senescent leaf litter: An incubation study

In the context of climate change, more frequent and severe extreme climate events are expected, which could lead to increased leaf fall before senescence. The decomposition of those abnormal fallen leaf litters may play a pivotal role in affecting the carbon (C) cycle in terrestrial ecosystems. Nevertheless, how their decomposition responds to temperature increase has rarely been studied, which limits the accurate estimation of the response of soil C dynamics to global warming and associated feedback. In the present study, green leaves (GL) were used to represent abnormal fallen leaf litters, and we compared the temperature sensitivity (Q(10)) of the decomposition of GL with that of the corresponding senescent litters (SL) from nine species, which are widely distributed in subtropical China. Results showed that GL experienced a faster decomposition than SL. Conversely, the Q(10 )of GL decomposition was significantly lower than that of SL decomposition. We also found that the Q(10) values of litter decomposition correlated positively with the C:N ratio and the lignin:N ratio, which supported the "C quality temperature" hypothesis. Furthermore, Q(10) was negatively controlled by phospholipid fatty acids of total microbes, fungi, and bacteria in soils. Experimental warming evidently increased the metabolic quotient of litter decomposition (qCO(2)); a greater increase occurred in the decomposition of SL rather than that of GL. A positive correlation between Q(10) and warming-induced relative change in qCO(2) was also detected. We highlighted that the increasing inputs of abnormal fallen leaf litters caused by climate change could decrease the Q(10) of litter decomposition.