Standing decomposition of dead leaves in winter and its legacy effects should not be ignored in subtropical forests

Background and Aims

Dead leaves may remain standing all winter before entering the soil as litter in subtropical forests. However, little is known about the standing decomposition of dead leaves and how this might influence subsequent litter decomposition in the soil.

Methods

We conducted an investigation of the standing decomposition of dead leaves in winter in a subtropical forest. In the following summer, we conducted a decomposition experiment of pre-standing litter (dead leaves picked immediately after leaf death) and post-standing litter (dead leaves picked after winter) in the soil using the litterbag method, further exploring the influences of the standing process on subsequent litter decomposition in the soil.

Results

After 159 days of standing decomposition, up to 43% of leaf mass was lost, with lignin and cellulose degraded by 30% and 35%, respectively. After 163 days of decomposition in the soil, the mass losses of pre-standing and post-standing litter were 31% and 52%, respectively. The decomposition rate (k) of post-standing litter was 2 times that of pre-standing litter. Restrained by the low photodegradability of litter in the later stage of decomposition, standing decomposition still conformed to the exponential decomposition model.

Conclusion

The standing decomposition of dead leaves in winter is driven predominantly by the abiotic process of photodegradation with leaching, resulting in substantial carbon loss in the standing phase and a doubling of the subsequent litter decomposition rate in soil, thus profoundly influencing the carbon process of subtropical forest ecosystems.