Short-term effects of forest recovery on soil carbon and nutrient availability in an experimental chestnut stand

Soil organic matter (SOM) pools and soil available calcium (Caexch) were monitored during a 4-year period in an experimental chestnut stand treated for the restoration of timber production. In 2004 the stand was cut and stumps were grafted. Before the forestry operations, the biocycling process seemed to contrast soil nutrient loss, returning Ca to mineral soil through plant activity. Therefore, we hypothesized that the regrowing vegetation after forestry operations would supply Ca to the soil surface and maintain a certain soil fertility level. In fact, from 2005, a progressive recovery of 460 mg Caexch kg−1 year−1 at the soil surface was found, corresponding to about 5 % of the Ca of the leaf litter (8,605 mg Ca kg−1, chestnut leaves sampled in 2007). However, the Caexch seemed to depend on the humified C (r200.858; p<0.01). At the soil surface, the humified C decreased. Therefore, other processes involving SOM dynamics may be taken into account. After the first year, the scarce presence of litter layer at the soil surface could have exacerbated soil erosion and reduction of SOM content, as shown by the change in horizon thickness and C amount. In later years a litterfall layer was present due to the regrowing vegetation and soil erosion was reduced, but SOM turnover did not change. In parallel the amount of microbial biomass C and soil respiration increased. Because the addition of new C source from regrowing vegetation can stimulate soil microbial activity, we hypothesized that the occurrence of a priming effect in our soil could further affect soil C and nutrient availability in later years management change.