Do young trees contribute to soil labile carbon and nitrogen recovery?

Purpose: This study aimed to evaluate the effects of tree cover (tree plots (Acacia disparrima and Eucalyptus crebra) vs. non-tree plots) on soil labile carbon (C) and nitrogen (N) recovery in revegetation trials, without and with topsoil removal, 3 years following tree planting. Materials and methods: Soil total C (TC) and total N (TN), hot-water-extractable organic C (HWEOC), hot-water-extractable total N (HWETN), microbial biomass (MB) and potentially mineralisable N (PMN) were measured. Results and discussion: Where topsoil had not been removed, soil TN, HWEOC, HWETN and PMN were significantly higher in the tree-covered plots compared to non-tree-covered plots. In contrast, tree cover did not significantly increase soil labile C and N when topsoil had been removed. Both leguminous and non-leguminous species (A. disparrima and E. crebra) had similar effects on soil labile C and N. Tree cover did not accelerate C and N recovery at their early stage of establishment when topsoil had been removed. Therefore, our finding suggests that topsoil-removed plots may need more than 3 years to replenish soil C and N to their initial levels. There was also a clear indication of C and N depletion in the topsoil in areas not covered by trees even though the topsoil had not been removed. Conclusions: Altogether, these results demonstrate the importance of longer-term monitoring of revegetation areas to be able to assess its success in improving soil quality. © 2014, Springer-Verlag Berlin Heidelberg.