Biological Activity and Carbon Pools As Ecological Indicators of a Subtropical Ecosystem Restoration.

The conversion of natural vegetation to agricultural land change soil structure, depletes soil organic carbon and leads to erosion processes. The aim of this study was to: assess if the Total Organic Carbon (TOC), the Carbon Management Index (CMI) and the enzyme activity (Arylsulfatase AA) can be a sensitive indicators of the restoration of ecosystems. We evaluate six land use types: (i) growing tobacco Nicotiana tabacum,  with intensive soil tillage, CT-TBC; (ii) reforestation of eucalyptus (Eucalyptus sp.), R-EUC, (iii) C4 grasses pasture, PAST (iv) Forest under 10 years of restoration, FL1; (v) Forest under 20 years of restoration, FL2 (vi) Forests under 35 years of restoration, FL3. Samples were collected from each kind of land use at 0-5; 5-10; 10-20; 20-40 cm depth with three replicates per layer. The TOC stocks followed the sequence: FL3 (140 Mg ha^-1)> FL1(113.8 Mg ha^-1)> FL2 (104.6 Mg ha^-1)> R-EUC (87.2 Mg ha^-1)> PAST (77.7 Mg ha^-1)> CT-TBC (63.1 Mg ha^-1), the CMI rated ecosystems in order FL3 (100) > FL2 (87.5)> R-EUC (81.6)> FL1 (72.2)> PAST (65.9)> CT-TBC (53.1), and the AA was also higher in FL2 and FL3. The TOC and the CMI accessed the ecosystems restoration better than the AA, the great sensitivity of the AA to factors not necessary related to ecosystems restoration, as soil moisture, should be the cause of this results. After an initial period, the accumulation of TOC shall occur at lower intensity. Thus, the CMI should be better to access the ecosystems restoration because it considers the labile carbon fraction, that have a short turnover time and can access short-term changes.