*3.2. Soil Biological Fertility Index*

The soil Biological Fertility Index (BFI) was calculated to determine the overall effect of land-use systems on soil quality. The BFI results and the average scores of the parameters with respect to land use are given in Table 5. Grass-covered vineyard showed the highest BFI score (20) and ranked in class IV (good) of soil biological fertility, which is assumed to be a sustainable ecosystem for the long-term. The other two managements (cereal field and cherry farm) had lower BFI scores (16 and 18, respectively), corresponding to a BFI of class III (medium) (Table 5).

**Table 5.** Scores of the soil parameters and biological fertility index for the different land uses.


SOM: total organic matter, MBC: microbial biomass C, BSR: basal soil respiration, CSR: cumulative soil respiration, qCO2: metabolic quotient, qM: mineralization quotient, BFI: biological fertility index.

The multiple linear regressions were used to explain which of the biological parameters could be more useful to predict the BFI under different land uses. In order to achieve this purpose, backward elimination method was used, and the results are shown in Table 6. Accordingly, SOM and CSR were identified as two independent variables which had most impact on BFI (dependent variable). The rankings of the parameters were SOM > CSR > qM > qCO2 > BSR > MBC. This multiple linear regression model with two explanatory variables (SOM and CSR) had an R<sup>2</sup> of 0.916. Therefore, 91.6% of the variation in%BFI can be explained by this model and variables (Table 6).

**Table 6.** Multiple linear regressions (backward method) among BFI (dependent variable) and six biological variables (independent variables) under three land uses.


SOM: total organic matter, MBC: microbial biomass C, BSR: basal soil respiration, CSR: cumulative soil respiration, qCO2: metabolic quotient, qM: mineralization quotient.
