Evaluation of soil quality indicators in land use changed forest of Northern Zagros (Case study: Oshnavieh, West Azerbaijan)

World population growth, human need of food, his interference in natural ecosystems and changing soil intrinsic properties by degradation, increases the need of evaluating land use changes impacts, on soil quality. This study was carried out to evaluate the effects of land use change on some of soil quality indicators in land use changed forest of Northern Zagros.
in this study about 96 soil samples were taken from North Zagros forests as well as adjacent areas with land use changed. Some soil properties including basal respiration (BR), substrate induced respiration (SIR), microbial biomass carbon (MBC), pH, electrical conductivity, total nitrogen, available phosphorus, dissolved and exchangeable potassium, cation exchange capacity (CEC), soil organic matter (SOM), sodium adsorbtion ratio (SAR) and exchangeble sodium percent (ESP) were measured. Soil quality index (SQI) was determined using principal component analysis (PCA).
The results showed that changing forest to other land uses significantly reduced microbial biomass carbon, basal respiration, substrate induced respiration, the amount of dissolved calcium and potassium, exchangeable calcium, magnesium and sodium, organic matter, CEC, SAR and potassium. Soil organic matter amount in pasture, garden and agriculture decreased 16, 47 and 57.5 percent compared to forest, respectively. As a result of changing forest to pasture, gardens and agriculture MBC amount decreased 28.34, 48.66 and 58.28, respectively. The amount of total nitrogen, potassium and CEC in forest were 2.5, 1.39 and 1.4 times more than agriculture, respectively. Also, in different land uses, depth effect on all measured parameters was significant. As the results showed, the highest amount of potassium, nitrogen, cation exchange capacity, basal respiration, microbial biomass carbon and substrate induced respiration was seen in forest surface soils. Principal component analysis showed that between 16 properties assessed soil quality as total data set (TDS), organic matter, carbon availability, microbial carbon proportion to organic carbon, available phosphorus, pH and SAR, as the most important or the least effective properties on soil quality (minimum data set or MDS), had the greatest impact on the quality of studied soils. According to the cumulative soil quality index (SQI), soil quality for forest (0.756) and pasture (0.73) was II (lowly restricted) and for agriculture (0.646) and garden (0.626) was III (with limitation for plant growth).
Therefore, any management and land use change that increases soil disturbance, will reduce soil quality and increase land susceptibility to soil erosion. So, in order to maintain soil quality, appropriate management practices should be done.