عنوان مقاله [English]
Background and Objectives: Forest degradation and land use change are among the factors affecting the changes of soil properties. Microbial characters and enzyme activity, as soil health indicators, are the most dynamic and sensitive soil properties, which play an important role in the nutrient cycle, long-term fertilization and energy flow in the soil. These characteristics provide useful and complete information on the biogeochemical cycles, since they react quickly to changes in the soil environment and provide comprehensive information on the soil physical, chemical and biological properties.
Materials and Methods: With the aim of studying and evaluating the effect of forest, rangeland and crop cover on soil microbial and enzymes activities, the mountainous habitat of Kodir was considered from the Kojur region in the south-east of the Noshahr city. In this study, four types of vegetation including natural forest (Carpinus orientalis - Quercus macrocarpa), rangeland dominated by Astragalus balearicus -Teucrium subspinosum, rangeland dominated by Stachys byzantina and agriculture field (culticated by Triticum aestivum) were selected. Following field trip, in each of the studied land uses, three transects (50 meters apart from each other) with 200 meters in length were considered. Soil samples (25 × 25 cm area) from a depth of 15 cm were taken at the first, middle and at the end of each transect. In total, 9 soil samples from land uses were transferred to the laboratory for analysis of soil physico-chemical, biological, microbial and enzyme activities.
Results: The ANOVA indicate that the higher values of aggregate stability, clay and water contents, organic carbon, total nitrogen, particulate organic carbon, dissolved organic nitrogen, phosphorus, potassium, calcium, magnesium, fine root biomass, nitrate and nitrogen mineralization and the lower amounts of soil bulk density and carbon to nitrogen ratio were found in forest site. The greater amounts of sand content and the lower values of silt and dissolved organic carbon were observed in the agricultural field. Soil pH, electrical conductivity, particulate organic nitrogen and ammonium were not significantly different among the studied land uses. The highest values of basal respiration, substrate induced respiration, microbial biomass (carbon and nitrogen, phosphorus) and enzyme activities (i.e. urease, acid phosphatase, arylsulfatase and invertase) were found in forest ecosystem, while the studied microbial indices (i.e. qCO2, microbial ratio and carbon capability index) did not show significant statistical differences among the studied land uses. Principal component analysis (PCA) also showed higher values of soil microbial and enzyme activities, biological and fertility in the forest site with a completely different location on the axis.
Conclusions: In general, the results of this study showed that different soil properties in forest ecosystem have better condition than the other studied land uses, while deforestation and land use change is due to decreasing organic matter quality, soil microbial and biochemical activities.