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Aggregate Stability Index (ASI) and particulate organic matter (POM) are strongly influenced by land use and management. This work illustrates the effects of plantations on ASI and POM-C and POM-N in northern Iran. Three plantations of P. deltoides (PD), T. distichum (TD), A. subcordata (AS), and a fourth site ‒ adjacent abandoned lands (BL, as control) were selected. Soil samples were taken within 16 quadrats of each plantation and BL from the two depths of 0-15 cm and 15-30 cm during the summer. Soil C was significantly higher under TD (2.10%) than under BL (2.02%) > PD (1.61%) > AS (1.30%). Soil N was found in ranked order of AS (8.99%) > TD (7.82%) > PD (5.30%) > BL (3.68%) (P < 0.019). The significantly higher ASI was found under TD (57.49) in comparison with PD (53.10), BL (51.23), and AS (36.57). The POM-C was as follows: TD (0.209%) > PD (0.141%) > AS (0.139%) > BL (0.075%) (P = 0.020). The highest POM-N was found under TD (0.035), followed by AS (0.0284%), PD (0.0288%), and BL (0.007%). The results indicate the positive effect of afforestation on soil ASI and POM-C and POM-N, especially in the surface layers of soil.

The present study aimed to assess four forest stands, Fagus orientalis Lipsky-Carpinus betulus L.-Acer velutinum Boiss. (FO-CB-AV), Fagus orientalis Lipsky-Carpinus betulus L. (FO-CB), Fagus orientalis Lipsky-Acer velutinum Boiss. (FO-AV), and Pure Fagus orientalis Lipsky (FO) on basis of some soil quality indices in Mazandaran Province, northern Iran. Five samples per stand were taken (0-30 cm), the physical, chemical, and biological characteristics of soil were determined. Nine criteria were selected according to Principal Component Analysis as Minimum Data Set. According to the results, the highest value of litter Ca, density and biomass of earthworm, and C microbial biomass were found in FO-CB-AV. After applying the analytical hierarchy process, the calculated overall priority based on nine criteria showed that the FO-CB-AV stand had a higher ecological potential compared to the other stands. Therefore, the FO-CB-AV stand had more of appropriate conditions for improving soil quality in degraded forest regions compared to the other stands under current conditions.