To recognize the impacts of soil acidity on quantitative and qualitative conditions of broadleaf and coniferous trees in Syyahkal watershed region of northern Iran, hand-cultivated adjacent stands of different species of Pinus taeda, Acer insinge,and Alnus subcordata were compared. To gather general information about the soil type in each site, one profile and in total five soil profiles were dug, identified, and classified. In each site 35 individual plots have been selected and thus from all 175plots available vegetative characteristics of above said tree species including height, diameter and volume have been determined. In order to determine the soil characteristiscs in each plot and based on our previous knowledge, samples from two specific horizon depths (0-15cm, and 15-30cm) were collected. Then, in total of 135 samples specific chemical analyses of concern (pH, N.K.P) were carried out. Next, based on appropriate statistical studies (Student t-test, Fisher F-test, or ANOVA, Tukey test or HSD and Regression analysis) the relation between vegetative characteristics of forest trees and different soil parameters in each adjacent sites have been compared. This comparison clearly showed that the hand-cultivated stands do not share similar vegetative characteristics status and in fact due to past thinning nurturing operations Pinus taeda has gained the most volume in acre. Statistical tests reveal that an increase in the amount of soluble nitrogen as a nutrient substance with regard to the vegetative parameters for all three plant species involved translates into a direct dependent relation. This means that an increase in tree diameter, height, and volume is expected wherever more concentrations of soluble nitrogen exists.The soil profile descriptive tables clearly show that Pinus taeda has taken root deep in the soil due to the lack of nutrients at soil surface layers. Thus, it would not be logical to suggest the re-plantation of this species in ruined forested areas of interest. On the other hand, vertical taking root process in Acer insigne, and Alnus subcordata stands down to 63 centimeters depth and has occurred accordingly. Furthermore, dead leaf decomposition at the forest floor has carried out quickly and therefore has helped with the richness of nutrient elements at soil surface layers in both stands. Thus, reuse and re-plantation of these species becomes quite possible and therefore is strongly suggested.