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The complete vegetation data set, herb, moss and seedling species, consisting 169 sample plots,
were analyzed using the Braun-Blanquet combined scale and TWINSP AN classification in order to distinguish the relationship between humus type and cover vegetation in a mixed hardwood stand. The edaphical differences and vegetation composition between two stands (oak-beech and ash) were the major factors influencing the grouping produced by a TWINSP AN. The result of the classification showed that the main direction of variation in the vegetation pattern can be explained by an underlying gradient that reflects soil acidity and humus quality. It was concluded that TWINSP AN classified the vegetation data set based on ecological groups, which are well known as indicator species. The first division with the highest Eigen value (0.54) serves rather well in revealing the main derection of the vegetation variation. The species of two poles of die first axis seem to reflect the soil fertility gradient.
On the basis of Ellen berg mean indicator value, it was concluded that the group (100) of the fourth division consists of rich favored species like Urtica dioca, Stachys sylvatica and Ranunculus repens, which is an indicator of mull humus characteristics. Whereas, the group (111) of the seventh division includes the acidophile species like Dicranella heteromella" Polytrichum formosum and Pteridium aquilinum, which reflects the moder humus quality.
Similarity assessment between the TWINSP AN separated groups was examined by three methods; similarity coefficient (Jaccard, 1928), Ellen berg mean indicator value (mR, fiN, mF & mL) and ecological affinity coefficient, showed a significant difference and discontinuity between groups (100)
and (110) and groups (100) and (111).
On the basis of the phytosociological classification, the vegetation of group (100) had typical mull humus and the group (101) showed an acid mull type. The species of the group (110) indicated a stand with the mull - moder characteristics. The species of group (111) indicated a moder humus type. It was concluded that plant association could be a useful indicator for the humus type in a forest ecosystem or Vice versa.