Forest is a natural ecosystem consisting of all land, wood resources, bushes and grasses, animals, microorganisms and other components of the natural habitat, along with the natural environment. In a forest ecosystem, litter is the accumulation of plant tissue material that is decomposed or degraded during the biological processes. Physical and chemical conditions, litter quality and composition of the decomposing society are the three main factors controlling the decomposition of litters under the environmental conditions. Litter decomposition plays an important role in the cycling and the balance of nutritional elements, which maintain soil fertility and provide nutrients for plant growth. This research was carried out to investigate i) the response of alkaline and acid phosphatase, available P to successional changes in anoak leaf litter at different biodegradation stages and ii) the degradability of litters with different degrees of degradation in two soils with contrasting landuse .For this purpose, an oak forest in Dalvara region was considered and the samples were collected from fresh oak leaves (L 0 ), litter with low rates of decomposition (L 1 ), litter with medium rates of decomposition (L 2 ) and and litter with high rates of decomposition (L 3 ). Some important biological and biochemical properties in leaf and litters, including organic carbon, total nitrogen, available P, lignin content, and alkaline phosphatase and acid phosphatase activities were measured. Results showed that in litter samples, the amount of organic carbon and alkaline and acid phosphatase activity decreased with increasing the degradation rateswhereas, total nitrogen, available P and lignin content decreased. Negative correlations observed between soil organic carbon and indices such as total nitrogen (r =-0.87**), available P (r =-0.71**) and lignin cnontent (r =-0.84**), However, there were positive correlation between organic carbon and biological indices such as alkaline phosphatase (r =0.8) and acid phosphatase (r =0.87**). The activity of alkaline and acid phosphatase as well as soil microbial respiration were consistently greaterin litter-treated soils. Moreover, natural forest soil supported greater enzyme activities and microbial respiration regardless of plant litter treatment. in Also, in one type of land use, A decreasing trend was monitored in alkaline and acid phosphatase enzyme andmicrobial respiration as biodegradation stage was greater (L 3 L 2 L 1 L 0 ) ., in contrast a decreasing trend was observed for available P. The main effect of the land use, plant residues well as their interaction were significant for alkaline phosphatase, acid phosphatase, basal respiration and available P. Microbial respiration was positively correlated with alkaline phosphatase (r =0.75**) and acid phosphatase (r =0.8) activities. Therefore, progressing the decomposition rocess of litters, resulted in declining either C or biodegradability of the litters. It also looks likely that the progress in the litter decomposition induce a stress to soil microbial population as indicated by greater values measured for metabolic quotient. The stress was interpreted by the fact that as successional stages progress, a shortage in C adequacy would be appeared. Key words: litter ecosystem, decomposition succession, available P, alkaline phosphatase, acid phosphatase