Changes in plant litter quality characteristics in relation to secondary succession in semi-arid Mediterranean rangelands

Plant litter produced by rangeland ecosystems plays an important role in nutrient cycling dynamics of the plant-soil system, as they function as a substrate for soil microorganisms during decomposition process. The quality of organic matter is highly dependent on the relative amounts of its constituent chemical structural compounds. In this study, we checked the hypothesis that the evolution of secondary succession in rangeland communities modifies the quality properties of plant litter produced at the time of natural senescence in a way that can influence organic matter decomposition rates. The research was carried out in a typical semiarid Mediterranean environment of Lagadas County of Thessaloniki Prefecture, where four types of rangeland vegetation were recognized in order to represent four stages of secondary succession i.e. abandoned field, grassland, open and dense shrubland. In recent plant litter collected during October 2003, we determined the following litter quality characteristics: C and N concentrations, concentration of structural components (NDF, ADF, ADL), C:N, lignin:N, lignin:cellulose ratios and HLQ, LCH and LCI indices. It was found that litter quality characteristics at time of peak senescence: a. change as secondary succession proceeds probably due to changes in species composition, b. are superior in the early stages of succession and c. have distinctive properties in the abandoned field that need further investigation.