INITIAL LITTER QUALITY VARIABLES AND DISTURBED SITE CHARACTERISTICS BY FOREST HARVESTING PRACTICES INFLUENCE LITTER DECOMPOSITION RATES OF SCOTS PINE, TROJAN FIR AND SWEET CHESTNUT IN NORTHWEST OF TURKEY

Soil compaction and forest floor removal are two most common disturbances caused by forest harvesting practices and mechanical site preparation in forest soils. Those forest activities can affect soil physical and chemical properties such as aeration, water storage, temperature, infiltration and flow, susceptibility to erosion, and heat transfer. However, effects of those forest activities on biological processes such as forest litter decomposition have been received less attention. The objectives of this study were to determine the variation in initial litter quality variables (carbon, nitrogen, cellulose, lignin) of three tree species and differences between the site factors of the disturbed sites from forest harvesting activities as forest floor thickness, soil texture, fine and coarse fragments, loss on ignition, bulk density, porosity, soil compaction (penetrometer), dispersion rate, soil carbon and nitrogen content, soil pH, soil moisture content and water content in the forest floor. Among the site factors, one or more factors could be used to explain the differences in litter mass loss rates observed between the disturbed sites. Results indicate that low-lignin litter (chestnut litter) was more responsive to the site disturbance activities than the high-lignin litter (Scots pine and fir litters). Of the soil and forest floor factors, mass loss was strongly positively correlated with forest floor water content (r = 0.975, P < 0.001), soil water content (r = 0.924, P < 0.001), forest floor thickness (r = 0.779, P < 0.01), and soil nitrogen content (r=0.646, P < 0.05) whereas negatively correlated with soil compaction (r = 0.793, P < 0.01). This indicates that among the soil and forest floor characteristics, soil and forest floor water content, and soil compaction after the site disturbance activities were having the greatest effects on litter mass loss rates.