Effects of stand age on litter quality, decomposition rate and nutrient release of Kazdagi fir (Abies nordmanniana subsp. equi-trojani)

Abstract

The influence of stand age on litter quality, decomposition rate and nutrient release was examined in pure stands of Kazdagi fir (Abies nordmanniana subsp. equi-trojani [Steven] Spach) differing in age (Fir38, Fir60, Fir90 and Fir100 years). The needle litters were collected and analysed for initial total carbon, cellulose, hemicellulose, lignin and nutrient concentrations (N, P, K, Ca, S, Mg, Mn and Fe). Initial litter quality parameters varied significantly among the four stand age classes. The Fir60 and Fir100 stands had higher total C than the Fir38 and Fir90 stands, while the Fir38 and Fir100 stands had higher N than the Fir60 and Fir90 stands. Mean cellulose and hemicellulose concentrations were highest in the Fir90 stand, while mean lignin concentration was highest in the Fir38 stand. Fir90 stand showed the highest ratios of C/N and Lignin/N. In general, the older fir stands showed higher Ca, Mg and K concentrations and lower P and S concentrations than the younger stands. The litter, however, showed higher a Mn concentration under the Fir60. Mean Fe concentration was highest under the Fir38 stand and lowest under the Fir60 stand. Litter decomposition was studied in the field using the litterbag technique. The litterbags were placed on the soil under each stand age class and sampled every 6 months for 2 years. The interaction of stand age and time on the mass loss was significant (p<0.01). The repeated measures ANOVA showed that the main effect of time on the mass loss was also significant (p<0.001). Needle litters under Fir100 and Fir60 stands decomposed faster than the needle litters under Fir90 and Fir38 stands. The calculated times required for 50% mass loss were higher under Fir38 (1.35 y) and Fir90 (1.27 y) stands than under Fir100 (1.05 y) and Fir60 (1.06 y) stands. The litters in Fir38 and Fir90 stands need approximately 4 years for 95% mass loss compared to the litters in Fir60 and Fir100 stands, which need 3 years. In general, Ca, Mg and S concentrations increased over time, whereas K and Mn decreased. These results illustrate that stand age is a key factor to be considered when studying litter decomposition dynamics.