Soil organic carbon：distribution and storage with five regeneration patterns in Cunninghamia lanceolata forests

Key words: 
• forest pedology /
• Chinese fir forest /
• regeneration pattern /
• soil organic carbon /
• soil C/N ratio /
• soil organic carbon storage

Abstract: The vertical distribution and storage of soil organic carbon （SOC） in the depth of 0 － 75 cm were contrasted and discussed by sampling and laboratory analysis under forests of primary Cunninghamia lanceolata （Chinese fir） forests converted with regeneration patterns of a）secondary Chinese fir forests （Chinese fir 12 years and 20 years），b）natural woods，c）Castanea mollissima tree plantations，d）Citrus reticulata plantations and e）Andropogon chinensis grass in Huitong County，Hunan Province. The results showed SOC and C/N in vertical directions decreased generally with depth under different regeneration patterns. In 30 － 45 cm soil depth，the SOC content in the C. mollissima field was significantly higher than that in A. chinensis grass （P = 0.049，t test），but difference of SOC content was not significant in other layers among other regeneration patterns（P＞0.05，t test）. The sequence of mean SOC content of 0 － 75 cm was C. mollissima ＞ Chinese fir 12 years ＞ Chinese fir 20 years ＞ natural woods ＞ Citrus retculata ＞ A. chinensis grass. The five regeneration patterns resulted in loss of SOC storage（0 － 60 cm），with mean annual decrease being C. mollissima（2.201 t·hm－2·a－1）＜ Chinese fir 12 years（2.666 t·hm－2·a－1）＜ Chinese fir 20 years（2.837 t·hm－2·a－1） ＜ natural woods （3.207 t·hm－2·a－1）＜A. chinensis grass（3.278 t·hm－2·a－1）＜Citrus reticulata（3.565 t·hm－2·a－1）. Thus，for Chinese fir stands，regeneration with leaf-fall and deeper rooted trees will have a greater potential for SOC storage. ［Ch，2 fig. 6 tab. 26 ref.］