关键词: 林分类型, 基质质量, 凋落叶, 质量损失率, ¹³C NMR

Abstract: [Objective] The leaf-litter, as a main part of the litter in a forest ecosystem, is a main source of soil organic matter and plays a key role in the carbon cycle of the forest system. The purpose of this study is to reveal the action mechanism of carbon fractions with different structures during the decomposition process of leaf-litter.[Method] This study selected the leaf-litter under Moso bamboo (Phyllostachys edulis) plantation, Masson pine (Pinus massoniana) natural secondary forest, Chinese fir (Cunninghamia lanceolata) plantation and Cyclobalanopsis glauca natural secondary forest in the Linglong mountain, Lin'an county, Zhejiang province as study materials, and determined the contents of total C and N,and different forms of carbon compounds in the leaf litter of different stands by using chemical analysis and ¹³C NMR spectroscopy technology.[Result] Mass loss rates of the leaf-litter of 4 forest stands decreased in the order: Cyclobalanopsis glauca natural secondary forest (53.80%) > Pinus massoniana plantation (52.69%) >Cunninghamia lanceolata natural secondary forest (48.31%) > Phyllostachys edulis plantation (41.17%) 12 months after decomposition of leaf-litter. During decomposition process of the leaf-litter, N contents in the leaf-litter increased gradually, while the contents of C and ratios of C/N decreased gradually; the relative contents of alkoxy carbon reduced by 9.34%-15.48% (P<0.05), while the relative contents of aromatic carbon and carbonyl C increased by 25.14%-37.37% and 0.75-2.08 times (P<0.05), respectively. Both C contents and ratios of C/N in leaf-litter correlated positive and significant with the leaf-litter mass remaining rates (r=0.901 0-0.984 0, P<0.01), while the N contents in leaf litter correlated positive and significant with the leaf-litter mass remaining rates (r=-0.921 1- -0.983 1, P<0.01); The contents of O-alky1 C in the leaf-litter correlated positive and significant with the leaf-litter mass remaining rates (r=0.808 2-0.962 2,P<0.01), while the contents of aromatic C and carbony1 C in the leaf-litter both correlated negative and significant with the leaf-litter mass remaining rates (r=-0.779 9--0.936 6,P<0.01); the contents of alkyl C in the leaf litter did not correlate with leaf-litter mass remaining rates except leaf-litter of Pinus massoniana natural secondary forest.[Conclusion] In the leaf litter under 4 forest stands, leaf-litter from Phyllostachys edulis plantation were more easier to degrade than other three stands. In the total organic carbon, the components of alkoxy C, aromatic C, and carbonyl C play a decisive role in the degradation of leaf-litter.¹³C NMR spectroscopy technique was found to be more accurate in understanding the decomposition mechanism of leaf-litter than conventional matrix indicators during monitoring the changes of different carbon components in the leaf-litter decomposition process.

Key words: forest type, substrate quality, leaf litter, mass loss rate, ¹³C NMR