亚热带常绿阔叶林区凋落叶木质素和纤维素在不同雨热季节的降解特征

Degradation characteristics of lignin and cellulose of foliar litter at different rainy stages in subtropical evergreen broadleaved forest

采用凋落物分解袋法研究了亚热带常绿阔叶林区6个典型树种马尾松(Pinus massoniana)、柳杉(Cryptomeria fortunei)、杉木(Cunninghamia lanceolata)、香樟(Cinnamomum camphora)、红椿(Toona ciliata)和麻栎(Quercus acutissima)凋落叶木质素与纤维素第1年降解特征。结果表明:6种凋落叶质量损失率的大小顺序依次为红椿(72.09%)>柳杉(58.61%)>杉木(51.07%)>麻栎(50.38%)>马尾松(31.08%)>香樟(27.75%);6种凋落叶木质素浓度动态不一致,纤维素浓度则整体上呈现一直下降的变化动态;第1个分解年,木质素降解率大小顺序依次为红椿(88.36%)>麻栎(61.21%)>柳杉(56.41%)>杉木(55.44%)>香樟(37.10%)>马尾松(24.10%),纤维素降解率大小顺序依次为红椿(99.22%)>杉木(90.58%)>柳杉(86.84%)>麻栎(84.70%)>香樟(76.40%)>马尾松(71.30%);季节性降雨极显著地影响凋落叶木质素和纤维素降解率(P<0.01),6种凋落叶木质素和纤维素在雨季时期均有较大的降解量;亚热带常绿阔叶林6种凋落叶木质素和纤维素第1年降解主要发生在雨季,凋落叶木质素和纤维素在分解初期旱季的降解速率基本一致,而在季节性降雨期,纤维素降解速率快于木质素的降解速率。

In order to understand the decomposition characteristics of foliar litter as affected by rainy pattern in the subtropical evergreen broadleaved forest region, the degradation of lignin and cellulose in different seasons were investigated in foliar litter of Pinus massoniana, Cunninghamia lanceolata, Cryptomeria fortunei, Cinnamomum camphora, Toona ciliate, and Quercus acutissi- ma, six representative tree species in the subtropical evergreen broadleaved forest at the upper reaches of Yangtze River, by litterbag method. After one-year decomposition, mass loss rates in foliar litter were in order of T. ciliate （72.09%） 〉 C. forttmei （58.61%） 〉 C. lanceolata （51.07%） 〉 Q. acutissima （50.38%） 〉 P. massoniana （31.08%） 〉 C. camphora （27.75%）. During the first-year decomposition, the dynamics of lignin concentration in foliar litter varied with tree species, while cellulose concentration in foliar litter declined continually. Lignin loss rates in foliar litter were in order of T. ciliate （ 88.36% ） , Q. acutissima （ 61.21% ） , C. fortunei （56.41%） , C. lanceolata （55.44%） , C. camphora （37.10%） , and P. massoniana （24.10%）. Meanwhile, cellulose loss rates in foliar litter were ranked in order of T. ciliate （99.22%） , C.lanceolata （90.58%）, C. fortunei （86.84%）, Q. acutissima （84.70%）, C. camphora （76.40%）, and P. massoniana （ 71.30% ）. Seasonal rainfall had a significant （ P〈O.O1 ） effect on the degradation rates of lignin and cellulose in foliar litter of the tree species studied. The deg- radation of lignin and cellulose in foliar litter in the rainy season was higher than in the dry sea- son. Furthermore, both lignin and cellulose degradation of foliar litter in the subtropical region occurred mainly in the rainy season, In the dry season of the first decomposing year, lignin in foliar litter showed a similar degradation trend with cellulose. In the seasonal rainy period, however, the degradation rate of cellulose in foliar litter was faster than that of lignin.