不同氧气条件下红枫湖流域典型陆源植物有机质降解特征

Degradation of Organic Matter from Terrestrial Plants in Hongfeng Lake Basin under Different Redox Conditions

植物残体有机质降解是生态系统中养分循环的主要过程。本研究选取红枫湖流域典型陆源植物开展了为期1年的不同氧气条件下有机质降解模拟实验,利用Power模型刻画有机质降解变化特征,并对影响植物残体有机质降解的主要因素进行了分析。研究结果表明,缺氧环境和富氧环境下,C3植物残体分解剩余生物量比例分别为64%~77.3%和59.5%~76.8%,不同环境下的差异较小;C4植物残体分解剩余生物量比例分别为42.6%~57.4%和31.2%~43.5%,呈现出富氧环境降解程度高于缺氧环境的特征,且降解程度显著高于C3植物。C4植物具有较高的半纤维素、纤维素含量和较低的木质素含量,这是导致其具有较高降解程度和降解速率的主要原因。其中,半纤维素含量对降解速率的影响最显著,半纤维素含量越高,植物降解速率常数越大。不同C3植物残体的降解速率常数具有一定差异,在不同氧气条件下均呈现出马尾松>梧桐>水稻的变化规律。不同环境条件下C4植物降解速率显著不同,缺氧环境和富氧环境下,降解速率常数分别呈现出玉米>狗牙根>茅草和玉米>茅草>狗牙根的变化规律。

Degradation of organic matter in plant residues is a major process of nutrient cycling in ecosystems.In this study,terrestrial plants in the Hongfeng Lake basin were selected to conduct one-year simulation experiments of organic matter degradation under different redox conditions.The Power model was used to characterize the degradation of organic matter and reveal the main factors affecting the degradation of organic matter in plant residues.Generally,the proportion of residual biomass from decomposed C3 plants in anoxic and oxic conditions differed very little,ranging respectively from 64%to 77.3%and 59.5%to 76.8%.The proportion of residual biomass from decomposed C4 plants ranged from 42.6%to 57.4%and 31.2%to 43.5%,showing a higher degree of degradation under oxic conditions than under anoxic conditions.The higher degradation degree and rate of C4 than C3 plant residues mainly reflected that C4 plants had higher hemicellulose,cellulose and lower lignin contents.The composition and structure of organic matter in plant residues had significant effects on the degradation rate,among which the hemicellulose content had the most remarkable impact.The higher the hemicellulose content was,the greater the plant degradation rate constant.The degradation rate constants of C3 plant residues differed considerably,showing a pattern of Masson pine>Chinese parasol>rice under different redox conditions.The degradation rates of C4 plant residues varied significantly with orders of corn>Bermudagrass>thatch under anoxic conditions and corn>thatch>Bermudagrass under oxic conditions.