Ecosystem ecology of the polyphenols that link herbivory defense with a detritus food chain in a forest

本研究的目的是研究植物产生的次生代谢物多酚在完整的树叶-凋落物-土壤循环中的流动及其对森林生态系统的生态影响。用DAX-8树脂从土壤水中提取疏水部分的溶解有机物。用6N-HCl-ET120℃对疏水组分中的蛋白质进行水解，并用高效液相色谱法测定氨基酸浓度。对两种土壤养分状况不同的常绿阔叶林土壤水分的测定结果表明，养分贫乏的常绿阔叶林土壤中溶解总酚的浓度一直较高，且溶解蛋白浓度与溶解酚浓度呈显著正相关，表明土壤中存在多酚-蛋白质复合体。前一种模式似乎是由于营养贫乏的森林中完整的叶片中浓缩单宁的浓度一直较高所致。人工合成的多酚-蛋白质复合体在加入和接种土壤微生物时表现出极强的顽固性。从5个树种的5棵树下采集的表层土壤表明，多酚氧化酶活性与总酚浓度之间存在显著的正相关。上述发现表明，树木产生的多酚与土壤或土壤水中的蛋白质结合形成一种顽固性物质，并影响随后的土壤氮循环。

The purpose of this study was to investigate the flow of polyphenols, that were produced by plants as secondary metabolites, in the loop of intact leaves-litter-soils, and their ecosystem consequences in a forest ecosystem. A hydrophobic fraction of dissolved organic matter was extracted from soil water with DAX-8 resin. The protein included in the hydrophobic fraction was hydrolyzed with 6N HCl et 120℃, and the concentrations of amino acids were determined on a HPLC. The methods applied to the soil water collected from two evergreen broad-leaved forests of contrasting soil nutrient status suggested that consistently greater concentrations of dissolved total phenolics occurred in the nutrient-poor forest, and that the concentration of dissolved protein was significantly positively correlated with the concentration of dissolved phenolics, suggesting the existence of polyphenol-protein complexes. The former pattern appeared to be caused by the consistently grater concentrations of condensed tannin in intact leaves in the nutrient-poor forest. Artificially synthesized polyphenol-protein complexes were extremely recalcitrant when soil microbes were added and inoculated. Surface soils collected from underneath five trees each from five species of wide polyphenol variability demonstrated a significant positive correlation between polyphenol-oxidase activities and total-phenolics concentrations. The above findings suggested that the polyphenols produced by trees were bound with protein in soils or in soil water to form a recalcitrant matter, and affected a subsequent soil nitrogen cycle.