Abiotic Lignin Degradation: The Key to Litter Transformation after Forest Disturbance?

非生物木质素降解：森林扰动后凋落物转化的关键？

• 批准号: 501469439
• 负责人: Professor Dr. Bruno Glaser
• 金额: --
• 依托单位: Professur für Bodenökologie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/501469439?language=en
• 关键词: Abiotic; Lignin; Degradation; Key; Litter

Disturbances such as drought and storm events that cause canopy cover loss alter microclimatic conditions that in turn influence litter transformation and carbon cycling in forest ecosystems. A major bottleneck to litter transformation is lignin, which is degraded by abiotic effectors such as light and heat in addition to microorganisms. In disturbed forest ecosystems of Central Europe, the quantity and quality of soil organic matter can be strongly impacted by abiotic degradation of lignin and its synergistic effects on litter decomposition. However, little is known about this so far. To identify and quantify canopy cover controls of litter transformation matter after forest disturbance, we will test the following hypotheses: (H1) Abiotic lignin degradation increases more with light irradiance than heat and moisture deficits. (H2) Abiotic lignin degradation produces compounds more depolymerized than products of brown rot and with less oxygen functional groups than products of white rot. (H3) Abiotic lignin degradation alleviates fungal bottlenecks to bacterial degradation of litter in the forest floor, and thus favors enrichment of dissolved organic matter with depolymerized and de-oxygenated lignin compounds in the forest floor. (H4) Therefore, when canopy cover is lost, enhanced light irradiance and corresponding abiotic depolymerization and de-oxygenation of lignin in the forest floor renders organic matter entering mineral soil less available to microorganisms and less reactive to minerals. We will test these hypotheses first for model substances and litter of Norway spruce and European beech in laboratory incubations under controlled microbial, light, moisture and temperature conditions in order to determine abiotic lignin degradation rates and corresponding byproducts by water extracts, cupric-oxide oxidation and X-ray photoelectron spectroscopy. In the same incubations, fungal and bacterial response to abiotic degradation will be determined through via analysis of decay type, phospholipid fatty acids and microbial carbon, nitrogen and phosphorus. In mixed spruce stands along a disturbance gradient in the Black Forest National Park, we will assess in-situ transformation of 13C-labelled beech litter. During a simultaneous two-year inventory in the same mixed spruce stands, indicators of abiotic degradation as well as the reactivity and stability of soil organic matter will be measured. The combined results of our project will enable abiotic lignin degradation to be quantified and thus deliver essential insights into its relevance to the formation and stability of soil organic matter in disturbed forest stands.

干旱和风暴等造成林冠覆盖损失的干扰事件改变了小气候条件，反过来又影响到森林生态系统中的凋落物转化和碳循环。凋落物转化的一个主要瓶颈是木质素，除了微生物外，木质素还被非生物效应物如光和热降解。在中欧受干扰的森林生态系统中，木质素的非生物降解及其对凋落物分解的协同效应会强烈影响土壤有机质的数量和质量。然而，到目前为止，人们对此知之甚少。为了确定和量化森林干扰后凋落物转化物质的冠层覆盖控制，我们将测试以下假设：（H1）非生物木质素降解增加更多的光辐照度比热量和水分不足。(H2)非生物木质素降解产生的化合物比褐腐产物解聚得更多，并且比白色腐产物具有更少的氧官能团。(H3)非生物木质素降解消除了真菌对森林地面中凋落物的细菌降解的瓶颈，从而有利于森林地面中溶解的有机物与解聚和脱氧的木质素化合物的富集。(H4)因此，当冠层覆盖丧失时，增强的光照和森林地面中木质素的相应非生物解聚和脱氧使得进入矿物质土壤的有机物质对微生物的利用率降低，对矿物质的反应性降低。我们将测试这些假设首先为模型物质和垃圾挪威云杉和欧洲山毛榉在实验室培养控制微生物，光照，水分和温度条件下，以确定非生物木质素降解率和相应的副产品的水提取物，氧化铜氧化和X-射线光电子能谱。在相同的培养中，将通过分析衰变类型、磷脂脂肪酸和微生物碳、氮和磷来确定真菌和细菌对非生物降解的反应。在混合云杉站沿着干扰梯度在黑森林国家公园，我们将评估原位转化13 C标记的山毛榉凋落物。在同一混合云杉林的同时两年清查期间，将测量非生物退化指标以及土壤有机质的反应性和稳定性。我们项目的综合结果将使非生物木质素降解得以量化，从而提供其与受干扰森林中土壤有机质形成和稳定性相关的重要见解。