Jiangsu Key Laboratory of Environmental Change and Ecological Construction, School of Environment, Nanjing Normal University, No.1 Wenyuan Rd, Nanjing, 210023, China.
College of Biology and Environment, Nanjing Forestry University, Nanjing, China.
Oecologia. 2024 Aug;205(3-4):487-496. doi: 10.1007/s00442-024-05590-3. Epub 2024 Jul 8.
Litter-derived dissolved organic matter (DOM) plays an essential role in biogeochemical cycles. In wetlands, species relative abundance and its change have great influences on input features of litter-derived DOM, including chemical characteristics per se and functional diversity of chemical characteristics. Functional diversity is an important factor controlling organic matter biodegradation, but little is known in terms of the DOM. We mixed litter leachates of four macrophytes with a constant concentration (20 mg DOC L) but varying dominant species and volume ratios, i.e. 15:1:1:1 (low-evenness), 5:1:1:1 (mid-evenness), and 2:1:1:1 (high-evenness), generating a gradient of chemical characteristics and functional diversity (represented by functional dispersion index FDis). Based on a 42-d incubation, we measured degradation dynamics of these DOM mixtures, and analyzed potential determinants. After 42 days of incubation, the high-evenness treatments, along with mid-evenness treatments sometimes, had most degradation, while the low-evenness treatments always had least degradation. The degradation of mixtures related significantly to not only the volume-weighted mean chemical characteristics but also FDis. Furthermore, the FDis even explained more variation of degradation. The non-additive mixing effects, synergistic effects (faster degradation than predicted) in particular, on degradation of DOM mixtures were rather common, especially in the high- and mid-evenness treatments. Remarkably, the mixing effects increased linearly with the FDis values (r = 0.426). This study highlights the critical role of functional diversity in regulating degradation of mixed litter-derived DOM. Resulting changes in chemistry and composition of litter leachates due to plant community succession may exert substantial influences on biogeochemical cycling.
由凋落物衍生的溶解有机物质（DOM）在生物地球化学循环中起着至关重要的作用。在湿地中，物种相对丰度及其变化对凋落物衍生 DOM 的输入特征具有重要影响，包括其化学特征本身和化学特征的功能多样性。功能多样性是控制有机物质生物降解的一个重要因素，但在 DOM 方面知之甚少。我们将四种大型植物的凋落物浸出液以恒定浓度（20 mg DOC L）混合，但优势物种和体积比不同，即 15:1:1:1（低均匀度）、5:1:1:1（中均匀度）和 2:1:1:1（高均匀度），从而产生化学特征和功能多样性（以功能离散指数 FDis 表示）的梯度。基于 42 天的培养，我们测量了这些 DOM 混合物的降解动力学，并分析了潜在的决定因素。培养 42 天后，高均匀度处理，有时中均匀度处理，具有最高的降解率，而低均匀度处理则始终具有最低的降解率。混合物的降解与不仅体积加权平均化学特征，而且与 FDis 显著相关。此外，FDis 甚至可以解释更多的降解变化。混合效应，特别是非加性混合效应（比预测的降解更快），对 DOM 混合物的降解非常常见，特别是在高均匀度和中均匀度处理中。值得注意的是，混合效应与 FDis 值呈线性增加（r = 0.426）。这项研究强调了功能多样性在调节混合凋落物衍生 DOM 降解中的关键作用。由于植物群落演替导致的凋落物浸出液化学性质和组成的变化可能对生物地球化学循环产生重大影响。
