Key Laboratory of Vegetation Restoration and Management of Degraded Ecosystems, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou 510650, China; College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China; Department of Environmental Chemistry, University of Kassel, 37213 Witzenhausen, Germany.
College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China; Department of Environmental Chemistry, University of Kassel, 37213 Witzenhausen, Germany.
Sci Total Environ. 2024 Jan 10;907:167925. doi: 10.1016/j.scitotenv.2023.167925. Epub 2023 Oct 19.
Subtropical ecosystems are strongly affected by nitrogen (N) deposition, impacting soil organic matter (SOM) availability and stocks. Here we aimed to reveal the effects of N deposition on i) the structure and functioning of microbial communities and ii) the temperature sensitivity (Q) of SOM decomposition. Phosphorus (P) limited evergreen forest in Guangdong Province, southeastern China, was selected, and N deposition (factor level: N (100 kg N ha y (NHNO)) and control (water), arranged into randomized complete block design (n = 3)) was performed during 2.5 y. After that soils from 0 to 20 cm were collected, analyzed for the set of parameters and incubated at 15, and 25, and 35 °C for 112 days. N deposition increased the microbial biomass N and the content of fungal and Gram-positive bacterial biomarkers; activities of beta-glucosidase (BG) and acid phosphatase (ACP) also increased showing the intensification of SOM decomposition. The Q of SOM decomposition under N deposition was 1.66 and increased by 1.4 times than under control. Xylosidase (BX), BG, and ACP activities increased with temperature under N but decreased with the incubation duration, indicating either low production and/or decomposition of enzymes. Activities of polyphenol-(PPO) and peroxidases (POD) were higher under N than in the control soil and were constant during the incubation showing the intensification of recalcitrant SOM decomposition. At the early incubation stage (10 days), the increase of Q of CO efflux was explained by the activities of BX, BQ, ACP, and POD and the quality of the available dissolved organic matter pool. At the later incubation stages (112 days), the drop of Q of CO efflux was due to the depletion of the labile organic substances and the shift of microbial community structure to K-strategists. Thus, N deposition decoupled the effects of extracellular enzyme activities from microbial community structure on Q of SOM decomposition in the subtropical forest soil.
亚热带生态系统受氮（N）沉降的影响较大，影响土壤有机物质（SOM）的可利用性和储量。在这里，我们旨在揭示 N 沉降对以下两个方面的影响：i）微生物群落的结构和功能，ii）SOM 分解的温度敏感性（Q）。选择中国东南部广东省受磷（P）限制的常绿林作为研究地点，并进行了为期 2.5 年的 N 沉降（因子水平：N（100 kg N ha y（NHNO））和对照（水），采用随机完全区组设计（n = 3））。之后，采集了 0-20 cm 深度的土壤，分析了一组参数，并在 15、25 和 35°C 下培养 112 天。N 沉降增加了微生物生物量 N 和真菌和革兰氏阳性细菌生物标志物的含量；β-葡萄糖苷酶（BG）和酸性磷酸酶（ACP）的活性也增加，表明 SOM 分解的加剧。N 沉降下 SOM 分解的 Q 值为 1.66，比对照下增加了 1.4 倍。在 N 沉降下，木聚糖酶（BX）、BG 和 ACP 的活性随温度升高而升高，但随培养时间延长而降低，这表明酶的产量和/或分解较低。多酚氧化酶（PPO）和过氧化物酶（POD）的活性在 N 处理下高于对照土壤，并且在培养过程中保持不变，表明难分解的 SOM 分解加剧。在培养的早期阶段（10 天），CO 排放通量 Q 值的增加可以用 BX、BQ、ACP 和 POD 的活性以及可利用溶解有机物质库的质量来解释。在培养的后期阶段（112 天），CO 排放通量 Q 值的下降是由于易分解有机物的消耗以及微生物群落结构向 K-策略者的转变。因此，N 沉降使胞外酶活性与微生物群落结构对亚热带森林土壤 SOM 分解 Q 值的影响脱钩。
