State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conservation, Northwest A&F University, Yangling, 712100, Shaanxi Province, China.
State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conservation, Northwest A&F University, Yangling, 712100, Shaanxi Province, China; Institute of Soil and Water Conservation, Chinese Academy of Science and Ministry of Water Resources, Yangling, 712100, Shaanxi, China.
Sci Total Environ. 2021 Aug 1;780:146298. doi: 10.1016/j.scitotenv.2021.146298. Epub 2021 Mar 8.
Nitrogen (N) addition has variable effects on chemical composition, function, and turnover of roots with different diameters. However, it is unclear whether N addition has variable effects on greenhouse gas (GHG) emission in rhizosphere soil. We performed N addition (0-9 g N m y) experiment in a Pinus tabulaeformis forest and a lab-incubation experiment to determine the effects of N addition on carbon dioxide (CO), nitrous oxide (NO), and methane (CH) emissions in rhizosphere soils of roots with different diameters (very fine roots: <0.5 mm, intermediate fine roots: 0.5-1.0 mm, largest fine roots: 1.0-2.0 mm). Nitrogen addition significantly promoted CO emission and CH uptake, with maximum values (CO, 623.15 mg C kg soil; CH, 1794.49 μg C kg soil) in the 6 or 9 g N m y treatments (P < 0.05). Nitrous oxide emissions were inhibited, with the greatest inhibitory effect in the 9 g N m y treatment (48.63 μg N kg soil). Total phosphorus (TP) content significantly decreased and increased in rhizosphere soil and non-rhizosphere soil after N addition, respectively, while organic carbon (OC), total N (TN), ammonium (NH), and nitrate (NO) contents in rhizosphere soil increased. A greater change in chemical properties occurred in rhizosphere soil of largest fine roots than very fine roots. Carbon dioxide and nitrous oxide emissions in rhizosphere soil among root sizes exhibited similar responses to N addition. While CH uptake was more responsive to N addition in rhizosphere soil with very fine roots than with largest fine roots. Basically, OC, TN, NO, and NH were key soil components driving GHG emissions; NO promoted CH uptake and NO emissions, NH inhibited CO emissions. GHG response to N addition varied greatly, particularly in rhizosphere soil with different root sizes mainly related to its chemical properties.
氮（N）添加对不同直径根系的化学成分、功能和周转有不同的影响。然而，目前尚不清楚 N 添加对根际土壤中温室气体（GHG）排放是否有不同的影响。我们在油松人工林进行了 N 添加（0-9 g N m y）实验，并进行了实验室培养实验，以确定 N 添加对不同直径根系（细根：<0.5 mm，中间细根：0.5-1.0 mm，最大细根：1.0-2.0 mm）根际土壤中二氧化碳（CO）、氧化亚氮（NO）和甲烷（CH）排放的影响。N 添加显著促进了 CO 排放和 CH 吸收，最大值（CO，623.15 mg C kg 土壤；CH，1794.49 μg C kg 土壤）出现在 6 或 9 g N m y 处理中（P < 0.05）。N 添加抑制了氧化亚氮的排放，9 g N m y 处理的抑制作用最大（48.63 μg N kg 土壤）。添加 N 后，根际土壤和非根际土壤中的总磷（TP）含量分别显著减少和增加，而根际土壤中的有机碳（OC）、总氮（TN）、铵（NH）和硝酸盐（NO）含量增加。与细根相比，最大细根根际土壤的化学性质变化更大。不同大小的根系根际土壤中 CO 和氧化亚氮排放对 N 添加的响应相似，而细根根际土壤中 CH 吸收对 N 添加的响应大于最大细根根际土壤。基本上，OC、TN、NO 和 NH 是驱动 GHG 排放的关键土壤成分；NO 促进 CH 吸收和 NO 排放，NH 抑制 CO 排放。GHG 对 N 添加的响应差异很大，特别是在不同大小的根际土壤中，这主要与根际土壤的化学性质有关。
