Soil gross N2O emission and uptake under two contrasting agroforestry systems: riparian tree buffer versus alley-cropping tree row

IF 3.9 3区环境科学与生态学 Q2 ENVIRONMENTAL SCIENCES

Biogeochemistry Pub Date : 2024-05-16 DOI:10.1007/s10533-024-01141-3

Jie Luo, Lukas Beule, Guodong Shao, Dan Niu, Edzo Veldkamp, Marife D. Corre

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Abstract

In addition to the removal of excess mineral nitrogen (N) via root uptake, trees in agroforestry systems may mitigate negative effects of high N fertilization of adjacent crops by enhancing complete denitrification of excess mineral N aside from root uptake. Presently, little is known about the potential for NO₃⁻ reduction through denitrification (conversion to greenhouse gas N₂O and subsequently to non-reactive N₂) in contrasting agroforestry systems: riparian tree buffer versus tree row of an upland alley-cropping system. Our study aimed to (1) quantify gross N₂O emissions (both N₂O + N₂ emissions) and gross N₂O uptake (N₂O reduction to N₂), and (2) determine their controlling factors. We employed the ¹⁵N₂O pool dilution technique to quantify gross N₂O fluxes from 0 to 5 cm (topsoil) and 40 to 60 cm (subsoil) depths with seasonal field measurements in 2019. The riparian tree buffer exhibited higher topsoil gross N₂O emissions and uptake than the alley-cropping tree row (P < 0.03). Gross N₂O emissions were regulated by N and carbon (C) availabilities and aeration status rather than denitrification gene abundance. Gross N₂O uptake was directly linked to available C and nirK gene abundance. In the subsoil, gross N₂O emission and uptake were low in both agroforestry systems, resulting from low mineral N contents possibly due to N uptake by deep tree roots. Nonetheless, the larger available C and soil moisture in the subsoil of riparian tree buffer than in alley-cropping tree row (P < 0.05) suggest its large potential for N₂O uptake whenever NO₃⁻ is transported to the subsoil.

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两种截然不同的农林系统下的土壤总 N2O 排放量和吸收量：河岸树木缓冲区与巷作树行

除了通过根部吸收去除多余的矿物氮（N）外，农林系统中的树木还可以通过加强对根部吸收以外的多余矿物氮的完全反硝化作用，减轻邻近作物高氮施肥的负面影响。目前，人们对河岸树木缓冲区与高地小巷种植系统中的树木行通过反硝化作用（转化为温室气体 N2O，然后再转化为非反应性 N2）减少 NO3- 的潜力知之甚少。我们的研究旨在：(1) 量化 N2O 排放总量（N2O + N2 排放）和 N2O 吸收总量（N2O 还原为 N2）；(2) 确定其控制因素。我们采用 15N2O 池稀释技术量化了 0 至 5 厘米（表土）和 40 至 60 厘米（底土）深度的 N2O 总通量，并在 2019 年进行了季节性实地测量。河岸树木缓冲区的表土总 N2O 排放量和吸收量均高于小巷种植树木行（P < 0.03）。一氧化二氮总排放量受氮和碳的利用率以及通气状态的影响，而不是受反硝化基因丰度的影响。N2O 总吸收量与可用碳和 nirK 基因丰度直接相关。在两种农林系统中，底土的 N2O 排放总量和吸收总量都很低，这可能是由于树木深根吸收 N 导致矿质 N 含量较低。尽管如此，河岸树木缓冲区底土中的可利用 C 和土壤水分比小巷种植树木行中的大（P < 0.05），这表明只要 NO3- 被运输到底土，其吸收 N2O 的潜力就很大。

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来源期刊

Biogeochemistry 环境科学-地球科学综合

CiteScore

7.10

自引率

5.00%

发文量

112

审稿时长

3.2 months

期刊介绍： Biogeochemistry publishes original and synthetic papers dealing with biotic controls on the chemistry of the environment, or with the geochemical control of the structure and function of ecosystems. Cycles are considered, either of individual elements or of specific classes of natural or anthropogenic compounds in ecosystems. Particular emphasis is given to coupled interactions of element cycles. The journal spans from the molecular to global scales to elucidate the mechanisms driving patterns in biogeochemical cycles through space and time. Studies on both natural and artificial ecosystems are published when they contribute to a general understanding of biogeochemistry.