Potential gross nitrogen mineralization and its linkage with microbial respiration along a forest transect in eastern China
Potential gross nitrogen mineralization and its linkage with microbial respiration along a forest transect in eastern China
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DOI：
10.1016/j.apsoil.2021.104347
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发表时间：
2021-11-30
影响因子：
4.8
通讯作者：
Cheng, Weixin
中科院分区：
文献类型：
--
作者：
Fan, Bo;Yin, Liming;Cheng, Weixin
土壤中氮的矿化作用通常控制着陆地生态系统中氮的生物有效性。作为整个氮矿化过程中关键的第一步，总氮矿化（GNM，定义为从有机氮的微生物矿化产生铵）与土壤有机碳（C）的微生物矿化（通常称为微生物呼吸（MR））固有地耦合，并且经常被用作C可用性的代理。然而，GNM的模式及其在区域范围内的基本机制及其与MR的联系仍然不清楚。通过对中国东部3800 km南北样带沿着不同森林类型100个土壤样品的分析，采用N-15池稀释法和动态CO2捕获法同时测定了潜在GNM和MR。我们进行了一个结构方程模型（SEM），以研究气候，土壤pH值，微生物基质的可用性，和微生物生物量的潜在GNM沿着森林样带的相互作用。此外，我们进行了非线性回归分析之间的潜在GNM和MR。我们发现，潜在GNM和MR变化很大，从0.55至16.14毫克N kg（-1）土壤d（-1）和从3.64至24.30毫克C kg（-1）土壤d（-1），分别为，但不受森林类型的显着影响。SEM分析表明，潜在GNM的变化解释了51%，微生物底物的有效性是最重要的影响因素。GNM电位与MR呈非线性正相关（R-2 = 0.52，P < 0.0001）。值得注意的是，MR单独发挥了相当的作用，在解释潜在GNM的变化相比，在SEM中使用的多个因素之间的相互作用。我们的研究结果证实了潜在的GNM微生物的C可用性的主导控制，并有必要纳入MR更好地模拟GNM在森林土壤中。
Nitrogen (N) mineralization in soils generally controls biological N availability in terrestrial ecosystems. As the pivotal first step in the overall N mineralization process, gross N mineralization (GNM, defined as the production of ammonium from microbial mineralization of organic N) is inherently coupled with microbial mineralization of soil organic carbon (C) which is commonly referred to as microbial respiration (MR), and that has often been used as a proxy of C availability. However, the pattern of GNM and its underlying mechanisms at a regional scale, and its linkage with MR remain unclear. By analyzing 100 soil samples collected across different forest types along a 3800 km long north-south transect in eastern China, we simultaneously measured the potential GNM using a N-15 pool dilution method and MR using a dynamic CO2 trapping technique. We conducted a structural equation model (SEM) to examine the interactive effects of climate, soil pH, microbial substrate availability, and microbial biomass on potential GNM along the forest transect. Furthermore, we conducted a non-linear regression analysis between potential GNM and MR. We found that both potential GNM and MR varied largely, from 0.55 to 16.14 mg N kg(-1) soil d(-1) and from 3.64 to 24.30 mg C kg(-1) soil d(-1), respectively, but were not significantly affected by forest type. The SEM analysis showed that 51% of the variation in potential GNM was explained, with microbial substrate availability being the most important influencing factor. There was a positive non-linear relationship between potential GNM and MR (R-2 = 0.52, P < 0.0001). Notably, MR alone exerted a comparable role in explaining the variation in potential GNM compared to the interactive effects between multiple factors used in the SEM. Our findings confirm the dominant control of C availability to microbes on potential GNM, and necessitate the incorporation of MR for better modeling GNM in forest soils.