Carbon and nitrogen inputs differentially affect priming of soil organic matter in tropical lowland and montane soils
Carbon and nitrogen inputs differentially affect priming of soil organic matter in tropical lowland and montane soils
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DOI：
10.1016/j.soilbio.2018.10.015
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发表时间：
2019-02-01
影响因子：
9.7
通讯作者：
Whitaker, Jeanette
中科院分区：
文献类型：
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作者：
Hicks, Lettice C.;Meir, Patrick;Whitaker, Jeanette
土壤有机质(SOM)的微生物分解可以通过一种被称为“启动”的现象，通过碳(C)和养分输入的综合作用来加速或减少。热带低地和山地土壤含有大量的碳，由于全球变化，未来可能会在碳和养分输入方面发生重大变化，但这些输入如何相互作用影响启动在这些生态系统中知之甚少。我们使用来自3400米热带海拔梯度的土壤解决了这个问题，这些土壤的氮(N)和磷(P)有效性差异很大。为了确定不同热带土壤中现有的养分有效性如何调节微生物的活动，以及微生物对养分的需求是否导致启动，用简单和更复杂的C-13标记底物结合无机N、P和N+P对土壤进行了改良。同位素分配(C-13在二氧化碳和磷脂脂肪酸中；PLFA)用于识别呼吸作用和微生物群落中C(底物来源或SOM来源)的来源。养分处理不影响任何土壤底物呼吸的碳量，但影响启动效应的方向和大小。对于上山地森林和草原土壤，C的添加对SOM周转的影响相对较小，但N的添加(无论有没有C)减少了SOM的矿化(负启动)，这表明当外部供应N时，微生物对SOM的N开采减少。相比之下，在低山地和低地森林土壤中，碳的添加增加了土壤有机质的矿化(正启动)，但这种反应不受养分添加的影响。C-13底物被功能活性微生物的同化表明，C底物的复杂性，而不是添加的养分，强烈地影响了微生物群落中的C-利用：在低地和山地森林土壤中，真菌同化了更大比例的简单C底物，而革兰氏阳性细菌同化了更复杂的C底物的更大比例。总体而言，我们的结果对热带山地和低地生态系统在未来全球变化下土壤碳循环的响应具有不同的影响。
Microbial decomposition of soil organic matter (SOM) can be accelerated or reduced by the combined effects of carbon (C) and nutrient inputs through a phenomenon known as 'priming'. Tropical lowland and montane soils contain large stores of C and may undergo substantial future changes in C and nutrient inputs due to global change, yet how these inputs might interact to influence priming is poorly understood in these ecosystems. We addressed this question using soils from a 3400 m tropical elevation gradient which vary strongly in nitrogen (N) and phosphorus (P) availability. To determine how existing nutrient availability in different tropical soils regulates microbial activity, and whether microbial demand for nutrients leads to priming, soils were amended with simple and more complex C-13-labelled substrates in combination with inorganic N, P and N + P. Isotopic partitioning (C-13 in CO2 and in phospholipid fatty acids; PLFA) was used to identify sources of C (substrate-or SOM-derived) in respiration and in microbial communities. Nutrient treatments did not influence the amount of substrate-respired C for any of the soils, but did affect the direction and magnitude of priming effects. For the upper montane forest and grassland soils, C addition had a relatively minor influence on the turnover of SOM, but N addition (with or without C) reduced SOM mineralisation (negative priming), suggesting reduced microbial N-mining from SOM when N was externally supplied. By contrast, in the lower montane and lowland forest soils, C addition increased SOM mineralisation (positive priming), but the response was unaffected by nutrient additions. The assimilation of C-13 substrates into functionally active microorganisms revealed that C substrate complexity, but not added nutrients, strongly affected C-use within the microbial community: in both lowland and montane forest soils, fungi assimilated a greater proportion of the simple C substrate, while gram positive bacteria assimilated a greater proportion of the more complex C substrate. Overall, our results have contrasting implications for the response of soil C cycling in tropical montane and lowland ecosystems under future global change.