Soil carbon stocks in temperate grasslands differ strongly across sites but are insensitive to decade-long fertilization,Global Change Biology

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Soil carbon stocks in temperate grasslands differ strongly across sites but are insensitive to decade-long fertilization
Global Change Biology ( IF 10.8 ) Pub Date : 2021-11-12 , DOI: 10.1111/gcb.15988
Adrienne B Keller ₁ , Elizabeth T Borer ₁ , Scott L Collins ₂ , Lang C DeLancey ₁ , Philip A Fay ₃ , Kirsten S Hofmockel _{4,

5} , Andrew D B Leakey ₆ , Melanie A Mayes _{7,

8} , Eric W Seabloom ₁ , Christopher A Walter ₉ , Yong Wang ₇ , Qian Zhao ₁₀ , Sarah E Hobbie ₁

Affiliation

Department of Ecology, Evolution, and Behavior, University of Minnesota, Saint Paul, USA.
Department of Biology, University of New Mexico, Albuquerque, New Mexico, USA.
USDA-ARS Grassland, Soil, and Water Research Laboratory, Temple, Texas, USA.
Earth and Biological Sciences Directorate, Pacific Northwest National Laboratory, Richland, Washington, USA.
Department of Agronomy, Iowa State University, Ames, Iowa, USA.
Departments of Plant Biology and Crop Sciences, Institute for Genomic Biology, Center for Advanced Bioenergy and Bioproduct Innovation, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA.
Department of Earth and Planetary Sciences, University of Tennessee, Knoxville, Tennessee, USA.
Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA.
Department of Biology, West Virginia University, Morgantown, West Virginia, USA.
Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington, USA.

Enhancing soil carbon (C) storage has the potential to offset human-caused increases in atmospheric CO₂. Rising CO₂ has occurred concurrently with increasing supply rates of biologically limiting nutrients such as nitrogen (N) and phosphorus (P). However, it is unclear how increased supplies of N and P will alter soil C sequestration, particularly in grasslands, which make up nearly a third of non-agricultural land worldwide. Here, we leverage a globally distributed nutrient addition experiment (the Nutrient Network) to examine how a decade of N and P fertilization (alone and in combination) influenced soil C and N stocks at nine grassland sites spanning the continental United States. We measured changes in bulk soil C and N stocks and in three soil C fractions (light and heavy particulate organic matter, and mineral-associated organic matter fractions). Nutrient amendment had variable effects on soil C and N pools that ranged from strongly positive to strongly negative, while soil C and N pool sizes varied by more than an order of magnitude across sites. Piecewise SEM clarified that small increases in plant C inputs with fertilization did not translate to greater soil C storage. Nevertheless, peak season aboveground plant biomass (but not root biomass or production) was strongly positively related to soil C storage at seven of the nine sites, and across all nine sites, soil C covaried with moisture index and soil mineralogy, regardless of fertilization. Overall, we show that site factors such as moisture index, plant productivity, soil texture, and mineralogy were key predictors of cross-site soil C, while nutrient amendment had weaker and site-specific effects on C sequestration. This suggests that prioritizing the protection of highly productive temperate grasslands is critical for reducing future greenhouse gas losses arising from land use change.

中文翻译：

温带草原的土壤碳储量在不同地点之间差异很大，但对长达十年的施肥不敏感

加强土壤碳 (C) 储存有可能抵消人为造成的大气 CO ₂增加。CO _2上升随着氮 (N) 和磷 (P) 等生物限制性营养物质的供应量增加，同时发生。然而，目前尚不清楚 N 和 P 供应的增加将如何改变土壤碳固存，特别是在占全球非农业用地近三分之一的草原中。在这里，我们利用全球分布的养分添加实验（营养网络）来研究十年来的 N 和 P 施肥（单独和组合）如何影响横跨美国大陆的九个草原地点的土壤 C 和 N 储量。我们测量了土壤 C 和 N 储量以及三种土壤 C 组分（轻和重颗粒有机物，以及与矿物相关的有机物组分）的变化。养分改良对土壤 C 和 N 池的影响从强阳性到强阴性不等，而土壤 C 和 N 池大小在不同地点之间变化超过一个数量级。分段 SEM 阐明，施肥后植物碳输入量的小幅增加并不会转化为更大的土壤碳储存量。然而，在 9 个地点中的 7 个地点，旺季地上植物生物量（但不是根生物量或产量）与土壤碳储量密切相关，并且在所有 9 个地点，土壤碳与水分指数和土壤矿物学相关，无论施肥如何。总体而言，我们表明，水分指数、植物生产力、土壤质地和矿物学等场地因素是跨场地土壤碳的关键预测因子，而养分改良对碳封存的影响较弱且因场地而异。

更新日期：2022-01-16

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