Data for the manuscript 'Smart mixture design can steer the fate of root derived carbon into mineral-associated and particulate organic matter in intensively managed grasslands'

To determine the fate of root-derived carbon (C) input from grassland mixtures into distinct soil organic carbon pools — particulate organic matter (POC) and mineral-associated organic carbon (MAOC) — a field trial was established, comparing pure stands of perennial ryegrass under high and low nitrogen (N) fertilizer application rates with grassland mixtures containing legumes and forbs at increasing levels of species richness. The mixtures received the low N application rate.

Through multiple-pulse ¹³C-CO₂ labeling during the first growing season (2022), we captured the net formation of MAOC and POC. At the end of the growing season, soil cores with a diameter of 30 cm were excavated to a depth of 25 cm (topsoil) and transferred to the lab. We removed roots from the soil and performed particle-size fractionation to trace fresh organic carbon (net rhizodeposited C) into particulate organic matter (POM) and mineral-associated organic matter (MAOM). Using a cut-off of 50 μm, particles larger than 50 μm were classified as POM, while those smaller than 50 μm were classified as MAOM.

We related these soil C fractions to five morphological root traits, as well as to the lignocellulose index and the C:N ratio in root biomass.

为明确草地群落根系来源碳在两类土壤有机碳库——颗粒态有机碳（particulate organic carbon, POC）与矿质结合态有机碳（mineral-associated organic carbon, MAOC）——中的归趋，本研究设置田间试验，对比高、低氮肥施用量下的多年生黑麦草单播群落，以及物种丰富度梯度递增的包含豆科与杂类草的草地混播群落，其中混播群落均采用低氮肥施用量。在首个生长季（2022年）通过多脉冲¹³C-CO₂标记技术，我们追踪了MAOC与POC的净形成过程。生长季结束时，采集直径30 cm、深度25 cm的表层土壤原状土柱并转运至实验室。我们从土壤中分离根系，通过粒径分级法追踪新鲜有机碳（净根际沉积碳）在颗粒态有机物质（particulate organic matter, POM）与矿质结合态有机物质（mineral-associated organic matter, MAOM）中的分配。以50 μm作为分界阈值，粒径大于50 μm的组分被划分为POM，小于50 μm的组分则划分为MAOM。本研究将上述土壤碳组分与5种根系形态性状、根系生物量的木质纤维素指数及碳氮比（C:N）进行关联分析。