Original data on the soil properties for afforestation

We selected three paired cropland (control) and adjacent R. pseudoacacia forest (treatment) sites with similar topography and parent materials. Croplands were planted with maize (Zea mays L.) and millet (Setaria italica), whereas forests were dominated by R. pseudoacacia (mean tree density ≈ 2,600 stems ha⁻¹; mean height ≈ 10.4 m). No fertilization or tillage had been applied to forest soils since afforestation. Within each site, one 20 m × 20 m plot was established, and five representative points were randomly chosen for sampling. Soil cores (5 cm diameter) were collected at 20 cm intervals to 1,000 cm depth and composited by depth within each plot. Samples were transported on ice to the laboratory and subdivided for physical, chemical, biochemical, and molecular analyses. We focused on five representative depths (0–20, 180–200, 380–400, 580–600, and 880–900 cm), which capture major gradients in soil moisture and mineral nitrogen along the vertical profile. The relevant soil properties were measured. The data that support the findings of this study are openly available in the Genome Sequence Archive (GSA) at https://ngdc.cncb.ac.cn/gsa, reference number CRA030332.

我们选取了3处配对样地，每处样地均包含农田（对照组）与邻近的刺槐（Robinia pseudoacacia）林（处理组），且所有样地的地形与母质均相似。各样地内的农田均种植玉米（Zea mays L.）和谷子（Setaria italica），而刺槐林以该树种为绝对优势种，其平均林分密度约为2600株/公顷，平均树高约10.4米。该刺槐林自完成造林以来，未对林地土壤施加过任何肥料，也未进行过耕作活动。在每处样地内设置1个20米×20米的标准样方，随后随机选取5个代表性采样点开展样品采集。以20厘米为采样间隔，采集直径5厘米的土芯直至1000厘米深度，每个样方内的样品按深度层混合制样。采集的样品全程以低温条件运至实验室，经分样后分别用于土壤物理、化学、生物化学及分子生物学相关指标的测定。本研究重点关注5个代表性深度层（0–20、180–200、380–400、580–600及880–900厘米），这些深度层可覆盖土壤垂直剖面中土壤水分与矿质氮的主要分布梯度。相关土壤属性指标均已完成测定。本研究支撑研究结论的原始数据可于基因组序列归档库（Genome Sequence Archive, GSA）公开获取，访问链接为https://ngdc.cncb.ac.cn/gsa，检索编号为CRA030332。