Supplement 1. Three files containing BLAST identifications for fungal OTUs and abundances across samples.

File List Blast_IDs.csv (MD5: 62e5100c20160c284f4d0c0d7e966652) OTU_by_site_matrix.csv (MD5: fd8cb6e0180fda1c17b283fb1bb9de0e) Phyla_Guild_Assignments.csv (MD5: 835a54ac9732fb782bc6756fd8e10fa6) Description Blast_IDs is a comma-delimited spreadsheet with a row for each OTU encountered in this study. The columns are as follows: Rank = the relative abundance of that OTU across the entire dataset. Rank #1 was the most abundant OTU (in terms of number of clone sequences falling into that OTU). Operational Taxonomic Unit = the code assigned to that OTU when the sequences were clustered using Cap3. Representative Clone = the code for the original clone sequence that was chosen to represent that OTU. Best Match GenBank Accession = the accession number for the sequence in GenBank with the highest bit score when the OTU representative sequence was blasted against our in-house database. Best Match Description = edited text from the title of the top GenBank blast hit meant to convey the putative identity. Percent Identity = the percent of identical bases over the region of the query and hit that were sufficiently similar to be aligned by BLAST. Length of Overlap = the length of the region that was sufficiently similar to be aligned by BLAST. Bit Score = the quality of the match assigned by BLAST. Quality of Top Match = the taxonomic level to which the query sequence could be identified based on a set of rules involving percent identity combined with overlap length, as described in the text of the article. OTU_by_site_matrix is a comma-delimited spreadsheet providing OUT abundances. Counts of clones belonging to a particular OTU in each sample (site × year × horizon combination) are given. Each row represents one OTU. The site is designated by the first number (e.g., '109'), the horizon by M = mineral and O = organic and the sampling year by 4 = 2004 and 5 = 2005. The first column gives the OTU designation, the second column gives the rank of that OTU and subsequent columns give the clone counts in each sample. The last column provides a cumulative total clone count for each OTU. Phyla_Guild_Assignments is a comma-delimited spreadsheet showing the guilds that were assigned to particular fungal OTUs. The first five columns are identical to those described above for the file Blast_IDs. The next columns, labeled “Phylum or Subphylum” and “Order” give the corresponding GenBank taxonomy designations for the top BLAST match. The last column, labeled “Guild”, provides our best estimate of the trophic guild to which the OTU belongs. ECM = ectomycorrhizal; sap = saprotrophic (typically wood or litter decay); lichen = lichen; ?? = unknown. We only attempted to define guild for a subset of well-defined OTUs.文件列表：Blast_IDs.csv（MD5: 62e5100c20160c284f4d0c0d7e966652）、OTU_by_site_matrix.csv（MD5: fd8cb6e0180fda1c17b283fb1bb9de0e）、Phyla_Guild_Assignments.csv（MD5: 835a54ac9732fb782bc6756fd8e10fa6） Blast_IDs为逗号分隔的电子表格，本研究中检出的每个操作分类单元（Operational Taxonomic Unit，以下简称OTU）对应一行。各列说明如下： Rank：该OTU在全数据集内的相对丰度。Rank #1为丰度最高的OTU（以归入该OTU的克隆序列数量计）。 Operational Taxonomic Unit（操作分类单元）编码：使用Cap3对序列进行聚类时为该OTU分配的标识编码。 Representative Clone：选中用于代表该OTU的原始克隆序列编码。 Best Match GenBank Accession：将OTU代表序列与自建数据库进行BLAST比对后，比特得分最高的GenBank序列登录号。 Best Match Description：取自GenBank最优BLAST比对结果标题的编辑文本，用于说明该OTU的推定分类身份。 Percent Identity：BLAST比对时，查询序列与比对序列间经有效比对匹配的同源碱基占比。 Length of Overlap：BLAST有效比对的同源区域长度。 Bit Score（比特得分）：BLAST分配的比对质量得分。 Quality of Top Match：基于结合了比对同源百分比与匹配区域长度的一套规则（详见论文正文），查询序列可被鉴定到的分类学层级。 OTU_by_site_matrix为逗号分隔的电子表格，提供各OTU的丰度信息。表格给出了每个样本（按样地×年份×土层组合划分）中属于特定OTU的克隆序列计数。每行代表一个OTU：样地由首位数字标识（例如"109"），土层分为矿质层（M）与有机质层（O），采样年份4代表2004年、5代表2005年。第一列为OTU标识，第二列为该OTU的丰度排名，后续各列为各样本中的克隆计数，最后一列为每个OTU的克隆总数累加值。 Phyla_Guild_Assignments为逗号分隔的电子表格，展示了已分配营养类群的真菌OTU信息。前5列与上述Blast_IDs.csv文件的列定义完全一致。后续列分别为"门或亚门（Phylum or Subphylum）"与"目（Order）"，对应最优BLAST比对结果的GenBank分类学标注。最后一列"营养类群（Guild）"为该OTU所属营养类群的最优推定：ECM为外生菌根真菌（ectomycorrhizal）；sap为腐生营养型（saprotrophic，通常为木质或凋落物分解菌）；lichen为地衣型真菌；??代表未知类群。本研究仅对部分特征明确的OTU进行了营养类群界定。