重庆酸雨区不同林型对土壤酸化和真菌群落的影响

不同林型土壤的酸化缓冲能力不同，真菌在土壤系统中扮演着重要的角色，而对土壤真菌群落结构和组成与土壤酸化的关系缺乏深入研究。以重庆铁山坪林场的马尾松纯林（Pi）和经马尾松纯林改造后的香樟纯林（Ci）、木荷纯林（Sc）、马尾松-香樟混交林（Pi_Ci）以及马尾松-木荷混交林（Pi_Sc）为研究对象，每个林型分别设置4个20 m×20 m的样地，分别采集腐殖质层（O层）和淋溶层（A层）土壤进行土壤性质及真菌群落分析，以探讨酸雨区森林土壤真菌群落与缓解土壤酸化的关系。研究表明：（1）与Pi相比，Ci土壤酸化明显缓解（高pH低NH₄ ： NO₃），且能有效提高土壤全磷（TP）含量；而Sc虽然土壤pH值与Pi没有显著差异，但显著（P<0.05）提高了NH₄ ： NO₃，且显著降低土壤TP和全钾（TK）含量（P<0.05）；（2）不同林型土壤真菌群落多样性以Ci最为丰富，且表征土壤酸化的指标pH值、阳离子交换量（CEC）与真菌多样性显著正相关（P<0.05），NH₄ ： NO₃与多样性显著负相关（P<0.05）；（3）林型和土层都对真菌群落结构有显著影响（P<0.001），且林型的影响大于土层的影响；而土壤酸化程度将五个林型的土壤真菌群落区分成两个大类：Ci和Pi_Ci；Pi，Sc以及Pi_Sc。（4） Ci中有益菌（如Mortierella）更多，Pi以外生菌根真菌占优势（Russulaceae、Russula、Tomentella以及Sebacina）；Sc以及Pi_Sc则含有更多的植物病原菌（Cladophialophora，Paecilomyces，Venturiales）、嗜酸菌及产酸菌（Paecilomyces，Penicillium）。在酸雨区受损马尾松林地种植香樟促进土壤真菌多样性提高，且产酸真菌、嗜酸菌丰度降低，而有益真菌丰度增加，可有效缓解土壤酸化；而种植木荷后土壤中的病原菌、嗜酸菌和产酸菌相对丰度增加，导致土壤进一步酸化。因此，通过将受酸雨损害严重的马尾松纯林改造成香樟纯林或马尾松-香樟混交林，有助于缓解土壤的酸化，实现酸雨区森林生态系统的可持续发展。

Effects of different plantation types on soil acidification and soil fungal community in acid rain area of Chongqing

Soils associated with different plantation types have different buffering capacities for acidification, and fungi play an important role in the soil system. However, there is lack of in-depth research on the relationship between soil fungal community structure and composition and soil acidification. In this paper, we investigated soil properties and fungal communities across five plantation types and different soil horizons in a severely acid-polluted site in Southwest China and evaluated the potential relationship between soil fungal community and soil acidification. Four plots were established in each of the five forest stands in Tieshanping, Chongqing, including pure stands of Pinus massoniana Lamb (Pi), Cinnamomum camphora (Linn) Presl (Ci), and Schima superba Gardn. et Champ (Sc), and the mixed stands of conifer and broadleaves (Pi_Ci and Pi_Sc, respectively). Soils from O and A horizon were collected in August 2018, and soil fungal community composition was characterized via high-throughput sequencing using the Illumina Miseq PE300 sequencing platform (Illumina, Inc., CA, USA). The results showed that (1) Ci significantly improved soil acidity with higher pH and lower NH₄:NO₃ compared to Pi and also increased total phosphorus (TP), while Sc significantly (P<0.05) increased soil NH₄:NO₃ and decreased TP and total potassium (TK). (2) Ci was characterized by significantly greater fungal diversity indicated by Chao 1, Sobs and ace; the fungal diversity in Pi_Sc was the lowest indicated by Shannon, Chao1 and Sobs; and soil pH and cation exchange capacity (CEC) were positively and NH₄:NO₃ was negatively correlated with fungal diversity (P<0.05). (3) Both forest types and soil horizons significantly affected soil fungal community structure (P=0.001), and the effect of forest types was greater than soil horizons. And soil fungal community was divided into two clusters by soil acidification indices (pH, CEC), including Ci and Pi_Ci; Pi, Sc and Pi_Sc. (4) More beneficial taxa (like Mortierella) were found in soils associated with Ci; and ectomycorrhizal fungi dominated in soils of Pi including Russulaceae, Russula, Tomentella and Sebacina; while in soils associated with Sc and Pi_Sc, greater abundant plant pathogen (Cladophialophora, Paecilomyces and Venturiales), acid-producing and acidophilic taxa (Paecilomyces, Penicillium) were detected. Fewer acid-producing and acidophilic taxa found in soils associated with C. camphora indicated that planting C. camphora might help soils recovery from acidification, while planting S. superba might not be beneficial. Our findings illustrate how differences in soil fungal communities may affect soil-acidification-buffering capacity across different forest types, which have important implications for understanding environmental functions within the context of microbial diversity.