林分密度对刺槐人工林土壤养分和微生物群落的影响

doi:10.13866/j.azr.2025.02.08

摘要/Abstract

摘要：

土壤养分水平和微生物群落结构特征是评估人工林生态系统服务功能的重要指标。为探究干旱半干旱地区人工林林分密度对土壤养分与微生物群落的影响，以黄土高原东缘30 a生刺槐（Robinia pseudoacacia）人工林为研究对象，基于Reineke林分密度效应法则和区域管理标准，将林分划分为低密度（950~1350株·hm^-2）、中密度（1600~2050株·hm^-2）和高密度（2400~3300株·hm^-2）组。通过野外调查、土壤养分测定及16S rRNA和ITS高通量测序，系统分析了林分密度对土壤养分、微生物群落及其生态互作关系的影响，对于优化人工林密度和实现可持续经营具有重要意义。结果表明：土壤全氮、硝态氮、全碳和有机碳含量随林分密度增加而提高，尤其在高密度组中差异显著（P<0.05）；有效磷含量则在中密度组达到峰值。细菌群落主要由变形菌门（38.70%）、放线菌门（19.37%）、芽单胞菌门（8.23%）和绿弯菌门（7.71%）构成，其中高密度组放线菌门的相对丰度显著高于低密度组（P<0.05）；在真菌群落中，子囊菌门（51.79%）、被孢霉门（30.70%）和担子菌门（10.07%）为优势菌门。高密度组细菌和真菌群落多样性显著增强，Shannon指数和Chao1指数均显著提高（P<0.05）。PCoA分析显示，中、低密度组的细菌群落结构呈现聚集性，并与高密度组存在显著差异（P<0.05）；真菌群落结构在不同密度组间未表现出显著差异。Mantel检验表明，细菌和真菌群落结构均与土壤全氮显著相关（P<0.05）。共现网络分析显示，适度提高林分密度能够增强微生物群落的互作强度与复杂性，当林分密度超过2400株·hm^-2时，网络稳定性下降，不利于资源高效利用。综上所述，林分密度处于1600~2050株·hm^-2时，能够有效提高土壤养分水平，并优化微生物群落结构，从而为黄土高原刺槐人工林的生态系统管理与可持续经营提供科学依据。

关键词: 林分密度, 刺槐人工林, 土壤养分, 微生物群落, 干旱半干旱地区

Abstract:

Soil nutrient levels and microbial community structures are critical indicators for evaluating the ecosystem services of artificial forests. In arid and semi-arid regions, which are the major distribution areas for artificial forests, the regulatory effects of stand density on soil nutrients and microbial communities remain poorly understood. This study analyzed a 30-year-old Robinia pseudoacacia plantation on the Loess Plateau’s eastern edge. Based on Reineke’s stand density effect law and regional management standards, the stands were categorized into low (950-1350 trees·hm^-2), medium (1600-2050 trees·hm^-2), and high (2400-3300 trees·hm^-2) density groups. Data were collected through field surveys, soil nutrient analyses, and high-throughput sequencing of 16S rRNA and ITS. These methods systematically assessed the soil nutrient characteristics and microbial community structures and diversity across different stand densities. The study’s findings indicate that as the stand density increases, the soil total nitrogen, nitrate nitrogen, total carbon, and organic carbon contents significantly increase, especially in the high-density group (P<0.05). Conversely, the available phosphorus content peaks in the medium-density group. The bacterial community was primarily composed of Proteobacteria (38.70%), Actinobacteria (19.37%), Gemmatimonadetes (8.23%), and Chloroflexi (7.71%), with Actinobacteria’s relative abundance significantly increasing alongside the stand density (P<0.05). In the fungal community, Ascomycota (51.79%), Mortierellomycota (30.70%), and Basidiomycota (10.07%) were the dominant phyla. In the high-density group, bacterial and fungal community diversity was significantly enhanced, as evidenced by notable increases in the Shannon and Chao1 indices (P<0.05). Principal Coordinates Analysis revealed that the bacterial community structures in the medium- and low-density groups exhibited significant clustering, distinctly differing from those in the high-density group (P<0.05). In contrast, the fungal community structures remained relatively stable across different stand densities. The Mantel test revealed that bacterial and fungal community structures were significantly associated with TN (P<0.05). Cooccurrence network analysis indicated that moderate stand density increases microbial interaction strength and network complexity. However, when the stand density exceeded 2400 trees·hm^-2, the network stability decreased, potentially hindering efficient resource utilization. Maintaining a stand density of 1600-2050 trees·hm^-2 improves soil nutrient levels and enhances microbial community diversity and stability, providing a scientific basis for the sustainable management of R. pseudoacacia plantations on the Loess Plateau.

Key words: stand density, Robinia pseudoacacia plantations, soil nutrients, microbial community, arid and semi-arid regions

张佳凝, 张建军, 赖宗锐, 赵炯昌, 胡亚伟, 李阳, 卫朝阳. 林分密度对刺槐人工林土壤养分和微生物群落的影响[J]. 干旱区研究, 2025, 42(2): 274-288.

ZHANG Jianing, ZHANG Jianjun, LAI Zongrui, ZHAO Jiongchang, HU Yawei, LI Yang, WEI Chaoyang. Effects of stand density on soil nutrients and microbial communities in Robinia pseudoacacia plantations[J]. Arid Zone Research, 2025, 42(2): 274-288.

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分组	林分密度 /(株·hm^-2)	海拔 /m	坡位	坡向	平均坡度/(°)	平均树高/m	平均胸径/cm	平均地径/cm	平均水平冠幅/m	平均顺坡冠幅/m	主要林下植被
低密度	1218.75±141.89	1133.49±42.05	中坡	阳坡	23.31±4.91	10.53±1.07	13.12±2.13	16.93±1.98	4.03±0.22	4.76±0.39	茅莓、青杞、黄刺玫、铁杆蒿
中密度	1893.75±135.46	1102.90±43.57	中坡	阳坡	24.00±7.65	8.89±1.09	9.93±1.22	13.77±1.46	3.67±0.27	4.04±0.35	虉草、黑麦草、茅莓、青蒿、白首乌
高密度	2723.25±297.09	1098.41±36.26	中坡	阳坡	21.13±15.43	7.11±1.35	8.30±1.04	11.63±1.30	3.19±0.32	3.85±0.62	虉草、茅莓、青蒿、铁杆蒿、蒌蒿、黄刺玫、茜草

分组	全氮/(g·kg^-1)	铵态氮/(mg·kg^-1)	硝态氮/(mg·kg^-1)	全碳/(g·kg^-1)	有机碳/(g·kg^-1)	全磷/(g·kg^-1)	有效磷/(mg·kg^-1)
低密度组(n=40)	0.65±0.17b	10.05±2.39a	9.01±3.66b	23.44±3.00b	5.34±1.33b	0.56±0.04a	1.64±0.61b
中密度组(n=40)	0.80±0.34ab	10.10±2.63a	11.14±3.21ab	23.91±2.03ab	5.41±1.62b	0.55±0.04a	2.99±1.02a
高密度组(n=40)	1.10±0.38a	10.27±3.00a	15.43±7.25a	28.32±5.39a	8.01±1.38a	0.53±0.06a	2.53±0.87ab

网络拓扑参数	细菌			真菌
网络拓扑参数	低密度	中密度	高密度	低密度	中密度	高密度
节点数	434	450	536	126	111	189
边数	609	698	1239	197	142	294
正相关数	606	696	1234	197	142	294
负相关数	3	2	5	0	0	0
平均度	2.81	3.10	4.62	3.13	2.56	3.11
平均路径长度	1.04	1.02	1.06	1.24	1.14	1.22
网络直径	2.98	1.99	1.99	1.98	1.98	3.97
网络密度	0.01	0.01	0.01	0.03	0.02	0.02
聚类系数	0.99	0.99	0.99	0.9	0.94	0.94