Plant diversity and soil stoichiometric characteristics of different mixed forests of Pinus tabuliformis in western Liaoning Province

To explore the effects of stand types on plant diversity and soil stoichiometric characteristics, and to provide theoretical references for afforestation and vegetation restoration and reconstruction in arid and semi-arid regions.

In this study, Pinus tabuliformis×Cotinus coggygria (Pt×Cc), Pinus tabuliformis×Quercus mongolica (Pt×Qm), Pinus tabuliformis×Caragana korshinskii (Pt×Ck), Pinus tabuliformis×Prunus sibirica (Pt×Ps), Pinus tabuliformis×Acer mono (Pt×Am) and Pinus tabuliformis (Pt) were selected as the research objects. Based on the investigation of typical plots and the results of indoor experiments, the understory diversity and contents, stocks and stoichiometric ratios of soil organic carbon (SOC), total nitrogen (TN) and total phosphorus (TP) in the soil were calculated.

Stand types significantly influence the composition and diversity characteristics of understory shrubs and herbs. The understory plant species are as follows: Pt×Qm (39 species), Pt×Ck (38 species), Pt×Cc (27 species), Pt×Ps (27 species), Pt (21 species), and Pt×Am (20 species). The dominant species in the shrub layer consist primarily of regenerating saplings from the mixed tree species, while the herb layer is co-dominated by Lespedeza bicolor and Carex lanceolata. In the shrub layer, the plant diversity index of the Pt×Qm was significantly higher than that of other stands. The plant richness of Pt is the lowest, but the evenness index is relatively high. In the herb layer, the Pt×Ck exhibited the highest plant diversity index, while the Pt showed a relatively high plant diversity index with no significant difference compared to most other forest stands. The content and stocks of SOC and TN in mixed forests were significantly higher than those in pure forests, and there was no significant difference in TP content and stocks. The soil C∶N of Pt×Qm and Pt×Cc showed no significant differences compared to Pt, while their soil C∶P and N∶P were significantly higher than that of Pt. The comprehensive scores of the six stand types were ranked as follows: Pt×Qm>Pt×Cc>Pt×Ck>Pt×Ps>Pt×Am>Pt.

Introducing broadleaf tree species into Pt can enhance understory plant diversity and promote soil nutrient retention. The Pt×Qm demonstrates optimal performance in terms of species diversity and soil nutrient content, making it an ideal configuration for ecological restoration efforts.