Abstract
Thinning can significantly promote forest productivity and ecological function. Rhizosphere fungi play an indispensable role in regulating nutrient cycling between plants and the environment, and their community composition can positively respond to anthropogenic disturbance. However, the initial effects of thinning on rhizosphere fungal community assembly have seldom been reported. In this research, we studied the alterations in the rhizosphere fungal communities of 29-year-old Pinus massoniana in East Sichuan 2 years after three different thinning intensity treatments. In addition, the responses of fungal community and functional group composition to alterations in understory vegetation and soil physiochemical properties were analyzed. Three thinning intensities were set, which were 0 (CK), 25% (LIT), and 50% (HIT), respectively. The results suggested that the richness index and Shannon index of understory vegetation increased significantly with increasing thinning intensity. The alpha diversity indices of rhizosphere fungal community and soil physiochemical properties did not show significant differences among the three treatments. The relative abundances of 17 fungal indicator species varied regularly with increasing thinning intensity, and most of them belong to Hypocreales and Eurotiales, indicating that these two orders were potential indicators for different thinning treatments. Rhizosphere fungal community assembly was determined by deterministic process, and it was driven by the diversity of understory vegetation in the initial stage of thinning. The Simpson index and Pielou index of herbs were useful measures of the main environmental factors driving the differentiation of fungal functional group composition. Based on network analysis, thinning resulted in distinct co-occurrence patterns of rhizosphere fungal functional groups. This research elucidates the initial role of thinning in rhizosphere fungal community assembly of P. massoniana and has practical significance for the functional restoration and protection of local forest ecosystem.
Highlights
As a frequent means of forest management, thinning can promote the diversity of understory vegetation, regulate the structure of forest ecosystems and improve forest ecological function (Chen et al, 2015; Deng et al, 2019)
Values for the richness index and Shannon index for the HIT treatment were significantly higher than in CK, but there was no significant difference between the LIT treatment and CK
Thinning had no significant effect on total nitrogen (TN), Total phosphorus (TP), TK, available nitrogen (AN), Available phosphorus (AP), AK, Soil organic carbon (SOC), and Soil water content (SWC) contents or pH in the tested soils (Table 3)
Summary
As a frequent means of forest management, thinning can promote the diversity of understory vegetation, regulate the structure of forest ecosystems and improve forest ecological function (Chen et al, 2015; Deng et al, 2019) This silvicultural measure changes the light and hydrothermal conditions in forests, thereby directly or indirectly affecting the aboveground and underground forest features (Vesterdal et al, 1995; Taki et al, 2010). Alterations in understory vegetation communities influence litter, root system and plant exudates, influencing soil exogenous carbon composition and other edaphic properties (Urbanová et al, 2015; Zhalnina et al, 2018). Understanding of the relationships among understory vegetation, soil properties and rhizosphere fungal communities is certainly essential for the study on forest thinning
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