Slope Position Rather Than Thinning Intensity Affects Arbuscular Mycorrhizal Fungi (AMF) Community in Chinese Fir Plantations

Abstract

Background and Objectives: Arbuscular mycorrhizal fungi (AMF) play a crucial role in individual plant capability and whole ecosystem sustainability. Chinese fir, one of the most widely planted tree species in southern China, forms associations with AMF. However, it is still unclear what impacts thinning management applied to Chinese fir plantations has on the structure and diversity of soil AMF communities. This research attempts to bridge this knowledge gap. Materials and Methods: A thinning experiment was designed on different slope positions in Chinese fir plantations to examine the impacts of slope position and thinning intensity on colonization, diversity, and community composition of AMF. Results: Our research showed that the altitudinal slope position had significant effects on colonization, diversity, and community composition of AMF in Chinese fir plantations. In addition, the interaction between slope position and thinning intensity had significant effects on AMF diversity. Colonization by AMF on the lower slope position was significantly higher than on the upper slope position, while AMF diversity on the upper slope position was higher than on the middle and lower slope positions. Glomus was the most abundant genus in all slope positions, especially on the middle and lower slope positions. The relative abundance of Diversispora was significantly different among slope positions with absolute dominance on the upper slope position. Scutellospora was uniquely found on the upper slope position. Furthermore, soil Mg and Mn contents and soil temperature positively affected AMF community composition at the operational taxonomic unit (OTU) level. Conclusions: These findings suggested that slope position should be considered in the management of Chinese fir plantations. Furthermore, both chemical fertilization and AMF augmentation should be undertaken on upper hill slope positions as part of sustainable management practices for Chinese fir plantations.Forests 2020, 11, 273 2 of 20 both timber production and ecosystem maintenance. In such production forests, growth has not been satisfactorily uniform, although the area of the plantations has increased substantially in recent decades [3,4]. This is because most plantations were initially planted at high density and have not been efficiently managed with thinning [1,5,6]. In addition, these plantations may exhibit other problems associated with monocultures [3,7], such as simple community structure, lack of biological stability, litter decomposition tardiness, and soil nutrient and land fertility losses [4,8,9], which seriously affect the long-term productivity and sustainable management of the plantations [8,10,11].Thinning, as an important silvicultural practice, affects forest characteristics directly and indirectly, such as overstory, understory, soil properties [1,12,13], and microbial communities [14,15]. Several studies have shown that the development of understory after thinning results in an increasing proportion of rapidly decomposable litter, which could...

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