Functional Diversity of the Soil Culturable Microbial Community in Eucalyptus Plantations of Different Ages in Guangxi, South China

Xiu Lan,Yongxian Liu,Hu Du,Tongqing Song,Wanxia Peng,Zhilian Fang

doi:10.3390/f10121083

Abstract

We selected five different ages of eucalyptus plantation sites to understand the culturable microbial functional diversity and the ecological functions of the soil from the eucalyptus plantations in Guangxi. We investigated the carbon source metabolic activity and diversity features of surface soil microbes using the Biolog EcoPlate method (Biolog Inc., Hayward, CA, USA), along with the microbial functional diversity and physicochemical properties of the soil. The results suggest that the carbon source utilization capacity of the soil microbes at various forest ages manifested as 3-year-old > 5-year-old > 2-year-old > 1-year-old > 8-year-old. The abundance, Shannon–Weiner, Pielou, Simpson, and McIntosh diversity indices of the soil microbes initially increased and then decreased with further increase in forest age, with the highest levels in 3- and 5-year-old forests. As per the heatmap analysis, the 3-year-old forest could metabolize the most carbon source species, while the 1- and 8-year-old forests could metabolize the least. Carbohydrates were the most frequently metabolized carbon source. The principal component analysis (PCA) shows that PC1 and PC2 extracted from the 31 factors have 52.42% and 13.39% of the variable variance, respectively. Carbohydrates contributed most to PCA, followed by amino acids and carboxylic acids, and phenolic acids and amines, the least. Canonical correspondence analysis shows that total carbon, alkali-hydrolyzable nitrogen, total nitrogen, total potassium, and pH negatively correlate with soil microbial functional diversity, whereas total and available phosphorus positively correlate with it. To sum up, the soil microbial community structure of eucalyptus plantations at various ages reflects the soil environmental conditions and nutrient availability, which is of great significance in the efficient management and high-quality operation of their plantations in Guangxi.

Highlights

Soil is a complex and dynamic ecosystem, composed of several abiotic and biotic components that constantly interact with each other
The average well color development (AWCD) values of soil microbiota at different forest ages gradually increased with time, suggesting that soil microbiota has an enhanced capacity to utilize the single carbon source when there is an extended interaction time between them (Figure 1)
The AWCD values rapidly increased between 48–192 h because during this period, the microbiotas were at their growth phase and the carbon sources were greatly utilized; after the growth phase, they entered the stationary phase stage at 192 h, with slow growth

Summary

Introduction

Soil is a complex and dynamic ecosystem, composed of several abiotic and biotic components that constantly interact with each other. Several methods are known for measuring microbial functional diversity, such as phospholipid fatty acid analysis, high-throughput sequencing, Biolog EcoPlate assay, and conventional dilution plating [7], of which, the Biolog EcoPlate assay is currently one of the most used [8] The principle of this assay is based on the utilization of a carbon substrate, present together with a redox dye, by the microbial communities [9] in a microplate to develop a colored product, which is used to obtain the physiological traits [10] and functional diversity [11] of the microbial community. Analyzing the structure and functional features of microbial communities can help in understanding the ecological environment quality and trend of the forest stand [22,23,24]

Methods

Results

Discussion

Conclusion