Age and Species of Eucalyptus Plantations Affect Soil Microbial Biomass and Enzymatic Activities.

Jie Xu,Zhao-Lei Qu,Bing Liu,Hui Sun,Yang Ma

doi:10.3390/microorganisms8060811

Abstract

Soil microorganisms and extracellular enzymes play important roles in soil nutrient cycling. Currently, China has the second-largest area of eucalyptus plantations in the world. Information on the effects of eucalyptus age and species of trees on soil microbial biomass and enzyme activities, however, is limited. In this paper, the soil microbial biomass and enzyme activities were studied in eucalyptus plantations with different ages (1 and 5+ years) and species of trees (E. urophylla×E. grandis, E. camaldulens and E. pellita) in South China. The results showed that both plantation age and eucalyptus species could affect the total microbial biomass and fungal biomass, whereas the bacterial biomass was affected only by plantation age. The fungal biomass and the fungi-to-bacteria ratio significantly increased along with increasing plantation age. Similarly, the plantation age and eucalyptus species significantly affected the enzyme activities associated with carbon cycling (β-xylosidase, β-d-glucuronidase, β-cellobiosidase and β-glucosidase). The activities of β-d-glucuronidase and β-glucosidase were significantly higher in the E. camaldulens plantation. The enzymes involved in nitrogen (N-acetyl-glucosamidase) and sulfur (sulfatase) cycling were only affected by the eucalyptus plantation age and species, respectively. The results highlight the importance of the age and species of eucalyptus plantations on soil microbial activities.

Highlights

Soil microbes play a vital role in soil quality and function due to their ability to participate in the degradation of soil organic matter [1]
For the eucalyptus plantations with different ages, the soil fungal and bacterial biomasses, and the ratio of fungal and bacterial biomass (F:B) differed (p < 0.05, Table 1), whereas the soil total microbial biomass did not differ (Figure 1a)
The bacterial biomass significantly increased in the E. urophylla × E. grandis (EUG) and E. pellita (EP) plantations, whereas it decreased by 33% in the E. camaldulensis (EC) plantation (p < 0.05, Figure 1c)

Summary

Introduction

Soil microbes play a vital role in soil quality and function due to their ability to participate in the degradation of soil organic matter [1]. The extracellular enzymes are involved in many chemical reactions related to soil nutrient cycling and plant and microbial growth and have a significant effect on the initial decomposing of litter or soil organic matter prior to microbial assimilation and consumption [6,7]. Many environmental factors, such as forest age and plant species, can affect soil enzyme activities [8,9,10]. The enzyme activities of β-cellobiosidase and β-glucosidase, N-acetyl-glucosamidase, sulfatase and phosphatase can reflect the microbial changes involved in carbon, nitrogen, sulfur and phosphorus cycles, respectively [13]

Methods

Results

Discussion

Conclusion