Abstract
The patterns and drivers of soil microbial communities in forest plantations remain inadequate although they have been extensively studied in natural forest and grassland ecosystems. In this study, using data from 12 subtropical plantation sites, we found that the overstory tree biomass and tree cover increased with increasing plantation age. However, there was a decline in the aboveground biomass and species richness of the understory herbs as plantation age increased. Biomass of all microbial community groups (i.e. fungi, bacteria, arbuscular mycorrhizal fungi, and actinomycete) decreased with increasing plantation age; however, the biomass ratio of fungi to bacteria did not change with increasing plantation age. Variation in most microbial community groups was mainly explained by the understory herb (i.e. herb biomass and herb species richness) and overstory trees (i.e. tree biomass and tree cover), while soils (i.e. soil moisture, soil organic carbon, and soil pH) explained a relative low percentage of the variation. Our results demonstrate that the understory herb layer exerts strong controls on soil microbial community in subtropical plantations. These findings suggest that maintenance of plantation health may need to consider the management of understory herb in order to increase the potential of plantation ecosystems as fast-response carbon sinks.
Highlights
Soil organisms through resources produced by the roots, and the decomposer food web by determining the quantity and quality of the litter that enters the soil[16]
An increase in plantation tree cover could suppress the amount of light available for the understory herb community, which affects carbon allocation as well as soil microbes[9,16]
How do understory herb community and soil properties change along plantation age gradient? Second, how do the relative effects of overstory trees, soil properties, and the understory herb community on the soil microbial community in subtropical plantations? With respect to the first question, we hypothesized that higher plantation tree biomass would result in a decrease in the understory herb biomass and species richness, soil moisture, and soil pH, but an increase in the soil organic carbon content
Summary
Soil organisms through resources produced by the roots (root exudates), and the decomposer food web by determining the quantity and quality of the litter that enters the soil[16]. How do the relative effects of overstory trees (plantation tree biomass and tree cover), soil properties (soil moisture, pH, and soil organic carbon), and the understory herb community (herb species richness and herb aboveground biomass) on the soil microbial community in subtropical plantations? With respect to the first question, we hypothesized that higher plantation tree biomass would result in a decrease in the understory herb biomass and species richness, soil moisture, and soil pH, but an increase in the soil organic carbon content. We hypothesized that plantation tree biomass would be more important than the understory herb and soil factors because plantation trees directly regulate the soil microbial community through the relative high quantity of root exudates and plant litter returned to soils
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