Abstract
Soil structure and microbial communities are sensitive to forest disturbance. However, little is known about the long-term effects of forest thinning on water-stable aggregates (WSA), and the community composition and diversity of soil microorganisms. In this study, we investigated soil chemical properties, WSA, and communities of bacteria and fungi in conventionally managed Chinese fir plantation stands and repeatedly thinned plantation stands with medium and high tree densities 18 years after the thinning treatments. The distribution patterns of WSA fractions were similar in the three thinning treatments. The mass proportion was the highest in the macro-aggregates fraction, followed by the clay + silt fraction, and it was the lowest in the micro-aggregates fraction. The soil organic carbon (SOC) concentrations in different WSA fractions decreased with decreasing aggregate size. The WSA fractions, stability, and aggregate-associated carbon were not significantly different among the three treatments 18 years after the thinning treatments. The total nitrogen concentration of the macro-aggregates fraction was significantly higher in the stands thinned intensively than in the conventionally managed stands. The abundance of minor bacteria and fungi species was different, although no significant differences were observed in the overall bacterial and fungal composition and diversity between the three treatments. Our results indicate that, compared with the conventionally managed stands, soil WSA stability and soil microbial communities in repeatedly thinned Chinese fir stands may recover over one rotation of Chinese fir plantation and that this is accompanied by the recovery of stand growth and soil nutrition.
Highlights
Forest management plays a key role in improving forest production and stand quality [1].Thinning reduces tree densities and enhances growth of the remaining trees and understory vegetation [2]
We found that canopy coverage and aboveground biomass of Chinese firs recovered after repeated thinning treatments, and we found no differences in forest floor biomass between treatments
Minor differences in microbial communities between the treatments could be attributed to similar soil structure and nutrient properties, especially soil organic carbon (SOC) status, because the diversity and composition of the microbial community mainly depends on carbon availability [45,76]. These results indicate that bacterial and fungal communities recovered following repeated thinning, suggesting that there was no effect of the thinning practices on soil microbial community structures during one rotation of the Chinese fir plantation
Summary
Forest management plays a key role in improving forest production and stand quality [1].Thinning reduces tree densities and enhances growth of the remaining trees and understory vegetation [2]. Changes in stand structure strongly influence abiotic and biotic factors both aboveground and belowground within modified stands, i.e., aboveground and belowground productivity, root density, total radiation, and litterfall [3,4,5]. Such changes lead to modifications in soil physical, chemical, and biological properties [6,7]. Other studies have shown that thinning has a negligible [12,13] or positive effect on soil properties [6,14,15]. Limited information is available on the effects of repeated thinning on soil properties, over a long period [2]
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