Abstract
Soil enzymes and microbial communities are key factors in forest soil ecosystem functions and are affected by stand age. In this study, we studied soil enzyme activities, composition and diversity of bacterial and fungal communities and relevant physicochemical properties at 0–10 cm depth (D1), 10–20 cm depth (D2) and 20–30 cm depth (D3) soil layers in 3-(3a), 6-(6a), 12-(12a), 18-(18a), 25-(25a), 32-(32a) and 49-year-old (49a) Chinese fir plantations to further reveal the effects of stand age on soil biotic properties. Spectrophotometry and high-throughput sequencing was used to assess the soil enzyme activity and microbial community composition and diversity of Chinese fir plantation of different stand ages, respectively. We found that soil catalase activity increased as the stand age of Chinese fir plantations increased, whereas the activities of urease, sucrase and β-glucosidase in 12a, 18a and 25a were lower than those in 6a, 32a and 49a. Shannon and Chao1 indices of bacterial and fungal communities first decreased gradually from 6a to 18a or 25a and then increased gradually from 25a to 49a. Interestingly, the sucrase and β-glucosidase activities and the Shannon and Chao1 indices in 3a were all lower than 6a. We found that the relative abundance of dominant microbial phyla differed among stand ages and soil depths. The proportion of Acidobacteria first increased and then decreased from low forest age to high forest age, and its relative abundance in 12a, 18a and 25a were higher than 3a, 32a and 49a, but the proportion of Proteobacteria was opposite. The proportion of Ascomycota first decreased and then increased from 6a to 49a, and its relative abundance in 12a, 18a and 25a was lower than 3a, 6a, 32a and 49a. Our results indicate that soil enzyme activities and the richness and diversity of the microbial community are limited in the middle stand age (from 12a to 25a), which is important for developing forest management strategies to mitigate the impacts of degradation of soil biological activities.
Highlights
Plant–microbe interactions are central to soil fertility and ecosystem function
Differences in soil Soil bulk density (SBD), pH, soil organic matter (SOM), total nitrogen (TN), Total phosphorus (TP), total potassium (TK), alkali hydrolysis nitrogen (AN), available phosphorus (AP), and AK contents were found among the seven stand ages and among three depths (Figure 2)
Our study demonstrated that the stand age of Chinese fir plantations can drive changes in soil physicochemical properties, enzyme activities and the richness and diversity of the microbial community at 0–30 cm depth
Summary
Plant–microbe interactions are central to soil fertility and ecosystem function. In both natural and managed ecosystems, research has demonstrated the strong selective effects of plants on soil microbialForests 2019, 10, 11; doi:10.3390/f10010011 www.mdpi.com/journal/forestsForests 2019, 10, 11 communities and how resultant soil microbial communities may directly impact plant communities and soil nutrient cycling [1,2,3]. Plant–microbe interactions are central to soil fertility and ecosystem function. In both natural and managed ecosystems, research has demonstrated the strong selective effects of plants on soil microbial. Soil enzymes and microorganisms are useful biotic indicators of soil fertility and ecosystem functions because they are the main drivers of soil nutrient cycling and carbon cycling [4]. Catalase (CAT) is a specific enzyme for the metabolism of hydrogen peroxide [5]; sucrase (SC) plays an important role in decomposing sucrose and promoting the conversion of activated carbon [6]; β-glucosidase (BG) is mainly involved in the degradation of cellulose [4]; urease (UE). Microorganisms play an important role in the production of enzymes, and the production of specific enzymes can be partly explained by the need of microorganisms to limit nutrients [8].
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