| Natural secondary forest is an important part of Chinese forest resources, and it’s area is the half of the total forest area in our country. How to manage the natural secondary forest has become one of the major themes of the forest development. The forest ecosystems’update way and management strategies have effect on the direction and extent of changes in the development of soil fertility. As the representative of soil fertility, the soil microorganisms and the soil enzyme activity are the important indicator to reveal the variation and trends of the evolution in soil. So this paper studied on natural secondary forest, and three artificial plantations, Cryptomeria fortunei, E.urophyllaS.T. Blake XE.grandisW. Hillex. and Neosinocalamus affinis forests, which formed by artificial regeneration of natural secondary forest in rainy zone of west China, and analyzed what effects artificial regeneration of the natural secondary forest have on soil microorganisms and soil enzyme activity. The main results are as follows:(1) Different degrees of changes had been taken place in soil physical properties after natural secondary forest artificially regenerate Cryptomeria fortunei, E.urophyllaS.T. Blake XE.grandisW. Hillex. and Neosinocalamus affinis forests.4 kinds of forest soil pH was between 4.12±0.03 and 5.38±0.20. Neosinocalamus affinis, E.urophyllaS.T. Blake XE.grandisW. Hillex. and Cryptomeria fortunei forest soil pH were increased by 0.87 (P<0.05),0.59 (P<0.05) and 0.10. The soil bulk density was between 1.05±0.15 g·cm-3 and 1.4±0.03 g·cm-3. Compared with the natural secondary forest, Neosinocalamus affinis, E.urophyllaS.T. Blake XE.grandisW. Hillex. and Cryptomeria fortunei forest soil bulk density were increased by 0.23g±cm-3,0.22 g±cm-3 and 0.11 g-cm"3. The natural water content was between 70.9% and 60.53%. The natural water of Cryptomeria fortunei, E.urophyllaS.T. Blake ×E.grandisW-Hillex. and Neosinocalamus affinis forest were decreased by 2%,5.25% and 9.21%. The soil became relatively harden and retaining water capacity also were dropped when natural secondary forest artificial regeneration.(2)After natural secondary forest artificially regenerate Cryptomeria fortunei, E.urophyllaS.T. Blake XE.grandisW. Hillex. and Neosinocalamus affinis forests, the content of soil organic carbon, total nitrogen, hydrolyzable nitrogen, total potassium, available potassium, total phosphorus and available phosphorus decreased significantly (P <0.05). In 0-40 cm layer the soil, organic carbon were decreased by 2.24 g/kg,6.75 g/kg and 8.62 g/kg. The total nitrogen were reduced by 0.23 g/kg,0.46 g/kg and 0.52 g/kg. Hydrolyzable nitrogen were decreased by 34.01 mg/kg,54.26 mg/kg and 86.96 mg/kg, Total potassium were decreased by 4.99 g/kg,6.10 g/kg and 6.46 g/kg, The available potassium were decreased respectively 20.15 mg/kg,35.47 mg/kg and 44 mg/kg. The total phosphorus decreased by 168.87 mg/kg,241.72 mg/kg and 307.79 mg/kg. The available phosphorus were reduced by 0.55 mg/kg,1.1 mg/kg and 1.57 mg/kg. It shows that the soil nutrient content reduced after secondary forest artificial regeneration.(3)After natural secondary forest artificially regenerate Cryptomeria fortunei, E.urophyllaS.T. Blake×E.grandisW. Hillex. and Neosinocalamus affinis forests, soil microbial biomass C,N were significantly decreased (P< 0.05), but there were no significant differences during the 3 kinds of artificial forest. Compared with the natural secondary forest, the number of bacteria, actinomycetes and fungi of the 3 kinds of artificial forest were decreased, and the number of bacteria of natural secondary forest was significantly higher than the 3 kinds of artificial forest (P<0.05). The number of actinomycetes and fungi of Neosinocalamus affinis forest were significantly lower than the natural secondary forest(P<0.05),but the number of actinomycetes and fungi of Cryptomeria fortunei and E.urophyllaS.T. Blake ×E.grandisW. Hillex forest were not significant between the natural secondary forest.3 kinds of soil microbial quantity relationship in natural secondary forest and three kinds of artificial forests:bacteria> actinomycetes> fungi. bacteria were dominant in 4 kinds of forest stand strains. Soil microbial biomass carbon, nitrogen and the number of bacteria, actinomycetes, fungi quantity were extremely correlated (P< 0.01). This indicated that the soil microbial quantity could better characterize the soil microbial quantity.(4)After natural secondary forest artificially regenerate Cryptomeria fortunei, E.urophyllaS.T. Blake XE.grandisW. Hillex. and Neosinocalamus affinis forests, the soil urease activity, invertase activity and catalase activity were significantly decreased (P< 0.05). In 0-40 cm layer the soil, compared with the natural secondary forest, the urease activity were reduced by 11.74%,24.98% and 42.48% in the Cryptomeria fortunei, E.urophyllaS.T. Blake XE.grandisW. Hillex. and Neosinocalamus affinis forest. The invertase activity were decreased by 30.79%,48.76% and 72.78%, and the catalase activity were reduced by 28.79%,40.77% and 60.15%.(5)Through the correlation analysis during soil nutrient, soil microorganism and soil enzyme activity, it makes clear that each two of them was a significant positive correlation.In summary, after natural secondary forest artificially regenerate Cryptomeria fortunei E.urophyllaS.T. Blake×E.grandisW. Hillex. and Neosinocalamus affinis forests, soil fertility, soil microbial biomass and soil enzyme activity are all reduced. This result has provide a scientific basis for alteration of natural secondary forest and vegetation restoration. |
PDF Full Text Request