湘西北小流域不同植被恢复区土壤微生物数量、生物量碳氮及其分形特征

Soil Microbe Quantities,Microbial Carbon and Nitrogen and Fractal Characteristics under Different Vegetation Restoration Patterns in Watershed,Northwest Hunan

研究湘西北女儿寨小流域退化土地马尾松天然林(Ⅰ)、杉木人工林(Ⅱ)、杜仲人工林(Ⅲ)、油桐人工林(Ⅳ)、润楠次生林(Ⅴ)、毛竹杉木混交林(Ⅵ)及荒草灌丛(Ⅶ)7种典型植被恢复模式土壤微生物数量、生物量碳氮及分形特征。结果表明:细菌是土壤微生物的主要类群,数量多达2.153×105～5.60×106cfu·g-1,占全部微生物比例为72.83%～92.77%;其次为放线菌数量,为7.57×104～3.89×105cfu·g-1,所占比例为6.44%～25.61%;真菌数量最少,为4.60×103～4.77×104cfu·g-1,所占比例仅0.79%～1.99%。荒草灌丛模式土壤微生物量碳、微生物量氮含量总体偏低;微生物量碳排序为Ⅴ>Ⅲ>Ⅵ>Ⅳ>Ⅱ>Ⅰ>Ⅶ,各模式依次比荒草灌丛模式高出38.99%～39.67%,30.90%～35.31%,23.86%～26.60%,10.17%～10.24%,5.89%～6.11%,0.27%～1.09%;微生物量氮排序为Ⅴ>Ⅵ>Ⅲ>Ⅱ>Ⅳ>Ⅶ>Ⅰ,除马尾松天然林模式外,其他5种模式土壤微生物量N依次高于荒草灌丛43.46%～44.27%,29.10%～29.60%,22.91%～24.11%,5.20%～5.93%,2.20%～4.45%。微生物量碳与细菌数量空间分布的分形特征最明显(D=5.4465,R=0.6720,P=0.0085),其次为微生物量碳与放线菌数量(D=5.3584,R=0.6391,P=0.0139),再次为微生物量氮与细菌数量(D=3.6874,R=0.5932,P=0.0253),而微生物量氮与土壤放线菌数量的分形模型未达到显著水平(R=0.3321,P=0.2460),微生物量碳、微生物量氮与真菌数量之间均不存在分形关系。

Soil microbe quantities, microbial carbon and nitrogen contents, and their fractal characteristics were studied in seven typical vegetation restoration patterns in Nverzhai watershed in northwest Hunan, including Pinus massoniana natural forest（Ⅰ）, Cunninghamia lanceolata plantation （Ⅱ）, Eucommia ulmoides plantation （Ⅲ）, Verniciafordii plantation （Ⅳ）, Machilus pingii secondary forest（Ⅴ）, Phyllostachys edulis-C, lanceolata mixed forest （Ⅵ）, wasteland-shrub（Ⅶ）. It was found that the bacterial number was 2.153×10^5-5.60×10^6 cfu·g^-1 which was the highest proportion of 72.83%-92.77% in total soil microbe,followed by actinomycial and fungous ones whose number and proportion were 7.57×10^4-3.89×10^5 cfu·g^-1, 6.44%-25.61% and 4.60×10^3-4.77×10^4 cfu·g^-1,0.79%-1.99% respectively. Soil microbial biomass C（MBC） was higher in all the other six forest patterns than in Ⅶ, and ranked as the following： V（38.99%-39.67%） 〉Ⅲ（30.90%-35.31%）〉 Ⅵ（23.86%-26.60%） 〉 Ⅳ（10.17% -10.24%） 〉 Ⅱ（5.89%-6.11%） 〉 I（0.27%-1.09%） 〉 Ⅶ in the soil layer of 0-40 cm. Except for pattern I, soil microbial biomass N（MBN） was higher in the other five forest patterns than that in Ⅶ,with a rank of V（43.46% - 44.27% ） 〉 Ⅵ（29.10% - 29.60%） 〉 Ⅲ（22.91% - 24.11% ） 〉 Ⅱ（5.20% - 5.93 % ） 〉 Ⅳ（2.20 % - 4.45 % ） 〉 Ⅶ. These results showed that MBC and MBN of pattern Ⅶ were lower than that of forest patterns on the whole. There was an obvious fraetal characteristics between MBC and bacterial number （D = 5.4465, R = 0.6720, P = 0.0085） ,followed by MBC and actinomyeial number （ D = 5.3584, R = 0.6391, P = 0.0139）, MBN and bacterial number （D=3.687 4, R =0.593 2, P =0.0253）. However, the fractal model of MBN and aetinomycial number was not significant （ R = 0.3321, P = 0.2460）, and there also did not exist fractal relations for MBC, MBN and fungous number.