米槠天然林土壤真菌对N_2O产生的贡献

Fungal Contribution to N_2O Production in Soil for a Natural Castanopsis carlesii Forest in Wuyi Nature Reserve,Southeastern China

研究表明亚热带地区森林土壤硝化和反硝化能力都非常低,但却是全球N2O最大的自然源之一,因而推测极有可能存在N2O潜在源未被认识,有迹象表明真菌最有可能是这一潜在源的贡献者,但实际研究证据并不多.为此本研究以中亚热带地区典型常绿阔叶林———武夷山自然保护区米槠天然林土壤为对象,利用室内基质诱导呼吸选择抑制方法,研究在水分60%WHC和温度25℃条件下土壤真菌细菌活性比及其对N2O产生的相对贡献.结果显示真菌和细菌的活性比例分别是0.7±0.3和0.3±0.1,前者显著大于后者(P<0.05),真菌与细菌的活性比为2.00±1.00;与对照相比,添加放线菌酮(真菌抑制剂)处理N2O产生速率减少了50.8±11.3%,添加链霉素(细菌抑制剂)处理则减少了43.7±11.8%,前者减少是后者的1.15倍,但差异不显著.研究结果表明该米槠天然林土壤在给定实验条件下真菌活性比细菌的大,但二者对土壤N2O产生的贡献几乎相等.基质诱导呼吸选择抑制方法具有较多的限制条件,若得出可靠结论,还应该利用包括生物化学、分子生物学方法在内的多种方法进行相互验证.同时今后应加强真菌产生N2O途径及机理研究.

For more than a century, bacteria has been believed a major contributor to N2O emission in soil, through nitrification and denitrification, but recent researches indicate that fungi has denitrifica-tion and codenitrification capacity for soil N2O emission. Meanwhile fungi can simuhaneously perform denitrfication under micro anaerobic or aerobic conditions, yet mechanisms of N2 O emission by fungi is still not very clear. For this issue, Selective Substrate-Induced Respiration inhibition techniques wereused to investigate fungat and bacterial biomass and determine N2O production during biotic pathways in the soil of natural Castanopsis carlesii forest of Wuyi Nature Reserve at 60% WHC. The results show that the proportion of fungal and bacterial activity are 0. 7 ± 0. 3 and 0. 3 ± 0. 1 respectively, with the former significantly greater than the latter （P 〈 0. 05 ）. The ratio of fungal and bacterial activity was 2.00 ± 1.00, indicating that fungi biomass in subtropical soils is larger than bacteria. Meanwhile Cycloheximide decreased the flux of N2O by 50. 8 ± 11.3% and streptomycin decreased the flux of N2O by 43.7 ± 11.8 %, compared with the control, the former is not significantly greater than the lat-ter which demonstrated that contributions of N2O production from the fungi and bacteria are almost equal. Further research into the use of sir will be combined with a variety of methods, such as biochemistry and molecular biology methods. At the same time study on mechanisms of N2O produc-tion and fungal N2O production should be strengthened.