持续碳源添加对油松和连香树林地土壤氮转化的影响

Effect of Continuous Glucose Addition on Soil N Transformation of the Pinus tabulaeformis and Cercidiphyllum japonicum Plantations

采用室内培养方法研究了持续添加不同浓度葡萄糖溶液(0、75、150和225μg g-1,以土壤中C浓度计,下同)对不同养分状况的油松和连香树林地土壤氮转化过程的影响.结果显示,在培养的56 d里,持续添加75μg g-1的葡萄糖溶液有效促进了油松林土壤氮净矿化,持续添加150μg g-1的葡萄糖溶液在培养后期促进了油松林土壤氮净矿化,而持续添加225μg g-1的葡萄糖溶液在整个培养期内显著抑制油松林土壤氮净矿化.3个浓度的碳源持续添加处理均降低了油松林土壤可溶性有机氮含量,仅在第56天时,高浓度碳添加处理油松林土壤可溶性有机氮与对照处理差异不显著.3个浓度的碳源持续添加处理对油松林土壤微生物量氮变化的影响有所不同.对于连香树林土壤,3个浓度的碳源持续添加处理均显著促进了氮的净矿化,在培养后期不同程度地增加了可溶性有机氮的含量.研究结果表明不同林地土壤氮转化对持续外加可溶性碳源的响应过程有所不同,养分状况较差的土壤的响应模式更为复杂.

The glucose solution with different concentrations （0, 75, 150 and 225 gg C g-1 soil） were continuously added into the soil samples collected from the adjacent Pinus tabulaeformis and Cercidiphyllumjaponicum plantations in the upper reaches of Minjiang River. NH4-N, NO[-N, total dissolved nitrogen （TDN）, microbial biomass carbon （MBC）, microbial biomass nitrogen （MBN）, dissolved organic nitrogen （DON）, and net N mineralization rate in the treated soil were determined. For P. tabulaeformis plantation, the addition of 75 μg C g-1soil promoted the net soil N mineralization throughout the 56-day incubation; the 150 gg C gt soil C addition only enhanced the net N mineralization after 14 days of the addition and the 225 ktg C g-1 soil C addition restrained the net N mineralization during the whole incubation period. All glucose addition treatments decreased soil DON content of the P. tabulaeformis plantation, with exception of the 56th day, when the soil DON content showed no significant differences between the 225 μg C g-1 soil treatment and the control. Soil MBN of the P. tabulaeformis plantation in different glucose addition treatments developed different changing tendency over time. For the C. japonicum plantation, the net soil N mineralization was increased by glucose addition of all the three concentrations. At the end of this experiment, soil DON content of the C. japonicum plantation increased under all glucose addition treatments. The above results suggested that the responses of nitrogen transformation in forest soils to continuous addition of dissolved carbon vary with forest soil fertility, with the response much more complex in the nutrient-poor forest soil than in the nutrient-rich one. Fig 6, Tab 1, Ref 38