红豆草与土壤氮含量对大气二氧化碳浓度升高的响应

在封闭的植物培养箱中，通过盆栽实验，研究了红豆草和土壤氮含量对CO₂浓度增加的响应.结果表明，与正常CO₂浓度(355～370 μmol·mol^-1)相比，CO₂浓度升高(700 μmol·mol^-1)，植物生物量增加25.1%(P＜0.01)，但植物体氮浓度降低25.3%(P＜0.001)，植物全氮没有显著的变化.经3个月盆栽实验后，与原始土壤相比，两种CO₂浓度处理土壤全N、NO₃^--N和NH₄⁺-N都有所降低，而土壤微生物氮则显著增加，这可能与植物生长有关.不同CO₂浓度处理土壤NH₄⁺-N浓度基本一致，但在高CO₂浓度下，土壤NO₃^--N浓度显著降低，而微生物生物氮显著增加.对整个土壤-植物系统而言，盆栽实验后，整个系统全氮有少量增加，但变化不显著，特别是在高CO₂浓度条件下，土壤-植物系统全氮最大，这可能与培养材料红豆草为豆科植物，而且在高CO₂浓度下生物量增加，导致氮的固定量增加有关.

Responses of Onobrychis viciaefolia Scop and soil nitrogen contents to elevated atmospheric CO2 concentration

The effects of elevated CO2 on terrestrial ecosystem processes are highly related to the N cycling in the ecosystem. In two closed chambers with different CO2 concentration (ambient CO2 355 - 370 micromol x mol(-1), and elevated CO2 700 micromol x mol(-1)), pot experiments were conducted to study the responses of Onobrychis viciaefolia Scop and soil nitrogen contents to elevated CO2. The results showed that compared with ambient CO2, elevated CO2 increased the plant dry biomass by 25.1% (P < 0.01), but decreased the plant N concentration by 25.3% (P < 0.001), resulting in little change of total plant N. After three months experiment, soil total N, NO3 (-) -N and NH4 (+) -N under both ambient and elevated CO2 conditions decreased, while soil microbial biomass N increased significantly. Soil NH4 (+) -N concentration had little difference under ambient and elevated CO2 conditions, but under elevated CO2 condition, soil NO3 (-) -N concentration decreased significantly, while microbial biomass N increased significantly. By the end of the experiment, the total N content of whole soil-plant ecosystem had a slight increase, especially under elevated CO2 condition, which was probably due to the higher N-fixation capability of O. viciaefolia Scop under CO2 enrichment.