季节性冻融期间五台山典型植被土壤氮矿化特征

Soil nitrogen mineralization characteristics of typical vegetations of Wutai Mountain during seasonal freeze-thaw period

针对气候变暖、土壤季节性冻融格局改变对高山地区土壤氮矿化过程的影响,采用土壤原位培养法,研究五台山林线附近草甸(CD)、华北落叶松(HL)和云杉(YS)等典型植被群落土壤氮矿化特征。结果表明:各群落土壤铵态氮含量大于硝态氮含量。CD土壤矿质氮总量(铵态氮+硝态氮)在冻结初期减少,深冻期增加,融化期减少,生长季增加。HL和YS土壤矿质氮总量在冻结初期减少,深冻期到生长季一直增加。各群落土壤净氮矿化量和净氮矿化速率在冻结初期到深冻期增加,融化期降低,生长季增加。HL和YS之间土壤矿质氮总量、土壤净氮矿化量和净氮矿化速率始终无显著差异,CD与HL(p<0.05)、YS(p<0.05)之间存在显著差异。季节性冻融期各群落土壤净氮矿化量和净氮矿化速率低于生长季,但也表现出明显的矿化作用。在整个培养期内(季节性冻融期+生长季),HL供氮能力最强,YS次之,CD最弱。冻融循环可促进土壤氮矿化,增加土壤矿质氮含量,为春季植物生长提供了必要的营养物质,但这一过程也增加了土壤氮素的流失风险。研究成果对高山生态系统土壤氮矿化的研究提供参考。

Aiming at the impacts from climate warming and change of seasonal soil freeze-thaw pattern on the process of the soil nitrogen mineralization in alpine region,the soil nitrogen mineralization characteristics of the typical vegetation communities near the timberline of Wutai Mountain,such as meadow（ CD）,Larix principis-rupprechtii（ HL）,Picea meyeri（ YS）,etc.,are studied herein with the in-situ soil cultivation method. The result shows that the contents of NH4~＋ of all the communities are larger than those of NO3^-. The total amount of the soil mineral nitrogen content（ NH4~＋＋ NO3^-） of CD decreases in the onset of freezing period,increases in the deep freezing period,decreases in the thawing period and increases in the growing season. The total amounts of the soil mineral nitrogen contents of HL and YS decrease in the onset of freezing period and increase all along from the deep freezing period to the growing period. The net rates and amounts of the soil nitrogen mineralization of all the communities increase in the deep freezing period,decrease in the thawing period and increase in the growing period. No obvious differences are all along there between the total amounts of the soil mineral nitrogen and the net rates and amounts of the soil nitrogen mineralization of both HL and YS,while significant differences are there between CD and HL（ p〈0. 05） and YS（ p〈0. 05）. The net rates and amounts of soil nitrogen mineralization of all the communities in the seasonal freeze-thaw period are lower than those in the growing period,but significant mineralizations exhibit as well. During the whole cultivation period（ from freeze-thaw period to growing season）,the nitrogen supply capability of HL is strongest,YS is the secondary and CD is the weakest. The freeze-thaw cycle can promote the soil nitrogen mineralization and increase the content of soil mineral nitrogen,thus provide the essential nutrients for the growth of plant in spring; however,this process also increases the risk of nutrients loss from soil. The study result provides a reference for the study on the soil nitrogen mineralization of ecosystem of alpine region.