不同施氮频度对川西北高寒草甸牧草生长及土壤碳氮的影响

The Influence of Frequency of Nitrogen Addition on Grass Growth and Soil Carbon and Nitrogen in Northwest Sichuan Alpine Meadow

为探究不同施氮频度对川西北高寒草甸牧草生长和土壤碳氮的影响,设置了对照(NC)、低频度施氮(NL)和高频度施氮(NH)等三个不同处理,其中施氮处理分别为等量而不同频度施加氮素(NH4NO3),采取野外观测和实验室分析相结合的方法,分析了施氮频度对高寒草甸土壤环境因子、牧草高度和土壤可溶性有机碳(DOC)、土壤可溶性有机氮(DON)、铵态氮(NH4+-N)和硝态氮(NO3--N)含量的影响及其动态变化。结果表明:(1)施氮显著增加了牧草的高度,与高频施氮相比,低频施氮对牧草高度的影响较大,此外,牧草高度与土壤湿度和导电率呈显著负相关;(2)低频施氮降低了土壤DOC和DON含量,在植物整个生长时期,所有处理的土壤DOC含量呈上升趋势,高寒草甸生态系统表现出DOC的积累,而土壤DON的含量与温度变化一致;(3)低频率施氮对土壤NH4+-N和NO3--N均有影响,而NL处理比NH处理影响显著,在植物整个生长时期,NH4+-N呈先增后降的趋势,而NO3--N则呈一直下降的趋势。综上可知,低频度施氮促进了土壤有机碳氮的矿化。

For studying the influence of the different frequency of nitrogen on pasture growth and soil carbon and nitrogen in northwest Sichuan alpine meadow.This research set up three different treatments:control(NC),low frequency added nitrogen(NL)and high frequency added nitrogen(NH),which means applying equal nitrogen fertilizer in different frequency(NH4 NO3),Adopting the method of combining field observation and laboratory analysis,measuring the pasture height in alpine meadow,soil environmental factors and the content of soil dissolved organic carbon(DOC),soil dissolved organic nitrogen(DON),ammonium nitrogen(NH4+-N)and nitrate nitrogen(NO3--N)dynamic change.The results showed that:(1)nitrogen application significantly increased pasture height,compared with NH treatment,NL treatment had a greater impact on the height of pasture,in addition,the height of pasture was negatively correlated with soil moisture and conductivity;(2)NL treatment reduced soil DOC content,meanwhile,during the whole growth period of pasture,soil DOC content in all treatment showed an upward trend,which showed soil DOC accumulation in alpine meadow ecosystem,however,soil DON content was consistent with the change of soil temperature.(3)Both soil NH4+-N and soil NO3--N were affected by applying nitrogen at a low frequency,while NL treatment had a greater influence than NH treatment.During the whole growth period of pasture,soil NH4+-N shows a trend of increasing first and then decreasing,while NO3--N shows a trend of decreasing all the time.In a words,applying nitrogen in a low frequency promoted the mineralization of soil organic carbon and nitrogen.