Effects Of Warming And Nitrogen Deposition On The Underground Biomass Of Leymus Chinensis Community

Nowadays, the Global Warming and Nitrogen Deposition have become the twomain ecological problems for human beings. Temperature and nitrogen are the twolimiting factors for the growth of plants, which may have great influence on theunderground biomass of natural communities. The author research the responses ofLeymus chinensis community in Songnen Plain by imitating the warming and nitrogendeposition. Our purpose here is to report on underground biomass responses.We found significant positive responses to warming and nitrogen addition forLeymus chinensis community in terms of underground biomass in different depths.In the whole grow season, the change of underground biomass goes this way,comparison<heating≤nitrogen<heating and nitrogen., Warming significantly increasedunderground biomass in the low temperature months but had no effect on it in thehigh temperature months. Nitrogen enhanced underground biomass in moreprecipitation months, while decreased in the dry months. On the other hand, warmingand nitrogen addition is significant to the plant growth. Thus, nitrogen andprecipitation, temperature and precipitation are synergistic effect to the undergroundbiomass on Songnen Plain.In the whole observation period, with the help of simulated greenhouse effect andnitrogen, the underground biomass is being tested and analyzed. The result shows thatthe root biomass on Songnen Plain grow more with the longer growing time. The rootin vertical distribution is in the typical surface accumulation type, which isaccumulated between0-10cm and10-20cm earth surface.The results show that the underground biomass of Leymus chinensis communityin Songnen Grassland takes an obvious upward trend with the extension of growingseason. The root vertical space distribution is characterized by surface accumulationtype, which mainly distributed in0-10cm and10-20cm soil surface. To the soil depthof0-10cm and10-20cm, the change of underground biomass has reached a significantlevel (P <0.05) only in the year2010and2011both for July and September with fourtreatments of comparison, heating, nitrogen and the interaction of heating andnitrogen. And with the same condition in different months, the changes show in theclear unimodal shape. In general, there is solid increase in June, July and August. Itreaches the top in September, and gradually goes down in October. The root growthhas adaptability. Warming and nitrogen addition in long term would lead to themonthly dynamic stability of underground biomass. With the same condition but indifferent years, in June, July and August, the underground biomass in2010is less thanin2011, and the trend is accumulated each year. There was no difference in underground biomass in different years. In summary, warming and nitrogen additionhad an improving effect on underground biomass in Leymus chinensis grassland.