Effects Of Simulated Warming And Nitrogen Deposition On The Characteristics Of Leymus Chinensis Community And Reproductive Phenophase

Global warming and nitrogen deposition are the crucial problems that people are faced with nowadays. We used infrared ray heat instrument to simulate the effects of global warming and nitrogen deposition on community structure and constructive species reproductive phenophase of Leymus chinensis in songnen plain.This study indicated that the dominant species order of important value are: Leymus chinensis,Kalimeris integrifolia,Carex duriuscula and Phragmites australis. In the whole growing season, the important value of L. chinensis declined but then enhanced and finally decreased, whereas the important value of K. integrifolia,C. duriuscula and P. australis increased in the beginning and reduced in the later when carry through warming, nitrogen addition and warming with nitrogen addition treatment.In the lower temperature, the Shannon-Wiener index (SWI) of community could be increased after warming. In the case of more rainfall, SWI of community reduced, which was due to importance value of L. chinensis enhanced after nitrogen addition. It shows that the competition ability of L. chinensis will increase after fertilizer N if rainfall was sufficient. The interaction of warming and nitrogen addition declined the species evenness index significantly in June and August. We summarized that in the case of deficient rainfall, the species number would increased owing to negative effect of dominance species after warming. But at the time of sufficient rainfall, the species number will decreased because of the dominance species have more competition ability under fertilize nitrogen condition.In all observational period, the effects of nitrogen on aboveground biomass and underground biomass of L. chinensis community are significant, which is more significantly in the period of sufficient rainfall. Lower temperature could be advantageous condition on enhancement of underground biomass. That is, nitrogen with rainfall and temperature with rainfall have cooperative effects on aboveground biomass of L. chinensis community.The phenophase marks of L. chinensis decreased with the treatment of warming and warming with nitrogen addition from 5, June to 7, August. It means that phenophase of L. chinensis delayed in this period. After warming and warming with nitrogen addition, the marks of K. integrifolia have increased from 14, August to 28, August. It indicated that the phenopase of K. integrifolia has advanced in this period. The phenophase marks of P. australis increased after treatment of warming, nitrogen addition and warming with nitrogen addition since 4, September to 18, September. It shows that phenopase of P. australis has advanced.