| Since the industrial revolution, rising atmospheric CO2 concentration and temperature on the effect of farmland ecosystem has became a research hot pot in global climate change.A field experiment was established and managed with experimental warming plus Free-Air Carbon dioxide Enrichment experiment. Three treatments were ① elevated atmospheric CO2 concentration to 500 ppm(CE);②ambient+2℃(WA);③elevated atmospheric CO2 concentration to 500 ppm, ambient+2℃(CW),normal atmospheric environment for comparison(CK),to study the influence of the elevated atmospheric CO2 concentration and temperature, and both on soil nematode community structure and the enzyme activity in paddy soil. The main results are as follows:(1) The effect of simulated climate change on the impact of different soil nematode are different. The Acrobeloides and Hirschmanniella are the dominant population in the rice season, the abundance of them were 10.6%-23.4% and 15.4%-34.4%.The abundance of Filenchus and Acrobeloides were increased by 54.7%-187.3%,48.9%-241.8% and 15.2%-110.8%.25.5%-41.1% compared with control in treatment CE and CW.Compared with the control, the abundance of Ditylenchus increased by 61.2%,63.2% in the treatment WA; the abundance of Mesodorylaimus increased by 25.6%、130.0% in the treatment CW. But the abundance of Cephalobus decreased by 36.8%、64.7% and 41.1%、41.1% in the treatment CE and CW. In the treatment CE, the abundance of Hirschmanniella decreased by 13.5%、25.3%. The Cephalobus and Hirschmanniella are the dominant population in the rice season, the abundance of them were 14.4%-23.7% and 10.5%-24.6%. The abundance of Filenchus increased by 242.0% in the treatment WA; the abundance of Eucephalobus and Cephalobus increased by 63.7% and 41.1% in the treatment CW; the abundance of Hirschmanniella and Acrobeloides increased by 78.0%、93.7% and 82.1% and 42.9% in the treatment CE and CW.(2) The effect of simulated climate change have a certain influence on the total number of soil nematode. Compared with the control, the number of soil nematode increased by 55.7%-127.6% and 92.3%-117.8% in the treatment CW and WA in the rice season; in the wheat season, the number increased by 67.9% in the treatment WA. Thus, in both upland and paddy field, temperature can significantly increase the number of soil nematode.(3) The effect of simulated climate change affect the nutritional proportion of soil nematode. Bacterivore and Plant-Parasites are the dominant population in this field, their abundance reach 80%. Proportion of Bacterivores and Fungivores is stable. A big increase was in Plant-Parasites, the abundance in rice season of 2012 was 23.3%-37.3%, but 39.4%-47.3% in year of 2013,increased about 10%.The abundance of Predators-Omnivore has a large decline, from 9.3%-17.5% in 2012 to 1.8%-6.5% in 2013.Thus it can be seen, The simulated climate change have a big influence in Plant-Parasites and Predators-Omnivore.(4) In the rice season of year 2012, the PPI decreased 10.1% and 9.4% in the treatment CE and CW; there was no significant difference between treatment WA and control; In the wheat season of year 2013, the PPI significantly decreased 10.7% in treatment CW and significantly increased 13.9% in the treatment WA. While in the rice season of year 2013, there was no significant difference compared with control. MI has no significant difference in rice and wheat season, indicate that The simulated climate change have a little effect on MI.(5) The simulated climate change have a effect on soil enzyme activity in rice and wheat season. To Urease enzyme activity, it increased by 21.4% and 22.6% in the treatment CW and WA of heading stage in wheat season; in the rice season, it increased 21.1%.24.1%, 12.4% and 27.0%.50.8%.36.9% in the treatment CE. C W and WA of heading stage and ripening stage. To Invertase enzyme activity, in the treatment CE. CW and WA, it increased 48.7%,84.5% .60.3% in the ripening stage of wheat season, and increased 39.4%,64.8%. 60.8% in the tillering stage of rice season. To Alkaline phosphatase enzyme activity,it increased 66.4%.70.6% and 39.6% in the treatment CE. CW and WA in the tillering stage of rice season; in the heading stage, it increased 58.6%,103.4% and 56.9%; in the ripening stage, it increased 52.9% in CW. |
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