| Ecological redundancy theory was developed in the nineties last century, which attracted many researchers. Some of them are doubtful of this theory, but more and more researchers are probing into it and applying it to solve some ecological problems.Ecological redundancy theory studies mainly on redundant species, the relationship between redundant species and the function of ecosystem, growth redundancy and gene redundancy. Foreign researchers study mainly on redundant species identification, the relationship between redundant species and the stability of ecosystems, the relations between redundant species and the services and function of ecosystems. The research on gene redundancy is also a main field, mainly on the function of redundant gene in evolution. In our country, growth redundancy is mainly studied, using this theory to improve the yield of crops.China is a very big country, there are too many people living here. The total land area of our country is large, but the farm-land area is very small. The average farm-land is only 0.095hm2(according to the land resource communique of PRC, 2003), and it is only 1/4 per capita of the world average. Food is very important to our daily life, and food supply is a big problem. On the limited farm-land, we should improve the unit yield so that we can solve this big problem. Rice is one of the most important crops in our country; it is cultivated in the South and North of China. In recent years, the direct-seeded rice area is expanding, because the direct-seeded rice using less work and less time. The purpose of this research is applying ecological redundancy theory to manage direct-seeded rice, and to improve the yield of direct-seeded rice.There were four research materials: Shanyou 10, Xieyou 63, Xiushui 63 and Yongjing 18. Shanyou 10 and Xieyou 63 belong to hybrid rice; Xiushui 63 and Yongjing 18 belong to conventional rice. Under different density treatments and different water treatments, the tillering and yield of different growing period of the 4 rice varieties were studied. The N, P, K and chlorophyll content of leaves, leaf area and dry weight were mensurated in different growing period. We defined stem and tiller redundancy degree; proposed optimal growth redundancy degree hypothesis (OGRD) and used this experiment to test the hypothesis. Main research results and conclusions of the study are as follows:(l)Draining too early (water treatment) could control the ineffective tillers; but draining too early would adversely affect the growing of rice. Results showed that draining too early could delay the time of reaching highest tiller number; could control some ineffective tillers; could reduce the highest tiller number. Under Wl, some of tillers were dead and at last its effective tiller numbers reduced. So the yield of this treatment was low.(2)Different water treatments had more influence on growth redundancy and little influence on yield. Different density treatments had much more influence on growth redundancy and yield. The water treatment influence on Shanyou 10 and Xiushui 63's growth redundancy reached significant difference level (Sig.=0.05), the earliest water treatment had the lowest growth redundancy. There was not significant difference among water treatments on the yield. The density treatment significantly influenced Shanyou 10 and Yongjing 18's yield and the influence on the growth redundancy degree of the 4 varieties was also significant (Sig.=0.05). The higher the density, the lower the growth redundancy degree.(3)Water treatment had certain influence on growth and physiological characteristics. At tillering period, the N, P and chlorophyll content of leaves under W2 or W3 was lower than underWl and W4. The K content of leaves and dry weights under W2 or W3 was higher than under Wl and W4.The leaf area of hybrid varieties was in the sequence of: W1 |
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