| China has the largest plantation area in the world. With the development and utilize of the plantation, a number of ecological problems(fertility decline, the carbon sink function weakened) were gradual emerged. Forest and Grass Complex mode as a complex ecosystem,the rational use of space resources, is an sustainable land use patterns. Fine roots is the main organs of the plants to absorb water and nutrients, the most active part of the plant underground physiological functions. It is also the most sensitive part of the reaction by soil environment affect. Root has a complex system of branches. Fine root physiological and ecological functions were determined by there location in the root branching system, and the fine root branch plasticity affect the ecosystem level estimates and projections of the distribution of carbon and nutrient cycling. In this paper we collected the fine root by excavation, and we researched the Forest and Grass Complex mode and fertilization on Alnus formosana1-5orders fine root morphological characteristic, biomass and tissue C and N concentrations. By the time, we researched the dynamic changes of fine root in the growing season. The result were showed that:In each mode, the morphological characteristics, biomass, carbon and nitrogen content of fine root showed obvious dynamic of the growing season, but in different modes and different soil layer these features of fine root showed different dynamic trend. Overall, dynamic trend of the1-3orders fine root of the indicators is more consistent, but4,5order fine root performance of another trend. The average diameter of the former three fine root showed a decreasing trend after the first increase in the April-October, and the peak generally appeared in August. The maximum average diameter of the4,5order fine root usually appeared in April, the minimum in October, showed a continued downward trend. The dynamic changes of SRL usually showed in the1-3orders fine root. The SRL of the first order fine root showed a decreased trend after the first increased, and the peak appeared in June. The2,3order fine root showed decrease-increase trend, and the peak appeared in October. The change of SRL of4,5order fine root was very small. The dynamic trend of fine root surface area, biomass, carbon and nitrogen content of the three modes is much more complex, showed a variety of different variation.Forest-grass complex mode had greater impact on the fine root morphological characteristics, biomass, carbon and nitrogen concentrations. The implant of Dactylis glomerata reduced the diameter of Alnus formosanal-4orders fine root in the surface soil while increased the5order fine root diameter in surface soil and the1-5order fine root diameter in subsurface soil. And the analysis of variance showed that the implant of Dactylis glomerata had significant effect (p<0.01) on the surface3,4order fine root diameter and the subsurface1,3,4order fine root diameter. In the surface layer, the surface area of1-4order fine root in Alnus formosana-Dactylis glomerata complex mode were significantly (p<0.01) less than that in natural grass mode, while the fifth order was extremely significantly (p<0.01) greater than natural mode. But in the subsurface layer, all order fine root surface area in Alnus formosana-Dactylis glomerata complex mode were greater than natural grass mode. And except the second order fine root difference was not significant (p>0.05), the remaining orders of fine root surface area differences were highly significant(p<0.01). Whether surface layer or subsurface layer, the SRL of1,2,4,5orders fine root in Alnus formosana-Dactylis glomerata complex mode were great significantly (p<0.01) bigger than that in natural mode. But the third order fine root was smaller than it in natural mode, and the analysis of variance showed that the difference was not significant (p>0.05) in two modes. The research showed that no matter surface layer or subsurface layer, each orders fine root biomass in Alnus formosana-Dactylis glomerata complex mode were bigger than that in natural mode. And the analysis of variance showed that except the subsurface layer3,5orders fine root, planted Dactylis glomerata impacted the rest orders fine root biomass great significantly (p<0.01). And the result showed that carbon and nitrogen content of1-4order fine root in Alnus formosana-Dactylis glomerata complex mode was much bigger than that in natural mode, and the affection was significantly (p<0.05).3. Fertilization reduced the average diameter of alder1-3orders fine root in both soil layer, while increased the average diameter of4,5order fine root. And the result showed that fertilization were very significantly (p<0.01) effected all order fine root in the surface layer. In terms of surface or subsurface, fertilization increased all orders fine root surface area. And except the third order fine root in subsurface layer, fertilization were most significant (p<0.01) effected the others. Fertilization showed different influence in surface layer and subsurface layer. In surface layer, fertilization increased SRL of1,2,3,5orders fine root, but reduced the4order fine root. The analysis of variance showed that fertilization extremely significant (p<0.01) effected the former3order fine root, while not significant (p>0.05) effected the senior order fine root. In subsurface layer, fertilization increased SRL of1,3,5orders fine root, but reduced the2,4order fine root. Analysis of variance showed that fertilization for1,4order fine root SRL affect significantly (p<0.05), the2,3order fine root SRL very significant (p<0.01), and5order fine roots was not significant (p>0.05). Fertilization also improved all orders fine root. The analysis of variance showed that except the subsurface layer3,5orders fine root, fertilization impacted the rest orders fine root biomass great significantly (p<0.01). Fertilization reduced fine root carbon content, but except3,4order fine root in surface layer. The analysis of variance showed that the affect was not significant (p>0.05). Fertilization increased all orders fine root total nitrogen content, and the analysis of variance showed that Forest and Grass Complex mode affect was significant (p<0.05), but the affect of fertilization was not significant (p>0.05). |
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