| Fine root is not only the most vigorous life activities part and the fastest turnover rate of tree roots, but also is one of the important factors of material cycle and energy flow in ecological system. When the distributions of energy and material among orders and different diameter in fine roots are differences, the production, turnover and eco-physiological function also can not be the same. To get the maximum soil nutrient, both morphology and physiology of fine roots have high plasticity. Change of fine root color is an important biological phenomenon; different colors represent the different stages of growth and development. Study the influence of fertilization on root morphology and distribution of carbon and nitrogen is helpful to reveal the response of fine root on soil resources change, and it is of great significance to understand the adaptation strategy of fine root when soil resources changing and material circulation, energy flow in forest ecological system accurately. In this study we chose five-year-old poplars I-107 (Populus x euramericana cv.’74/76’) in hilly region in Sichuan central as the research object. Through fertilization (nitrogen fertilizer, compound fertilizer) in March and contrast, researched the change of rhizosphere soil nutrients (total nitrogen, hydrolyze nitrogen, total phosphorus, effective phosphorus, total potassium, available potassium, microbial biomass carbon and nitrogen), first order fine root morphology (diameter, root length, root length density) in different colors (white, yellow, brown), carbon and nitrogen allocation patterns (total nitrogen, total carbon, non-structural carbon, soluble protein) and anatomical structure of July (fine root cortex thickness, vascular cylinder diameter) response to fertilizer application during fine root growth rapidly period (May, July, September). The results of the study are as follows:(1)The effects of fertilizer treatments of rhizosphere soil total nitrogen and hydrolysis nitrogen concentration higher than that of control, while hydrolysis nitrogen concentration of May and July was significantly differed (P<0.05); Effective phosphorus content was lower than those of contrast, besides the compound fertilizers plot, the differences were significant (P<0.05); The total potassium content of the treatments was not significant between the groups (P>0.05), with time pass on rapidly-available potassium content differences was in narrow fertilization. In May and July, of the rhizosphere soil microbial biomass carbon and nitrogen as the contrast, nitrogen treatment, compound fertilizer processing gradually reduced, and the difference of fertilizer treatment reached the significant level (P<0.05).(2)Biomass after fertilization of thelst of fine roots in September than in the control outside the low fertilizer treatment. July fertilizer processing biomass was significantly lower (P<0.05); white, yellow colour fine roots of the 1st at different treatment had different biomass, July white, brown fine roots biomass was significantly higher than that of the brown (P<0.05), brown fine root biomass in fine roots growing period, gradually increasing over time; in growth fine root biomass exuberant period showed a single peak, July was the highest in September next.(3) Fertilizer treatments in May and September 1 level of fine roots diameter were higher than the control, may the fine roots between the same color differences reached the significant level (P< 0.05). In July, in addition to the white fine roots with nitrogen treatment, the control of the same color fine root diameter significantly higher fertilization treatment (P< 0.05). In May, the control of specific root length of the brown and white fine roots were significantly higher than fertilization treatments (P<0.05), and in July and September, fertilization treatment was higher than control, except the white fine roots in July had reached significant level (P< 0.05). Fertilization treatments might deal with yellow fine roots of specific root length was significantly higher than other colors, but in July, the white and yellow fine root was significantly higher than brown (P< 0.05). Similar to specific root length the white and brown fine root length density was relatively high fertilizer treatment, and the control and nitrogen treatment reached the significant level (P< 0.05). The nitrogen treatment in July of root length density was significantly lower than control (P< 0.05). However, September fertilization treatment of root length density were significantly higher than that of controls (P< 0.05).July fertilizer treatments of yellow and brown level 1 fine root cortex thickness were higher than the control, the control white fine root cortex thickness was relatively high fertilization, and the differences reached significant level (P< 0.05). Nitrogen treatment 3 kinds of color first order fine root vascular cylinder diameter was higher than control and compound fertilizer with corresponding color, fine root and there was to no significant difference compared with yellow fine roots (P> 0.05),but the others reached significant level (P< 0.05).(4) In May, when the fine root biomass and root length density was low, the fine roots of organic carbon content was higher, and yellow and brown fine root were significantly higher than white fine organic carbon content (P< 0.05), and in September the difference were not significant (P> 0.05). Except for the brown fine roots in May, fine root total nitrogen concentration was also significantly higher than that of controls (P< 0.05). Along with the color deepening fine roots of non-structural carbon and soluble protein reduced gradually, and the difference between white and brown reached the significant level (P< 0.05), Non-structural carbon of fine root with same color in July and September, reduced with contrast, nitrogen fertilizer, compound fertilizer processing gradually reduce, soluble protein content increase.(5) The total nitrogen, organic carbon of fine root and hydrolyzable nitrogen of soil was significantly positive correlation (R2=0.445 R2=0.725, P<0.01), soluble protein and non-structural carbon and hydrolysis of soil nitrogen and soil organic carbon was significantly negative correlation (R2=0.677 R2=0.647 R2=0.464 R2=0.655, P<0.05). Root of organic carbon and soil organic carbon, soil total phosphorus was positively correlation (R2=0.861 R2=0.501, P<0.01), and rhizosphere soil microbial biomass carbon negative correlation (R2=0.408, P<0.05). And the soluble protein fine root and microbial biomass carbon and nitrogen were significantly positive correlation (R2=0.528 R2=0.692, P<0.01).As one of the major management measures for plantations, fertilization could influence the form of fine root morphology and physiological activity by changing the soil effective resources, and the influences were different on different color fine root growth and distribution pattern.the fine root research on this aspect can be a deeper understanding ef fine root on the response mechanism of fertilization:(1)The different fertilization change with the spatial heterogeneity of soil nutrients and effectiveness did not agree, level 1 fine root through fine root morphological plasticity keep efficient utilization of soil nutrients, so that the fine root morphology performance of different treatment has the difference; (2)Fertilization can affect plant carbon distribution pattern of underground part, and plant can make a new adjustment to adapt to the balance of Assigned to the underground part for root growth of "source-sink"; (3) In the fine roots activity apparent, providing sufficient nitrogen source by fertilization can improve the absorption function of fine root and the utilization of available nutrients; (4) The different fertilization practices influence carbon allocation proportion of different part of aerial part and underground part, and different function fine root of underground part, after the carbon sequestration the difference carbon allocation on nodes and ratio for the carbon cycle has difference significance. |
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