Fine Root Distribution Patterns And Seasonal Dynamics Of Poplar Plantation

Fine root, an important part of the forest community, is the most active and sensitive part of root system and the major organ to obtain moisture and nutrients for the plant, meanwhile, it has great absorption surface. Its growth, death, decomposition and turnover play an important role in the nutrient cycling of the forest ecological system. In the past, researches had mainly focused on the vertical distribution of biomass and the relationship to soil nutrient and other factors, in addition specific age was the main basic of these researches, while few researches refer to the comparative research of space distribution features of poplar plantation. root of different ages periods, lacked of necessary study on Characteristics of root distribution and the seasonal dynamics and were short of basis to select afforestation site and improve soil and implement the forest land fertilizer technology.Before the leaves fell in the autumn of2010, this paper took Populus deltoites cv.’Zhonghe-1’in different aged stands in the Yellow River alluvial plain in Shandong province as research object, the improved full root survey method was used to study the space distribution features of fine roots and the EPSON Flatbed Scanner was adopted to analyze fine root parameters which diameter is less than2mm, at the same time, obtaining the root biomass by parching. In2011growth seasons, taking6-aged Europe and America poplar1-107as research object at Dawen river coast, mechanical sampling method was used to survey seasonal dynamics investigation of fine roots every two months (in the same way of spatial distribution of the fine roots), The data of survey were analyzed to explore the distribution rule and seasonal dynamics of the root system of different aged poplar plantations, so as to Provide the basis for the afforestation and fertilizer management.The results of the study showed as followed:(1) Vertical distribution characteristics of the fine root:fine roots of different plantation aged poplar plantation focused between0-20cm soil, biomass decreases gradually with the increase of soil depth, In6aged poplar plantation, the clay layer deposition appear in60cm- 100cm soil layer, where the biomass increased and its distribution showed a concave. Specific root length in0～40cm layers gradually increased, in40cm to80cm layers gradually reduced and then in80cm～100cm soil layer showed the tendency of gradually increase. In3a and9a poplar plantations, the fine roots density, surface area, volume, root tips, forks and fractal dimension in0～60cm of soil declined by degrees, in60cm to100cm layers had the relative stability.(2) The vertical distribution model of fine root in populus: S=AhB(C+Dh+Eh2+Fh3)there was a mathematical model of populus artifical forest fine roots distribution characteristics. Of the equation,letters-A、B、and C、D、E and F were on behalf of empricial coefficients, among them A>0、B>0, but F≠0,letter S indicated fine roots surface area (cm2, dm-3) of unit soil which from the surface to a certain depth. And the h was the soil depth (cm). The size of the parameter B reflected the depth of the maximum fine roots distribution in the soil. Software ORIGIN fitted for statistical analysis and processing of poplar plantations fine roots in the mathematical model (R2=0.9358) by the model we knew that (1) the maximum depth of poplar fine roots was hmax=:104.46cm;(2) the maximum point of poplar fine roots distributed was hp=18.75cm;(3)The maximum depth of the impact of infiltrated water on poplar roots was hq=56.5cm. According to the situation of fine roots vertical distribution, the soil moisture below the surface level can be divided into three parts:0-18.75cm for water active layer,18.75cm-56.5cm for water attenuation layer, and below56.5cm for a relatively stable layer.(3) Features of fine roots horizontal distribution:biomass of fine roots of populus plantation was mainly distributed. in range of0-lm, and the differences of horizontal distribution was significant; biomass of six-year old steadily distributed in range of1m～4m. The specific root length of all the ages had less obvious differences in the horizontal direction. The characteristics of root length density, root number, surface area, volume rendering were basically the same:with the increasing distance from the center of the tree,the determination of indicators such as root length density, root number, surface area and volume of six years old poplar plantation showed a trend first decrease and then increase in ranged of0～4m. But the nine-year-old plantation indicated the opposite situation that was first decreased and then increased.(4) Poplar plantation season development dynamic of fine roots:the seasonal dynamics of poplar fine roots biomass, root length density, root number, root surface area, fine root volume showed an overall bimodal feature, which had two peaks in April and October and one trough in August. After into the summer, the aerial parts showed fast growth, as the nutrients were transported from the roots to the aerial parts, which promoted rapid growth of the grounded part but declined the root growth activity. Before autumn the mechanical fertilization cut off the part of the root system, which could result in root death, and the end peak appeared in August. After fertilization, the root activity showed recovery coupled with fall of poplar leaves, lead to the nutrients storing in the soil surface, so being had a small peak in October. The roots entered into dormancy in winter and simultaneously its activity was reduced.