Vertical Distribution And Seasonal Dynamics Of Fine Roots In Populus Euphratica Plantation In The Extreme Drought Area

It is important to know the growth characteristics of fine roots for riching underground ecology research. The objective of this study was to investigate the vertical distribution and seasonal dynamics of fine rootsof Populus euphratica, the only forest tree species in the desert area, in a natural forest in the extreme drought area of Ejina, inner Mongolia. The minirhizotron technique was used to study the growth of fine roots of populous. Based on the data obtained during the growing season (from April to September) in 2013, we analyzed the spatial-temporal patterns of fine root length density (RLD, mm · cm-2), fine root surface area density (RAD, mm2 · cm-2), fine root growth rate(RLDg, mm · cm-2·d-1; RADg, mm2 · cm-2 · d-1), fine root death rate(RLDd, mm·cm-2 ·d-1; RADd, mm2 · cm-2 · d-1) and ratio of growth to death(RLDgd, RADgd), and explored the relationships of RLDg, RADg, RLDd and RADd with the environment factors (soil temperature and soil water content). The results showed that (1) the maximum value of RLD and RAD appeared in 0-20 cm soil layer while the minimum value in 40～60 cm or 60～80 cm soil layer in the 80 cm soil profile in general. There were significant differences (P< 0.05) between 0-20 cm soil layer and other soil layers in the value of RLD and RAD. (2) The average RLDg, RADg, RLDgd and RADgd in the top soil layer (0～40 cm) were all higher than in the deep soil layer (40～80 cm) in the growth season. (3)As a whole, the RLD, RAD, RLDg and RADg showed a common seasonal trend with the peak value in the middle period of growing season. The RLDd and RADd increased gradually in the growth season. The RLDgd(RADgd) decreased gradually from April to September and fell to<1 at the end of the growing season. (4)The seasonal changes of RLDg, RADg, RLDd and RADd were significantly and positively correlated with soil temperature (P<0.01). There were significant correlations between seasonal trends of RLDg(RADg) and soil water content (P<0.01). However, the seasonal changes of RLDd (RADd) were not significantly correlated with soil water content (P> 0.05). (5)Applying a certain amount of nitrogen and phosphorus can obviously promote the growth of Populus fine roots.