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• Investigate the root traits of rapeseed of the whole growth cycle in the field. • Root morphological traits are more important for phosphorus uptake and seed yield. • Coarse roots benefit to phosphorus acquisition, served as a scaffold for fine roots. Oilseed rape (Brassica napus L.) is an important crop in China. Although its yields are restricted by phosphorus (P) supply, the response of its root system to P supply has not been explored systematically. This study aimed to investigate the contribution of root morphological and biochemical traits to P acquisition from soils with deficient P (30 kg P 2 O 5 ha−1) and sufficient P (90 kg P 2 O 5 ha−1) supplies in the field at the leaf development, stem elongation, flowering, pod development and ripening stages. The total root length and root surface area in the surface soil (0−10 cm soil layer) were both reduced significantly by decreasing P supply. However, a larger root/shoot ratio and root length ratio were observed in plants with the deficient P supply at the flowering stage. Roots of plants with a deficient P supply also secreted more acid phosphatase and organic acid into the rhizosphere from stem elongation to pod development than plants with a sufficient P supply. Seed yield (SY), shoot dry weight (SDW) and total P content (TPC) were strongly correlated with root morphological traits at the leaf development and flowering stages, especially with the coarse root length (CRL) and root surface area in the surface soil. However, there were no correlations between SDW or TPC and root biochemical traits (rhizosphere pH, acid phosphatase activity and organic acid content). It is hypothesized that greater CRL in the surface soil (0−10 cm soil layer) at the leaf development and flowering stages, served as a scaffold for fine roots, enhancing soil exploration and P acquisition, and, thereby, increasing seed yield. [ABSTRACT FROM AUTHOR]

To explore root architecture and its effects on soil reinforcement of main tree species in typical black soil region, we measured root spatial distribution characteristics, root fractal characte-ristics, and geometric morphological characteristics of Amygdalus triloba , Caragana microphylla , Betula platyphylla , Acer negundo , Picea koraiensis , Pinus sylvestris var . mongolica , using whole root excavation method and WinRHIZO Pro LA2004 root analysis system. All the examined species are distributed widely in typical black soil region. The vertical uprooting force was determined by in-situ uprooting tests. The results showed that inclined roots were dominant in A. triloba , horizontal roots were dominant in C. microphylla , B. platyphylla , A. negundo and P. koraiensis , and the horizontal and vertical distribution of roots were commensurable in P. sylvestris var . mongolica . Except for the total root surface area of B. platyphylla and the total root length of P. koraiensis , the total root length and root surface area of shrub species were significantly greater than those of arbor species, while deciduous broad-leaved trees were significantly larger than coniferous evergreen trees. The total root volume of B. platyphylla was significantly larger than that of C. microphylla , A. negundo , P. koraiensis and P. sylvestris var . mongolica . The root fractal dimension and abundance of A. triloba , C. microphylla , B. platyphylla were significantly higher than those of P. koraiensis and P. sylvestris var . mongolica . The average maximum uprooting force of A. triloba , C. microphylla , and A. negundo was significantly higher than that of B. platyphylla , P. koraiensis , and P. sylvestris var . mongolica . Due to the role of total root length, total root surface area and the number of inclined roots, root system of A. triloba , C. microphylla and A. negundo showed strong soil reinforcement capacity. A. triloba , C. microphylla and A. negundo could be used as the option-preferred tree species when constructing soil and water conservation vegetation in typical black soil region.

To clarify the morphological characteristics of soil preferential flow and the effect of plant roots on its formation, plants from the typical vegetation types of an artificial woodland (Leucaena acacia) and a dry watershed grassland (Heteropogon contortus) of Yuanmou County, Jinsha River were selected as the experimental objects. Based on the staining and tracing method combined with Photoshop CS5 and the Image-Pro Plus 6.0 image processing technology, we analyzed the morphological and distribution characteristics of soil preferential flow under the two planting types and examined the effects of plant roots. We found significant difference in soil preferential flow dyeing area between the woodland and grassland species, and the overall variation trend of the forestland dyeing area ratio decreased with increasing soil depth. The dyeing area of the grassland decreased monotonously with the increases of soil depth. The occurrence degree of soil preferential flow in forest was higher than that of grassland. Root systemaffected the formation of soil preferential flow. At the root diameter ranges of 0≤d≤5 mm and d>10 mm, root length density of the woodland showed a monotonous decreasing trend with increasing soil depth, while in the root diameter range of 5 mm5 mm. The overall change trend of soil preferential flow dyeing area of two vegetation types in the study area decreased with increasing soil depth. Plant root system was closely related to the formation of soil preferential flow. Fine roots could promote while coarse roots may retard the formation of preferential flows.