【摘要】 根系构型决定根系分布及其对养分和水分的吸收效率,是植物根系与胁迫生境相互适应的结果。采用标准化主轴估计(Standardized major axis estimation, SMA)法,并采用全根挖掘和Win-RHIZO根系分析仪相结合的方法,按照甘肃马先蒿种群密度设置I(10—31株/m~2)、Ⅱ(32—53株/m~2)、Ⅲ(54—75株/m~2)3个样地,研究了尕海湿地不同密度下甘肃马先蒿(Pedicularis kansuensis)根系分叉数与连接数及分支角度的关系。结果表明:随着种群密度由高到低转变,甘肃马先蒿的高度、盖度、地上生物量、根系分叉数及外部连接数逐渐减小,地下生物量、根系内部连接数、分支角度逐渐增大;甘肃马先蒿根系分叉数与内部连接数、外部连接数及分支角度均呈异速生长关系,随着种群密度由高到低转变,甘肃马先蒿根系内部连接数与分支角度增加的速度逐渐大于分叉数与外部连接数减小的速度,根系分叉数与内部连接数的异速斜率逐渐减小,与外部连接数、分支角度的异速斜率逐渐增大。甘肃马先蒿在高密度倾向于密集型根系构型构建模式,在低密度选择扩散型根系生长模式,体现了高寒湿地植物种群应对资源多重竞争的生态适应机制。更多还原

【Abstract】 The root architecture determines the root distribution and the search efficiency of water and nutrients, which is the result of the adaptability of plant roots and stress habitats. The object of this study was to examine the relationship between root forks and link number, branch angle of Pedicularis kansuensis in response to density conditions. The study site was located in Gahai Wetland, Gansu Province, China(102.08°—102.47° E, 33.97°—34.32° N). The altitude of the study site is 3430—3435 m, whereas the average annual temperature is 2.3℃. Sixty samples(1 m×1 m) were set up along the river bank to investigate the density of P. kansuensis in August 2016. Population density was categorized as low(I, 10—31 plant/m~2), medium(II, 32—53 plant/m~2), and high(III, 54—75 plant/m~2). The density, height, coverage, and above-ground biomass of the plant communities were recorded from 1 m × 1 m plots in the three densities with six replications. Thirty plants of P. kansensis were selected; the above-ground parts of those plants were cut while roots were collected by excavating the whole root system, and both were taken back to lab. Afterwards, the soil cores(30 cm × 30 cm × 50 cm) were dug from six grids(30 cm × 30 cm) in three densities. The sieve(mesh size = 0.25 mm) was used to clean the soil core in the nearby river, and the roots were taken to the lab. Afterwards, we adopted a method to stratify sampling(0—50 cm). In the laboratory, the roots were scanned with Win-RHIZO to measure the root forks and link number. The biomasses of different plots were put in an oven(at 105℃ for 30 min) for green removal, and drying(at 80℃ for 12 h), and then measured. Similarly, the soil moisture content was also measured by oven-drying(at 105℃ for 24 h). The results showed that as the population density changed from high-medium to low-medium, the coverage, height and above-ground biomass, root forks and external link number of the P. kansuensis decreased, whereas the below-ground biomass, root internal link number, and branch angle of P. kansuensis increased. The was an allometric relation between the root forks and link number, and branch angle of P. kansuensis. Additionally, the growth speed of the root internal link number and branch angle was greater than the decrease speed of root forks and external link number. The allometric slope of the root forks and external link number decreased, but that of the root forks and internal link number and branch angle increased. With a change in density, the root forks and external link number of P. kansuensis decreased, and the root internal link number and branch angle increased. These results revise the ecological adaptation mechanism of plant populations to multiple resource competitions in alpine wetlands under the restriction of density.更多还原