垂直方向磷素竞争对杉木根系生长及生物量分配的影响

针对自然环境中有效磷养分主要分布于土壤表层而容易导致植物根系激烈竞争的问题,选择同一杉木(Cunninghamia lanceolata)无性系幼苗为研究对象,采用水平方向空间狭小而垂直方向空间大的室内盆栽模拟装置,以单株种植为对照,构建双株种植的竞争处理,通过设置3个供磷水平:不供磷处理(0 mg/kg KH_2PO_4)、低磷处理(6 mg/kg KH_2PO_4)和正常供磷处理(12 mg/kg KH_2PO_4),采用破坏性试验方式收获,分别在试验的前期(50 d)、中期(100 d)和后期(150 d)测定不同处理条件下杉木幼苗根系生物量与根系形态的变化,研究邻株杉木根系在垂直方向上对有限磷素资源的竞争策略。结果表明:竞争处理和供磷水平对杉木幼苗根系长度、平均直径等形态指标的影响存在交互作用(P0.05),对杉木幼苗生物量分配、比根长等指标的影响均不存在明显的交互作用(P0.05)。竞争处理中杉木根系形态增量均明显高于非竞争处理的单株幼苗,且随着胁迫时间的增加,根系形态增量均呈现显著的上升趋势,其中在胁迫中期和后期的增量明显高于前期,且邻株竞争处理明显提高了杉木的比根长,提升了根系觅磷的能力;随着供磷水平的提高,根表面积和根体积增量大体上呈现先上升后下降的趋势。与非竞争处理相比,竞争条件下杉木地上部生物积累量差异不明显,而根系生物量、根冠比均低于非竞争处理的单株幼苗。

Effects of vertical phosphorus competition on root growth and biomass distribution of Chinese fir seedlings

This study was conducted to solve the problem of available phosphorus, which is mainly distributed on the soil surface and easily leads to the severe P competition of plant roots in natural environments. The morphological competition strategy of limited P resources in the vertical direction of adjacent Chinese fir roots was studied by measuring the changes in the root biomass and morphology of Chinese fir seedlings under different treatment conditions. The experiment was performed in a greenhouse at Fujian Agriculture and Forestry University using a Chinese fir clone "YANG-020". Specially designed glass pots 10 cm long, 10 cm wide, and 40 cm high were prepared for the P stress and competition simulation. Two seedlings were planted in each pot, except for the control which contained a single seedling in the center of all the pot. All the treatments were performed using three P treatment levels, i.e., no, low, and normal P treatment (0, 6, and 12 mg/kg KH₂PO₄, respectively). The seedlings of each treatment were harvested separately at the prime, interim, and last stages (September 9, October 30, and December 19, 2013, respectively) to determine the shoot biomass, root:shoot ratio, and root biomass, after determining the root length, surface area, mean diameter, and volume increment over the entire experimental period. According to the results, obvious effects of the interactions between the competitive and P treatments were observed on the root morphology (P < 0.05), root length, and the average diameter of root morphology of Chinese fir seedlings. However, no apparent effects of the interactions between the competitive treatment and P supply on the biomass allocation were observed (P > 0.05) in the specific root length of Chinese fir seedlings. Competition in processing Chinese fir root morphology and growth was significantly higher than that of non-competition processing in single plant seedlings, and with increasing stress time, the growth and root morphology tended to increase significantly. In the early stage of stress, the growth at the period at the middle and cessation was obviously higher than that at the onset. Moreover, the competitive treatment of adjacent plants significantly improved the specific root length of the Chinese fir and improved their ability to actively seek P in the root system. The root surface area and volume increment generally increased and then tended to decrease with increasing P level in the soil. Compared with non-competition treatment, the biomass accumulation of Chinese fir was not obvious, whereas the root biomass and root:shoot ratio were lower than that of non-competitive single seedlings were.