Bakker M R, Jolicoeur E, Trichet P, Augusto L, Plassard C, Guinberteau J, Loustau D
ENITA de Bordeaux, UMR 1220 TCEM, F-33883 Villenave d'Ornon, France.
Tree Physiol. 2009 Feb;29(2):229-38. doi: 10.1093/treephys/tpn020. Epub 2008 Dec 5.
Effects of fertilization and irrigation on fine roots and fungal hyphae were studied in 13-year-old maritime pine (Pinus pinaster Aït. in Soland), 7 years after the initiation of the treatments. The fertilization trials consisted of a phosphorus treatment, a complete fertilizer treatment (N, P, K, Ca and Mg), and an unfertilized treatment (control). Fertilizers were applied annually and were adjusted according to foliar target values. Two irrigation regimes (no irrigation and irrigation of a set amount each day) were applied from May to October. Root samples to depths of 120 cm were collected in summer of 2005, and the biomass of small roots (diameter 2-20 mm) and fine roots (diameter </= 2 mm) and fine root morphology were assessed. Biomass and length of hyphae were studied by a mesh ingrowth bag technique. Total fine root biomass in the litter and in the 0-120 cm soil profile ranged between 111 and 296 g m(-2). Results derived from the measurements of biomass and root length, or root area, showed that both fertilizer treatments reduced the size of the fine root system, especially in the top soil layers, but did not affect small roots. Compared with control treatments, fine root morphology was affected by both fertilizer treatments with the fine roots having increased specific root length/area, and irrigation tended to reinforce this finer morphology. The amount of hyphae in the mesh ingrowth bags was higher in the fertilization and irrigation treatments than in the controls, suggesting further extension of the root system (ectomycorrhizal infection) and thus of the uptake system. Irrigation had no significant effect on the size of the fine root system, but resulted in a shallower rooting system. Total root to shoot ratios were unaffected by the treatments, but fine root mass:needle mass and fine root area index:leaf area index ratios decreased with increasing nutrient supply. Overall, compared with the control fine roots, increased nutrient supply resulted in a lower fine root biomass but the dynamic fraction of the finest roots was greater. Irrigation had only limited effects on fine root size, distribution and morphology.
在处理开始7年后，对13年生的海岸松（Pinus pinaster Aït. in Soland）施肥和灌溉对细根及真菌菌丝的影响进行了研究。施肥试验包括磷处理、完全肥料处理（氮、磷、钾、钙和镁）以及未施肥处理（对照）。肥料每年施用，并根据叶片目标值进行调整。从5月到10月采用两种灌溉方式（不灌溉和每天固定量灌溉）。2005年夏季采集了深度达120厘米的根系样本，并评估了小根（直径2 - 20毫米）和细根（直径≤2毫米）的生物量以及细根形态。通过网袋法研究了菌丝的生物量和长度。凋落物层及0 - 120厘米土壤剖面中的细根总生物量在111至296克/平方米之间。生物量、根长或根面积测量结果表明，两种施肥处理均减小了细根系统的大小，尤其是在表层土壤中，但对小根没有影响。与对照处理相比，两种施肥处理均影响了细根形态，细根的比根长/面积增加，灌溉倾向于强化这种更细的形态。网袋中的菌丝量在施肥和灌溉处理中高于对照，表明根系（外生菌根感染）进而吸收系统有进一步扩展。灌溉对细根系统大小没有显著影响，但导致根系分布变浅。处理对总根冠比没有影响，但细根质量：针叶质量比和细根面积指数：叶面积指数比随养分供应增加而降低。总体而言，与对照细根相比，养分供应增加导致细根生物量降低，但最细根的动态部分更大。灌溉对细根大小、分布和形态的影响有限。
