Quantitative imaging of infiltration, root growth, and root water uptake via neutron radiography
Quantitative imaging of infiltration, root growth, and root water uptake via neutron radiography
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DOI：
10.2136/vzj2007.0156
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发表时间：
2008-08-01
影响因子：
2.8
通讯作者：
Schulin, Rainer
中科院分区：
文献类型：
--
作者：
Oswald, Sascha E.;Menon, Manoj;Schulin, Rainer
植被土壤水分入渗受土壤性质和植物活动相互作用的影响。植物根系的吸水量取决于土壤的水力性质和入渗速率。反过来，根是重要的水分运送器，导致水分含量分布不均匀，从而影响入渗率。我们的目标是使用中子照相术来研究快速入渗事件和随后的水分再分配过程中的根系水分吸收情况。中子照相是一种成像技术，能够以高空间和时间分辨率测量根部密度、土壤结构和根部附近的水分分布。我们使用时间序列中子照相技术对0.17x0.15x0.013米盒子中的渗透事件进行了成像，盒子里装满了沙子混合物和羽扇豆(Lupinus L.)或玉米(Zea Mays L.)植物。我们在植物生长的两个阶段测量了四个重复。中子照相技术能够以高精度和高时空分辨率探测到水分的微小变化。由于根的高含水率，在入渗前的X线片上很容易看到根。在校准之后，我们量化了每次渗透事件期间和之后样品中的水分含量。土壤异质性的影响是明显的，如土层较薄，根的吸水量也是如此。在入渗初期，羽扇豆主根部的水分含量较低，在水分再分配的后期，湿润锋向下扩展，土壤中的水分含量下降，水分再分配的后期吸收较慢，弥散较多。观察到的根系吸水并不是均匀的，而是局限于某些区域。对于玉米，我们观察到水分的损失主要在根系的上部，离茎更近，而不是在根
Water infiltration into vegetated soils is affected by interactions between soil properties and plant activity. Water uptake by plant roots depends on the soil hydraulic properties and infiltration rate. In turn, roots are important water movers and induce nonuniform water content distributions with consequent impact on the infiltration rate. Our goal was to use neutron radiography to investigate root water uptake during rapid infiltration events and subsequent water redistribution. Neutron radiography is an imaging technique capable of measuring with high spatial and temporal resolution root density, soil structure, and water distributions in the vicinity of roots. We used time-series neutron radiography to image infiltration events in 0.17- by 0.15- by 0.013-m boxes filled with a sand mixture and that contained either lupine (Lupinus L.) or maize (Zea mays L.) plants. We measured four replications at two stages of plant growth. Neutron radiography can detect small variations in water content with high accuracy and high spatial and temporal resolution. Due to their high water content, roots were easily visible in the radiograms before infiltration. Following calibration, we quantified the water content in the sample during and after each infiltration event. Effects of soil heterogeneities such as thin soil layers were visible, as was water uptake by roots. We observed lower water contents along the main root of lupine during the early stage of infiltration, and slower and more diffuse uptake during the later stages of water redistribution, when the wetting front had propagated downward and the water content in the soil decreased. The observed root water uptake was not uniform but rather was localized in certain regions. For maize we observed a loss of water mainly in the upper part of the root system, closer to the stem rather than at root