Capucine Marion, Mana Gharun, Matthias S Brennwald, Rolf Kipfer
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引用次数: 0
Abstract
Trees transport gases from below ground into the atmosphere through the process of transpiration. Tracing gases transported through this mechanism continuously and under field conditions remains an experimental challenge. Here we measured gases dissolved in tree sap in-situ and in real time, aiming to simultaneously analyse the transport of several gases (He, Ar, Kr, N2, O2, CO2) from the soil, through the trees, into the atmosphere. We constructed and inserted custom-made semi-permeable membrane probes in the xylem of a fir tree and measured gas abundances at different heights using a portable gas equilibrium membrane-inlet mass spectrometer ('miniRUEDI'). With this method we were able to continuously measure the abundances of He, Ar, Kr, N2, O2, CO2 in sap over several weeks. We observed diurnal variations of CO2 and O2 concentrations that reflected tree physiological activities. As a proof of concept that trees do uptake dissolved gases in soil water, we irrigated the tree with He-enriched water in a tracer experiment, and were able to determine upwards sap flow velocity. Measurements of inert gases together with reactive species as CO2 and O2 allows to separate physical transport and exchange of gases derived from the soil or the atmosphere from biological reactions. We discuss the opportunities that our technique provides for continuous in-situ measurements of gases in tree sap.
树木通过蒸腾作用将气体从地下输送到大气中。在野外条件下持续追踪通过这种机制运输的气体仍然是一项实验挑战。在这里,我们对溶解在树液中的气体进行了现场实时测量,旨在同时分析几种气体(He、Ar、Kr、N2、O2、CO2)从土壤通过树木进入大气的传输过程。我们在一棵杉树的木质部建造并插入了定制的半透膜探针,并使用便携式气体平衡膜入口质谱仪('miniRUEDI')测量了不同高度的气体丰度。利用这种方法,我们能够在数周内连续测量树液中 He、Ar、Kr、N2、O2 和 CO2 的丰度。我们观察到二氧化碳和氧气浓度的昼夜变化反映了树木的生理活动。为了证明树木确实吸收了土壤水中的溶解气体,我们在示踪实验中用富含氦气的水灌溉树木,并测定了树液向上流动的速度。通过对惰性气体以及二氧化碳和氧气等活性物质的测量,可以将来自土壤或大气的气体的物理传输和交换与生物反应区分开来。我们讨论了我们的技术为连续现场测量树液中的气体提供的机会。
期刊介绍:
Tree Physiology promotes research in a framework of hierarchically organized systems, measuring insight by the ability to link adjacent layers: thus, investigated tree physiology phenomenon should seek mechanistic explanation in finer-scale phenomena as well as seek significance in larger scale phenomena (Passioura 1979). A phenomenon not linked downscale is merely descriptive; an observation not linked upscale, might be trivial. Physiologists often refer qualitatively to processes at finer or coarser scale than the scale of their observation, and studies formally directed at three, or even two adjacent scales are rare. To emphasize the importance of relating mechanisms to coarser scale function, Tree Physiology will highlight papers doing so particularly well as feature papers.