How does the cambium survive where plant stems emerge through hot soil?
Gutschick, Vincent1, 1 ABSTRACT- In desert soils, the surface temperature of bare soil readily exceeds 60°C and can approach 70°C. The living cells of the cambium must be protected from such extremes in stems that emerge through such hot soil. Thermally-insulating bark alone is necessary but not sufficient; heat must be transported away from this region by molecular conduction in wood or by convective heat transport afforded by sapflow (which is minimal in the times of hottest soil surfaces, though not zero). I present a physical model of heat transport in stem, bark, soil, and air to examine patterns of temperature amelioration arising from molecular and convective conduction. I also evaluate ancillary mechanisms, including shading by the upper canopy and by other stems, and reduction of radiative load by stem angle. Some experimental data in less extreme conditions have been obtained by placing fine thermocouples in tissue, bark, and soil; some interpretation is offered.
