During the experiment,the tubes were kept in a temperature-
controlled water bath(a modified,rectangular chest freezer)to
stabilize the soil temperature at +13 C(Fig.2).The bath was
divided into two sides:ambient illumination(AMB)and artificially
induced night-time darkness (DARK).Two aquarium pumps were
installed to circulate the water for equal temperature distribution
in the bath.Three tubes with earthworms from each geographical
origin were placed randomly at opposite sides of the bath,so that
there were two 3x3 groups of tubes.The two tubes without
earthworms were placed on the AMB side between the treatments
and monitored for soil water content using a pair of 0.15 m long
Time Domain Reflectometry rods(TDR Model no. 6050X1 Trase
System,Soilmoisture Equipment Corp.,Santa Barbara,CA)and
temperature at 0.1 m depth using a permanently installed mercury
thermometer.