Abstract:

Minirhizotrons provide a nondestructive, in situ method for directly viewing and studying fine root dyanmics. In this paper, we introduce the minirhizotron methodology for measuring root systems, compare results between the minirhizotron and the soil corer method, and compare root growth dynamics under different soil water conditions. The experiments were conducted on a re-vegetated Caragana korshinskii quadrat at the Water Balance Experimental Field (WBEF) of Shapotou Desert Research and Experimental Station, Chinese Academy of Sciences (CAS) during the growing season in 2004. Shapotou is located at 37°33' N, 105°02' E in Ningxia Hui Autonomous Region at the southeastern edge of the Tengger Desert in northern China, elevation 1 250 m with a mean annual precipitation of 186.2 mm. It is classified as a steppified desert zone and is a transitional zone between desert and oasis. In September,2003, a block of soil was excavated from the C. korshinskii quadrat and 3 minirhizotrons were placed at a 45° angle at a distance of 20, 50 and 100 cm from the sample plant and the soil repacked. Beginning on March 27,2004, root images were collected every two weeks, and the soil water content was measured by neutron probe and TDR. Roots were colleted with a soil corer each month from a depth of 0-200 cm at 10 cm depth intervals. The results indicated that 10 months were required to allow the roots to recolonize the soil following the tube installation. The 2-D minirhizotron images were equivalent to a 2.6 mm depth of field (DOF) around the tube, within which all roots were observed. The root growth dynamics of C. korshinskii supplemented with soil water resulted in a great deal of root growth; however, root water uptake and evapotranspiration by C. korshinskii subsequently would reduce the soil water content and slow growth. The interactions between root growth and soil water content went through two cycles, and the lag time between growth of root apices and reductions of soil water content was about 20 days.

Key words: Caragana korshinskii, Root growth dynamics, Minirhizotrons, Soil auger, Soil water content