2.4. Length and dry weight density analyses of roots harvested by the monolith method
All soil monoliths were soaked in water, then stirred and poured through a sieve (0.25 mm2 mesh). The sieve was suspended in a large water bath and shaken continuously until roots were washed free of soil. Soil materials remaining on the sieve were removed manually. The separated root fractions were scanned with the scanner as mentioned above. In this way, the lengths of roots with different diameters in each soil monolith could be obtained. After scanning, the root fractions were dried at 70 °C until constant weight and then weighed. The results were presented as wireframe diagrams. The wireframe diagrams of RLD and RDWD were constructed with Surfer 7.0 (Golden Software Inc., 2000).